,,coal2 ,,and ,,what ,,we ,,get ,,from  
,,it4       ,,the ,,romance ,,of        
,,science4     ,,coal ,,and ,,what ,,we 
,,get ,,from ,,it4     ,a ,romance of   
,applied ,science4     ,,expanded ,,from
 ,,the ,,notes ,,of ,a ,,lecture        
,,delivered ,,in ,,the ,,theatre ,,of   
,,the   ,,london ,,institution1 ,,jan4  
#bjth1 #ahij4     ,,by ,,raphael        
,,meldola1 ,f4,r4,s41 ,f4,i4,c41 ,c41   
,,professor ,,of ,,chemistry ,,in ,,the 
,,finsbury ,,technical ,,college1       
,,city ,,and ,,guilds ,,of ,,london     
,,institute4     ,,published ,,under    
,,the ,,direction ,,of ,,the ,,committee
   ,,of ,,general ,,literature ,,and    
,,education ,,appointed ,,by ,,the      
,,society ,,for ,,promoting ,,christian 
,,knowledge4    ,,london3   ,,society   
,,for ,,promoting ,,christian           
,,knowledge1   ,,northumberland         
,,avenue1 ,,charing ,,cross1 ,w4,c42    
#dc1 ,,queen ,,victoria ,,street1 ,e4,c4
   ,,brighton3 #ace1 ,,north ,,street4  
,,new ,,york3 ,e4  ,j4 ,b4 ,,young      

,,co4   #ahia4       ,,to ,,william     
,,henry ,,perkin1   ,,ph4,d41 ,f4,r4,s41
   ,,the ,,founder ,,of ,,the           
,,coal-,,tar ,,colour ,,industry1       
,,this ,,book ,,is ,,dedicated ,,by     
,,the ,,author4     ,,preface4   ,this  
is neither a technical manual1 nor a    
treatise dealing with the history of a  
particular branch of applied science1   
but it partakes somewhat of the         
character of both4 ,it is an            
attempt--perhaps somewhat bold--to      
present in a popular form an account of 
the great industry which has arisen out 
of the waste from the gas-works4 ,in the
 strictest sense it is a romance of     
dirt4 ,to render intelligible the       
various stages in the evolution of the  
industry1 without assuming any knowledge
 of chemical science on the part of the 
general reader1 has by no means been an 
easy task1 and ,i have great misgivings 
as to the success of my effort4 ,but    
there is so much misapprehension        
concerning the history and the mode of  

production of colouring-matters from    
coal-tar1 that any attempt to strip the 
industry of its mystery in this1 the    
land of its birth1 cannot but find      
justification4 ,although the theme is a 
favourite one with popular lecturers1 it
 is generally treated in a superficial  
way1 leaving the audience only in       
possession of the bare fact that        
dyestuffs1 c41 have by some means or    
other been obtained from coal-tar4 ,i   
have endeavoured to go somewhat beyond  
this1 and to give some notion of the    
scientific principles underlying the    
subject4 ,if the reader can follow these
 pages1 in which not a chemical formula 
appears1 with the same interest and with
 the same desire to know more about the 
subject that was manifested by the      
audience at the ,london ,institution1   
before whom the lecture was delivered1  
my object will have been accomplished4  
,to the ,board of ,managers of that     
,institution my thanks are due for the  
opportunity which they have afforded me 

of attempting to extend that popular    
knowledge of applied science for which  
there is such a healthy craving in the  
public mind at the present time4    ,r4 
,m4   #f ,brunswick ,square1 ,w4,c4     
,,contents4   ,,chapter ,i4  ,origin of 
,coal1 #i4 ,coal of various ages1 #aa4  
,graphite1 #ab4 ,recent ,vegetable      
,deposits1 #ac4 ,mode of occurrence of  
,coal1 #ac4 ,structure of ,coal1 #ae4   
,uses of ,coal1 #af4 ,coal a source of  
,energy1 #ag4 ,mechanical ,equivalent of
 ,heat1 #ai4 ,value of ,coal as a ,fuel1
 #bj4 ,small efficiency of              
,steam-engines1 #ba4 ,mechanical value  
of ,coal1 #bb4 ,whence ,coal derives its
 ,energy1 #bb4 ,chemical ,composition of
 ,coal1 #bc4 ,growth of ,plants1 #bf4   
,solar ,energy1 #bh4 ,transformation of 
,wood into ,coal1 #cj4 ,destructive     
,distillation of ,coal1 #cc4            
,experiments of ,becher1 #cd2 of ,dean  
,clayton1 #ce2 of ,stephen ,hales1 #cg2 
of ,bishop ,watson1 #cg2 of the ,earl of
 ,dundonald1 #ci4 ,coal-gas introduced  

by ,murdoch1 #dj4 ,spread of the new    
,illuminant1 #da4 ,manufacture of       
,coal-gas1 #db4 ,quantitative results1  
#de4 ,uses of ,coke1 #dg4 ,goethe's     
visit to ,stauf1 #dh4 ,bishop ,watson on
 waste from ,coke-ovens1 #ej4 ,shale-oil
 ,industry1 #ej4 ,history of            
,coal-mining1 #eg4 ,introduction of     
,coal into ,london1 #eh4 ,the ,coal     
resources of the ,united ,kingdom1 #fj4 
,competition between ,electricity and   
,coal-gas1 #fb4   ,,chapter ,,ii4       
,ammoniacal ,liquor of ,gas-works1 #fd4 
,origin of the ,ammonia1 #fe4 ,ammonia  
as a ,fertilizer1 #fe4 ,other uses of   
,ammonia1 #fg4 ,annual production of    
,ammonia1 #fh4 ,utilization of          
,coal-tar1 #fi4 ,the ,creosoting of     
,timber1 #gj4 ,early uses of the ,light 
,tar ,oils1 #ga4 ,discovery of ,benzene 
by ,faraday2 isolation from ,tar ,oil by
 ,hofmann and ,mansfield1 #gc4          
,discovery of ,mauve by ,perkin1 #gd4   
,history of ,aniline1 #ge4 ,the         
,distillation of ,coal-tar1 #gg4        

,separation of the ,hydrocarbons of the 
,benzene ,series1 #hb4 ,manufacture of  
,aniline and ,toluidine1 #hg4 ,history  
and ,manufacture of ,magenta1 #hi4      
,blue1 ,violet1 and ,green ,dyes from   
,magenta1 #ib4 ,the ,triphenylmethane   
,group1 #ig4 ,the ,azines1 #ajh4        
,lauth's ,violet and ,methylene ,blue1  
#aaa4 ,aniline ,black1 #aad4            
,introduction of ,azo-dyes1 #aae4       
,aniline ,yellow1 ,manchester ,brown1   
and ,chrysoidine1 #aah4 ,the ,indulines1
 #aba4 ,chronological ,summary1 #abb4   
,,chapter ,,iii4  ,natural ,sources of  
,indigo1 #abd4 ,syntheses of the        
,colouring-matter1 #abf4 ,carbolic ,oil1
 its treatment and its constituents1    
#abi4 ,phenol ,dyes1 #acb4 ,salicylic   
,acid and its uses1 #acd4 ,picric ,acid1
 #acf4 ,naphthalene and its             
applications1 #aci4 ,the ,albo-carbon   
,light1 #adj4 ,phthalic ,acid and the   
,phthaleins1 #ade4 ,magdala ,red1 #adi4 
,azo-dyes from the ,naphthols1          
,naphthylamines1 and their              

,sulpho-acids1 #aej4 ,naphthol ,green1  
the ,oxazines1 and the ,indophenols1    
#afa4 ,creosote ,oil1 #afc4 ,the        
,lucigen ,burner1 #afc4 ,anthracene     
,oil1 #afg4 ,the ,discovery of          
,artificial ,alizarin1 and its effects  
on ,madder growing1 #afg4 ,the          
industrial isolation of ,anthracene and 
its conversion into ,colouring-matters1 
#aga4 ,pitch1 and its uses1 #agf4       
,patent ,fuel1 or ,briquettes1 #agh4    
,coal-tar products in ,pharmacy1 #agh4  
,aromatic ,perfumes1 #ahe4 ,coal-tar    
,saccharin1 #ahf4 ,coal-tar ,products in
 ,photography1 #ahh4 ,coal-tar ,products
 in ,biology1 #aib4 ,value of the       
,coal-tar ,industry1 #aid4 ,the         
,coal-tar ,industry in relation to pure 
,science1 #aif4 ,permanence of the      
,artificial ,colouring-matters1 #aih4   
,chronological ,summary1 #bjj4          
,addendum1 #bjb4     ,,coal2 ,,and      
,,what ,,we ,,get ,,from ,,it4          
,,chapter ,i4       ,hier #agga fand    
sich eine zusammenhaengende ,ofenreihe1 

wo      ,steinkohlen abgeschwefelt und  
zum ,gebrauch bei ,eisenwerken tauglich 
gemacht werden sollten2 allein zu       
gleicher ,zeit wollte man ,oel und      
,harz auch zu ,gute machen1 ja sogar den
 ,russ nicht missen1 und so             
unterlag den vielfachen ,absichten alles
 zusammen4--,goethe1 ,wahrheit      und 
,dichtung1 ,book ,x4   ,to get at the   
origin of the familiar fuel which blazes
 in our grates with such lavish waste of
 heat1 and pollutes the atmosphere of   
our towns with its unconsumed particles1
 we must in imagination travel backwards
 through the course of time to a very   
remote period of the world's history4   
,ages before man1 or the species of     
animals and plants which are            
contemporaneous with him1 had appeared  
upon the globe1 there flourished a      
vegetation not only remarkable for its  
luxuriance1 but also for the            
circumstance that it consisted to a     
preponderating extent of non-flowering  
or cryptogamic plants4 ,in swampy areas1

 such as the deltas at the mouths of    
great rivers1 or in shallow lagoons     
bordering a coast margin1 the jungles of
 ferns and tree-ferns1 club-mosses and  
horse-tails1 sedges1 grasses1 c41 grew  
and died down year by year1 forming a   
consolidated mass of vegetable matter   
much in the same way that a peat bed or 
a mangrove swamp is accumulating organic
 deposits at the present time4 ,in the  
course of geological change these beds  
of compressed vegetation became         
gradually depressed1 so that marine or  
fresh-water sediment was deposited over 
them1 and then once more the vegetation 
spread and flourished to furnish another
 accumulation of vegetable matter1 which
 in its turn became submerged and buried
 under sediment1 and so on in successive
 alternations of organic and sedimentary
 deposits4  ,but these conditions of    
climate1 and the distribution of land   
and water favourable to the accumulation
 of large deposits of vegetable matter1 
gradually gave way to a new order of    

things4 ,the animals and plants adapted 
to the particular conditions of         
existence described above gave rise to  
descendants modified to meet the new    
conditions of life4 ,enormous           
thicknesses of other deposits were laid 
down over the beds of vegetable remains 
and their intercalated strata of clay1  
shale1 sandstone1 and limestone4 ,the   
chapter of the earth's history thus     
sealed up and stowed away among her     
geological records relates to a period  
now known as the ,carboniferous1 because
 of the prevalence of seams or beds of  
coal throughout the formation at certain
 levels4 ,by the slow process of        
chemical decomposition without access of
 air1 modified also by the mechanical   
pressure of superincumbent formations1  
the vegetable deposits accumulated in   
the manner described have1 in the lapse 
of ages1 become transformed into the    
substance now familiar to us as coal4   
,although coal is thus essentially a    
product of ,carboniferous age1 it must  

not be concluded that this mineral is   
found in no other geological formation4 
,the conditions favourable for the      
deposition of beds of vegetable matter  
have prevailed again and again1 at      
various periods of geological time and  
on different parts of the earth1        
although there is at present no distinct
 evidence that such a luxuriant growth  
of vegetation1 combined with the other  
necessary conditions1 has ever existed  
at any other period in the history of   
the globe4 ,thus in the very oldest     
rocks of ,canada and the northern       
,states of ,america1 in strata which    
take us back to the dawn of geological  
history1 there is found abundance of the
 mineral graphite1 the substance from   
which black-lead pencils are made1 which
 is almost pure carbon4 ,now most       
geologists admit that graphite          
represents the carbon which formed part 
of the woody tissue of plants that lived
 during those remote times1 so that this
 mineral represents coal in the ultimate

 stage of carbonization4 ,in some few   
instances true coal has been found      
converted into graphite in situ by the  
intrusion of veins of volcanic rock     
7basalt71 so that the connection between
 the two minerals is more than a mere   
matter of surmise4  ,then again we have 
coal of pre-,carboniferous age in the   
,old ,red ,sandstone of ,scotland1 this 
being of course younger in point of time
 than the graphite of the ,archaean     
rocks4 ,coal of post-,carboniferous date
 is found in beds of ,permian age in    
,bavaria1 of ,triassic age in ,germany1 
in the ,inferior ,oolite of ,yorkshire  
belonging to the ,jurassic period1 and  
in the ,lower ,cretaceous deposits of   
north-western ,germany4 ,coming down to 
more recent geological periods1 we have 
a coal seam of over thirty feet in      
thickness in the northern ,tyrol of     
,eocene age2 we have brown coal deposits
 of ,oligocene age in ,belgium and      
,austria1 and1 most remarkable of all1  
coal has been found of ,miocene1 that   

is1 mid-,tertiary age1 in the ,arctic   
regions of ,greenland within a few      
degrees of the ,north ,pole4 ,thus the  
formation of coal appears to have been  
going on in one area or another ever    
since vegetable life appeared on the    
globe1 and in the peat bogs1 delta      
jungles1 and mangrove swamps of the     
present time we may be said to have the 
deposition of potential coal deposits   
for future ages now going on4  ,although
 in some parts of the world coal seams  
of pre-,carboniferous age often reach   
the dignity of workable thickness1 the  
coal worked in this country is entirely 
of ,carboniferous date4 ,after the      
explanation of the mode of formation of 
coal which has been given1 the phenomena
 presented by a section through any of  
our coal measures will be readily       
intelligible 7see ,fig4 #a74 ,we find   
seams of coal separated by beds of      
sandstone1 limestone1 or shale          
representing the encroachment of the sea
 and the deposition of marine or        

estuarine sediment over the beds of     
vegetable remains4 ,the seams of coal1  
varying in thickness from a few inches  
to three or four feet1 always rest on a 
bed of clay1 known technically as the   
underclay1 which represents the soil on 
which the plants originally grew4 ,in   
some instances the seams of coal with   
their thin partings of clay reach an    
aggregate thickness of twenty to thirty 
feet4 ,in many cases the very roots of  
the trees are found upright in a        
fossilized condition in the underclay1  
and can be traced upwards into the      
overlying coal beds2 or the completely  
carbonized trunk is found erect in the  
position in which the tree lived and    
died 7see ,fig4 #b74   ,illustration3   
,,fig4 #a4--,section through            
,carboniferous strata showing seams of  
coal4 ,dislocations1 or faults1 so      
common in the ,coal ,measures1 are shown
 at ,h1 ,t1 and ,f4 ,intrusions of      
igneous rock are shown at ,d4 ,at ,b is 
shown the coalescence of two seams1 and 

at ,n the local thinning of the seam4   
,the vertical lines indicate the shafts 
of coal mines4  ,illustration3 ,,fig4   
#b4--,section showing coal seams and    
upright trunks attached to roots in     
situ4 ,a'1 ,a''1 ,a'''1 beds of shale4  
,b1 coal seams4 ,c1 underclay4 ,d1      
sandstone4   ,owing to the chemical and 
mechanical forces to which the original 
vegetable deposit has been subjected1   
the organic structure of coal has for   
the most part been lost4 ,occasionally1 
however1 portions of leaves1 stems1 and 
the structure of woody fibre can be     
detected1 and thin sections often show  
the presence of spore-cases of          
club-mosses in such numbers that certain
 kinds of coal appear to be entirely    
composed of such remains4 ,but although 
coal itself now furnishes but little    
direct evidence of its vegetable origin1
 the interstratified clays1 shales1 and 
other deposits often abound with        
fossilized plant remains in every state 
of preservation1 from the most delicate 

fern frond to the prostrate tree trunk  
many yards in length4 ,it is from such  
evidence that our knowledge of the      
,carboniferous flora has been chiefly   
derived4  ,now this carbonized          
vegetation of a past age1 the history of
 which has been briefly sketched in the 
foregoing pages1 is one of the chief    
sources of our industrial supremacy as a
 nation4 ,we use it as fuel for         
generating the steam which drives our   
engines1 or for the production of heat  
wherever heat is wanted4 ,in            
metallurgical operations we consume     
enormous quantities of coal for         
extracting metals from their ores1 this 
consumption being especially great in   
the case of iron smelting4 ,for this    
last operation some kinds of raw coal   
are unsuitable1 and such coal is        
converted into coke before being used in
 the blast furnace4 ,the fact that the  
iron ore and the coal occur in the same 
district is another cause of our high   
rank as a manufacturing nation4  ,it has

 often been a matter of wonder that iron
 ore and the material essential for     
extracting the metal from it should be  
found associated together1 but it is    
most likely that this combination of    
circumstances1 which has been so        
fortunate for our industrial prosperity1
 is not a mere matter of accident1 but  
the result of cause and effect4 ,it is1 
in fact1 probable that the iron ore owes
 its origin to the reduction and        
precipitation of iron compounds by the  
decomposing vegetation of the           
,carboniferous period1 and this would   
account for the occurrence of the bands 
of ironstone in the same deposits with  
the coal4 ,in former times1 when the    
area in the south-east of ,england known
 as the ,weald was thickly wooded1 the  
towns and villages of this district were
 the chief centres of the iron          
manufacture4 ,the ore1 which was of a   
different kind to that found in the     
coal-fields1 was smelted by means of the
 charcoal obtained from the wood of the 

,wealden forests1 and the manufacture   
lingered on in ,kent1 ,sussex1 and      
,surrey till late in the last century1  
the railings round ,st4 ,paul's1        
,london1 being made from the last of the
 ,sussex iron4 ,when the northern       
coal-fields came to be extensively      
worked1 and ironstone was found so      
conveniently at hand1 the ,wealden iron 
manufacture declined1 and in many places
 in the district we now find disused    
furnaces and heaps of buried slag as the
 last witnesses of an extinct industry4 
,from coal we not only get mechanical   
work when we burn it to generate heat   
under a steam boiler1 but we also get   
chemical work out of it when we employ  
it to reduce a metallic ore1 or when we 
make use of it as a source of carbon in 
the manufacture of certain chemical     
products1 such as the alkalies4 ,we have
 therefore in coal a substance which    
supplies us with the power of doing     
work1 either mechanical1 chemical1 or   
some other form1 and anything which does

 this is said to be a source of energy4 
,it is a familiar doctrine of modern    
science that energy1 like matter1 is    
indestructible4 ,the different forms of 
energy can be converted into one        
another1 such1 for example1 as chemical 
energy into heat or electricity1 heat   
into mechanical work or electricity1    
electricity into heat1 and so forth1 but
 the relationship between these         
convertible forms is fixed and          
invariable4 ,from a given quantity of   
chemical energy represented1 let us say1
 by a certain weight of coal1 we can get
 a certain fixed amount of heat and no  
more4 ,we can employ that heat to work a
 steam-engine1 which we can in turn use 
as a source of electricity by causing it
 to drive a dynamo-machine4 ,then this  
doctrine of science teaches us that our 
given weight of coal in burning evolves 
a quantity of heat which is the         
equivalent of the chemical energy which 
it contains1 and that this quantity of  
heat has also its equivalent in         

mechanical work or in electricity4 ,this
 great principle--known as the          
,conservation of ,energy--has been      
gradually established by the joint      
labours of many philosophers from the   
time of ,newton downwards1 and foremost 
among these must be ranked the late     
,james ,prescott ,joule1 who was the    
first to measure accurately the exact   
amount of work corresponding to a given 
quantity of heat4  ,in measuring heat   
7as distinguished from temperature7 it  
is customary to take as a unit the      
quantity necessary to raise a given     
weight of water from one specified      
temperature to another4 ,in measuring   
work1 it is customary to take as a unit 
the amount necessary to raise a certain 
weight at a specified place to a certain
 height against the force of gravity at 
that place4 ,joule's unit of heat is the
 quantity necessary to raise one pound  
of water from #fj deg4 to #fa deg4 ,f41 
and his unit of work is the foot-pound1 
i4e4 the quantity necessary to raise a  

weight of one pound to a height of one  
foot4 ,now the quantitative relationship
 between heat and work measured by      
,joule is expressed by saying that the  
mechanical equivalent of heat is about  
#ggb foot-pounds1 which means that the  
quantity of heat that would raise one   
pound of water #a deg4 ,f4 would1 if    
converted into work1 be capable of      
raising a one-pound weight to a height  
of #ggb feet1 or a weight of #ggb lbs4  
to a height of one foot4  ,this         
mechanical equivalent ought to tell us  
exactly how much power is obtainable    
from a certain weight of coal if we     
measure the quantity of heat given out  
when it is completely burnt4 ,thus an   
average ,lancashire coal is said to have
 a calorific power of #ac1hij1 which    
means that #a lb4 of such coal on       
complete combustion would raise #ac1hij 
lbs4 of water through a temperature of  
#a deg4 ,f41 if we could collect all the
 heat generated and apply it to this    
purpose4 ,but if we express this        

quantity of heat in its mechanical      
equivalent1 and suppose that we could   
get the corresponding quantity of work  
out of our pound of coal1 we should be  
grievously mistaken4 ,for in the first  
place1 we could not collect all the heat
 given out1 because a great deal is     
communicated to the products of         
combustion by which it is absorbed1 and 
locked up in a form that renders it     
incapable of measurement by our         
thermometers4 ,in the next place1 if we 
make an allowance for the quantity of   
heat which thus disappears1 even then   
the corrected calorific power converted 
into its mechanical equivalent would not
 express the quantity of work           
practically obtainable from the coal4   
,in the most perfectly constructed      
engine the whole amount of heat         
generated by the combustion of the coal 
is not available for heating the        
boiler--a certain quantity is lost by   
radiation1 by heating the material of   
the furnace1 c41 by being carried away  

by the products of combustion and in    
other ways4 ,moreover1 some of the coal 
escapes combustion by being allowed to  
go away as smoke1 or by remaining as    
cinders4 ,then again1 in the engine     
itself a good deal of heat is lost      
through various channels1 and much of   
the working power is frittered away     
through friction1 which reconverts the  
mechanical power into its equivalent in 
heat1 only this heat is not available   
for further work1 and is thus lost so   
far as the efficiency of the engine is  
concerned4 ,these sources of loss are   
for the most part unavoidable1 and are  
incidental to the necessary             
imperfections of our mechanism4 ,but    
even with the most perfectly conceivable
 constructed engine it has been proved  
that we can only expect one-sixth of the
 total energy of the fuel to appear in  
the form of work1 and in a very good    
steam-engine of the present time we only
 realize in the form of useful work     
about one-tenth of the whole quantity of

 energy contained in the coal4 ,although
 steam power is one of the most useful  
agencies that science has placed at the 
disposal of man1 it is not generally    
recognized by the uninitiated how       
wasteful we are of ,nature's resources4 
,one of the greatest problems of applied
 science yet to be solved is the        
conversion of the energy latent in coal 
or other fuel into a quantity of useful 
work approximating to the mechanical    
equivalent much more closely than has   
hitherto been accomplished4  ,but       
although we only get this small fraction
 of the whole working capability out of 
coal1 the actual amount of energy       
dormant in this substance cannot but    
strike us as being prodigious4 ,it has  
already been said that a pound of coal  
on complete combustion gives out #ac1hij
 heat units4 ,this quantity of heat     
corresponds to over #aj1jjj1jjj         
foot-pounds of work4 ,a horse-power may 
be considered as corresponding to #eej  
foot-pounds of work per second1 or      

#a1ihj1jjj foot-pounds per hour4 ,thus  
our pound of coal contains a store of   
energy which1 if capable of being       
completely converted into work without  
loss1 would in one hour do the work of  
about five and a half horses4 ,the      
strangest tales of necromancy can hardly
 be so startling as these sober figures 
when introduced for the first time to   
those unaccustomed to consider the      
stupendous powers of ,nature4  ,if      
energy is indestructible1 we have a     
right to inquire in the next place from 
whence the coal has derived this        
enormous store4 ,a consideration of the 
origin of coal1 and of its chemical     
composition1 will enable this question  
to be answered4 ,the origin of coal has 
already been discussed4 ,chemically     
considered1 it consists chiefly of      
carbon together with smaller quantities 
of hydrogen1 oxygen1 and nitrogen1 and a
 certain amount of mineral matter which 
is left as ash when the coal is burnt4  
,the following average analyses of      

different varieties will give an idea of
 its chemical composition3--            
----------------------------------------
---------------------------     ,variety
 of ,coal4  ,carbon4  ,hydrogen4        
,oxygen4  ,nitrogen4  ,ash4             
----------------------------------------
------------------------   ,s4          
,staffordshire     #gc4d       #e4j     
#aa4g       #a4g     #b4c   ,newcastle  
7,caking7   #hj4j       #e4c      #aj4g 
#b4b     #a4g   ,cannel 7,wigan7        
#ha4b       #e4f       #g4i       #b4a  
#b4e   ,anthracite 7,welsh7   #ij4a     
#c4b       #b4e       #j4h     #a4f     
----------------------------------------
-----------------------------  ,there   
are in addition to these constituents   
small quantities of sulphur and a       
certain variable amount of water 7#e to 
#aj per cent47 in all coals1 but the    
elements which most concern us are those
 heading the respective columns4  ,from 
the foregoing analyses1 which express   
the percentage composition1 it will be  

seen that carbon is by far the most     
important constituent of coal4 ,carbon  
is a chemical element which is found in 
a crystalline form in nature as the     
diamond1 and which forms a most         
important constituent of all living     
matter1 whether animal or vegetable4    
,woody fibre contains a large quantity  
of this element1 and the carbon of coal 
is thus accounted for2 it was           
accumulated during the growth of the    
plants of the ,carboniferous period4    
,now carbon is one of those elementary  
substances which are said to be         
combustible1 which means that if we heat
 it in atmospheric air it gives out heat
 and light1 and gradually disappears1   
or1 as we say1 burns away4 ,the heat    
which is given out during combustion    
represents the chemical energy stored up
 in the combustible1 for combustion is  
in fact the chemical union of one       
substance with another with the         
development of heat and light4 ,when    
carbon burns in air1 therefore1 a       

chemical combination takes place1 the   
air supplying the other substance with  
which the carbon combines4 ,that other  
substance is also an element--it is the 
invisible gas which chemists call       
oxygen1 and which forms one-fifth of the
 bulk of atmospheric air1 the remainder 
consisting of the gas nitrogen and small
 quantities of other gases with which we
 shall have more to do subsequently4    
,when oxygen and carbon unite under the 
conditions described1 the product is an 
invisible gas known as carbon dioxide1  
and it is because this gas is invisible 
that the carbon seems to disappear      
altogether on combustion4 ,in reality1  
however1 the carbon is not lost1 for    
matter is as indestructible as energy1  
but it is converted into the dioxide    
which escapes as gas under ordinary     
circumstances4 ,if1 however1 we burn a  
given weight of carbon with free access 
of air1 and collect the product of      
combustion and weigh it1 we shall find  
that the product weighs more than the   

carbon1 by an amount which represents   
the weight of oxygen with which the     
element has combined4 ,by careful       
experiment it would be found that one   
part by weight of carbon would give     
three and two-third parts by weight of  
carbon dioxide4 ,if1 moreover1 we could 
measure the quantity of heat given out  
by the complete combustion of one pound 
of carbon1 it would be found that this  
quantity would raise #ad1edd lbs4 of    
water through #a deg4 ,f41 a quantity of
 heat corresponding to over eleven      
million foot-pounds of work1 or about   
seven and three-quarters horse-power per
 hour4  ,here then is the chief source  
of the energy of coal--the carbon of the
 plants which lived on this earth long  
ages ago has lain buried in the earth1  
and when we ignite a coal fire this     
carbon combines with atmospheric oxygen1
 and restores some of the energy that   
was stored up at that remote period4    
,but the whole of the energy dormant in 
coal is not due to the carbon1 for this 

fuel contains another combustible       
element1 hydrogen1 which is also a gas  
when in the free state1 and which is one
 of the constituents of water1 the other
 constituent being oxygen4 ,in fact1    
there is more latent energy in hydrogen1
 weight for weight1 than there is in    
carbon1 for one pound of hydrogen on    
complete combustion would give enough   
heat to raise #fb1jcb lbs4 of water     
through #a deg4 ,f4 ,hydrogen in burning
 combines with oxygen to form water1 so 
that the products of the complete       
combustion of coal are carbon dioxide   
and water4 ,the amount of heat          
contributed by the hydrogen of coal is1 
however1 comparatively insignificant1   
because there is only a small percentage
 of this element present1 and we thus   
come to the conclusion that nearly all  
the work that is done by our            
steam-engines of the present time is    
drawn from the latent energy of the     
carbon of the fossilized vegetation of  
the ,carboniferous period4  ,the        

conclusion to which we have now been led
 leaves us with the question as to the  
origin of the energy of coal still      
unanswered4 ,we shall have to go a step 
further before this part of our story is
 complete1 and we must form some kind of
 idea of the way in which a plant grows4
 ,carbon being the chief source of      
energy in coal1 we may for the present  
confine ourselves to this element1 of   
which woody fibre contains about #ej per
 cent4 ,consider the enormous gain in   
weight during the growth of a plant2    
compare the acorn1 weighing a few       
grains1 with the oak1 weighing many     
tons1 which arises from it after        
centuries of growth4 ,if matter is      
indestructible1 and never comes into    
existence spontaneously1 where does all 
this carbon come from8 ,it is a matter  
of common knowledge that the carbon of  
plants is supplied by the atmosphere in 
the form of carbon dioxide--the gas     
which has already been referred to as   
resulting from the combustion of carbon4

 ,this gas exists in the atmosphere in  
small quantity--about four volumes in   
#aj1jjj volumes of air2 but             
insignificant as this may appear1 it is 
all important for the life of plants1   
since it is from this source that they  
derive their carbon4 ,the origin of the 
carbon dioxide1 which is present as a   
normal constituent of the atmosphere1   
does not directly concern us at present1
 but it is important to bear in mind    
that this gas is one of the products of 
the respiration of animals1 so that the 
animal kingdom is one of the sources of 
plant carbon4  ,the transition from     
carbon dioxide to woody fibre is brought
 about in the plant by a series of      
chemical processes1 and through the     
formation of a number of intermediate   
products in a manner which is not yet   
thoroughly understood2 but since carbon 
dioxide consists of carbon and oxygen1  
and since plants feed upon carbon       
dioxide1 appropriating the carbon and   
giving off the oxygen as a waste        

product1 it is certain that work of some
 kind must be performed4 ,this is       
evident1 because it has been explained  
that when carbon combines with oxygen a 
great deal of heat is given out1 and as 
this heat is the equivalent of the      
energy stored in the carbon1 it follows 
from the doctrine of the ,conservation  
of ,energy1 that in order to separate   
the carbon from the oxygen again1 just  
the same amount of energy must be       
supplied as is evolved during the       
combustion of the carbon4 ,if a pound of
 carbon in burning to carbon dioxide    
gives out heat equivalent to eleven     
million foot-pounds of work1 we must    
apply the same amount of work to the    
carbon dioxide produced to separate it  
into its constituents4 ,neither a plant 
nor any living thing can create energy  
any more than it can create matter1 and 
just as the matter composing a living   
organism is assimilated from external   
sources1 so must we look to an external 
source for the energy which enables the 

plant to do this large amount of        
chemical work4  ,the separation of      
carbon from oxygen in the plant is      
effected by means of energy supplied by 
the sun4 ,the great white hot globe     
which is the centre of our system1 and  
round which this earth and the planets  
are moving1 is a reservoir from which   
there is constantly pouring forth into  
space a prodigious quantity of energy4  
,it must be remembered that the sun is  
more than a million times greater in    
bulk than our earth4 ,it has been       
calculated by ,sir ,william ,thomson    
that every square foot of the sun's     
surface is radiating energy equivalent  
to #gjjj horse-power in work4 ,on a     
clear summer day the earth receives from
 the sun in our latitude energy equal to
 about #adej horse-power per acre4 ,to  
keep up this supply by the combustion of
 coal1 we should have to burn for every 
square foot of the sun's surface between
 three and four pounds per second4 ,a   
small fraction of this solar energy     

reaches our earth in the form of radiant
 heat and light1 and it is the latter   
which enables the plant to perform the  
work of separating the carbon from the  
oxygen with which it is chemically      
combined4 ,it is1 in fact1 well known   
that the growth of plants--that is1 the 
assimilation of carbon and the          
liberation of oxygen--only takes place  
under the influence of light4 ,this     
function is performed by the leaves     
which contain the green colouring-matter
 known as chlorophyll1 the presence of  
which is essential to the course of the 
chemical changes4  ,if we now sum up the
 results to which we have been led1 it  
will be seen--  7#a7 ,that the chief    
source of the energy contained in coal  
is the carbon4  7#b7 ,that this carbon  
formed part of the plants which grew    
during the ,carboniferous period4  7#c7 
,that the carbon thus accumulated was   
supplied to the plants by the carbon    
dioxide existing in the atmosphere at   
that time4  7#d7 ,that the separation of

 the carbon from the oxygen was effected
 in the presence of chlorophyll1 by     
means of the solar energy transmitted to
 the earth during the ,carboniferous    
period4  ,we thus arrive at the         
interesting conclusion1 that the heat   
which we get from coal is sunlight in   
another form4 ,for every pound of coal  
that we now burn1 and for every unit of 
heat or work that we get from it1 an    
equivalent quantity of sunlight was     
converted into the latent energy of     
chemical separation during the time that
 the coal plant grew4 ,this energy has  
remained stored up in the earth ever    
since1 and reappears in the form of heat
 when we cause the coal to undergo      
combustion4 ,it is related that ,george 
,stephenson when asked what force drove 
his locomotive1 replied that it was     
bottled-up sunshine1 and we now see that
 he was much nearer the truth in making 
this answer than he could have been     
aware of at the time4  ,before passing  
on to the consideration of the different

 products which we get from coal1 it    
will be desirable to discuss a little   
more fully the nature of the change     
which occurs during the transformation  
of wood into coal4 ,pure woody fibre    
consists of a substance known to        
chemists as cellulose1 which contains   
fifty per cent4 of carbon1 the remainder
 of the compound being made up of       
hydrogen and oxygen4 ,it is thus obvious
 that during the fossilization of the   
wood some of the other constituents are 
lost1 and the percentage of carbon by   
this means raised4 ,we can trace this   
change from wood1 through peat1 lignite1
 and the different varieties of coal up 
to graphite1 which is nearly pure       
carbon4 ,it is in fact possible to      
construct a series showing the          
conversion of wood into coal1 this      
series comprising the varieties given in
 the table on p4 #bc1 as well as younger
 and older vegetable deposits4 ,the     
series will be--      ,i4 ,woody fibre  
7cellulose74    ,,ii4 ,peat from        

,dartmoor4   ,,iii4 ,lignite1 or brown  
coal1 an imperfectly carbonized         
vegetable        deposit of more recent 
geological age than true coal4    ,,iv4 
,average bituminous coal4     ,v4       
,cannel coal from ,wigan4    ,,vi4      
,anthracite from ,wales4   ,,vii4       
,graphite1 the oldest carbonaceous      
mineral4  ,the percentage of the chief  
elements in the members of this series  
is--           ,carbon4 ,hydrogen4      
,oxygen4      ,i4      #ej4j    #f4j    
#dd4j    ,,ii4      #ed4j    #e4b       
#bh4b   ,,iii4      #ff4c    #e4f       
#bb4h    ,,iv4      #gg4j    #e4j       
#aa4b     ,v4      #ha4b    #e4f        
#g4i    ,,vi4      #ij4a    #c4b        
#b4e   ,,vii4   #id-ii4e1 the remainder 
being ash4  ,in the above table the     
increase of carbon and the decrease of  
oxygen is well brought out2 the hydrogen
 also on the whole decreases1 although  
with some irregularity4 ,the exact      
course of the chemical change which     
occurs during the passage of wood into  

coal is at present involved in          
obscurity4 ,the oxygen may be eliminated
 in the form of water or of carbon      
dioxide or both2 some of the carbon is  
got rid of in the form of marsh gas1 a  
compound of carbon and hydrogen1 which  
forms the chief constituent of the      
dangerous fire-damp of coal mines4      
,marsh gas is an inflammable gas which  
becomes explosive when mixed with air   
and ignited2 it often escapes with great
 violence during the working of coal    
seams1 the jets blowing out from the    
coal or underclay with a rushing noise1 
indicative of the high pressure under   
which the hydrocarbon gas has           
accumulated4 ,these jets of escaping gas
 are known amongst miners as blowers4   
,if the air of a mine contains a        
sufficient quantity of the gas1 and a   
flame accidentally fires the mixture1   
there results one of those disastrous   
explosions with which the history of    
coal mining has unfortunately only made 
us too familiar4  ,from the account of  

coal which has thus far been rendered1  
it will be seen that as a source of     
mechanical power1 we are far from using 
it as economically as could be desired2 
and when we look at our open grates with
 clouds of unburnt carbon particles     
escaping up the chimney1 and so         
constructed that only a small fraction  
of the total heat warms our rooms1 it   
will be seen that the tale of waste is  
still more deplorable4 ,but we are at   
present rather concerned with what we   
actually do get from coal than with what
 we ought to get from it1 and here1 when
 we come to deal with the various       
material products1 we shall have a      
better account to present4  ,if instead 
of heating coal in contact with air and 
allowing it to burn1 we heat it in a    
closed vessel1 such as a retort1 it     
undergoes decomposition with the        
formation of various gaseous1 liquid1   
and solid products4 ,this process of    
heating an organic compound in a closed 
vessel without access of air and        

collecting the products1 is called      
destructive distillation4 ,the          
tobacco-pipe experiment of our boyhood  
is our first practical introduction to  
the destructive distillation of coal4   
,we put some powdered coal into the bowl
 of the pipe1 plaster up the opening    
with clay and then insert the bowl in a 
fire1 allowing the stem to project from 
between the bars of the grate4 ,in a few
 minutes a stream of gas issues from the
 orifice of the stem2 on applying a     
light it burns with a luminous flame1   
and we have made coal-gas on a small    
scale4  ,in the destructive distillation
 of organic substances1 such as wood or 
coal1 there are always produced four    
things--gas1 watery liquid1 and viscous 
products known as tar1 while a residue  
of coke or charcoal is left in the      
retort4 ,this is a very old observation1
 and was made so long ago that it       
becomes interesting as a point in the   
history of applied science to know who  
first submitted coal to destructive     

distillation4 ,according to ,dr4 ,gustav
 ,schultz1 we must credit a ,german with
 this observation1 which was made       
towards the end of the seventeenth      
century 7about #afhj7 by a chemist named
 ,johann ,joachim ,becher4 ,the         
experiment is described in such a quaint
 manner that the exact words of the     
author are worthy of being reproduced1  
and the passage is here given as        
translated by ,dr4 ,lunge in his work on
 ,coal ,tar and ,ammonia--  ,in ,holland
 they have peat1 and in ,england        
pit-coals2 neither of them is very good 
for burning1 be it in rooms or for      
smelting4 ,but ,i have found a way1 not 
merely to burn both kinds into good coal
 7coke7 which not any more smokes nor   
stinks1 but with their flame to smelt   
equally well as with wood1 so that a    
foot of such coal makes flames #aj feet 
long4 ,that ,i have demonstrated with   
pit-coal at the ,hague1 and here in     
,england at ,mr4 ,boyles'1 also at      
,windsor on the large scale4 ,in this   

connection it is also noteworthy that1  
equally as the ,swedes make their tar   
from firwood1 ,i have here in ,england  
made from pit-coal a sort of tar which  
is equal to the ,swedish in every way1  
and for some operations is even superior
 to it4 ,i have made proof of it on wood
 and on ropes1 and the proof has been   
found right1 so that even the king has  
seen a specimen of it1 which is a great 
thing in ,england1 and the coal from    
which the tar has been taken out is     
better for use than before4  ,this      
enterprising chemist1 moreover1 brought 
his results to a practical issue1 for he
 secured a patent1 in conjunction with  
,henry ,serle1 in #afha1 for a new way  
of making pitch and tarre out of        
pit-coale1 never before found out or    
used by any other4  ,no less interesting
 is the work of our own clergy during   
the last century1 when many eminent     
divines appear to have devoted their    
leisure to experimental science4 ,thus1 
about the year #afhh the ,rev4 ,john    

,clayton1 ,d4,d41 ,dean of ,kildare1    
went to examine a ditch two miles from  
,wigan in ,lancashire1 the water in     
which had been stated to burn like      
brandy when a flame was applied to it4  
,the ,dean ultimately traced the        
phenomenon to an escape of inflammable  
gas from an underlying coal seam1 and he
 followed up the matter experimentally  
by studying the destructive distillation
 of ,wigan coal in retorts4 ,the results
 were communicated to the ,hon4 ,robert 
,boyle1 but were not published till     
after the death of the latter1 and long 
after the death of the author4 ,the     
following account is taken from the     
abridged edition of the ,philosophical  
,transactions 7#agci73--  ,at first     
there came over only phlegm1 afterwards 
a black oil1 and then also a spirit     
arose1 which he could noways condense1  
but it forced the luting1 or broke the  
glasses4 ,once1 when it had forced the  
lute1 coming close to it to try to      
repair it1 he observed that the spirit  

which issued out caught fire at the     
flame of the candle1 and continued      
burning with violence as it issued out  
in a stream1 which he blew out and      
lighted again alternately for several   
times4 ,he then tried to save some of   
this spirit4 ,taking a turbinated       
receiver1 and putting a candle to the   
pipe of the receiver while the spirit   
rose1 he observed that it caught flame1 
and continued burning at the end of the 
pipe1 though you could not discern what 
fed the flame4 ,he then blew it out1 and
 lighted it again several times2 after  
which he fixed a bladder1 flatted and   
void of air1 to the pipe of the         
receiver4 ,the oil and phlegm descended 
into the receiver1 but the spirit1 still
 ascending1 blew up the bladder4 ,he    
then filled a good many bladders with   
it1 and might have filled an            
inconceivable number more2 for the      
spirit continued to rise for several    
hours1 and filled the bladders almost as
 fast as a man could have blown them    

with his mouth2 and yet the quantity of 
coals he distilled was inconsiderable4  
,he kept this spirit in the bladders a  
considerable time1 and endeavoured      
several ways to condense it1 but in     
vain4 ,and when he wished to amuse his  
friends1 he would take one of the       
bladders1 and pricking a hole with a    
pin1 and compressing gently the bladder 
near the flame of a candle till it once 
took fire1 it would then continue       
flaming till all the spirit was         
compressed out of the bladder4#a  ,the  
,rev4 ,stephen ,hales1 ,d4,d41 ,rector  
of ,farringdon1 ,hants1 was the author  
of a book entitled ,statical ,essays1   
containing ,vegetable ,staticks1 printed
 in #agbf-bg1 and of which the third    
edition bears the date #agch4 ,at p4    
#ahb of this work1 after a previous     
description of the destructive          
distillation of all kinds of substances 
in iron or other retorts1 he says--  ,by
 the same means also ,i found plenty of 
air gas might be obtained from minerals4

 ,half a cubick inch1 or #aeh grains of 
,newcastle coal1 yielded in distillation
 #ahj cubick inches of air gas1 which   
arose very fast from the coal1          
especially while the yellowish fumes    
ascended4  ,still later1 viz4 about     
#agfg1 we have the ,rev4 ,r4 ,watson1   
,d4,d41 ,regius ,professor of ,divinity 
in the ,university of ,cambridge1 and   
,bishop of ,llandaff1 interesting       
himself in chemistry4 ,he wrote a series
 of ,chemical ,essays1 one of which is  
entitled1 ,of ,pit ,coal1 and in this he
 describes the production from coal 7by 
destructive distillation7 of            
illuminating gas1 ammonia-water1 tar1   
and coke4 ,he further compares the      
relative quantities of the different    
products from various kinds of coal1 but
 he appears to have been chiefly        
interested in the tar1 and disregarded  
the gas and other products4 ,not the    
least interesting part of his book is   
the preface1 in which he apologizes for 
his pursuits in the following words--   

,divines1 ,i hope1 will forgive me if ,i
 have stolen a few hours1 not1 ,i trust1
 from the duties of my office1 but      
certainly from the studies of my        
profession1 and employed them in the    
cultivation of natural philosophy4 ,i   
could plead in my defence1 the example  
of some of the greatest characters that 
ever adorned either this ,university or 
the ,church of ,england4  ,this is      
quoted from the #eth edition1 dated     
#aghi1 the essay on coal being in the   
second of five volumes4 ,as the learned 
bishop published other works on         
chemistry1 we may suppose that the      
forgiveness which he asks from his      
brother divines was duly accorded4      
,none of these preliminary experiments1 
however1 led to any immediate practical 
result so far as concerns the use of    
coal-gas as an illuminating agent4      
,towards the end of the last century the
 lighting of individual establishments  
commenced1 and the way was thus prepared
 for the manufacture of the gas on a    

large scale4 ,one of the earliest       
pioneers was the ninth ,earl of         
,dundonald1 an inventive genius1 who in 
#aghb at ,culross ,abbey became one of  
the first practical tar distillers4 ,he 
secured letters patent in #agha for     
making tar1 pitch1 essential oils1      
volatile alkali1 mineral acids1 salts1  
and cinders from coal4 ,the gas was only
 a waste product1 and1 strange as it may
 appear1 the ,earl1 whose operations    
were financial failures1 did not realize
 the importance of the gas1 the tar and 
coke being considered the only products 
of value4 ,here is the account of the   
experiments by his son1 ,admiral        
,dundonald1 the ,sailor ,earl1 quoted   
from his ,autobiography of a ,seaman3-- 
,in prosecution of his coal-tar patent1 
my father went to reside at the family  
estate of ,culross ,abbey1 the better to
 superintend the works on his own       
collieries1 as well as others on the    
adjoining estates of ,valleyfield and   
,kincardine4 ,in addition to these      

works1 an experimental tar-kiln was     
erected near the ,abbey1 and here       
coal-gas became accidentally employed in
 illumination4 ,having noticed the      
inflammable nature of a vapour arising  
during the distillation of tar1 the     
,earl1 by way of experiment1 fitted a   
gun-barrel to the eduction pipe leading 
from the condenser4 ,on applying fire to
 the muzzle1 a vivid light blazed forth 
across the waters of the ,frith1        
becoming1 as was afterwards ascertained1
 distinctly visible on the opposite     
shore4  ,a few years later the          
foundation of the coal-gas manufacture  
was laid by ,william ,murdoch1 a        
,scotchman1 who must be credited with   
the practical introduction of this      
illuminating agent4 ,the idea had about 
the same time occurred to a ,frenchman1 
,lebon1 but in his hands the suggestion 
did not take a practical form4 ,murdoch 
was overseer of some mines in ,cornwall1
 and in #agib he first lighted his own  
house at ,redruth4 ,he then transferred 

his services to the great engineering   
firm of ,boulton and ,watt at ,soho1    
near ,birmingham1 where he erected      
apparatus in #agih1 and in the course of
 a few years the whole of this factory  
was permanently lighted by gas4 ,from   
this time the introduction of gas into  
other factories at ,manchester and      
,halifax was effected by ,murdoch and   
his pupil1 ,samuel ,clegg4 ,from single 
factories coal-gas at length came into  
use as a street illuminant1 although    
somewhat tardily4 ,experiments were made
 in ,london at the ,lyceum ,theatre in  
#ahjc1 in ,golden ,lane in #ahjg1 and in
 ,pall ,mall two years later4  ,it was  
fifteen years from the time of          
,murdoch's first installation at ,soho  
before the streets of ,london were      
lighted by gas on a commercial scale4   
,our grandfathers seem to have had a    
great dread of gas1 and public          
opposition no doubt had much to do with 
its exclusion from the metropolis4      
,there were even at that time eminent   

literary and scientific men who did not 
hesitate to cast ridicule upon the      
proposal1 and to declare the scheme to  
be only visionary4 ,but about #ahjf     
there came into this country an         
energetic ,german who passed by the name
 of ,winsor1 and who is described as an 
ignorant adventurer1 whose real name was
 ,winzler4 ,whatever his origin1 he     
certainly helped to rouse the public    
interest in gas lighting4 ,he took out a
 patent1 he gave public lectures1 and   
collected large sums of money for the   
establishment of gas companies4 ,most of
 the capital was1 however1 squandered in
 futile experiments1 but at length in   
#ahac1 ,westminster ,bridge1 and a year 
later ,st4 ,margaret's parish1 was      
successfully lighted4 ,from that period 
the use of gas extended1 but it was some
 time before the public fears were      
allayed1 for it is related that ,samuel 
,clegg1 who undertook the lighting of   
,london ,bridge1 had at first to light  
his own lamps1 as nobody could be found 

to undertake this perilous office4 ,even
 after gas had come into general use as 
a street illuminant1 it must have found 
its way but slowly into private houses4 
,in an old play-bill of the ,haymarket  
,theatre1 dated #ahdc--thirty years     
after the first introduction into the   
streets--it is announced--  ,among the  
most important ,improvements1 is the    
introduction 7for the first time7 of    
,gas as the ,medium of ,light6  ,the    
manufacture of coal-gas1 first rendered 
practicable by the energy and skill of  
the ,scotch engineer ,murdoch1 is now   
carried on all over the country on a    
colossal scale4 ,it is not the province 
of the present volume to deal with the  
details of manufacture1 but a short     
description of the process is necessary 
for the proper understanding of the     
subsequent portions of the subject 7see 
,fig4 #c74 ,the coal is heated in clay  
cylinders1 called retorts1 provided with
 upright exit pipes through which the   
volatile products escape1 and are       

conducted into water contained in a     
horizontal pipe termed the hydraulic    
main4 ,in the latter the gas is         
partially cooled1 and deposits most of  
the tar and watery liquor which distil  
over at the high temperature to which   
the retorts are heated4 ,the tar and    
watery liquor are allowed to flow from  
the hydraulic main into a pit called the
 tar well1 and the gas then passes      
through a series of curved pipes exposed
 to the air1 in which it is further     
cooled1 and deposits more of the tar4   
,from this atmospheric condenser the gas
 passes into a series of vessels filled 
with coke1 down which a fine spray of   
water is constantly being blown4 ,these 
vessels1 known as scrubbers1 serve to   
remove the last traces of tar1 and some 
of the volatile sulphur compounds which 
are formed from the small quantity of   
sulphur present in most coals4 ,the     
removal of sulphur compounds is a matter
 of importance1 because when gas is     
burnt these compounds give rise to acid 

vapours1 which are deleterious to health
 and destructive to property4           
,illustration3 ,,fig4 #c4--,sectional   
diagram of gas plant4 ,the retorts and  
furnace are on the right2 the gas rises 
through the upright pipe ,t into the    
hydraulic main ,b2 from there it passes 
into the atmospheric condensers ,d1 from
 the lower cistern of which the         
condensed tar flows into the tar-well1  
,h4 ,passing up through ,k1 the gas is  
conducted into the scrubber1 ,o1 and    
from there into the purifier1 ,m4 ,from 
there it emerges through ,k' into the   
purifier1 ,m1 and then into the         
gas-holder for distribution4 7,from     
,schultz's ,chemie des                  
,steinkohlentheers47   ,from the        
scrubbers the gas is sent through       
another series of vessels packed with   
trays of lime or oxide of iron1 in order
 to remove sulphuretted hydrogen and    
other sulphur compounds as completely as
 possible4 ,a small quantity of carbon  
dioxide is also removed by these        

purifiers1 as the presence of this gas  
impairs the illuminating power of       
coal-gas4 ,from the purifiers the gas   
passes into the gas-holders1 where it is
 stored for distribution4 ,it remains   
only to be stated that the distillation 
of coal is effected under a pressure    
somewhat less than that of the          
atmosphere1 the products of distillation
 being pumped out of the retorts by     
means of a kind of air-pump1 called an  
exhauster1 which is interpolated between
 the hydraulic main and the condenser1  
or at some other part of the purifying  
system4 ,the coke left in the retort is 
used as fuel for burning under the      
retorts or for other purposes4 ,the     
oxide of iron used in the purifiers can 
be used over and over again for a       
certain number of times by exposing it  
to the air1 and when it is finally      
exhausted1 the sulphur can be burnt out 
of it and used for making that most     
important of all chemical products1     
sulphuric acid4 ,thus the small quantity

 of sulphur present in the original coal
 7probably in the form of iron pyrites7 
is rendered available for the           
manufacture of a useful product4  ,the  
necessarily brief description of this   
important industry will suffice for the 
general reader4 ,those who desire       
further information on points of detail 
will refer to special works4 ,we are    
here rather concerned with the          
subsequent fate of the different        
products1 four of which have to be dealt
 with1 viz4 the gas1 watery liquor1 tar1
 and coke4 ,the first and last of these 
having already been accounted for--the  
one as an illuminating agent and the    
other as fuel--may now be dismissed4    
,no story of applied science is complete
 unless we can form some idea of the    
quantities of material used1 and the    
amount of the products obtained4 ,from  
one ton of ,newcastle coal we get about 
#aj1jjj cubic feet of gas1 #aaj to #abj 
lbs4 of tar1 #bj to #be gallons of      
watery liquor1 and about #aejj lbs4 of  

coke4 ,different coals of course give   
different quantities1 and the latter    
vary also according to the heat of      
distillation2 but the above estimate    
will furnish a good basis for forming   
our ideas with some approach to         
precision4 ,it has been estimated also  
that we are now distilling coal at the  
rate of about ten million tons per      
annum1 so that there is annually        
produced #ajj1jjj million cubic feet of 
gas1 and about #ejj1jjj tons of tar1    
besides proportionate quantities of the 
other products4 ,the great metropolitan 
companies alone are consuming nearly    
three million tons annually for the     
production of gas1 a consumption        
corresponding to about #fjjj cubic feet 
per head of the population4 ,this of    
course takes no account of the coal used
 for other manufactures or for domestic 
purposes1 but it is interesting to      
compare these estimates with the        
consumption of coal in ,london about a  
century ago1 before the introduction of 

gas1 when1 as ,bishop ,watson tells us  
in his work already referred to1 the    
annual consumption was #ibb1cid tons4   
,the enormous quantity of tar resulting 
from our gas manufacture furnishes the  
raw material for the production of a    
multitude of valuable                   
substances--colouring-matters1          
medicines1 perfumes1 flavouring-matters1
 burning and lubricating oils1 c4 ,out  
of this unsavoury waste material of the 
gas-works1 the researches of chemists   
have enabled a great industry to spring 
up which is of continually growing      
importance4 ,it will be the object of   
the remaining portion of the present    
volume to set forth the achievements of 
science in this branch of its           
application4 ,the foundation of the     
coal-tar industry was laid in this      
country--the country where coal was     
first distilled on a large scale for the
 production of gas1 and where the first 
of the coal-tar colouring-matters was   
sent forth into commerce4 ,we are at the

 present time the largest tar producers 
in ,europe2 it has been stated that we  
produce more than double the whole      
quantity of tar made in the gas-using   
countries of ,europe2 but in spite of   
this1 our manufacture of finished       
products is by no means in that         
flourishing condition which might be    
expected from our natural resources in  
the way of coal1 and the facilities     
which we possess for manufacturing the  
raw materials out of it4  ,but we must  
now take a glance at some of the other  
uses to which coal is put in order to   
realize more completely the truth of the
 statement made some pages back1 viz4   
that this mineral has been the chief    
source of our industrial prosperity4    
,great as is the consumption of coal by 
the gas manufacturer1 there is an equal 
or even a greater demand for the        
carbonaceous residue left when the coal 
has been decomposed by destructive      
distillation or by partial combustion4  
,this residue is coke--the substance    

left in the retorts after the gas       
manufacture4 ,there is a great demand   
for coke for many purposes2 it is used  
in most cases where a cheap smokeless   
fuel is required2 it is burnt in the    
furnaces of locomotives and other       
engines1 and is very largely consumed by
 the iron smelter in the blast furnace4 
,to meet these demands a large quantity 
of coal is converted into coke by being 
burnt in ovens with an insufficient     
supply of air for complete combustion1  
or in suitably constructed close        
furnaces4 ,the tar and other products   
have in this country until recently been
 allowed to escape as waste1 but the    
time is approaching when these must be  
utilized4 ,it will give an idea of the  
industrial importance of coke when it is
 stated1 that about twelve million tons 
of our coal annually undergo conversion 
into this form of fuel4 ,chemically     
considered1 coke consists of carbon     
together with all the mineral           
constituents of the coal1 and small     

quantities of hydrogen1 oxygen1 and     
nitrogen4 ,the amount of carbon varies  
from #he to #ig1 and the ash from #c to 
#ad per cent4  ,the conversion of coal  
into coke is a very venerable branch of 
manufacture1 which was first carried out
 on a large scale in this country about 
the middle of the seventeenth century4  
,as an operation it may appear utterly  
devoid of romance1 but as ,goethe has   
described his visit to the earliest of  
coke-burners1 this fragment of history  
is worth narrating4 ,when the great     
,german philosophical poet was a student
 at ,strassburg 7#agga71 he rode over   
with some friends to visit the          
neighbourhood of ,saarbruecken where he 
met an old coal philosopher named       
,stauf1 who was there carrying on the   
industry4 ,this philosophus per ignem   
was manager of some alum works1 and the 
ruling spirit of the burning hill of    
,duttweiler4 ,the hill no doubt owed its
 designation to the coke ovens at work  
upon it1 and which had been in operation

 there for some six or seven years      
before ,goethe's visit1 i4e4 since      
#agfd4 ,the coke was wanted for iron    
smelting1 and even at that early period 
,stauf had the wisdom to condense his   
volatile products1 for we are told that 
he showed his visitors bitumen1         
burning-oil1 lampblack1 and even a cake 
of sal ammoniac resulting from his      
operations4 ,goethe has put upon record 
his visit to the little haggard old     
coke-burner1 living in his lonely       
cottage in the forest 7,aus meinem      
,leben3 ,wahrheit und ,dichtung1 ,book  
,x74 ,it is probably ,stauf's ovens     
which are described by the ,french      
metallurgist1 ,de ,gensanne1 in his     
,traite de la fonte des ,mines par le   
feu du ,charbon de ,terre1 published in 
,paris in #aggj4 ,after long years of   
coke-making1 without any regard to the  
value of the volatile products1 we are  
now beginning to consider the           
advisability of doing that which has    
long been done on the ,continent4  ,it  

is not unlikely that ,bishop ,watson in 
the last century had heard of the       
attempt to recover the products from    
coke ovens1 for he gives the following  
very sound advice in his ,chemical      
,essays3--  ,those who are interested in
 the preparation of coak would do well  
to remember that every #if ounces of    
coal would furnish four ounces at the   
least of oil1 probably six ounces might 
be obtained2 but if we put the product  
so low as five ounces from #ajj1 and    
suppose a coak oven to work off only    
#ajj tons of coal in a year1 there would
 be a saving of five tons of oil1 which 
would yield above four tons of tar2 the 
requisite alteration in the structure of
 the coak ovens1 so as to make them a   
kind of distilling vessels1 might be    
made at a very trifling expense4--#eth  
ed41 #aghi1 vol4 ii4 p4 #cea4  ,we have 
yet to chronicle another chapter in the 
history of coal philosophy before       
finishing with this part of the subject4
 ,there is a branch of manufacture      

carried on1 especially in ,scotland1    
which results in the production of      
burning and lubricating oils1 and solid 
paraffin1 a wax-like substance which is 
used for candle-making4 ,the manufacture
 of candles out of coal will perhaps be 
a new revelation to many readers of this
 book4 ,it must be admitted1 however1   
that the term coal is here being        
extended to only partially fossilized   
vegetation of younger geological age    
than true coal1 and to bituminous shales
 of various ages4 ,shale1 geologically  
considered1 is hardened mud2 it may be  
looked upon as clay altered by time and 
pressure4 ,now if the mud1 at the period
 of its deposition1 was much mixed up   
with vegetable matter1 we should have in
 course of time a mixture of more or    
less carbonized woody fibre with mineral
 matter1 and this would be called a     
carbonaceous or bituminous shale4       
,shales of this kind often contain as   
much as #hj to #ij per cent4 of mineral 
matter1 and seldom more than #bj per    

cent4 of volatile matter1 i4e4 the      
portion lost on ignition1 and consisting
 chiefly of the carbonaceous            
constituents4  ,the story of the        
shale-oil industry is soon told4 ,about 
the year #ahdg oil was struck in a coal 
mine at ,alfreton in ,derbyshire1 and in
 the hands of ,mr4 ,james ,young this   
supply furnished the market with        
burning-oil for nearly three years4     
,then the spring became exhausted1 and  
,mr4 ,young and his associates had to   
look out for another source of oil4 ,be 
it remembered that this happened some   
nine years before the utilization of the
 great ,american petroleum deposits4    
,many kinds of vegetable matter were    
submitted to destructive distillation   
before a substance was found which could
 be profitably worked1 but at length    
,mr4 ,young tried a kind of cannel coal 
which had about that time been          
introduced for gas making4 ,this        
substance was called ,boghead gas coal  
or ,torbane ,hill mineral1 from the     

place where it occurred1 which is at    
,bathgate in ,linlithgow4 ,this mineral 
was found to yield a large amount of    
paraffin oil and solid paraffin on      
destructive distillation1 and from that 
time 7#ahej7 to this1 the industry has  
been carried on at ,bathgate and other  
parts of ,scotland1 where similar       
carbonaceous deposits occur4  ,it may   
seem a matter of unimportance at the    
present time whether this ,torbane ,hill
 mineral is a true coal or not4 ,about  
forty years ago1 however1 the decision  
of this question involved a costly      
law-suit in ,edinburgh4 ,the proprietor 
of the estate had granted a lease to a  
firm1 conveying to the latter the right 
to work coal1 limestone1 ironstone1 and 
certain other minerals found thereon1   
but excluding copper and all other      
minerals not mentioned in the contract4 
,the lessees then found that this       
particular carbonaceous mineral was of  
very great value1 both on account of the
 high quality of the gas1 and afterwards

 on account of the paraffin which it    
furnished by ,young's process of        
distillation4 ,thereupon the lessor     
brought an action against the lessees1  
claiming ,l#aj1jjj damages1 on the      
ground that the latter had broken the   
contract by removing a mineral which was
 not coal4 ,experts gave evidence on    
both sides2 some declared in favour of  
the substance being coal1 others said it
 was a bituminous shale1 while others   
called it bituminated clay1 or refused  
to give it a name at all4 ,judgment was 
finally given for the defendants1 so    
that in the eye of the law the mineral  
was considered a true coal4 ,as a matter
 of fact1 it is impossible to draw a    
hard and fast line between coal and     
bituminous shale1 as the one is         
connected with the other by a series of 
intermediate minerals1 and the ,torbane 
,hill mineral happens to form one of the
 links4 ,it contains about #fi per cent4
 of volatile matter1 and leaves #ca per 
cent4 of residue1 consisting of #ab     

parts of carbon and #ai of ash4  ,the   
manufacture started by ,young has       
developed into an important industry1 in
 spite of the fact that the original    
,torbane ,hill coal has become          
exhausted1 and that enormous natural    
deposits of petroleum are worked in     
,america1 ,russia1 and elsewhere4 ,there
 are now some fifteen companies at work 
in ,scotland1 representing an aggregate 
capital of about two and a half million 
pounds sterling4 ,bituminous shales of  
different kinds are distilled at a low  
red heat in iron retorts1 and from the  
volatile portions there are separated   
those valuable products which have      
already been alluded to1 viz4 burning   
and lubricating oils1 solvent mineral   
oil1 paraffin wax for candles1 and      
ammonia4 ,we may fairly claim these as  
coal products1 although the shales used 
contain much mineral matter1 the carbon 
averaging about #bj per cent41 the      
hydrogen three per cent41 the nitrogen  
#j4g1 and the ash about #fg per cent4   

,the shales worked are approximately of 
the same age as true coal1 i4e4         
,carboniferous4 ,the ,scotch companies  
are distilling about two million tons of
 shale per annum1 this quantity         
producing about sixty million gallons of
 crude oil1 and giving employment to    
over #aj1jjj hands4  ,it is not the     
province of the present work to enter   
into the chemical nature of the products
 of destructive distillation in any     
greater detail than is necessary to     
enable the general reader to know       
something of the recent discoveries in  
the utilization of these products4 ,we  
shall1 however1 have occasion later on  
to make ourselves acquainted with the   
names of some of the more important raw 
materials which are derived from this   
source1 and certain preliminary         
explanations are indispensable4 ,in the 
first place then1 let us start from the 
fact that coal--including carbonaceous  
shale and lignite--when heated in a     
closed vessel gives gas1 tar1 coke1 and 

a watery liquor4 ,a clear understanding 
must be arrived at concerning the manner
 in which these products arise4  ,there 
is a widely-spread notion that the      
substances derived from coal and        
utilized for industrial purposes are    
present in the mineral itself1 and that 
the art of the chemist has been         
exercised in separating the said        
substances by various processes4 ,this  
idea must be at once dispelled4 ,it is  
true that there is a small quantity of  
water and a certain amount of gas       
already present in most coals1 but these
 are quite insignificant as compared    
with the total yield of gas and watery  
liquor4 ,so also with respect to the    
tar2 it is possible that in some highly 
bituminous minerals we might dissolve   
out a small quantity of tarry matter by 
the use of appropriate solvents1 but in 
the coals mostly used for gas-making not
 a trace of tar exists ready formed1 and
 still less can it be said that the coal
 contains coke4 ,all these products are 

formed by the chemical decomposition of 
the coal under the influence of heat1   
and their nature and quantity can be    
made to vary within certain limits by   
modifying the temperature of            
distillation4  ,having once realized    
this principle with respect to coal     
itself1 it is easy to extend it to the  
products of its destructive             
distillation4 ,the tar1 for instance1 is
 a complicated mixture of various       
substances1 among which                 
hydrocarbons--i4e4 compounds of carbon  
with hydrogen--largely predominate4 ,the
 different components of coal-tar can be
 separated by processes which we shall  
have to consider subsequently4 ,of the  
compounds thus isolated some few are    
immediately applicable for industrial   
purposes1 but the majority only form the
 raw materials for the manufacture of   
other products1 such as                 
colouring-matters and medicines4 ,now   
these colouring-matters and other       
finished products no more exist in the  

tar than the latter exists in the coal4 
,they are produced from the             
hydrocarbons1 c41 present in the tar by 
chemical processes1 and bear much about 
the same relationship to their parent   
substances that a steam-engine bears to 
the iron ore out of which its metallic  
parts are primarily constructed4 ,just  
as the mechanical skill of the engineer 
enables him to construct an engine out  
of the raw material iron1 which is      
extracted from its ore1 and converted   
into steel by chemical processes1 so the
 skill of the chemist enables him to    
build up complex colouring-matters1 c41 
out of the raw materials furnished by   
tar1 which is obtained from coal by     
chemical decomposition4  ,the           
illuminating gas which is obtained from 
coal by destructive distillation        
consists chiefly of hydrogen and gaseous
 hydrocarbons1 the most abundant of the 
latter being marsh gas4 ,there are also 
present in smaller quantities the two   
oxides of carbon1 the monoxide and the  

dioxide1 which are gaseous at ordinary  
temperatures1 together with other       
impurities4 ,coal-gas is burnt just as  
it is delivered from the mains--it is   
not at present utilized as a source of  
raw material in the sense that the tar  
is thus made use of4 ,in some cases gas 
is used as fuel1 as in gas-stoves and   
gas-engines1 and in the so-called       
gas-producers1 in which the coal1       
instead of being used as a direct source
 of heat1 is partially burnt in suitable
 furnaces1 and the combustible gas thus 
arising1 consisting chiefly of carbon   
monoxide1 is conveyed to the place where
 it undergoes complete combustion1 and  
is thus utilized as a source of heat4   
,summing up the uses of coal thus far   
considered1 we see that this mineral is 
being consumed as fuel1 for the         
production of coke1 for the manufacture 
of gas1 and in many other ways4         
,lavishly as ,nature has provided us    
with this source of power and wealth1   
the idea naturally suggests itself      

whether we are not drawing too liberally
 upon our capital4 ,the question of coal
 supply crops up from time to time1 and 
the public mind is periodically agitated
 about the prospects of its continuance4
 ,how long we have been draining our    
coal resources it is difficult to       
ascertain4 ,there is some evidence that 
coal-mining was carried on during the   
,roman occupation4 ,in the reign of     
,richard ,i4 there is distinct evidence 
of coal having been dug in the diocese  
of ,durham4 ,the oldest charters take us
 back to the early part of the          
thirteenth century for ,scotland1 and to
 the year #abci for ,england1 when ,king
 ,henry ,,iii4 granted a right of sale  
to the townsmen of ,newcastle4 ,with    
respect to the metropolis1 ,bishop      
,watson1 on the authority of ,anderson's
 ,history of ,commerce1 states that coal
 was introduced as fuel at the beginning
 of the fourteenth century4 ,in these   
early days1 when it was brought from the
 north by ships1 it was known as        

sea-coal3--       ,go2 and we'll have a 
posset for 't soon at night1 in faith1  
at the      latter end of a sea-coal    
fire4--,merry ,wives of ,windsor1 ,act  
,i41      ,sc4 iv4  ,that the fuel was  
received at first with disfavour appears
 from the fact that in the reign of     
,edward ,i4 the nobility and gentry made
 a complaint to the king objecting to   
its use1 on the ground of its being a   
public nuisance4 ,by the middle of the  
seventeenth century the use of coal was 
becoming more general in ,london1       
chiefly owing to the scarcity of wood2  
and its effects upon the atmosphere of  
the town will be inferred from a        
proclamation issued in the reign of     
,elizabeth1 prohibiting its use during  
the sitting of ,parliament1 for fear of 
injuring the health of the knights of   
the shire4 ,about #afdi the citizens    
again petitioned ,parliament against the
 use of this fuel on account of the     
stench2 and about the beginning of that 
century the nice dames of ,london would 

not come into any house or roome when   
sea-coales were burned1 nor willingly   
eat of meat that was either sod or      
roasted with sea-coale fire 7,stow's    
,annals74  ,for many centuries therefore
 we have been drawing upon our coal     
supplies1 and using up the mineral at an
 increasing rate4 ,according to a recent
 estimate by ,professor ,hull1 from the 
beginning of the present century to     
#ahge the output has been more than     
doubled for each successive quarter     
century4 ,the actual amount of coal     
raised in the ,united ,kingdom between  
#ahhb and the present time averages     
annually about #agj million tons1       
corresponding in money value to about   
,l#de1jjj1jjj per annum4 ,in #ahfj the  
amount of coal raised in ,great ,britain
 was a little more than #hj million     
tons1 and ,professor ,hull estimated    
that at that rate of consumption our    
supplies of workable coal would hold out
 for a thousand years4 ,since then the  
available stock has been diminished by  

some #c1fej million tons1 and even this 
deduction1 we are told on the same      
authority1 has not materially affected  
our total supply4 ,the possibility of a 
coal famine need1 therefore1 cause no   
immediate anxiety2 but we cannot eat our
 loaf and have it too1 and sooner or    
later the continuous drain upon our coal
 resources must make itself felt4 ,the  
first effect will probably be an        
increase in price owing to the greater  
depth at which the coal will have to be 
worked4 ,the whole question of our coal 
supply has1 however1 recently assumed a 
new aspect by the discovery 7,february  
#ahij7 of coal at a depth of #a1afj feet
 at ,dover4 ,to quote the words of ,mr4 
,w4 ,whitaker--,it may be indeed that   
the coal supply of the future will be   
largely derived from the ,south-,east of
 ,england1 and some day it may happen1  
from the exhaustion of our northern     
coal-fields1 that we in the south may be
 able successfully to perform a task now
 proverbially unprofitable--we may carry

 coal to ,newcastle4  ,the coal-fields  
of ,great ,britain and ,ireland occupy1 
in round numbers1 an area of #aa1hfj    
square miles1 or about one-tenth of the 
whole area of the land surface of the   
country4 ,within this area1 and down to 
a depth of #d1jjj feet1 lie the main    
deposits of our available wealth4 ,some 
idea of the amount of coal underlying   
this area will be gathered from the     
table#b on the next page4  ,this supply1
 amounting to over #ij1jjj million tons1
 refers to the exposed coal-fields and  
to workable seams1 i4e4 those above one 
foot in thickness4 ,but in addition to  
this1 we have a large amount of coal at 
workable depths under formations of     
later geological age than the           
,carboniferous1 such as the ,permian    
formation of northern and central       
,england4 ,adding the estimated quantity
 of coal from this source to that       
contained in the exposed coal-fields as 
given above1 we arrive at the total     
available supply4 ,this is estimated to 

be about #adf1ded million tons4 ,to this
 we may one day have to add the coal    
under the south-eastern part of         
,england4                               
,amount of coal in millions of          
tons to depths not exceeding   ,coal    
,fields of--                            
#d1jjj feet4    ,south ,wales           
#cb1def   ,forest of ,dean              
#bfe   ,bristol                         
#d1bai   ,warwickshire                  
#dei   ,s4 ,staffordshire1 ,shropshire1 
,forest of ,wyre and ,clee ,hills       
#a1ijf   ,leicestershire                
#hcg   ,north ,wales                    
#b1jje   ,anglesey                      
#e   ,n4 ,staffordshire                 
#c1hbe   ,lancashire and ,cheshire      
#e1edf   ,yorkshire1 ,derbyshire1 and   
,northumberland                         
#ah1agb   ,black ,burton                
#ga   ,northumberland and ,durham       
#aj1jcg   ,cumberland                   
#dje   ,scotland                        
#i1hdd   ,ireland                       

#aef  ,it is important to bear in mind1 
that out of the #agj million tons of    
coal now being raised annually we only  
use a small proportion1 viz4 from #e to 
#f per cent4 for gas-making4 ,the       
largest amount 7#cc per cent47 is used  
for iron-smelting1#c and about #ae per  
cent4 is exported2 the remainder is     
consumed in factories1 dwelling-houses1 
for locomotion1 and in the smaller      
industries4  ,the enormous advancement  
which has taken place of late years in  
the industrial applications of          
electricity has given rise to the belief
 that coal-gas will in time become      
superseded as an illuminating agent1 and
 that the supply of tar may in          
consequence fall off4 ,so far1 however1 
the introduction of electric-lighting   
has had no appreciable effect upon the  
consumption of gas1 and even when the   
time of general electric-lighting       
arrives there will arise as a           
consequence an increased demand for gas 
as a fuel in gas engines4 ,moreover1 the

 use of gas for heating and cooking     
purposes is likely to go on increasing4 
,nor must it be forgotten that the      
quantity of tar produced in gas-works is
 now greater than is actually required  
by the colour-manufacturer1 and much of 
this by-product is burnt as fuel1 so    
that if the manufacture of gas were to  
suffer to any considerable extent there 
would still be tar enough to meet our   
requirements at the present rate of     
consumption of the tar-products4 ,then  
again1 the value of the tar1 coke1 and  
ammoniacal liquor is of such a          
proportion as compared with the cost of 
the raw material1 coal1 that there is a 
good margin for lowering the price of   
gas when the competition between the    
latter and electricity actually comes   
about4 ,it will not then be only a      
struggle between the two illuminants1   
but it will be a question of electricity
 versus gas1 plus tar and ammonia4      
,while the electrician is pushing       
forward with rapid strides1 the chemist 

is also moving onwards1 and every year  
witnesses the discovery of new tar      
products1 or the utilization of         
constituents which were formerly of     
little or no value4 ,thus if the cost of
 generating and distributing electricity
 is being lowered1 on the other hand the
 value of coal tar is likely to go on   
advancing1 and it would be rash to      
predict which will come out triumphant  
in the end4 ,but even if electricity    
were to gain the day it would be worth  
while to distil coal at the pit's mouth 
for the sake of the by-products1 and    
there is1 moreover1 the tar from the    
coke ovens to fall back upon--a source  
which even before the use of coal-gas   
the wise ,bishop of ,llandaff advised us
 not to neglect4     ,,chapter ,,ii4    
,the nature of the products obtained by 
the destructive distillation of coal    
varies according to the temperature of  
distillation1 and the age or degree of  
carbonization of the coal4 ,the watery  
liquor obtained by the dry distillation 

of wood is acid1 and contains among     
other things acetic acid1 which is      
sometimes prepared in this way1 and from
 its origin is occasionally spoken of as
 wood vinegar4 ,the older the wood1 the 
more complete its degree of conversion  
into coal1 and the smaller the quantity 
of oxygen it contains1 the more alkaline
 does the watery liquid become4 ,thus   
the gas-liquor is distinctly alkaline1  
and contains a considerable quantity of 
ammonia1 besides other volatile bases4  
,the uses of ammonia are manifold1 and  
nearly our whole supply of this valuable
 substance is now derived from          
gas-liquor4 ,the presence of ammonia in 
this liquor is accounted for when it is 
known that this compound is a gas       
composed of nitrogen and hydrogen4 ,it  
has already been explained that coal    
contains from one to two per cent4 of   
nitrogen1 and during the process of     
distillation about one-fifth of this    
nitrogen is converted into ammonia1 the 
remainder being converted partly into   

other bases1 while a small quantity     
remains in the coke4  ,ammonia1 the     
volatile alkali of the old chemists1 and
 its salts are of importance in         
pharmacy1 but the chief use of this     
compound is to supply nitrogen for the  
growth of plants4 ,plants must have     
nitrogen in some form or another1 and as
 they cannot assimilate it directly from
 the atmosphere where it exists in the  
free state1 some suitable nitrogen      
compound must be supplied to the soil4  
,it is possible that certain leguminous 
plants may derive their nitrogen from   
the atmosphere through the intervention 
of micro-organisms1 which appear capable
 of fixing free nitrogen and of         
supplying it to the plant upon whose    
roots they flourish4 ,but this is       
second-hand nitrogen so far as concerns 
the plant4 ,it is true also that the    
atmosphere contains small traces of     
ammonia and acid oxides of nitrogen1    
which are dissolved by rain and snow1   
and thus get washed down into the soil4 

,these are the natural sources of plant 
nitrogen4 ,but in agricultural          
operations1 where large crops have to be
 raised as rapidly as possible1 some    
additional source of nitrogen must be   
supplied1 and this is the object of     
manuring the soil4  ,a manure1          
chemically considered1 is a mixture of  
substances capable of supplying the     
necessary nitrogenous and mineral food  
for the nourishment of the growing      
plant4 ,the ordinary farm or stable     
manure contains decomposing nitrogenous 
organic matter1 in which the nitrogen is
 given off as ammonia1 and thus         
furnishes the soil with which it is     
mixed with the necessary fertilizer4    
,but the supply of this manure is       
limited1 and we have to fall back upon  
gas-liquor and native nitrates to meet  
the existing wants of the agriculturist4
 ,important as is ammonia for the growth
 of vegetation1 it is not in this form  
that the majority of plants take up     
their nitrogen4 ,soluble nitrates are1  

in most cases1 more efficient           
fertilizers than the salts of ammonia1  
and the ammonia which is supplied to the
 soil is converted into nitrates therein
 before the plant can assimilate the    
nitrogen4 ,the oxidation of ammonia into
 nitric acid takes place by virtue of a 
process called nitrification1 and there 
is very good reason for believing that  
this transformation is the work of a    
micro-organism present in the soil4 ,the
 gas liquor thus supplies food to a     
minute organism which converts the      
ammonia into a form available for the   
higher plants4 ,some branches of        
agriculture--such as the cultivation of 
the beet for sugar manufacture--are so  
largely dependent upon an artificial    
source of nitrogen1 that their very     
existence is bound up with the supply of
 ammonia salts or other nitrogenous     
manures4 ,the relationship between the  
manufacture of beet-sugar and the       
distillation of coal for the production 
of gas is thus closer than many readers 

will have imagined2 for while the supply
 of native guano or nitrate is          
uncertain1 and its freight costly on    
account of the distance from which it   
has to be shipped1 the sulphate of      
ammonia from gas-liquor is always at    
hand1 and available for the purposes of 
fertilization4  ,then again1 there are  
other products of industrial value which
 are associated with ammonia1 such1 for 
example1 as ammonia-alum and caustic    
soda4 ,this last is one of the most     
important chemical compounds            
manufactured on a large scale1 and is   
consumed in enormous quantities for the 
manufacture of paper and soap1 and other
 purposes4 ,salts of this alkali are    
also essential for glass making4 ,of    
late years a method for the production  
of caustic soda has been introduced     
which depends upon the use of ammonia1  
and as this process is proving a        
formidable rival to the older method of 
alkali manufacture1 it may be said that 
such indispensable articles as paper1   

soap1 and glass are now to some extent  
dependent upon gas-liquor1 and may in   
course of time become still more        
intimately connected with the           
manufacture of coal-gas4  ,but          
quantitative statements must be given in
 order to bring home to general readers 
the actual value of the small percentage
 of nitrogen present in coal4 ,thus it  
has been estimated1 that one ton of coal
 gives enough ammonia to furnish about  
#cj lbs4 of the crude sulphate4 ,the    
present value of this salt is roughly   
about ,l#ab per ton4 ,the ten million   
tons of coal distilled annually for gas 
making would thus give #acc1ibi tons of 
sulphate1 equal in money value to       
,l#a1fjg1adh1 supposing the whole of the
 ammonia to be sold in this form4 ,to   
this may be added the ammonia obtained  
during the distillation of shale and the
 carbonization of coal for coke1 the    
former source furnishing about #bb1jjj  
tons1 and the latter about #bejj tons   
annually4 ,small as is the legacy of    

nitrogen bequeathed to us from the      
,carboniferous period1 we see that it   
sums up to a considerable annual        
addition to our industrial resources4   
,the three products resulting from the  
distillation of coal--viz4 the gas1     
ammoniacal-liquor1 and coke--having now 
been made to furnish their tale1 we have
 next to deal with the tar4 ,in the     
early days of gas manufacture this      
black1 viscid1 unsavoury substance was  
in every sense a waste product4 ,no use 
had been found for it1 and it was burnt1
 or otherwise disposed of4 ,no demand   
for the tar existed which could enable  
the gas manufacturers to get rid of     
their ever-increasing accumulation4     
,wood-tar had previously been used as a 
cheap paint for wood and metal-work1 and
 it was but a natural suggestion that   
coal-tar should be applied to the same  
purposes4 ,it was found that the quality
 of the tar was improved by getting rid 
of the more volatile portions by boiling
 it in open pans2 but this waste--to say

 nothing of the danger of fire--was     
checked by a suggestion made by ,accum  
in #ahae1 who showed that by boiling    
down the tar in a still instead of in   
open pans the volatile portions could be
 condensed and collected1 thus          
furnishing an oil which could be used by
 the varnish maker as a substitute for  
turpentine4 ,a few years later1 in      
#ahbb1 the distillation of tar was      
carried on at ,leith by ,drs4 ,longstaff
 and ,dalston1 the spirit being used by 
,mackintosh of ,glasgow for dissolving  
india-rubber for the preparation of that
 waterproof fabric which to this day    
bears the name of the original          
manufacturer4 ,the residue in the still 
was burnt for lamp-black4 ,of such      
little value was the tar at this time   
that ,dr4 ,longstaff tells us that the  
gas company gave them the tar on        
condition that they removed it at their 
own expense4 ,it appears also that tar  
was distilled on a large scale near     
,manchester in #ahcd1 the spirit being  

used for dissolving the residual pitch  
so as to make a black varnish4  ,but the
 production of gas went on increasing at
 a greater rate than the demand for tar 
for the above-mentioned purposes1 and it
 was not till #ahch that a new branch of
 industry was inaugurated1 which        
converted the distillation of this      
material from an insignificant into an  
important manufacture4 ,in that year a  
patent was taken out by ,bethell for    
preserving timber by impregnating it    
with the heavy oil from coal-tar4 ,the  
use of tar for this purpose had been    
suggested by ,lebon towards the end of  
the last century1 and a patent had been 
granted in this country in #ahcf to     
,franz ,moll for this use of            
tar-products4 ,but ,bethell's process   
was put into a working form by the great
 improvements in the apparatus          
introduced by ,breant and ,burt1 and to 
the latter is due the credit of having  
founded an industry which is still      
carried on by ,messrs4 ,burt1 ,bolton   

and ,haywood on a colossal scale4 ,the  
pickling or creosoting of timber is     
effected in an iron cylindrical boiler1 
into which the timber is run2 the       
cylinder being then closed the air is   
pumped out1 and the air contained in the
 pores of the wood thus escapes4 ,the   
creosoting oil1 slightly warmed1 is then
 allowed to flow into the boiler1 and   
thus penetrates into the pores of the   
wood1 the complete saturation of which  
is insured by afterwards pumping air    
into the cylinder and leaving the timber
 in the oil for some hours under a      
pressure of #h to #aj atmospheres4  ,all
 timber which is buried underground1 or 
submerged in water1 is impregnated with 
this antiseptic creosote in order to    
prevent decay4 ,it will be evident that 
this application of tar-products must   
from the very commencement have had an  
enormous influence upon the distillation
 of tar as a branch of industry4        
,consider the miles of wooden sleepers  
over which our railways are laid1 and   

the network of telegraph wires carried  
all over the country by wooden poles1 of
 which the ends are buried in the earth4
 ,consider also the many subaqueous     
works which necessitate the use of      
timber1 and we shall gain an idea of the
 demand for heavy coal-tar oil created  
by the introduction of ,breant's        
process4 ,under the treatment described 
a cubic foot of wood absorbs about a    
gallon of oil1 and by far the largest   
quantity of the tar oils is consumed in 
this way at the present time4 ,now in   
the early days of timber-pickling the   
lighter oils of the tar1 which first    
come over on distillation1 and which are
 too volatile for the purpose of        
creosoting1 were in much about the same 
industrial position as the tar itself   
before its application as a timber      
preservative4 ,the light oil had a      
limited use as a solvent for            
waterproofing and varnish making1 and a 
certain quantity was burnt as coal-tar  
naphtha in specially constructed lamps1 

the invention of the late ,read         
,holliday of ,huddersfield1 whose first 
patent was taken out in #ahdh 7see ,fig4
 #d74 ,up to this time1 be it           
remembered1 that chemists had not found 
out what this naphtha contained4 ,but   
science soon laid hands on the materials
 furnished by the tar-distiller1 and the
 naphtha was one of the first products  
which was made to reveal the secret of  
its hidden treasures to the scientific  
investigator4 ,from this period science 
and industry became indissolubly united1
 and the researches of chemists were    
carried on hand-in-hand with the        
technical developments of coal-tar      
products4   ,illustration3 ,,fig4       
#d4--,read ,holliday's lamp for burning 
light coal-tar oils4 ,the oil is        
contained in the cistern c1 from whence 
it flows down the pipe1 when the        
stopcock is opened1 into the burner a4  
,below the burner is a little cup1 in   
which some of the oil is kept burning1  
and the heat from this flame volatilizes

 the oil as it flows down the pipe1 the 
vapour thus generated issuing from the  
jets in the burner and there undergoing 
ignition4 ,the burner and cup are shown 
on an enlarged scale at a in the lower  
figure4   ,in #ahbe ,michael ,faraday   
discovered a hydrocarbon in the oil     
produced by the condensation of oil     
gas--an illuminating gas obtained by the
 destructive distillation of oleaginous 
materials4 ,this hydrocarbon was        
analysed by its illustrious discoverer1 
and named in accordance with his results
 bicarburet of hydrogen4 ,in #ahcd the  
same hydrocarbon was obtained by        
,mitscherlich by heating benzoic acid   
with lime1 and by ,peligot by the dry   
distillation of calcium benzoate4 ,for  
this reason the compound was named      
benzin by ,mitscherlich1 which name was 
changed into benzol by ,liebig4 ,in this
 country the hydrocarbon is known at the
 present time as benzene4 ,twenty years 
after ,faraday's discovery1 viz4 in     
#ahde1 ,hofmann proved the existence of 

benzene in the light oils from coal-tar1
 and in #ahdh ,hofmann's pupil1         
,mansfield1 isolated considerable       
quantities of this hydrocarbon from the 
said light oils by fractional           
distillation4 ,at the time of these     
investigations no great demand for      
benzene existed1 but the work of        
,hofmann and ,mansfield prepared the way
 for its manufacture on a large scale1  
when1 a few years later1 the first      
coal-tar colouring-matter was discovered
 by our countryman1 ,w4 ,h4 ,perkin4    
,it is always of interest to trace the  
influence of scientific discovery upon  
different branches of industry4 ,as soon
 as it had been shown that benzene could
 be obtained from coal-tar1 the         
nitro-derivative of this                
hydrocarbon--i4e4 the oily compound     
produced by the action of nitric acid   
upon benzene--was introduced as a       
substitute for bitter almond oil under  
the name of essence of mirbane4         
,nitrobenzene has an odour resembling   

that of bitter almond oil1 and it is    
still used for certain purposes where   
the latter can be replaced by its       
cheaper substitute1 such as for the     
scenting of soap4 ,although the         
isolation of benzene from coal-tar gave 
an impetus to the manufacture of        
nitrobenzene1 no use existed for the    
latter beyond its very limited          
application as essence of mirbane1 and  
the production of this compound was at  
that time too insignificant to take rank
 as an important branch of chemical     
industry4  ,the year #ahef marks an     
epoch in the history of the utilization 
of coal-tar products with which the name
 of ,perkin will ever be associated4 ,in
 the course of some experiments1 having 
for their object the artificial         
production of quinine1 this investigator
 was led to try the action of oxidizing 
agents upon a base known as aniline1 and
 he thus obtained a violet colouring    
matter--the first dye from              
coal-tar--which was manufactured under a

 patent granted in #aheh1 and introduced
 into commerce under the name of mauve4 
,a brief sketch of the history of       
aniline will serve to show how ,perkin's
 discovery gave a new value to the light
 oils from coal-tar and raised the      
manufacture of nitrobenzene into an     
important branch of industry4  ,thirty  
years before ,perkin's experiments the  
,dutch chemist ,unverdorben obtained    
7#ahbf7 a liquid base by the            
distillation of indigo1 which had the   
property of forming beautifully         
crystalline salts1 and which he named   
for this reason crystallin4 ,in #ahcd   
,runge discovered the same base in      
coal-tar1 although its identity was not 
known to him at the time1 and because it
 gave a bluish colour when acted upon by
 bleaching-powder1 he called it kyanol4 
,again in #ahdj1 by distilling a product
 obtained by the action of caustic      
alkalies upon indigo1 ,fritzsche        
prepared the same base1 and gave it the 
name of aniline1 from the ,spanish      

designation of the indigo plant1 anil1  
derived from the native ,indian word1 by
 which name the base is known at the    
present time4 ,that aniline could be    
obtained by the reduction of            
nitrobenzene was shown by ,zinin in     
#ahdb1 who used sulphide of ammonium for
 reducing the nitrobenzene1 and named   
the resulting base benzidam4 ,the       
following year ,hofmann showed that     
crystallin1 kyanol1 aniline1 and        
benzidam were all one and the same base4
 ,thus when the discovery of mauve      
opened up a demand for aniline on the   
large scale1 the labours of chemists1   
from ,unverdorben in #ahbf to ,hofmann  
in #ahdc1 had prepared the way for the  
manufacturer4 ,it must be understood    
that although ,runge had discovered     
aniline in coal-tar1 this is not the    
source of our present supply1 for the   
quantity is too small to make it worth  
extracting4 ,a mere trace of aniline is 
present in the tar ready formed2 from   
the time this base was wanted in large  

quantities it had to be made by         
nitrating benzene1 and then reducing the
 nitrobenzene4  ,the light oils of tar  
distillation rejected by the            
timber-pickling industry now came to the
 front1 imbued with new interest to the 
technologist as a source of benzene for 
the manufacture of aniline4 ,the        
inauguration of this manufacture1 like  
the introduction of steam locomotion1 is
 connected with a sad catastrophe4      
,mansfield1 who first showed            
manufacturers how to separate benzene   
and other hydrocarbons from the light   
oils of coal-tar1 and who devised for   
this purpose apparatus similar in       
principle to that used on a large scale 
at the present time 7see ,fig4 #e71 met 
with an accident which resulted in his  
death4 ,in the upper part of a house in 
,holborn in ,february #ahef1 this       
pioneer was carrying on his experiments1
 when the contents of a still boiled    
over and caught fire4 ,in his endeavours
 to extinguish the flames he received   

the injuries which terminated fatally4  
,applied science no less than pure      
science has had its martyrs1 and among  
these ,mansfield must be ranked4        
,illustration3 ,,fig4 #e4--,mansfield's 
still4 ,r the heating burner1 ,a the    
body of the still with stopcock1 i1 for 
running out the contents4 ,b the        
still-head kept in a cistern1 ,c1 of hot
 water or other liquid4 ,the vapour     
generated by the boiling of the liquid  
in ,a1 partly condenses in ,b1 from     
whence the higher boiling-point portion 
flows back into the still4 ,the         
uncondensed vapour passes into the      
condensing-worm1 ,d1 which is kept cool 
by a stream of water1 and from thence   
flows into the receiver ,s4 ,by opening 
m in the side-pipe any higher           
boiling-point oil condensing in the     
delivery-pipe can be run back into the  
still4   ,the operation of              
tar-distilling is about as unromantic a 
process as can be imagined1 but it must 
be briefly described before the         

subsequent developments of the industry 
can be appreciated properly4 ,it has    
already been explained that the tar is a
 complex mixture of many different      
substances4 ,these various compounds    
boil at certain definite temperatures1  
the boiling-point of a chemical compound
 being an inherent property4 ,if a      
mixture of substances boiling at        
different temperatures is heated in a   
suitable vessel the compounds distil    
over1 broadly speaking1 in the order of 
their boiling-points4 ,the separation by
 this process is not absolute1 because  
compounds boiling at a certain          
temperature have a tendency to bring    
over with them the vapours of other     
compounds which boil at a higher        
temperature4 ,but for practical purposes
 it will be sufficient to consider that 
the general tendency is for the         
compounds of low boiling-point to come  
over first1 then the compounds of higher
 boiling-point1 and finally those of the
 highest boiling-point4 ,this is the    

principle made use of by the            
tar-distiller4 ,the tar-still is a large
 iron pot provided with a still-head    
from which the vapours boil out into a  
coil of iron pipe kept cool in a vessel 
of water 7see ,fig4 #f74 ,the still is  
heated by a fire beneath it1 and the    
different portions which condense in the
 iron coil are received in vessels which
 are changed as the different fractions 
of the tar come over4 ,the process is   
what chemists would call a rough        
fractional distillation4 ,the first     
fractions are liquid at ordinary        
temperatures1 and the water in the      
condenser is kept cold2 then1 as the    
boiling-point rises1 the fraction       
contains a hydrocarbon which solidifies 
on cooling1 and the water in the        
condenser is made hot to prevent the    
choking up of the coil4 ,every one of   
these fractions of coal-tar1 from the   
beginning to the end of the process1 has
 its story to tell--all the chief       
constituents of the tar separated by    

this means have by chemical science been
 converted into useful products4        
,illustration3 ,,fig4 #f4--,sectional   
diagram of tar-still with arched bottom4
 ,the fireplace is at i2 the hot gases  
pass over the bridge k and through g    
into the flues h1 h4 ,the pipe at c is  
to supply the still with tar2 a is the  
exit pipe connected with the condenser1 
and b a man-hole for cleaning out the   
still4 ,the condenser and bottom pipe   
for drawing off pitch have been omitted 
to avoid complication4   ,it is         
customary at the present time to collect
 four distinct fractions from the period
 when the tar begins to boil quietly1   
i4e4 from the point when the small      
quantity of watery liquor which is      
unavoidably entangled with the tar has  
distilled over1 by which time the       
temperature in the still is about #aaj  
deg4 ,c4 ,the small fraction that comes 
over up to this temperature constitutes 
what the tar-distiller calls first      
runnings4 ,from #aaj deg4 ,c4 to #baj   

deg4 ,c4 there comes over a limpid      
inflammable liquid known as light oil1  
and this is succeeded by a fraction     
which shows a tendency to solidify on   
cooling1 owing to the separation of a   
solid crystalline hydrocarbon known as  
naphthalene4 ,this last fraction1       
boiling between #baj deg4 ,c4 and #bdj  
deg4 ,c41 is known as carbolic oil1     
because it contains1 in addition to the 
naphthalene1 the chief portion of the   
carbolic acid present in the tar4 ,from 
#bdj deg4 ,c4 to #bgj deg4 ,c4 there    
comes over another fraction which shows 
but little tendency to solidify in the  
condensing coil1 and which is known as  
heavy oil1 or creosote oil4 ,from #bgj  
deg4 ,c4 up to the end of the           
distillation there distils a fraction   
which is viscid in consistency1 and has 
a tendency to solidify on cooling owing 
to the separation of another crystalline
 hydrocarbon known as anthracene1 and   
which gives the name of anthracene oil  
to this last fraction4 ,when the latter 

has been collected there remains in the 
still the black viscid substance known  
as pitch1 which is obtained of any      
desired consistency by leaving more or  
less of the anthracene oil mixed with   
it1 or by afterwards mixing it with the 
heavy oil from previous distillations4  
,the process carried out in the         
tar-still thus separates the tar        
into--7#a7 ,first runnings1 up to #aaj  
deg4 ,c4 7#b7 ,light oil1 from #aaj deg4
 to #baj deg4 ,c4 7#c7 ,carbolic oil1   
from #baj deg4 to #bdj deg4 ,c4 7#d7    
,creosote oil1 from #bdj deg4 to #bgj   
deg4 ,c4 7#e7 ,anthracene oil1 from #bgj
 deg4 to pitch4 7#f7 ,pitch1 left in    
still4  ,it has already been said that  
coal-tar is a complex mixture of various
 distinct chemical compounds4 ,included 
among the gases1 ammoniacal liquor1 and 
tar1 the compounds which are known to be
 formed by the destructive distillation 
of coal already reach to nearly one     
hundred and fifty in number4 ,of the    
substances present in the tar1 about a  

dozen are utilized as raw materials by  
the manufacturer1 and these are         
contained in the fractions described    
above4 ,the first runnings and light oil
 contain a series of important          
hydrocarbons1 of which the three first  
members are known to chemists as        
benzene1 toluene1 and xylene1 the latter
 being present in three different       
modifications4 ,the carbolic oil        
furnishes carbolic acid and naphthalene1
 and the anthracene oil the hydrocarbon 
which gives its name to that fraction4  
,here we have only half a dozen distinct
 chemical compounds to deal with1 and if
 we confine our attention to these for  
the present1 we shall be enabled to gain
 a good general idea of what chemistry  
has done with these raw materials4 ,the 
products separated during the processes 
which have to be resorted to for the    
isolation of these raw materials have   
also their uses1 which will be pointed  
out incidentally4  ,beginning with the  
first runnings and the light oil1 from  

which the hydrocarbons of the benzene   
series are separated1 we have to make   
ourselves acquainted with the treatment 
to which these fractions are submitted  
by the tar-distiller4 ,the light oil is 
first distilled from an iron still1     
similar to a tar-still1 and the first   
portions which come over are added to   
the oily fraction brought over by the   
water of the first runnings4 ,the       
separation of the oil from the water in 
this last fraction is a simple matter1  
because the hydrocarbons float as a     
distinct layer on the water1 and do not 
mix with it4 ,we have at this stage1    
therefore1 four products to consider1   
viz4 #ast1 the oil from the first       
runnings2 #bnd1 the first portions of   
the light oil2 #crd1 the later portions 
of the light oil2 and #dth1 the residue 
in the still4 ,the first and second are 
mixed together1 and the third is washed 
alternately with alkali and acid to     
remove acid and basic impurities1 and   
can then be mixed with the first and    

second products4 ,the total product is  
then ready for the next operation4 ,the 
last portion of the light oil which     
remains in the still is useless as a    
source of benzene hydrocarbons1 and goes
 into the heavy oil of the later tar    
fractions4  ,the process of purification
 is thus far one of fractional          
distillation combined with chemical     
washing4 ,in fact1 all the processes of 
purification to which these oils are    
submitted are essentially of the same   
character4 ,the principle of fractional 
distillation has already been explained 
sufficiently for our present purpose4   
,the process of washing a liquid may    
appear mysterious to the uninitiated1   
but in principle it is extremely simple4
 ,if we pour some water into a bottle1  
and then add some liquid which does not 
mix with the water--say paraffin        
oil--the two liquids form distinct      
layers1 the one floating on the other4  
,on shaking the bottle so as to mix the 
contents1 the two liquids form a        

homogeneous mixture at first1 but on    
standing for a short time separation    
into two layers again takes place4 ,now 
if there was present in the paraffin oil
 some substance soluble in the oil1 but 
more soluble in water1 such as alcohol1 
we should by the operation described    
wash the alcohol out of the oil1 and    
when the liquids separated into layers  
after agitation the watery layer would  
contain the alcohol4 ,by drawing off the
 oil or the water the former would then 
be obtained free from alcohol--it would 
have been washed4 ,this operation is    
precisely what the manufacturer does on 
a large scale with the coal-tar oils4   
,these oils contain certain impurities  
of which some are of an acid character  
and dissolve in alkalies1 while others  
are basic and dissolve in acid4 ,the oil
 is therefore agitated in a suitable    
vessel provided with mechanical stirring
 gear with an aqueous solution of       
caustic soda1 and after separation into 
layers the alkaline solution retaining  

the acid impurities is drawn off4 ,then 
the oil may be washed with water in the 
same way to remove the lingering traces 
of alkali1 and then with acid--sulphuric
 acid or oil of vitriol--which dissolves
 out basic impurities and certain       
hydrocarbons not belonging to the       
benzene series which it is desirable to 
get rid of4 ,a final washing with water 
removes any acid that may be retained by
 the oil4  ,the total product containing
 the benzene hydrocarbons is put through
 such a series of washing operations as 
above described1 and is then ready for  
separation into its constituents by     
another and more perfect process of     
fractional distillation4 ,this final    
separation is effected in a piece of    
apparatus somewhat complicated in       
structure1 but simple in principle4 ,it 
is a development on a large scale of the
 apparatus used by ,mansfield in his    
early experiments4 ,the details of      
construction are not essential to the   
present treatment of the subject1 but it

 will suffice to say that the vapours of
 the boiling hydrocarbons ascend through
 upright columns1 in which the compounds
 of high boiling-point first condense   
and run back into the still1 while the  
lower boiling-point compounds do not    
condense in the columns1 but pass on    
into a separate condenser1 where they   
liquefy and are collected4 ,but even    
with this rectification we do not get a 
perfect separation--the hydrocarbons are
 not perfectly pure from a chemical     
point of view1 although they are pure   
enough for manufacturing purposes4 ,thus
 the first fraction consists of benzene 
containing a small percentage of        
toluene1 then comes over a mixture      
containing a larger proportion of       
toluene1 then comes a purer toluene     
mixed with a small percentage of xylene4
 ,the boiling-points of the three       
hydrocarbons are #ha deg4 ,c41 #aaa deg4
 ,c41 and #adj deg4 ,c4 respectively2   
but owing to the nature of fractional   
distillation1 a compound of a certain   

boiling-point always brings over with it
 a certain quantity of the compound of  
higher boiling-point1 and that is why   
the rectifying column effects only a    
partial separation4  ,of the            
hydrocarbons thus separated1 benzene and
 toluene are by far the most important2 
there is but a limited use for the      
xylenes at present1 and these and the   
hydrocarbons of higher boiling-point    
belonging to the same series which      
distil over between #adj deg4 and #aej  
deg4 constitute what is known as solvent
 naphtha1 because it is used for        
dissolving india-rubber for             
waterproofing purposes4 ,the            
hydrocarbons of still higher            
boiling-point which remain in the still 
are used as burning naphtha for lamps4  
,if benzene of a higher degree of purity
 is required--as it is for the          
manufacture of certain                  
colouring-matters--the fraction         
containing this hydrocarbon can be again
 distilled through the rectifying       

column1 and a large proportion of the   
toluene thus separated from it4         
,finally1 pure benzene can be obtained  
by submitting the rectified hydrocarbon 
to a process of refrigeration in a      
mixture of ice and salt1 when the       
benzene solidifies to a white           
crystalline solid1 while the toluene    
does not solidify1 and can be drained   
away from the benzene crystals which    
liquefy at about #e deg4 ,c4  ,the      
account rendered by the technologist    
with respect to the light oils of the   
tar is thus a pretty good one4 ,already 
we see that benzene1 toluene1 solvent   
naphtha1 and burning naphtha are        
separated from them4 ,even the alkaline 
and acid washings may be made to        
surrender their contained products1 for 
the first of these contains a certain   
quantity of carbolic acid1 and the acid 
contains a strongly smelling base called
 pyridine1 for which there is at present
 no great demand1 but which may one day 
become of importance4 ,the actual       

quantity of benzene in tar is a little  
over one per cent4 by weight1 and of    
toluene there is somewhat less4 ,the    
naphthas are present to the extent of   
about #ce per cent4  ,now let us        
consider some of the transformations    
which benzene and toluene undergo in the
 hands of the manufacturing chemist4    
,the production of aniline from benzene 
by acting upon this hydrocarbon with    
nitric acid1 and then reducing the      
nitrobenzene1 has already been referred 
to4 ,for this purpose we now heat the   
nitrobenzene with iron dust and a little
 hydrochloric 7muriatic7 acid1 and then 
distil over the aniline by means of a   
current of steam blown through the      
still4 ,by a similar process toluene is 
converted into nitrotoluene1 and the    
latter into toluidine4  ,the large      
quantity of aniline and toluidine now   
made has opened up a channel for the use
 of the waste borings from cast-iron4   
,these are ground to a fine powder under
 heavy mill-stones1 and constitute a    

most valuable reducing agent1 known     
technically as iron swarf4 ,the metallic
 iron introduced in this form into the  
aniline still is converted into an oxide
 of iron by the action of the           
nitrobenzene1 and this oxide of iron is 
used by the gas-maker for purifying the 
gas from sulphur as already described4  
,when the oxide of iron is exhausted1   
i4e4 when it has taken up as much       
sulphur as it can1 it goes to the       
vitriol-maker to be burnt as a source of
 this acid4 ,here we have a waste       
product of the aniline manufacture      
utilized for the purification of        
coal-gas1 and finally being made to give
 up the sulphur1 which it obtained      
primarily from the coal1 for the        
production of sulphuric acid1 which is  
consumed in nearly every branch of      
chemical industry4  ,nitrotoluene and   
toluidine each exist in three distinct  
modifications1 so that it is more       
correct to speak of the nitrotoluenes   
and the toluidines2 but the explanation 

of these differences belongs to pure    
chemical theory1 and cannot now be      
attempted in detail4 ,it must suffice to
 say that many compounds having the same
 chemical composition differ in their   
properties1 and are said to be isomeric1
 the isomerism being regarded as the    
result of the different order of        
arrangement of the atoms within the     
molecule4  ,consider a homely           
illustration4 ,a child's box of bricks  
contains a certain number of wooden     
blocks1 by means of which different     
structures can be built up4 ,supposing  
all the bricks to be employed for every 
structure erected1 the latter must in   
every case contain all the blocks1 and  
yet the result is different1 because in 
each structure the blocks are arranged  
in a different way4 ,the bricks         
represent atoms1 and the whole structure
 represents a molecule2 the structures  
all have the same ultimate composition1 
and are therefore isomeric4 ,this will  
serve as a rough analogy1 only it must  

not be understood that the different    
atoms of the elements composing a       
molecule are of different sizes and     
shapes2 on this point we are as yet     
profoundly ignorant4  ,now as long ago  
as #ahef1 at the time when ,perkin began
 making mauve by oxidizing aniline with 
bichromate of potash1 it was observed by
 ,natanson1 that when aniline was heated
 with a certain oxidizing agent a red   
colouring-matter was produced4 ,the same
 fact was observed in #aheh by ,hofmann1
 who used the tetrachloride of carbon as
 an oxidizing agent4 ,these chemists    
obtained the red colouring-matter as a  
by-product2 it was formed only in small 
quantity1 and was regarded as an        
impurity4 ,in the same year1 #aheh1 two 
,french manufacturers patented the      
production of a red dye formed by the   
action of chromic acid and other        
oxidizing agents on aniline1 the        
colouring matter thus made being used   
for dying artificial flowers4 ,then1 a  
year later1 the ,french chemist ,verguin

 found that the best oxidizing agent was
 the tetrachloride of tin1 and this with
 many other oxidizing substances was    
patented by ,renard ,freres and ,franc1 
and under their patent the manufacture  
of the aniline red was commenced on a   
small scale in ,france4 ,finally1 in    
#ahfj1 an oxidizing agent was made use  
of almost simultaneously by two ,english
 chemists1 ,medlock and ,nicholson1     
which gave a far better yield of the red
 than any of the other materials        
previously in use1 and put the          
manufacture of the colouring-matter on  
quite a new basis4 ,the oxidizing       
material patented by ,medlock and       
,nicholson is arsenic acid1 and their   
process is carried on at the present    
time on an enormous scale in all the    
chief colour factories in ,europe1 the  
colouring-matter produced by this means 
being generally known as fuchsine or    
magenta4  ,in four years the accidental 
observation of ,natanson and ,hofmann1  
made1 be it remembered1 in the course of

 abstract scientific investigation1 had 
thus developed into an important branch 
of manufacture4 ,a demand for aniline on
 an increased scale sprung up1 and the  
light oils of coal-tar became of still  
greater importance4 ,the operations of  
the tar-distiller had to undergo a      
corresponding increase in magnitude and 
refinement2 the production of           
nitrobenzene and necessarily of nitric  
acid had to be increased1 and a new     
branch of manufacture1 that of arsenic  
acid from arsenious acid and nitric     
acid1 was called into existence4        
,perkin's mauve prepared the way for the
 manufacture of aniline1 and the        
discovery of a good process for the     
production of magenta increased this    
branch of manufacture to a remarkable   
extent4 ,still later in the history of  
the magenta manufacture1 attempts were  
made1 with more or less success1 to use 
nitrobenzene itself as an oxidizing     
agent1 and a process was perfected in   
#ahfi by ,coupier1 which is now in use  

in many factories4  ,the introduction of
 magenta into commerce marks an epoch in
 the history of the coal-tar colour     
industry--pure chemistry and chemical   
technology both profited by the         
discovery4 ,the brilliant red of this   
colouring-matter is objected to by      
modern aestheticism1 but the dye is     
still made in large quantities1 its     
value having been greatly increased by a
 discovery made about the same time by  
,john ,holliday and the ,baden ,aniline 
and ,soda ,company1 and patented by the 
latter in #ahgg4 ,magenta is the salt of
 a base now known as rosaniline1 and it 
belongs therefore to the class of basic 
colouring-matters4 ,the dyes of this    
kind are as a group less fast1 and have 
a more limited application than those   
colouring-matters which possess an acid 
character1 so that the discovery above  
referred to--that magenta could be      
converted into an acid without          
destroying its colouring power by acting
 upon it with very strong sulphuric     

acid--opened up a new field for the     
employment of the dye1 and greatly      
extended its usefulness4 ,in this form  
the colouring-matter is met with under  
the name of acid magenta4  ,it must be  
understood that the production of       
magenta from aniline by the oxidizing   
action of arsenic acid or nitrobenzene  
is the result of chemical change2 the   
colouring-matter is no more present in  
the aniline than the latter is contained
 in the benzene4 ,and just in the same  
way that the colourless aniline oil by  
chemical transformation gives rise to   
the intensely colorific magenta1 so the 
latter by further chemical change can be
 made to give rise to whole series of   
different colouring-matters1 each       
consisting of definite chemical         
compounds as distinct in individuality  
as magenta itself4 ,thus in #ahfj1 about
 the time when the arsenic acid process 
was inaugurated1 two ,french chemists1  
,messrs4 ,girard and ,de ,laire1        
observed that by heating rosaniline for 

some time with aniline and an aniline   
salt1 blue and violet colouring-matters 
were produced4 ,this observation formed 
the starting-point of a new manufacture 
proceeding from magenta as a raw        
material4 ,the production of the new    
colouring-matters was perfected by      
various investigators1 and a magnificent
 blue was the final result4 ,but here   
also the dye was of a basic character1  
and being insoluble in water had only a 
limited application1 as a spirit bath   
had to be used for dissolving the       
substance4 ,in #ahfb1 however1 an       
,english technologist1 the late ,e4 ,c4 
,nicholson1 found that by the action of 
strong sulphuric acid the aniline blue  
could be rendered soluble in water or   
alkali1 and the value of the            
colouring-matter was enormously         
increased by this discovery4 ,the basic 
and slightly soluble spirit blue was by 
this means converted into acid blues1   
which are now made in large quantities1 
and sold under the names of ,nicholson's

 blue1 alkali blue1 soluble blue1 and   
other trade designations4 ,there is at  
the present time hardly any other blue  
which for fastness1 facility of dyeing1 
and beauty can compete with this        
colouring-matter introduced by          
,nicholson as the outcome of the work of
 ,girard and ,de ,laire4  ,other        
transformations of rosaniline have yet  
to be chronicled4 ,in #ahfb ,hofmann    
found that by acting upon this base--the
 base of magenta--with the iodide of    
methyl1 violet colouring-matters were   
produced1 and these were for some years 
extensively employed under the name of  
,hofmann's violets4 ,and still more     
remarkable1 by the prolonged action of  
an excess of methyl iodide upon         
rosaniline1 ,keisser found that a green 
colouring-matter was formed4 ,the latter
 was patented in #ahff1 and the dye was 
for some time in use under the name of  
iodine green4 ,the statement that       
technology profited by the introduction 
of magenta has therefore been justified4

  ,it remains to add1 that the tar      
obtained from one ton of ,lancashire    
coal furnishes an amount of aniline     
capable of giving a little over half a  
pound of magenta4 ,the colouring power  
of the latter will be inferred from the 
fact1 that this quantity would dye #cge 
square yards of white flannel of a full 
red colour1 and if converted into       
,hofmann violet by methylation1 would   
give enough colour to dye double this   
surface of flannel of a deep violet     
shade4 ,it should be stated also1 that  
during the formation of magenta by the  
arsenic acid process1 there are formed  
small quantities of other               
colouring-matters which are utilized by 
the manufacturer4 ,among these          
by-products is a basic orange dye1 which
 was isolated by ,nicholson1 and        
investigated by ,hofmann in #ahfb4      
,under the name of phosphine this       
colouring-matter is still used1         
especially for the dyeing of leather4   
,even the spent arsenic acid of the     

magenta-still has its use4 ,the         
arsenious acid resulting from the       
reduction of this arsenic acid is       
generally obtained in the form of a lime
 salt after the removal of the magenta  
by the purifying processes to which the 
crude product is submitted4 ,from the   
arsenical waste arsenious acid can be   
recovered1 and converted back into      
arsenic acid by the action of nitric    
acid4 ,quite recently the arsenical     
residue has been used with considerable 
success in ,america as an insecticide   
for the destruction of pests injurious  
to agricultural crops4  ,concurrently   
with these technical developments of    
coal-tar products1 the scientific       
chemist was carrying on his             
investigations4 ,the compounds which    
science had given to commerce were made 
on a scale that enabled the investigator
 to obtain his materials in quantities  
that appeared fabulous in the early days
 when aniline was regarded as a         
laboratory curiosity1 and magenta had   

been seen by only a few chemists4  ,the 
fundamental problem which the modern    
chemist seeks to solve is in the first  
place the composition of a compound1    
i4e4 the number of the atoms of the     
different elements which form the       
molecule1 and in the next place the way 
in which these atoms are combined in the
 molecule4 ,reverting to our former     
analogy1 the first thing to be found is 
how many different blocks enter into the
 composition of the structure1 and the  
next thing is to ascertain how the      
blocks are arranged4 ,when this is done1
 we are said to know the constitution or
 structure of the molecule1 and in many 
cases when this is known we can build up
 or synthesise the compound by combining
 its different groups of atoms by       
suitable methods4 ,the coal-tar industry
 abounds with such triumphs of chemical 
synthesis2 a few of these achievements  
will be brought to light in the course  
of the remaining portions of this work4 
,the chemical investigation of magenta  

was commenced by ,hofmann1 whose name is
 inseparably connected with the         
scientific development of the coal-tar  
colour industry4 ,in #ahfb he showed    
that magenta was the salt of a base     
which he isolated1 analysed1 and named  
rosaniline4 ,he established the         
composition of this base and of the     
violet and blue colouring-matters       
obtained from it by the processes       
already described4 ,in #ahfd he made the
 interesting discovery that magenta is  
not formed by the oxidation of pure     
aniline1 but that a mixture of aniline  
and toluidine is essential for the      
production of this colouring-matter4 ,in
 fact1 the aniline oil used by the      
manufacturer had from the beginning     
consisted of a mixture of aniline and   
toluidine1 and at the present time      
aniline for red is made by nitrating a  
mixture of benzene and toluene and      
reducing the nitro-compounds4  ,from    
this work of ,hofmann's suggestions     
naturally arose concerning the          

constitution of rosaniline1 and new and 
fruitful lines of work were opened up4  
,large numbers of chemists of the       
greatest eminence pursued the inquiry1  
but the details of their work1 although 
of absorbing interest to the chemist1   
cannot be discussed in the present      
volume4 ,the final touch to a long      
series of investigations was given by   
two ,german chemists1 ,emil and ,otto   
,fischer1 who in #ahgh proved the       
constitution of rosaniline by obtaining 
from it a hydrocarbon1 the parent       
hydrocarbon from which the              
colouring-matter is derived4 ,the purely
 scientific discovery of the ,fischers  
threw a flood of light on the chemistry 
of magenta1 and enabled a large number  
of colouring-matters related to the     
latter to be classed under one group1   
having the parent hydrocarbon as a      
central type4 ,this hydrocarbon1 it may 
be remarked1 is known as                
triphenylmethane1 as it is a derivative 
of methane1 or marsh gas4 ,the blues and

 violets obtained from rosaniline belong
 to this group1 and so also do certain  
other colouring-matters which had been  
manufactured before the ,fischers'      
discovery4 ,in order to carry on the    
story of the utilisation of aniline1 it 
is necessary to know something about    
these other colouring-matters which are 
obtained from it4  ,it has been         
explained that by the methylation of    
rosaniline ,hofmann obtained violet     
colouring-matters4 ,now as rosaniline is
 obtained by the oxidation of a mixture 
of aniline and toluidine1 it seems but  
natural that if these bases were        
methylated first and then oxidized a    
violet dye would be produced4 ,the      
,french chemist ,lauth first obtained a 
violet colouring-matter by this method  
in #ahfa4 ,in #ahff this violet dye was 
manufactured in ,france by ,poirrier1   
and it is still made in large           
quantities1 being known under the name  
of methyl violet4 ,this                 
colouring-matter1 and a bluer derivative

 of it discovered in #ahfh1 gradually   
displaced the ,hofmann violets1 chiefly 
owing to their greater cheapness of     
production4 ,we are thus introduced to  
methylated aniline as a source of       
colouring-matters1 and as the compound  
in question has many different uses in  
the coal-tar industry1 a few words must 
be devoted to its technology4  ,aniline1
 toluidine1 and similar bases can be    
methylated by the action of methyl      
iodide1 but the cost of iodine is too   
great to enable this process to be used 
by the manufacturer4 ,methyl chloride1  
however1 answers equally well1 and this 
compound1 which is a liquid of very low 
boiling point 7-#bc deg4 ,c471 is       
prepared on a large scale from the waste
 material of another industry1 viz4 the 
beet-sugar manufacture4 ,it is          
interesting to see how distinct         
industries by chemical skill are made to
 act and react upon one another4 ,thus  
the cultivation of the beet1 as already 
explained1 is largely dependent on the  

supply of ammonia from gas-liquor4      
,during the refining of the beet-sugar1 
a large quantity of uncrystallisable    
treacle is separated1 and this is       
fermented for the manufacture of        
alcohol4 ,when the latter is distilled  
off there remains a spent liquor        
containing among other things potassium 
salts and nitrogenous compounds4 ,this  
waste liquor1 called vinasse1 is        
evaporated down and ignited in order to 
recover the potash1 and during the      
ignition1 ammonia1 tar1 gas1 and other  
volatile products are given off4 ,among 
the volatile products is a base called  
trimethylamine1 which is a derivative of
 ammonia2 the salt formed by combining  
trimethylamine with hydrochloric acid   
when heated gives off methyl chloride as
 a gas which can be condensed by        
pressure4  ,here we have a very pretty  
cycle of chemical transmigration4 ,the  
nitrogen of the coal plants1 stored up  
in the earth for ages1 is restored in   
the form of ammonia to the crops of     

growing beet2 the nitrogen is made to   
enter into the composition of the latter
 plant by the chemico-physiological     
process going on1 and the nitrogenous   
compounds removed from the plant and    
heated to the point of decomposition in 
presence of the potash 7which also      
entered into the composition of the     
plant71 give back their nitrogen partly 
in the form of a base from which methyl 
chloride can be obtained4 ,the latter is
 then made to methylate a product1      
aniline1 derived indirectly from        
coal-tar4 ,the utilisation of the       
vinasse for this purpose was made known 
by ,camille ,vincent of ,paris in #ahgh4
  ,the methylation of aniline can       
obviously be carried out by the         
foregoing process only when beet-sugar  
residues are available4 ,there is       
another method which is more generally  
used1 and which is interesting as       
bringing in a distinct branch of        
industry4 ,the same result can1 in fact1
 be arrived at by heating dry aniline   

hydrochloride1 i4e4 the hydrochloric    
acid salt of aniline1 with methyl       
alcohol or wood-spirit in strong        
metallic boilers under great pressure4  
,this is the process carried on in most 
factories1 and it involves the use of   
pure methyl alcohol1 a branch of        
manufacture which has been called into  
existence to meet the requirements of   
the coal-tar colour maker4#d ,this      
alcohol or wood-spirit is obtained by   
the destructive distillation of wood1   
and is purified by a series of          
operations which do not at present      
concern us4 ,it must be mentioned that  
the product of the methylation of       
aniline1 which it is the object of the  
manufacturer to obtain1 is an oily      
liquid called dimethylaniline1 which1 by
 virtue of the chemical transformation1 
is quite different in its properties to 
the aniline from which it is derived4   
,by a similar operation1 using ethyl    
alcohol1 or spirit of wine1             
diethylaniline can be obtained1 and by  

heating dry aniline hydrochloride with  
aniline under similar conditions a      
crystalline base called diphenylamine is
 also prepared4  ,now these             
products--dimethylaniline1              
diethylaniline1 and diphenylamine--are  
derived from aniline1 and they are all  
sources of colouring-matters4           
,methyl-violet is obtained by the       
oxidation of dimethylaniline by means of
 a gentle oxidizer2 a mixture of bases  
is not necessary as in the case of the  
magenta formation4 ,then in #ahff       
diphenylamine was shown by ,girard and  
,de ,laire to be capable of yielding a  
fine blue by heating it with oxalic     
acid1 and this blue1 on account of the  
purity of its shade1 is still an article
 of commerce4 ,it can be made soluble by
 the action of sulphuric acid in just   
the same way as the other aniline blue4 
,furthermore1 by acting with excess of  
methyl chloride on methyl violet1 a     
brilliant green colouring-matter was    
manufactured in #ahgh1 which was        

obviously analogous to the iodine green 
already mentioned1 and which for some   
years held its own as the only good     
coal-tar green4 ,these are the          
dyes--methyl violet and green1 and      
diphenylamine blue--which were in       
commerce before the discovery of the    
,fischers1 and which this discovery     
enabled chemists to class with magenta1 
aniline blue1 and ,hofmann violet in the
 triphenylmethane group4  ,later        
developments bring us into contact with 
other dyes of the same class1 and with  
the industrial evolution of the purely  
scientific idea concerning the          
constitution of the colouring-matters of
 this group4 ,benzene and toluene again 
form the points of departure4 ,by the   
action of chlorine upon the vapour of   
boiling toluene there are obtained1     
according to the extent of the action of
 the chlorine1 three liquids of use to  
the colour manufacturer4 ,the first of  
these is benzyl chloride1 the second    
benzal chloride1 and the third          

benzotrichloride or phenyl chloroform4  
,benzyl chloride1 it may be remarked in 
passing1 plays the same part in organic 
chemistry as methyl chloride1 and       
enables certain compounds to be         
benzylated1 just in the same way that   
they can be methylated4 ,the bluer shade
 of methyl violet1 introduced in #ahfh1 
and still manufactured1 is a benzylated 
derivative4 ,by the action of           
benzotrichloride on dimethylaniline in  
the presence of dry zinc chloride1      
,oscar ,doebner obtained in #ahgh a     
brilliant green colouring-matter which  
was manufactured under the name of      
malachite green4 ,it will be remembered 
that this was about the time when the   
,fischers were engaged with their       
investigations4 ,these last chemists1 by
 virtue of their scientific results1    
were enabled to show that ,doebner's    
green was a member of the               
triphenylmethane group1 and they        
prepared the same compound by another   
method which has enabled the            

manufacturer to dispense with the use of
 the somewhat expensive and disagreeable
 benzotrichloride4 ,the ,fischers'      
method consists in heating              
dimethylaniline with bitter-almond oil  
and oxidizing the product thus formed1  
when the green colouring-matter is at   
once produced4 ,this method brings the  
technologist into competition with      
,nature1 and we shall see the result4   
,benzoic aldehyde or bitter-almond oil  
is one of the oldest known products of  
the vegetable kingdom1 and has from time
 to time been made the subject of       
investigation by chemists since the     
beginning of the century4 ,it arises    
from the fermentation of a nitrogenous  
compound found in the almond1 and known 
as amygdalin1 the nature of the         
fermentative change undergone by this   
substance having been brought to light  
by ,woehler and ,liebig4 ,the discovery 
of a green dye1 requiring for its       
preparation a vegetable product which   
was very costly1 compelled the          

manufacturer to seek another source of  
the oil4 ,pure chemistry again steps in1
 and solves the problem4 ,in #ahfc it   
was known to ,cahours that benzal       
chloride1 on being heated with water or 
alkali1 gave benzoic aldehyde1 and in   
#ahfg ,lauth and ,grimaux showed that   
the same compound could be formed by    
oxidizing benzyl chloride in the        
presence of water4 ,it was but a step   
from the laboratory into the factory in 
this case1 and at the present time the  
aldehyde is made on a large scale by    
chlorinating boiling toluene beyond the 
stage of benzyl chloride1 and heating   
the mixture of benzal chloride and      
benzotrichloride with lime and water    
under pressure4 ,by this means the first
 compound is transformed into benzoic   
aldehyde1 and the second into benzoic   
acid4 ,this last substance is also      
required by the colour-maker1 as it is  
used in the manufacture of blue by the  
action of aniline on rosaniline2 without
 some such organic acid the             

transformation of rosaniline into the   
blue is very imperfect4  ,benzoic acid1 
like the aldehyde1 is a natural product 
which has long been known4 ,it was      
obtained from gum benzoin at the        
beginning of the seventeenth century1   
and its preparation from this source was
 described by ,scheele in #agee4 ,the   
same chemist afterwards found it in     
urine1 and from these two sources1 the  
one vegetable and the other animal1 the 
acid was formerly prepared4 ,its        
relationship to benzene has already been
 alluded to in connection with the      
history of that hydrocarbon4 ,it will be
 remembered that by heating this acid   
with lime ,mitscherlich obtained benzene
 in #ahcd4 ,in one operation1 therefore1
 setting out from toluene1 we make these
 two natural products1 the aldehyde and 
acid1 which are easily separable by     
technical processes4 ,the wants of the  
technologist have been met1 and he has  
been enabled to compete successfully    
with ,nature1 for he can manufacture    

these products much more cheaply than   
when he had to depend upon bitter       
almonds or gum benzoin4 ,the synthetical
 bitter-almond oil is chemically        
identical with that from the plant4     
,besides its use for the manufacture of 
colouring-matters1 it is employed for   
flavouring purposes and in perfumery1   
this being the first instance of a      
coal-tar perfume which we have had      
occasion to mention4 ,the odour in this 
case1 it must be remembered1 is that of 
the actual compound which imparts the   
characteristic taste and smell to the   
almond2 it is not the result of         
substituting a substance which has a    
particular odour for another having a   
similar odour1 as is the case with      
nitrobenzene1 which1 as already         
mentioned1 is used in large quantities  
under the name of essence of mirbane1   
for imparting an almond-like smell to   
soap4  ,the introduction of malachite   
green marks another epoch in the history
 of the technology of the               

triphenylmethane colours4 ,the action   
between benzoic aldehyde and other bases
 analogous to dimethylaniline was found 
to be quite general1 and the principle  
was extended to diethylaniline and      
similarly constituted bases4 ,various   
green dyes--some of them acids formed by
 the action of sulphuric acid on the    
colour base--are now manufactured1 and  
many other colouring-matters of the same
 group are synthesised by the benzoic   
aldehyde process4  ,one other           
development of this branch of           
manufacture has yet to be recorded4 ,the
 new departure was made in #ahhc by     
,caro and ,kern1 who patented a process 
for the synthesis of colouring-matters  
of this group4 ,in this synthesis a gas 
called phosgene is used1 the said gas   
having been discovered by ,john ,davy in
 #ahaa1 who gave it its name because it 
is formed by the direct union of        
chlorine and carbon monoxide under the  
influence of sunlight4 ,caro and ,kern's
 process is the first technical         

application of ,davy's compound4 ,by the
 action of phosgene on dimethylaniline  
and analogous bases in the presence of  
certain compounds which promote the     
chemical interaction1 a number of basic 
colouring-matters of brilliant shades of
 violet 7crystal violet7 and blue       
7,victoria blue1 night blue7 are        
produced1 these being all members of the
 triphenylmethane group4 ,one of these  
dyes is a fine basic yellow known as    
auramine1 which is a derivative of      
diphenylmethane4                        
,,tar4                                  
7,light oil7                            
----------------        --------        
_/ ,benzyl chloride                     
,benzene                                
,toluene   ,benzal chloride             
,benzotrichloride-                      
------------                            
,aniline- ,magenta 7and                 
,phosphine7-,toluidine                  
_/                                      
_/                                      

---,benzoic acid and-   ,dimethylaniline
    ,diphenylamine                      
,benzoic aldehyde                       
_/                                      
,aniline ,blues3       _/               
,hofmann ,violet    ,nicholson and      
_/                            and       
,iodine ,green   ,soluble          _/   
,diph4 ,blue                            
_/                                      
_/                                      
----------------------------------------
--------         _/                     
_/   ,crystal ,violet1      ,methyl     
,violet                       _/        
,auramine1           and ,green         
,malachite   other ,phosgene dyes       
,green series  ,from benzene and toluene
 alone about forty distinct             
colouring-matters of the rosaniline     
group are sent into commerce4 ,the      
relationship of those compounds to each 
other and to their generating substances
 is not easy to grasp by those to whom  
the facts are presented for the first   

time4 ,the scheme on page #ajg shows    
these relationships at a glance4  ,the  
colouring-matters derived from these two
 hydrocarbons are far from being        
exhausted4 ,during the oxidation of     
aniline for the production of           
mauve--which colouring-matter1 it may be
 mentioned1 is no longer made--a red    
compound is formed as a by-product4     
,this was isolated by ,perkin in #ahfa1 
and studied scientifically by ,hofmann  
and ,geyger1 who established its        
composition in #ahgb1 the dye being at  
that time manufactured under the name of
 saffranine4 ,it appears to have been   
first introduced about #ahfh4 ,the      
conditions of formation of this dye were
 at first imperfectly understood1 but   
the problem was attacked by chemists and
 technologists1 and the first point of  
importance resulting from their work was
 that saffranine was derived from one of
 the toluidines present in the          
commercial aniline4 ,to record the      
various steps in this chapter of        

industrial chemistry would take us      
beyond the scope of the present work4   
,in addition to the chemists named1     
,caro1 ,bindschedler1 and others        
contributed to the technology1 while the
 scientific side of the matter was first
 taken up by ,nietzki in #ahgg1 by ,otto
 ,witt in #ahgh1 and by ,bernthsen in   
#ahhf4 ,it is to the work of these      
chemists1 and especially to that of     
,witt1 that we owe our present knowledge
 of the constitution of this and allied 
colouring-matters4 ,space will not admit
 of our traversing the ground1 although 
to chemists it is a line of             
investigation full of interest2 it will 
be sufficient to say that by #ahhf these
 investigators had accomplished for     
these colouring-matters what the        
,fischers had done for the rosaniline   
group--they established their           
constitution1 and showed that they were 
derivatives of diphenylamine1 containing
 two nitrogen atoms joined together in a
 particular way4 ,the parent-substance  

from which these compounds are derived  
is known at the present time as azine   
7,french1 azote  nitrogen71 and the dyes
 belong accordingly to the azine group4 
,the first coal-tar colouring-matter1   
,perkin's mauve1 is a member of this    
class4  ,the azine dyes are basic1 and  
mostly of a red or pink shade2 they are 
somewhat fugitive when exposed to light1
 but possess a certain value on account 
of their affinity for cotton1 and the   
readiness with which they can be used in
 admixture with other colouring-matters4
 ,some of the best known are made by    
oxidizing certain derivatives of aniline
 or toluidine1 in the presence of these 
or analogous bases4 ,to make this       
intelligible a little more chemistry is 
necessary4 ,aniline is a derivative of  
benzene in which one atom of hydrogen is
 replaced by the residue of ammonia4    
,ammonia is composed of one atom of     
nitrogen and three atoms of hydrogen2   
benzene is composed of six atoms of     
carbon and six of hydrogen4 ,if one atom

 of hydrogen is supposed to be withdrawn
 from ammonia1 there remains a residue  
called the amido-group1 and if we       
imagine this group to be substituted for
 one of the hydrogen atoms in benzene1  
we have an amido-derivative1 i4e4       
amidobenzene or aniline4 ,similarly1 the
 toluidines are amidotoluenes4 ,if two  
hydrogen atoms in benzene or toluene are
 replaced by two amido-groups1 we have  
diamidobenzenes and diamidotoluenes1    
which are strongly basic substances1    
capable of existing in several isomeric 
modifications4 ,certain of these        
diamido-compounds when oxidized in the  
presence of a further quantity of       
aniline1 toluidine1 and such            
amido-compounds1 give rise to unstable  
blue products1 which readily become     
transformed into red dyes of the azine  
group4  ,some azine dyes are produced by
 another method1 which is instructive   
because it brings us into contact with a
 derivative of dimethylaniline which    
figures largely in the coal-tar colour  

industry4 ,by the action of nitrous acid
 on this base1 there is produced a      
compound known as                       
nitrosodimethylaniline1 which was       
discovered by ,baeyer and ,caro in      
#ahgd1 and which contains the residue of
 nitrous acid in place of one atom of   
hydrogen4 ,the residue of nitric acid   
which replaces hydrogen in benzene is   
the nitro-group1 and the compound is    
nitrobenzene4 ,the analogy with nitrous 
acid will therefore be sufficiently     
understood--the residue of this acid is 
the nitroso-group1 and compounds        
containing this group are               
nitroso-derivatives4 ,in #ahgi1 ,otto   
,witt found that the nitroso-group in   
nitrosodimethylaniline acted as an      
oxidizing group1 and enabled this       
compound to act upon certain            
diamido-derivatives of benzene and      
toluene1 with the formation of unstable 
blue compounds1 which on heating the    
solution changed into red               
colouring-matters of the azine group4   

,this process soon bore fruit           
industrially1 and azines of a red1      
violet1 and blue shade were introduced  
under the names of neutral red1 violet1 
and blue1 ,basle blue1 c41 some of these
 surviving at the present time4  ,we    
have now to turn to another chapter in  
the history of dimethylaniline4 ,in     
#ahgf1 ,lauth discovered a new colour   
test for one of the diamidobenzenes4 ,by
 heating this base with sulphur1 and    
oxidizing the product1 a violet         
colouring-matter was formed1 and the    
same compound was produced by oxidizing 
the base in an aqueous solution in the  
presence of sulphuretted hydrogen4      
,lauth's violet was never manufactured  
in quantity because the yield is small2 
but in the hands of ,dr4 ,caro the work 
of ,lauth bore fruit in another         
direction4 ,instead of using the        
diamidobenzene1 ,caro used its          
dimethyl-derivative1 and by this means  
obtained a splendid blue dye1 which was 
introduced under the name of methylene  

blue4 ,here again we find scientific    
research reacting on technology4 ,a few 
words of chemical explanation will make 
this manufacture intelligible4 ,by the  
action of reducing agents on nitro and  
nitroso-compounds1 the nitro and        
nitroso-group become converted into the 
amido-group4 ,thus when nitrobenzene is 
reduced by iron and an acid we get      
aniline2 similarly when                 
nitrosodimethylaniline is reduced by    
zinc and an acid we get                 
amidodimethylaniline1 and this is the   
base used in the preparation of         
methylene blue4 ,by oxidizing this base 
in the presence of sulphuretted         
hydrogen1 the colouring-matter is       
formed4 ,other methods of arriving at   
the same result were discovered and     
patented in due course1 but the various 
processes cannot be discussed here4     
,lauth's violet and methylene blue      
became the subjects of scientific       
investigation in #ahgi by ,koch1 and in 
#ahhc a series of brilliant researches  

were commenced by ,bernthsen which      
extended over several years1 and which  
established the constitution of these   
compounds4 ,it was shown that they are  
derivatives of diphenylamine containing 
sulphur as an essential constituent4    
,the parent-compound is diphenylamine in
 which sulphur replaces hydrogen1 and is
 therefore known as thiodiphenylamine4  
,it can be prepared by heating          
diphenylamine with sulphur1 and is      
sometimes called thiazine1 because it is
 somewhat analogous in type to azine4   
,we must therefore credit               
dimethylaniline with being the          
industrial generator of the thiazines4  
,the blue is largely used for cotton    
dyeing1 producing on this fibre when    
properly mordanted an indigo shade4 ,by 
the action of nitrous acid the blue is  
converted into a green known as         
methylene green4  ,although the scope of
 this work admits of our dealing with   
only a few of the more important groups 
of colouring-matters1 it will already be

 evident that the chemist has turned    
benzene and toluene to good account4    
,but great as is the demand for these   
hydrocarbons for the foregoing purposes1
 there are other branches of the        
coal-tar industry which are dependent   
upon them4 ,it will serve as an answer  
to those who are continually raising the
 cry of brilliancy as an offence to     
aesthetic taste if we consider in the   
next place a most valuable and important
 black obtained from aniline4 ,all      
chemists who studied the action of      
oxidizing agents1 such as chromic acid1 
on aniline1 from ,runge in #ahcd to     
,perkin in #ahef1 observed the formation
 of greenish or bluish-black compounds4 
,after many attempts to utilize these as
 colouring-matters1 success was achieved
 by ,john ,lightfoot of ,accrington near
 ,manchester in #ahfc4 ,by using as an  
oxidizing agent a mixture of potassium  
chlorate and a copper salt1 ,lightfoot  
devised a method for printing and dyeing
 cotton fabrics1 the use of which spread

 rapidly and created an increased demand
 for the hydrochloride of aniline1 this 
salt being now manufactured in enormous 
quantities under the technical          
designation of aniline salt4            
,lightfoot's process was improved for   
printing purposes by ,lauth in #ahfd1   
and many different oxidizing mixtures   
have been subsequently introduced1      
notably the salts of vanadium1 which are
 far more effective than the salts of   
copper1 and which were first employed by
 ,lightfoot in #ahgb4 ,in #ahge-gf      
,coquillion and ,goppelsroeder showed   
that aniline black is produced when an  
electric current is made to decompose a 
solution of an aniline salt1 the        
oxidizing agent here being the nascent  
oxygen resulting from the electrolysis4 
,in these days when the generation of   
electricity is so economically effected1
 this process may become more generally 
used1 and the coal-tar industry may thus
 be brought into relationship with      
another branch of applied science4      

,aniline black is seldom used as a      
direct colouring-matter2 it is generally
 produced in the fibre by printing on   
the mixture of aniline salt and         
oxidizing compounds thickened with      
starch1 c41 and then allowing the       
oxidation to take place spontaneously in
 a moist and slightly heated atmosphere4
 ,by a similar process1 using a dye-bath
 containing the aniline salt and        
oxidizing mixture1 cotton fibre is      
easily dyed4 ,the black cannot be used  
for silk or wool1 as the oxidizing      
materials attack these fibres1 but for  
cotton dyeing and calico printing this  
colouring-matter has come seriously into
 competition with the black dyes        
obtained from logwood and madder4 ,the  
use of aniline for this purpose1 first  
rendered practicable by ,lightfoot1 is  
among the most important of the many    
wonderful applications of coal-tar      
products in the tinctorial industry4    
,the year #ahfc witnessed the           
introduction of the first of a new      

series of colouring-matters which have  
had an enormous influence both on the   
art of the dyer as well as in the       
utilization of tar-products which were  
formerly of but little value4 ,we can   
consider the history of some of these   
colours now1 because the earliest of    
them was produced from aniline4 ,the    
formation of a yellow compound when     
nitrous acid acts upon aniline was      
observed by several chemists prior to   
the date mentioned4 ,in #ahfc the firm  
of ,simpson1 ,maule and ,nicholson      
manufactured a yellow dye by passing    
nitrous gas into a solution of aniline  
in alcohol1 and this had a limited      
application under the name of aniline   
yellow4 ,soon afterwards1 viz4 in #ahff1
 the firm of ,roberts1 ,dale  ,co4 of   
,manchester introduced a brown dye under
 the name of ,manchester brown--this    
compound1 which was discovered by ,dr4  
,martius in #ahfe1 having been produced 
by the action of nitrous acid on one of 
the diamidobenzenes4 ,ten years later   

,caro and ,witt discovered an orange    
colouring-matter belonging to the same  
class1 and the latter introduced the    
compound into commerce as chrysoidine4  
,these three compounds are basic1 and   
the first of them is no longer used as a
 direct dye because it is fugitive4     
,chrysoidine is still used to a large   
extent1 and the brown--now known as     
,bismarck brown--is one of the staple   
products of the colour manufacturer at  
the present time4 ,from this fragment of
 technological history let us now turn  
to chemical science4  ,the chemist whose
 name will always be associated with the
 compounds of this group is the late    
,dr4 ,peter ,griess of                  
,burton-on-,trent4 ,he commenced his    
study of the action of nitrous acid on  
organic bases in #aheh1 and from that   
time till the period of his death in    
#ahhh1 he was constantly contributing to
 our knowledge of the resulting         
compounds4 ,in #ahff1 he and ,dr4       
,martius established the composition of 

aniline yellow1 and the following year  
,caro and ,griess did the same thing for
 the ,manchester brown4 ,in #ahgg       
,hofmann and ,witt established the      
constitution of chrysoidine1 the final  
outcome of all this work being to show  
that the three colouring-matters        
belonged to the same group4 ,the further
 development of these discoveries has   
been one of the most prolific sources of
 new colouring-matters4 ,a brief summary
 of our present position with respect to
 this group must now be attempted4      
,when nitrous acid acts upon an         
amido-derivative of a benzenoid         
hydrocarbon in the presence of a mineral
 acid1 there is formed a compound in    
which the amido-group is replaced by a  
pair of nitrogen atoms joined together  
in a certain way1 which is different to 
the mode of combination in the azines4  
,this pair of nitrogen atoms is combined
 on the one hand with the hydrocarbon   
residue1 and on the other with the      
residue of the mineral acid4 ,the       

resulting compound is very unstable2 its
 solution decomposes very readily1 and  
generally has to be kept cool by ice4   
,freezing machines turning out large    
quantities of ice are kept constantly at
 work in factories where these produces 
are made4 ,the latter are known as      
diazo-compounds--,griess's compounds par
 excellence--and they are prepared on a 
large scale by dissolving a salt of the 
amido-base1 generally the hydrochloride1
 in water with ice1 and adding sodium   
nitrite4 ,the result is a diazo-salt2   
aniline1 for example1 giving            
diazobenzene chloride1 and toluidine    
diazotoluene chloride4 ,similarly all   
amido-derivatives of a benzenoid        
character can be diazotised4 ,the       
importance of this discovery will be    
seen more fully in the next chapter4 ,at
 present we are more especially         
concerned with aniline4  ,the extreme   
instability of the diazo-salts enables  
them to combine with the greatest ease  
with amido-derivatives and with other   

compounds4 ,the very property which in  
the early days rendered their           
investigation so difficult1 and which   
taxed the ingenuity of chemists to the  
utmost1 has now placed these compounds  
in the front rank as colour generators4 
,when a diazo-salt acts on an           
amido-derivative there is formed a      
compound which is more or less unstable1
 but which readily undergoes            
transformation under suitable conditions
 into a stable substance in which two   
hydrocarbon residues are joined together
 by the pair of nitrogen atoms4 ,these  
products are dye-stuffs1 known as       
azo-colours1 and aniline yellow1        
,bismarck brown1 and chrysoidine are the
 oldest known technical compounds       
belonging to the group4 ,the parent     
substance is azobenzene1 and these three
 colouring-matters are mono-1 di- and   
triamido-azobenzene respectively4  ,a   
new phase in the technology of          
tar-products was entered upon when ,witt
 caused a diazo-salt to act upon        

diamidobenzene4 ,this was the first     
industrial application of ,griess's     
discovery4 ,azobenzene1 which was       
discovered by ,mitscherlich in #ahcd1   
and azotoluene are now manufactured by  
reducing nitrobenzene and nitrotoluene  
with mild reducing agents4 ,these parent
 compounds are not in themselves        
colouring-matters1 but they are         
transformed into bases which give rise  
to a splendid series of azo-dyes1 as    
will be described subsequently4 ,let it 
be recorded here that these two         
compounds are to be added to the list of
 valuable products obtained from benzene
 and toluene4 ,and it must also be      
remembered that the introduction of     
these azo-colours has necessitated the  
manufacture on a large scale of sodium  
nitrite as a source of nitrous acid4    
,without entering into unnecessary      
detail it may be stated broadly that    
this salt is made by fusing ,chili      
saltpetre1 which is the nitrate of      
sodium1 with metallic lead1 litharge or 

oxide of lead being obtained as a       
secondary product4 ,then again1 the     
manufacture of ,bismarck brown requires 
dinitrobenzene1 this being made by the  
nitration of benzene beyond the stage of
 nitrobenzene4 ,the brown is made by    
reducing the dinitrobenzene to          
diamidobenzene1 and then treating a     
solution of the latter with sodium      
nitrite and an acid4 ,the azo-colour is 
formed at once1 and no special          
refrigeration is required in this       
particular case4  ,it has already been  
stated that the old aniline yellow of   
#ahfc is no longer used on account of   
its fugitive character4 ,in #ahgh       
,graessler found that by the action of  
very strong sulphuric acid this         
azo-compound could be converted into a  
sulpho-acid in just the same way that   
magenta can be converted into acid      
magenta4 ,under the name of acid yellow 
this sulpho-acid is now used1 not only  
as a direct yellow colouring-matter1 but
 as a starting-point in the manufacture 

of other azo-dyes4 ,the use of acid     
yellow for this last purpose will be    
dealt with again in the next chapter4   
,there is one other use for aniline     
yellow which dates from the year of its 
discovery1 when ,dale and ,caro found   
that by adding sodium nitrite to aniline
 hydrochloride and heating the mixture1 
a blue colouring-matter is produced4    
,the latter was introduced in #ahfd     
under the name of induline4 ,it was     
shown subsequently by the scientific    
researches of several chemists that the 
blue produced by ,dale and ,caro's      
method results from the action of the   
aniline salt on the aniline yellow1     
which is formed by the action of the    
nitrous acid on the aniline and aniline 
salt4 ,this explanation was proved to be
 correct in #ahgb by ,hofmann and       
,geyger1 who prepared the               
colouring-matter by heating aniline     
yellow and aniline salt with alcohol as 
a solvent4 ,these chemists established  
the composition and gave it the name of 

azodiphenyl blue4 ,later1 viz4 in #ahhc1
 the manufacture was improved by ,otto  
,witt and ,e4 ,thomas1 and the dye1     
under the old name of induline1 is now  
largely manufactured by first preparing 
aniline yellow and then heating this    
with aniline and aniline salt4 ,the     
colouring-matter as formed by this      
method is basic and insoluble in water2 
it is made acid and soluble by treatment
 with sulphuric acid1 which converts it 
into a sulpho-acid4 ,induline belongs to
 the sober-tinted colours1 and produces 
a shade somewhat resembling indigo4     
,closely related thereto is a           
bluish-grey called nigrosine1 obtained  
by heating nitrobenzene with aniline1 as
 well as a certain bluish by-product    
obtained during the formation of        
magenta1 and known as violaniline4  ,it 
will be convenient here to pause and    
reflect upon the great industrial       
importance of the two coal-tar          
hydrocarbons upon which we have thus far
 concentrated our attention4 ,their uses

 are by no means exhausted as yet1 but  
they have already been made to account  
for such a number of valuable products  
that the reader may find it useful to   
have the results presented in a         
collected form4 ,this is given below as 
a chronological summary--    #ahef4     
,mauve discovered by ,perkin2 leading to
 manufacture of aniline4    #ahfj4      
,arsenic acid process for magenta       
discovered2 leading to                  
manufacture of arsenic acid4    #ahfj4  
,aniline blue discovered2 leading in    
#ahfb to soluble and ,nicholson         
blues4    #ahfa4 ,methyl violet         
discovered2 manufactured in #ahff2      
leading to a new         use of copper  
salts as oxidizing agents1 and to the   
manufacture of         dimethylaniline4 
#ahfb4 ,hofmann violets discovered2     
leading to manufacture of methyl        
iodide from iodine1 phosphorus1 and wood
 spirit4    #ahfb4 ,phosphine           
7chrysaniline7 discovered in crude      
magenta4    #ahfc4 ,aniline black       

introduced2 leading to a new use for    
potassium         chlorate and copper   
salts1 and to the manufacture of aniline
 salt4    #ahfc4 ,aniline yellow        
introduced1 the first azo-colour4       
#ahfd4 ,induline discovered2 leading to 
new use for aniline yellow4    #ahff4   
,manchester brown introduced1 the second
 azo-colour2 leading to the             
manufacture of sodium nitrite1 and of   
dinitrobenzene4    #ahff4 ,iodine green 
introduced2 leading to further use for  
methyl iodide4    #ahff4 ,diphenylamine 
blue introduced2 leading to manufacture 
of         diphenylamine4    #ahfh4     
,blue shade of methyl violet introduced2
 leading to manufacture of              
benzyl chloride4    #ahfh4 ,saffranine  
introduced4    #ahfi4 ,nitrobenzene     
process for magenta discovered4         
#ahgf4 ,chrysoidine introduced1 the     
third azo-colour4    #ahgf4 ,methylene  
blue introduced2 leading to manufacture 
of         nitrosodimethylaniline4      
#ahgg4 ,acid magenta discovered4        

#ahgh4 ,methyl green introduced2 leading
 to utilization of waste from           
beet-sugar manufacture4    #ahgh4       
,malachite green discovered2 leading to 
manufacture of benzoic         aldehyde4
    #ahgh4 ,acid yellow discovered2     
leading to new use for aniline yellow4  
#ahgi4 ,neutral red and allied azines   
introduced2 leading to a new use for    
nitrosodimethylaniline4    #ahhc4       
,phosgene colours of rosaniline group   
introduced2 leading to                  
manufacture of phosgene4     ,,chapter  
,,iii4   ,among the most venerable of   
natural dye-stuffs is indigo1 the       
substance from which ,unverdorben first 
obtained aniline in #ahbf4 ,the         
colouring matter is found in a number of
 leguminous 7see ,fig4 #g71 cruciferous1
 and other plants1 some of which are    
largely cultivated in ,india1 ,china1   
the ,malay ,archipelago1 ,south         
,america1 and the ,west ,indies2 while  
others1 such as woad 7see ,fig4 #h71 are
 grown in more temperate ,european      

climates4 ,the tinctorial value of these
 plants was known in ,india and ,egypt  
long before the ,christian era4         
,egyptian mummy-cloths have been found  
dyed with indigo4 ,the dye was known to 
the ,greeks and ,romans2 its use is     
described by the younger ,pliny in his  
,natural ,history4 ,indigo was          
introduced into ,europe about the       
sixteenth century1 but its use was      
strongly opposed by the woad            
cultivators1 with whose industry the dye
 came into competition4 ,in ,france the 
opposition was strong enough to secure  
the passing of an act in the time of    
,henry ,,iv4 inflicting the penalty of  
death upon any person found using the   
dye4 ,the importance of indigo as an    
article of commerce is sufficiently     
known at the present time2 more than    
#hjjj tons are produced annually1       
corresponding in money value to about   
four million pounds4 ,it is of          
importance to us as rulers of ,india to 
remember that the cultivation and       

manufacture of indigo is one of the     
staple industries of that country1 from 
which the ,european markets derive the  
greater part of their supply4           
,illustration3 ,,fig4 #g4--;,,indigo    
,,plant 7,indigofera tinctoria74        
,imagine the industrial revolution which
 would be caused by the discovery of a  
process for obtaining indigo            
synthetically from a coal-tar           
hydrocarbon1 at a price which would     
compare favourably with that of the     
natural product4 ,this has not actually 
been done as yet1 but chemists have     
attempted to compete with ,nature in    
this direction1 and the present state of
 the competition is that the natural    
product can be cultivated and made more 
cheaply4 ,nevertheless the dye can be   
synthesised from a coal-tar hydrocarbon1
 and this is one of the greatest        
achievements of modern chemistry in     
connection with the tar-products4 ,for  
more than half a century indigo had been
 undergoing investigation by chemists1  

and at length the work culminated in the
 discovery of a method for producing it 
artificially4 ,this discovery was the   
outcome of the labour of ,adolf v4      
,baeyer1 who commenced his researches   
upon the derivatives of indigo in #ahff1
 and who in #ahhj secured the first     
patents for the manufacture of the      
colouring-matter4 ,it is to the         
laborious and brilliant investigations  
of this chemist that we owe nearly all  
that is at present known about the      
chemistry of indigo and allied          
compounds4   ,illustration3 ,,fig4      
#h4--,,woad 7,isatis tinctoria74   ,two 
methods have been used for the          
production of artificial indigo--benzal 
chloride being the starting-point in one
 of these1 and nitrobenzoic aldehyde in 
the other4 ,the generating hydrocarbon  
is therefore toluene4 ,by heating benzal
 chloride with dry sodium acetate there 
is formed an acid known as cinnamic     
acid1 a fragrant compound which derives 
its name from cinnamon1 because the acid

 was prepared by the oxidation of oil of
 cinnamon by ,dumas and ,peligot in     
#ahcd4 ,the acid and its ethers occur   
also in many balsams1 so that we have   
here another instance of the synthesis  
of a natural vegetable product from a   
coal-tar hydrocarbon4 ,the subsequent   
steps are--7#a7 the nitration of the    
acid to produce nitrocinnamic acid2 7#b7
 the addition of bromine to form a      
dibromide of the nitro-acid2 7#c7 the   
action of alkali on the dibromide to    
produce what is known as propiolic acid4
 ,the latter1 under the influence of    
mild alkaline reducing agents1 is       
transformed into indigo-blue4 ,the      
process depending on the use of         
nitrobenzoic aldehyde is much simpler2  
but the particular nitro-derivative of  
the aldehyde which is required is at    
present difficult to make1 and therefore
 expensive4 ,if the production of this  
compound could be cheapened1 the        
competition between artificial and      
natural indigo would assume a much more 

serious aspect4#e  ,the light oil of the
 tar-distiller has now been sufficiently
 dealt with so far as regards           
colouring-matters2 let us pass on to the
 next fraction of the tar1 the carbolic 
oil4 ,the important constituents of this
 portion are carbolic acid and          
naphthalene4 ,the carbolic oil is in the
 first place separated into two distinct
 portions by washing with an alkaline   
solution4 ,carbolic acid or phenol      
belongs to a class of compounds derived 
from hydrocarbons of the benzene and    
related series by the substitution of   
the residue of water for hydrogen4 ,this
 water-residue is known to chemists as  
hydroxyl--it is water less one atom of  
hydrogen4 ,carbolic acid or phenol is   
hydroxybenzene2 and all analogous       
compounds are spoken of as phenols4 ,it 
will be understood in future that a     
phenol is a hydroxy-derivative of a     
benzenoid hydrocarbon4 ,now these       
phenols are all more or less acid in    
character by virtue of the              

hydroxyl-group which they contain4 ,for 
this reason they dissolve in aqueous    
alkaline solutions1 and are precipitated
 therefrom by acids4 ,this will enable  
us to understand the purification of the
 carbolic oil4  ,the two layers into    
which this oil separates after washing  
with alkali are 7#a7 the aqueous        
alkaline solution of the carbolic acid  
and other phenols1 and 7#b7 the         
undissolved naphthalene contaminated    
with oily hydrocarbons and other        
impurities4 ,each of these portions has 
its industrial history4 ,the alkaline   
solution1 on being drawn off and made   
acid1 yields its mixture of phenols in  
the form of a dark oil from which       
carbolic acid is separated by a         
laborious series of fractional          
distillations4 ,the undissolved         
hydrocarbon is similarly purified by    
fractional distillation1 and furnishes  
the solid crystalline naphthalene4 ,the 
tar from one ton of ,lancashire coal    
yields about #a-a_/b lbs4 of carbolic   

acid1 equal to about #a per cent4 by    
weight of the tar1 and about #f-a_/dlbs4
 of naphthalene1 so that this last      
hydrocarbon is one of the chief         
constituents of the tar1 of which it    
forms from #h to #aj per cent4 by       
weight4  ,the crude carbolic acid as    
separated from the alkaline solution is 
a mixture of several phenolic compounds1
 and all of these but the carbolic acid 
itself are gradually removed during the 
process of purification4 ,among the     
compounds associated with the carbolic  
acid are certain phenols of higher      
boiling-point1 which bear the same      
relationship to carbolic acid that      
toluene bears to benzene4 ,that is to   
say1 that while phenol itself is        
hydroxybenzene1 these other compounds1  
which are called cresols1 are           
hydroxytoluenes4 ,the cresols form an   
oily liquid largely used for            
disinfecting purposes under the         
designation of liquid carbolic acid1 or 
cresylic acid4 ,carbolic acid is a white

 crystalline solid possessing strongly  
antiseptic properties1 and is therefore 
of immense value in all cases where     
putrefaction or decay has to be         
arrested4 ,it was discovered in coal-tar
 by ,runge in #ahcd1 and was obtained   
pure by ,laurent in #ahdj4  ,the gradual
 establishment of the germ-theory of    
disease1 chiefly due to the labours of  
,pasteur1 has led to a most important   
application of carbolic acid4 ,once     
again we find the coal-tar industry     
brought into contact with another       
department of science4 ,arguing from the
 view that putrefactive change is       
brought about by the presence of the    
germs of micro-organisms ever present in
 the atmosphere1 ,sir ,joseph ,lister   
proposed that during surgical operations
 the incised part should be kept under a
 spray of the germicidal carbolic acid  
to prevent subsequent mortification4 ,no
 operation upon portions of the body    
exposed to the air is at present        
conducted without this precaution1 and  

many a human life must have been saved  
by ,lister's treatment4 ,to this result 
the chemist and technologist have       
contributed1 not only by the discovery  
of the carbolic acid in the tar1 but    
also by the development of the necessary
 processes for its purification4 ,it    
should be added that the phenol used    
must be of the greatest possible purity1
 and the requirements of the surgeon    
have been met by chemical and           
technological skill4  ,from surgery back
 to colouring-matters1 and from these to
 pharmaceutical preparations and        
perfumes1 are we led in following up the
 cycles of chemical transformation which
 these tar-products have undergone in   
the hands of the technologist1 guided by
 the researches of the chemist4 ,it was 
observed by ,runge in #ahcd that crude  
carbolic acid1 on treatment with lime1  
gave a red1 acid colouring-matter which 
he separated and named rosolic acid4    
,the observation was followed up1 and   
many other chemists obtained red        

colouring-matters by the oxidation of   
crude phenol4 ,in #ahei1 the            
colour-giving property of carbolic acid 
acquired industrial importance from a   
discovery made by ,kolbe and ,schmitt in
 ,germany1 and by ,persoz in ,france4   
,these chemists found that a good yield 
of the colouring-matter was obtained by 
heating phenol with oxalic and sulphuric
 acids4 ,under the names of corallin and
 aurin the dye-stuff was introduced into
 commerce1 and it is still used for     
certain purposes1 especially for the    
preparation of coloured lakes for       
paper-staining4  ,the scientific        
development of the history of this      
phenol dye is full of interest1 but we  
can only give it a passing glance4 ,its 
interest lies chiefly in the            
circumstance that it is related to      
magenta1 as was first pointed out by    
,caro and ,wanklyn in #ahff4 ,in fact   
they obtained rosolic acid from magenta 
by the action of nitrous acid on the    
latter4 ,we now know that a diazo-salt  

is first formed under these             
circumstances1 and that the             
decomposition of this unstable compound 
in the presence of water gives rise to  
the rosolic acid4 ,later researches have
 shown that by heating rosolic acid with
 ammonia it is converted into           
rosaniline4 ,it is also known that the  
commercial corallin1 like the commercial
 magenta1 is a mixture of closely       
related colouring-matters4 ,the close   
analogy between magenta and rosolic acid
 was further shown by ,caro in #ahff4   
,in the same way that ,hofmann found    
that magenta could not be produced by   
the oxidation of pure aniline1 ,caro    
found that a mixture of phenol and      
cresol was necessary for the production 
of rosolic acid when inorganic oxidizers
 were used4 ,it is indeed this series of
 investigations upon the phenol         
dyes--investigations which have been    
taken part in not only by the chemists  
named1 but also by ,graebe1 ,dale and   
,schorlemmer1 and the ,fischers--which  

led up to the discovery of the          
constitution of the colouring-matters of
 the rosaniline group1 and1 through     
this1 to the far-reaching industrial    
developments of the discovery as traced 
in the last chapter4 ,it is evident1    
from what has been said1 that rosolic   
acid and its related colouring-matters  
are members of the triphenylmethane     
group4 ,they are in fact the hydroxylic 
or acid analogues of the                
amido-containing or basic dyes of the   
rosaniline series4  ,in the fragrant    
blossom of the meadowsweet 7,spiraea    
ulmaria7 there is contained an acid     
which is found also as an ether in the  
oil of wintergreen 7,gautheria          
procumbens74 ,this is salicylic acid1 a 
white crystalline compound which has    
been known to chemists since #ahci4 ,in 
#ahfj ,kolbe prepared the sodium salt of
 this acid by passing carbon dioxide gas
 into phenol in which metallic sodium   
had been dissolved4 ,it was found       
subsequently that the same              

transformation was brought about by     
heating the dry sodium salt of carbolic 
acid in an atmosphere of carbon dioxide4
 ,this process of ,kolbe's is now worked
 on a manufacturing scale for the       
preparation of artificial salicylic     
acid4 ,the acid and its salts and ethers
 find numerous applications as          
antiseptics1 for the preservation of    
food1 and in pharmacy4  ,salicylic acid 
is employed also for the manufacture of 
certain azo-dyes in a way that it will  
be very instructive to consider1 because
 the process used may be taken as       
typical of the general method of        
preparing such compounds4 ,solutions of 
diazo-salts act not only upon amido- and
 diamido-compounds1 as we have seen in  
the case of aniline yellow and          
chrysoidine1 but also upon phenols1     
forming acid azo-colours4 ,this         
important fact was made known in #ahgj  
by the ,german chemists ,kekule and     
,hidegh1 but more than six years elapsed
 before this discovery was taken        

advantage of by the technologist4 ,large
 numbers of these acid azo-dyes are now 
made from various diazotised            
amido-compounds combined with different 
phenols and phenolic acids4 ,the mode of
 procedure is to diazotise the          
amido-compound by sodium nitrite and    
hydrochloric acid in the manner already 
described1 and then add the diazo-salt  
solution to the phenolic compound       
dissolved in alkali4 ,the               
colouring-matter is at once formed4     
,salicylic acid possesses the characters
 both of an acid and a phenol4 ,it      
combines readily with diazo-salts under 
the circumstances described1 and gives  
rise to azo-dyes1 some of which are of  
technical value4  ,the manufacture of   
azo-dyes from salicylic acid brings us  
into contact with certain amidic        
compounds which figure so largely in the
 tinctorial industry that they may be   
conveniently dealt with here4 ,these    
bases are not azo-compounds themselves1 
but they are prepared from              

azo-compounds1 viz4 from the azobenzene 
and azotoluene which were spoken about  
in the last chapter4 ,when these are    
reduced by acid reducing-agents1 they   
become converted into diamido-bases     
which are known as benzidine and        
tolidine respectively4 ,these bases can 
be diazotised1 and as they contain two  
amido-groups1 they form double          
diazo-salts1 i4e4 tetrazo-salts1 which  
are capable of combining with           
amido-compounds1 or phenols1 in the     
usual way4 ,thus diazotised benzidine   
and tolidine combine with salicylic acid
 to form valuable yellow azo-dyes known 
as chrysamines4 ,the dyes of this class 
obviously contain two azo-groups4  ,some
 other uses of carbolic acid must next  
be considered4 ,of the colouring-matters
 derived from coal-tar1 none is more    
widely known than the oldest artificial 
yellow dye1 picric acid4 ,this is a     
phenol derivative1 and was first        
obtained as long ago as #agga by        
,woulfe1 by acting upon indigo with     

nitric acid4 ,laurent in #ahdb was the  
first to obtain this dye from carbolic  
acid1 from which compound it is still   
manufactured by acting upon the         
sulpho-acid with nitric acid4           
,chemically considered1 it is           
trinitrophenol4 ,it has a very wide     
application as a dye1 and has been used 
as an explosive agent4 ,a similar       
colouring-matter was made from cresol in
 #ahfi1 and introduced under the name of
 ,victoria yellow1 which is             
dinitro-cresol4 ,other dyes derived     
directly or indirectly from phenol will 
take us back once again to toluene4  ,a 
new diazotisable diamido-compound was   
obtained from this last hydrocarbon1 and
 introduced in #ahhf by ,leonhardt  ,co4
 ,one of the three isomeric             
nitrotoluenes furnishes a sulpho-acid   
which1 on treatment with alkali1 gives a
 compound derived from a hydrocarbon    
known as stilbene1 and this1 on         
reduction1 is converted into the        
diamido-compound referred to4 ,the      

latter1 which is a disulpho-acid as well
 as a diamido-compound1 can be          
diazotised and combined with phenols1 c4
 ,the stilbene azo-dyes thus prepared   
from phenol and salicylic acid1 like the
 chrysamines1 are yellow                
colouring-matters1 containing two       
azo-groups4 ,it is a valuable           
characteristic of these secondary       
azo-dyes that they all possess a special
 affinity for vegetable fibre1 and their
 introduction has exerted a great       
influence upon the art of cotton-dyeing4
 ,we shall have to return to these      
cotton-dyes again shortly4  ,before     
leaving this branch of the subject1 the 
following scheme is presented to show   
the relationships and                   
inter-relationships of the products thus
 far dealt with in the present chapter--
                                        
,tar                                    
----------------------------------------
-----------------                       
,light ,oil                             

,carbolic ,oil       _/                 
_/- ,benzal ,chloride                   
_/                  _/                  
_/                  _/                  
,benzaldehyde          _/               
_/       ,cinnamic acid                 
,benzene       ,toluene                 
,nitrobenzaldehyde                      
,nitrocinnamic acid    7 acetone7       
_/                                      
_/    -----------   ,nitrobenzene       
,nitrotoluene   ,propiolic acid  _/     
_/    ,phenols   ,naphthalene           
_/                                      
_/                                      
_/              -,cresols   ,azobenzene 
,azotoluene      ,indigo--_/            
,phenol                                 
,stilbene-                              
,victoria                               
derivative   -------------------        
yellow                                  
7,diazotised7                           
,benzidine    ,tolidine                 
,salicylic  ,picric   ,corallin         

_/                       acid      acid 
,aurin       7,diazotised7              
_/                                      
--------------------------------  ,the  
existence of naphthalene in coal-tar was
 made known in #ahbj by ,garden1 who    
gave it this name because the oils      
obtained from the tar by distillation   
went under the general designation of   
naphtha4 ,the greater portion of the    
hydrocarbon is contained in the carbolic
 oil1 and is separated and purified in  
the manner described4 ,a further        
quantity of impure naphthalene separates
 out from the next fraction--the        
creosote oil1 and this is similarly     
washed and purified by distillation4    
,the large quantity of naphthalene      
existing in tar has already been        
referred to1 but although it is such an 
important constituent1 it was only late 
in the history of the colour industry   
that it found any extensive application4
 ,in early times it was regarded as a   
nuisance1 and was burnt as fuel1 or for 

the production of a dense soot1 which   
was condensed to form lampblack4 ,it    
will be remembered that the first of the
 coal-tar colours made required only the
 light oils4 ,there are at present only 
a few direct uses for naphthalene1 but  
one of its applications is sufficiently 
important to be mentioned4  ,the        
hydrocarbon is a white crystalline solid
 melting at #hj deg4 ,c41 and boiling at
 #bag deg4 ,c4 ,although it has a high  
boiling-point1 it passes readily into   
vapour at lower temperatures1 and the   
vapour on condensation forms beautiful  
silvery crystalline scales4 ,this       
product is sublimed naphthalene4 ,the   
vapour of naphthalene burns with a      
highly luminous flame1 and if mixed with
 coal-gas1 it considerably increases the
 luminosity of the flame4 ,advantage is 
taken-of this in the so-called          
albo-carbon light1 which is the flame of
 burning coal-gas saturated with        
naphthalene vapour4 ,the burner is      
constructed so that the gas passes      

through a reservoir filled with melted  
naphthalene kept hot by the flame itself
 7,fig4 #i74   ,illustration3 ,,fig4    
#i4--;,,albo-,,carbon ,,burner4   ,to   
appreciate properly the value of those  
discoveries which have enabled          
manufacturers to utilize this           
hydrocarbon1 it is only necessary to    
recall to mind the actual quantity      
produced in this country4 ,supposing    
that ten million tons of coal are used  
annually for gas-making1 and that the   
#ejj1jjj tons of tar resulting therefrom
 contain only eight per cent4 of        
naphthalene1 there would be available   
about #dj1jjj tons of this hydrocarbon  
annually4 ,great as have been the recent
 advancements in the utilization of     
naphthalene derivatives1 there is still 
a larger quantity of this hydrocarbon   
produced than is necessary to supply the
 wants of the colour-manufacturer4 ,from
 this last statement it will be inferred
 that naphthalene is now a source of    
colouring-matters4 ,let us consider how 

this has been brought about4  ,the      
phenols of naphthalene are called       
naphthols--they bear the same           
relationship to naphthalene that        
carbolic acid bears to benzene4 ,owing  
to the structure of the naphthalene     
molecule there are two isomeric         
naphthols1 whereas there is only one    
phenol4 ,the naphthols--known as alpha- 
and beta-naphthol1 respectively--are now
 made on a large scale from naphthalene1
 by heating the latter with sulphuric   
acid2 at a low temperature the alpha    
sulpho-acid is produced1 and at a higher
 temperature the beta sulpho-acid1 and  
these acids on fusion with caustic soda 
furnish the corresponding naphthols4    
,similarly there are two                
amidonaphthalenes1 known as alpha- and  
beta-naphthylamine respectively4 ,as    
aniline is to benzene1 so are the       
naphthylamines to naphthalene4 ,the     
alpha-compound is made in precisely the 
same way as aniline1 viz4 by acting upon
 naphthalene with nitric acid so as to  

form nitronaphthalene1 and then reducing
 the latter with iron dust and acid4    
,beta-napthylamine cannot be made in    
this way2 it is prepared from           
beta-naphthol by heating the latter in  
presence of ammonia1 when the hydroxyl  
becomes replaced by the amido-group in  
accordance with a process patented in   
#ahhj by the ,baden ,aniline ,company4  
,the principle thus utilized is the     
outcome of the scientific work of two   
,austrian chemists1 ,merz and ,weith4   
,setting out from the naphthols and     
naphthylamines we shall be led into     
industrial developments of the greatest 
importance4  ,the first naphthalene     
colour was a yellow dye1 discovered by  
,martius in #ahfd1 and manufactured     
under the name of ,manchester yellow4   
,it is1 chemically speaking1            
dinitro-alpha-naphthol2 but it was not  
at first made from naphthol1 as the     
latter was not at the time a technical  
product4 ,it was made from              
alpha-naphthylamine by the action of    

nitrous and nitric acids4 ,when a good  
method for making the naphthol was      
discovered in #ahfi1 the dye was made   
from this4 ,the process is just the same
 as that employed in making picric acid2
 the naphthol is converted into a       
sulpho-acid1 and this when acted upon by
 nitric acid1 gives the                 
colouring-matter4 ,manchester yellow is 
now largely used for colouring soap1 but
 as a dye-stuff it has been improved    
upon in a manner that will be readily   
understood4 ,the original               
colouring-matter being somewhat         
fugitive1 it was found that its         
sulpho-acid was much faster4 ,this      
sulpho-acid cannot be made by the direct
 action of sulphuric acid upon the      
colouring-matter--as in the case of acid
 yellow or acid magenta--but by acting  
upon the naphthol with very strong      
sulphuric acid1 three sulphuric acid    
residues or sulpho-groups enter the     
molecule1 and then on nitration only two
 of these are replaced by nitro-groups1 

and there results a sulpho-acid of      
dinitro-alpha-naphthol4 ,this was       
discovered in #ahgi by ,caro1 and       
introduced as acid naphthol yellow4 ,it 
is now one of the standard yellow dyes4 
,the history of another important group 
of colouring-matters dependent on       
naphthalene begins with ,a4 v4 ,baeyer  
in #ahga and with ,caro in #ahgd4 ,two  
products formerly known only as         
laboratory preparations were called into
 requisition by this discovery4 ,one of 
these compounds1 phthalic acid1 is      
obtained from naphthalene1 and the      
other1 resorcin or resorcinol1 is       
prepared from benzene4 ,phthalic acid1  
which was discovered in #ahcf by        
,laurent1 is a product of the oxidation 
of many benzenoid compounds4 ,chemically
 considered it is a di-derivative of    
benzene1 i4e4 two of the hydrogen atoms 
of benzene are replaced by certain      
groups of carbon1 oxygen1 and hydrogen  
atoms4 ,we have seen how the replacement
 of hydrogen by an ammonia-residue1     

amidogen1 gives rise to bases such as   
amidobenzene 7aniline71 or              
diamidobenzene4 ,similarly1 the         
replacement of hydrogen by a            
water-residue1 hydroxyl1 gives rise to a
 phenol4 ,the group of carbon1 oxygen1  
and hydrogen atoms which confers the    
property of acidity upon an organic     
compound is a half-molecule of oxalic   
acid--it is known as the carboxyl group4
 ,thus benzoic acid is the              
carboxyl-derivative of benzene1 and the 
phthalic acid with which we are now     
concerned is a dicarboxyl-derivative of 
benzene4 ,it is related to benzoic acid 
in the same way that diamidobenzene is  
related to aniline4 ,three isomeric     
phthalic acids are known1 but only one  
of these is of use in the present branch
 of manufacture4 ,the acid in question1 
although a derivative of benzene1 is    
most economically prepared by the       
oxidation of certain derivatives of     
naphthalene which1 when completely      
broken down by energetic oxidizing      

agents1 furnish the acid4 ,thus the     
dinitronaphthol described as ,manchester
 yellow1 if heated for some time with   
dilute nitric acid1 furnishes phthalic  
acid4 ,the latter is made on a large    
scale by the oxidation of a compound    
which naphthalene forms with chlorine1  
and known as naphthalene tetrachloride1 
because it contains four atoms of       
chlorine4  ,the other compound1         
resorcinol1 was known to chemistry ten  
years before it was utilized as a source
 of colouring-matters4 ,it was          
originally prepared by fusing certain   
resins1 such as galbanum1 asafoetida1   
c41 with caustic alkali4 ,soon after its
 discovery1 viz4 in #ahff1 it was shown 
by ,koerner to be a derivative of       
benzene1 and from this hint the         
technical process for the preparation of
 the compound on a large scale has been 
developed4 ,resorcinol is a phenolic    
derivative of benzene containing two    
hydroxyl groups2 it is therefore related
 to phenol in the same way that         

diamidobenzene is related to aniline or 
phthalic acid to benzoic acid4 ,the     
relationships can be expressed in a     
tabular form thus--    ,amidobenzene or 
,aniline4    ,benzoic acid4    ,carbolic
 acid or ,phenol4   ,diamidobenzene4    
,phthalic acid4   ,resorcinol4          
,resorcinol is now made by heating      
benzene with very strong sulphuric acid 
so as to convert it into a              
disulpho-acid1 and the sodium salt of   
the latter is then fused with alkali4   
,as a technical operation it is one of  
great delicacy and skill1 and the       
manufacture is confined to a few        
,continental factories4  ,when phthalic 
acid is heated it loses water1 and is   
transformed into a white1 magnificently 
crystalline substance known as phthalic 
anhydride1 i4e4 the acid deprived of    
water4 ,in #ahga1 ,a4 v4 ,baeyer1 the   
eminent chemist who subsequently        
synthesised indigo1 published the first 
of a series of investigations describing
 the compounds produced by heating      

phthalic anhydride with phenols4 ,to    
these compounds he gave the name of     
phthaleins4 ,baeyer's work1 like that of
 so many other chemists who have        
contributed to the advancement of the   
coal-tar colour industry1 was of a      
purely scientific character at first1   
but it soon led to technological        
developments4 ,the phthaleins are all   
acid compounds possessing more or less  
tinctorial power4 ,one of the first     
discovered was produced by heating      
phthalic anhydride with an acid known as
 gallic acid1 which occurs in vegetable 
galls1 and in the form of tannin in many
 vegetable extracts which are used by   
the tanner4 ,the acid is a phenolic     
derivative of benzoic acid1 viz4        
trihydroxybenzoic acid1 and on heating  
it readily passes into                  
trihydroxybenzene1 which is the         
pyrogallic acid or pyrogallol familiar  
as a photographic developer4 ,the       
phthalein formed from gallic acid and   
phthalic anhydride really results from  

the union of the latter with pyrogallol4
 ,it is now manufactured under the name 
of gallein1 and is largely used for     
imparting a bluish grey shade to cotton 
fabrics4 ,by heating gallein with strong
 sulphuric acid1 it is transformed into 
another colouring-matter which gives    
remarkably fast olive-green shades when 
dyed on cotton fibre with a suitable    
mordant4 ,this derivative of gallein is 
used to a considerable extent under the 
name of coerulein4 ,these two           
colouring-matters were the first        
practical outcome of v4 ,baeyer's       
researches4 ,there is another possible  
development in this direction which     
chemistry may yet accomplish1 and       
another natural colouring-matter may be 
threatened1 even as the indigo culture  
was threatened by the later work of the 
same chemist4 ,there is reason for      
believing that the colouring-matter of  
logwood1 known to chemists as haematein1
 is related to or derived in some way   
from the phthaleins1 and the synthesis  

of this compound may ultimately be      
effected4  ,the dye introduced by ,caro 
in #ahgd is the brominated phthalein of 
resorcinol4 ,the phthalein itself is a  
yellow dye1 and the solutions of its    
salts show a splendid and most intense  
greenish yellow fluorescence1 for which 
reason it is called fluorescein4 ,when  
brominated1 the latter furnishes a      
beautiful red colouring-matter known as 
eosin 7,gr4 ,greek3 eos1 dawn71 and the 
introduction of this gave an industrial 
impetus to the phthaleins which led to  
the discovery of many other related     
colouring-matters now largely used under
 various trade designations4 ,about a   
dozen distinct compounds producing      
different shades of pink1 crimson and   
red1 and all derived from fluorescein1  
are at present in the market1 and a few 
other phthaleins formed by heating      
phthalic anhydride with other phenolic  
compounds instead of resorcinol or      
pyrogallol 7e4g4 diethylamidophenol71   
are also of industrial importance4 ,by  

converting nitrobenzene into a          
sulpho-acid1 reducing to an             
amido-sulpho-acid1 and then fusing with 
alkali1 an amido-phenol is produced1 the
 ethers of which1 when heated with      
phthalic anhydride1 give rise to red    
phthaleins of most intense colouring    
power introduced by the ,baden ,aniline 
,company as rhodamines4  ,it remains to 
point out that the scientific spirit    
which prompted the investigation of the 
phthaleins in the first instance has    
followed these compounds throughout     
their technological career4 ,the        
researches started by v4 ,baeyer were   
taken up by various chemists1 whose work
 together with that of the original     
discoverer has led to the elucidation of
 the constitution of these              
colouring-matters4 ,the phthaleins are  
members of the triphenylmethane group1  
and are therefore related to magenta1   
corallin1 malachite green1 methyl       
violet1 and the phosgene dyes4  ,it has 
been said that the phenolic and amidic  

derivatives of naphthalene1 i4e4 the    
naphthols and naphthylamines1 are of the
 greatest importance to the colour      
industry4 ,one of the first uses of     
alpha-naphthylamine has already been    
mentioned1 viz4 for the production of   
the ,manchester yellow1 which was       
afterwards made more advantageously from
 alpha-naphthol4 ,a red colouring-matter
 possessing a beautiful fluorescence was
 afterwards 7#ahfi7 made from this      
naphthylamine and introduced as ,magdala
 red4 ,the latter was discovered by     
,schiendl of ,vienna in #ahfg4 ,it was  
prepared in precisely the same way as   
induline was prepared from aniline      
yellow4 ,the latter1 which is           
amido-azobenzene1 and which is prepared1
 broadly speaking1 by the action of     
nitrous acid on aniline1 has its        
analogue in amido-azonaphthalene1 which 
is similarly prepared by the action of  
nitrous acid on naphthylamine4 ,just as 
aniline yellow when heated with aniline 
and an aniline salt gives induline1 so  

amido-azonaphthalene when heated with   
naphthylamine and a salt of this base   
gives ,magdala red4 ,the latter is1     
therefore1 a naphthalene analogue of    
induline1 as was shown by ,hofmann in   
#ahfi1 and the knowledge of the         
constitution of the azines which has    
been gained of late years1 enables us to
 relegate the colouring-matter to this  
group4 ,this knowledge has also enabled 
the manufacture to be conducted on more 
rational principles1 viz4 by the method 
employed for the production of the      
saffranines1 as previously sketched4    
,the introduction of azo-dyes1 formed by
 the action of a diazotised             
amido-compound on a phenol or another   
amido-compound1 marks the period from   
which the naphthols and naphthylamines  
rose to the first rank of importance as 
raw materials for the colour            
manufacturer4 ,the introduction of      
chrysoidine in #ahgf was immediately    
followed by the manufacture of acid     
azo-dyes obtained by combining          

diazotised amido-sulpho-acids with      
phenols of various kinds1 or with bases1
 such as dimethylaniline and            
diphenylamine4 ,from what has been said 
in the foregoing portion of this volume1
 it is evident that all such            
azo-compounds result from the           
combination of two things1 viz4 7#a7 a  
diazotised amido-compound1 and 7#b7 a   
phenolic or amidic compound4 ,either    
7#a7 or 7#b7 or both may be a           
sulpho-acid1 and the resulting dye will 
then also be a sulpho-acid4  ,the first 
of these colouring-matters derived from 
the naphthols1 was introduced in        
#ahgf-gg by ,roussin and ,poirrier1 and 
by ,o4 ,n4 ,witt4 ,they were prepared by
 converting aniline into a sulpho-acid  
7sulphanilic acid71 diazotising this and
 combining the diazo-compound with      
alpha- or beta-naphthol4 ,the compounds 
formed are brilliant orange dyes1 the   
latter being still largely consumed as  
naphthol orange4 ,other dye-stuffs of a 
similar nature were introduced by ,caro 

about the same time1 and were prepared  
from the diazotised sulpho-acid of      
alpha-naphthylamine combined with the   
naphthols4 ,by this means alpha-naphthol
 gives what is known as acid brown1 or  
fast brown1 and beta-naphthol a fine    
crimson1 known as fast red1 or          
roccellin4 ,diazotised compounds combine
 also with this same sulpho-acid of     
alpha-naphthylamine 7known as           
naphthionic acid71 the first            
colouring-matter formed in this way     
having been introduced by ,roussin and  
,poirrier in #ahgh4 ,it was prepared by 
diazotising a nitro-derivative of       
aniline1 and acting with the diazo-salt 
on napthionic acid1 and this dye is     
still used to some extent under the name
 of archil substitute4 ,in #ahgh1 the   
firm of ,meister1 ,lucius  ,bruening of 
,hoechst-on-the-,main gave a further    
impetus to the utilization of           
naphthalene by discovering two isomeric 
disulpho-acids of beta-naphthol formed  
by heating that phenol with sulphuric   

acid4 ,by combining various diazotised  
bases with these sulpho-acids1 a        
splendid series of acid azo-dyes ranging
 in shade from bright orange to         
claret-red1 and to scarlets rivalling   
cochineal in brilliancy were given to   
the tinctorial industry4  ,the          
colouring-matters introduced in #ahgh by
 the ,hoechst factory under the names of
 ,ponceaux of various brands1 and       
,bordeaux1 although to some extent      
superseded by later discoveries1 still  
occupy an important position4 ,their    
discovery not only increased the        
consumption of beta-naphthol1 but also  
that of the bases which were used for   
diazotising4 ,these bases are           
alpha-naphthylamine and those of the    
aniline series4 ,the intimate           
relationship which exists between       
chemical science and technology--a      
relationship which appears so constantly
 in the foregoing portions of this      
work--is well brought out by the        
discovery under consideration4 ,a little

 more chemistry will enable this        
statement to be appreciated4  ,going    
back for a moment to the hydrocarbons   
obtained from light oil1 it will be     
remembered that benzene and toluene have
 thus far been considered as the only   
ones of importance to the colour-maker4 
,until the discovery embodied in the    
patent specification of #ahgh1 the      
portions of the light oil boiling above 
toluene were of no value in the colour  
industry4 ,benzene and toluene are      
related to each other in a way which    
chemists describe by saying that they   
are homologous4 ,this means that they   
are members of a regularly graduated    
series1 the successive terms of which   
differ by the same number of atoms of   
carbon and hydrogen4 ,thus toluene      
contains one atom of carbon and two     
atoms of hydrogen more than benzene4    
,above toluene are higher homologues1   
viz4 xylene1 cumene1 c41 which occur in 
the light oil1 the former being related 
to toluene in the same way that toluene 

is related to benzene1 while cumene     
again contains one atom of carbon and   
two atoms of hydrogen more than xylene4 
,this relationship between the members  
of homologous series is expressed in    
other terms by saying that the weight of
 the molecule increases by a constant   
quantity as we ascend the series4  ,the 
homology existing among the hydrocarbons
 extends to all their derivatives4 ,thus
 phenol is the lower homologue of the   
cresols4 ,also we have the homologous   
series--    ,benzene4                   
,nitrobenzene4      ,aniline4           
,toluene4      ,nitrotoluene4           
,toluidine4   ,xylene4                  
,nitroxylene4       ,xylidine4          
,cumene4       ,nitrocumene4            
,cumidine4  ,the bases of the third     
column when diazotised and combined with
 the disulpho-acids of beta-naphthol    
give a graduated series of dyes         
beginning with orange and ending with   
bluish scarlet4 ,thus it was observed   
that the toluidine colour was redder    

than the aniline colour1 and it was a   
natural inference that the xylidine     
colour would be still redder4 ,at the   
time of this discovery no azo-colour of 
a true scarlet shade had been           
manufactured successfully4 ,a demand for
 the higher homologues of benzene was   
thus created1 and the higher            
boiling-point fractions of the light    
oil1 which had been formerly used as    
solvent naphtha1 became of value as     
sources of colouring-matters4 ,the      
isolation of coal-tar xylene 7which is a
 mixture of three isomeric hydrocarbons7
 is easily effected by fractional       
distillation with a rectifying column1  
and by nitration and reduction1 in the  
same way as in the manufacture of       
aniline1 xylidine is placed at the      
disposal of the colour-maker4  ,xylidine
 scarlet1 although at the time of its   
introduction the only true azo-scarlet  
likely to come into competition with    
cochineal1 was still somewhat on the    
orange side4 ,the cumidine dye would    

obviously be nearer the desired shade4  
,to meet this want1 cumidine had to be  
made on a large scale1 but here         
practical difficulties interposed       
themselves4 ,the quantity of cumene in  
the light oil is but small1 and it is   
associated with other hydrocarbons which
 are impurities from the present point  
of view1 and from which it is separated 
only with difficulty4 ,a new source of  
the base had therefore to be sought1 and
 here again we find chemical science    
ministering to the wants of the         
technologist4  ,it was explained in the 
last chapter that aniline and similar   
bases can be methylated by heating their
 dry salts with methyl alcohol under    
pressure4 ,in this way dimethylaniline  
is made1 and dimethyltoluidine or       
dimethylxylidine can similarly be       
prepared4 ,now it was shown by ,hofmann 
in #ahga1 that if this operation is     
conducted at a very high temperature1   
and under very great pressure1 the      
methyl-alcohol residue1 i4e4 the        

methyl-group1 does not replace the      
amidic hydrogen or the hydrogen of the  
ammonia residue1 but the methylation    
takes place in another way1 resulting in
 the formation of a higher homologue of 
the base started with4 ,for example1 by 
heating aniline salt and pure           
wood-spirit to a temperature            
considerably above that necessary for   
producing dimethylaniline1 toluidine is 
formed4 ,in a similar way1 by heating   
xylidine hydrochloride and methyl       
alcohol for some time in a closed vessel
 at about #cjj deg4 ,c4 cumidine is     
produced4 ,hofmann's discovery was thus 
utilized in #ahhb1 and by its means the 
base was manufactured1 and cumidine     
scarlet1 very similar in shade to       
cochineal1 became an article of         
commerce4  ,while the development of    
this branch of the colour industry was  
taking place by means of the new        
naphthol disulpho-acids1 the cultivation
 of the fertile field of the azo-dyes   
was being carried on in other           

directions4 ,it came to be realized that
 the fundamental discovery of ,griess   
was capable of being extended to all    
kinds of amido-compounds4 ,the azo-dyes 
hitherto introduced had all been derived
 from amido-compounds containing only   
one amido-group1 and they accordingly   
contained only one azo-group2 they were 
primary azo-compounds4 ,it was soon     
found that aniline yellow1 which already
 contains one azo-group as well as an   
amido-group1 could be again diazotised  
and combined with phenols so as to      
produce compounds containing two        
azo-groups1 i4e4 secondary              
azo-compounds4 ,the sulpho-acid of      
aniline yellow--,graessler's acid       
yellow--was the first source of azo-dyes
 of this class4 ,by diazotising this    
amidoazo-sulpho-acid1 and combining it  
with beta-naphthol1 a fine scarlet dye  
was discovered by ,nietzki in #ahgi1 and
 introduced under the name of ,biebrich 
scarlet4 ,two years later a new         
sulpho-acid of beta-naphthol was        

discovered by ,bayer  ,co4 of           
,elberfeld1 and this gave rise1 when    
combined with diazotised acid yellow and
 analogous compounds1 to another series 
of brilliant dyes introduced as ,crocein
 scarlets4  ,from these beginnings the  
development of the azo-dyes has been    
steadily carried on to the present      
time--year by year new diazotisable     
amido-compounds or new sulpho-acids of  
the naphthols and naphthylamines are    
being discovered1 and this branch of the
 colour industry has already assumed    
colossal dimensions4 ,an important      
departure was made in #ahhd by          
,boettiger1 who introduced the first    
secondary azo-colours derived from      
benzidine4 ,as already explained in     
connection with salicylic acid1 this    
base and its homologue tolidine form    
tetrazo-salts1 which combine with       
phenols and amines or their             
sulpho-acids4 ,one of the first         
colouring-matters of this group was     
obtained by combining diazotised        

benzidine with the sulpho-acid of       
alpha-naphthylamine 7naphthionic acid71 
and was introduced under the name of    
,congo red4 ,then came the discovery    
7,pfaff1 #ahhe71 that the tetrazo-salts 
of benzidine and tolidine combine with  
phenols1 amines1 c41 in two stages1 one 
of the diazo-groups first combining with
 one-half of the whole quantity of      
phenol to form an intermediate compound1
 which then combines with the other half
 of the phenol to form the secondary    
azo-dye4 ,in the hands of the           
,actiengesellschaft fuer                
,anilinfabrikation of ,berlin this      
discovery has been utilized for the     
production of a number of such          
azo-colours containing two distinct     
phenols1 or amines1 or sulpho-acids4    
,tolidine has been found to give better 
colouring-matters in most cases than    
benzidine1 and it is scarcely necessary 
to point out that an increased demand   
for the nitrotoluene from which this    
base is made is the necessary           

consequence of this discovery4  ,it is  
impossible to attempt to specify by name
 any of these recent benzidine and      
tolidine dyes4 ,their introduction has  
been the means of finding new uses for  
the naphthylamines and naphthols and    
their sulpho-acids1 and has thus        
contributed largely to the utilization  
of naphthalene4 ,an impetus has been    
given to the investigation of these     
sulpho-acids1 and chemical science has  
profited largely thereby4 ,the process  
by which beta-naphthylamine is prepared 
from beta-naphthol1 already referred to1
 viz4 by heating with ammonia under     
pressure1 has been extended to the      
sulpho-acids of beta-naphthol1 and by   
this means new beta-naphthylamine       
sulpho-acids have been prepared1 and    
figure largely in the production of     
these secondary azo-colours4 ,the       
latter1 as previously stated1 possess   
the most valuable property of dyeing    
cotton fibre directly1 and by their     
means the art of cotton dyeing has been 

greatly simplified4 ,the shades given by
 these colours vary from yellow through 
orange to bright scarlet1 violet1 or    
purple4  ,in addition to benzidine and  
tolidine1 other diazotisable            
amido-compounds have of late years been 
pressed into the service of the         
colour-manufacturer4 ,the derivative of 
stilbene1 already mentioned as being    
prepared from a sulpho-acid of one of   
the nitrotoluenes1 forms tetrazo-salts1 
which can be combined with similar or   
dissimilar phenols1 amines1 or          
sulpho-acids1 as in the case of         
benzidine and tolidine4 ,various shades 
of red and purple are thus obtained from
 the diazotised compound1 when the      
latter is combined with the             
naphthylamines1 naphthols1 or their     
sulpho-acids4 ,these1 again1 are all    
cotton dyes4 ,the nitro-derivatives of  
the ethers of phenol and cresol1 when   
reduced in the same way that            
nitrobenzene and nitrotoluene are       
reduced to azobenzene and azotoluene1   

also furnish azo-compounds which1 on    
further reduction1 give bases analogous 
to benzidine and tolidine4 ,secondary   
azo-colours derived from these bases and
 the usual naphthalene derivatives are  
also manufactured4 ,it is among the     
secondary azo-dyes that we meet with the
 first direct dyeing blacks1 the        
importance of which will be realized    
when it is remembered that the ordinary 
aniline-black is not adapted for wool   
dyeing4 ,the azo-blacks are obtained by 
combining diazotised sulpho-acids of    
amidoazo-compounds of the benzene or    
naphthalene series with naphthol        
sulpho-acids or other naphthalene       
derivatives4  ,one other series of      
azo-compounds must be briefly referred  
to4 ,it has long been known that aniline
 and toluidine when heated with sulphur 
evolve sulphuretted hydrogen and give   
rise to thio-bases1 that is1 aniline or 
toluidine in which the hydrogen is      
partly replaced by sulphur4 ,one of the 
toluidines treated in this way is       

transformed into a thiotoluidine which1 
when diazotised and combined with one of
 the disulpho-acids of beta-naphthol1   
forms a red azo-dye1 introduced by ,dahl
  ,co4 in #ahhe as thiorubin4 ,by       
modifying the conditions of reaction    
between the sulphur and the base1 it was
 found in #ahhg by ,arthur ,green1 that 
a complicated thio-derivative of        
toluidine could be produced which       
possessed very remarkable properties4   
,the sulpho-acid of the thio-base is a  
yellow dye1 which was named by its      
discoverer primuline4 ,not only is      
primuline a dye1 but it contains an     
amido-group which can be diazotised4 ,if
 therefore the fabric dyed with         
primuline is passed through a nitrite   
bath1 a diazo-salt is formed in the     
fibre1 and on immersing the latter in a 
second bath containing naphthol or other
 phenol or an amine1 an azo-dye is      
precipitated in the fibre4 ,by this     
means there are produced valuable       
ingrain colours of various shades of    

red1 orange1 purple1 c4  ,so much for   
the azo-dyes1 one of the most prolific  
fields of industrial enterprise         
connected with coal-tar technology4     
,from the introduction of aniline yellow
 in #ahfc to the present time1 about    
#aej distinct compounds of this group   
have been given to the tinctorial       
industry4 ,of these over thirty are     
cotton dyes containing two azo-groups4  
,sombre shades1 rivalling logwood black1
 bright yellows1 orange-reds1 browns1   
violets1 and brilliant scarlets         
equalling cochineal1 have been evolved  
from the refuse of the gas-works4 ,the  
artificial colouring-matters have in    
this last case once again threatened a  
natural product1 and with greater       
success than the indigo synthesis1 for  
the introduction of the azo-scarlets has
 caused a marked decline in the         
cochineal culture4  ,in addition to the 
azo-colours1 there are certain other    
products which claim naphthalene as a   
raw material4 ,in #ahgi it was found    

that one of the sulpho-acids of         
beta-naphthol when treated with nitrous 
acid readily gave a nitroso-sulpho-acid4
 ,a salt of this last acid1 containing  
sodium and iron as metallic bases1 was  
introduced in #ahhd1 under the name of  
naphthol green4 ,it is used both as a   
dye for wool and as a pigment4 ,it may  
be mentioned here that other            
nitroso-derivatives of phenols1 such as 
those of resorcinol and the naphthols1  
under the name of gambines1 are largely 
used for dyeing purposes1 owing to the  
facility with which they combine with   
metallic mordants to form coloured salts
 in the fibre4 ,in this same year1      
#ahgi1 it was found that by heating     
nitrosodimethylaniline with             
beta-naphthol in an appropriate solvent1
 a violet colouring-matter was formed4  
,this is now manufactured under the name
 of new blue1 or other designations1 and
 is largely used for producing an       
indigo-blue shade on cotton prepared    
with a suitable mordant4 ,the discovery 

of this colouring-matter gave an impetus
 to further discoveries in the same     
direction4 ,it was found that           
nitrosodimethylaniline reacted in a     
similar way with other phenolic or with 
amidic compounds4 ,in #ahha ,koechlin   
introduced an analogous dye-stuff       
prepared by the action of the same      
nitroso-compound on gallic acid4        
,gallocyanin1 as it is called1 imparts a
 violet blue shade to mordanted cotton4 
,other colouring-matters of the same    
group are in use2 some of them1 like new
 blue1 being derivatives of naphthalene4
 ,these compounds all belong to a series
 of which the parent substance is       
constructed on a type similar to azine2 
it contains a nitrogen and oxygen atom  
linking together the hydrocarbon        
residues1 and is therefore known as     
oxazine4 ,the researches of ,nietzki in 
#ahhh first established the true        
constitution of the oxazines4  ,closely 
related to this group is a              
colouring-matter introduced by ,koechlin

 and ,witt in #ahha under the name of   
indophenol4 ,it is prepared in the same 
way as the azines of the neutral red    
group2 viz4 by the action of            
nitrosodimethylaniline on               
alpha-naphthol1 or by oxidizing         
amidodimethylaniline in the presence of 
alpha-naphthol4 ,indophenol belongs to  
that group of blue compounds formed as  
intermediate products in the manufacture
 of azines1 as mentioned in connection  
with neutral red4 ,but while these      
intermediate blues resulting from the   
oxidation of a diamine in the presence  
of another amine are unstable1 and pass 
readily into red azines1 indophenol is  
stable1 and can be used for dyeing and  
printing in the same way as indigo4 ,the
 shades which it produces are very      
similar to this last dye1 but for       
certain practical reasons it has not    
been able to compete with the natural   
dye-stuff4  ,the story of naphthalene is
 summarized in the schemes on pp4 #afd1 
#afe4  ,light ,oil3                     

,benzene-,disulpho-acid--,resorcinol4#f 
--,nitrobenzene         ,sulphanilic    
acid4#g                         ,aniline
 ,amidoazobenzene and sulpho-acid4#g    
,nitrosodimethylaniline#h and           
amidodimethylaniline4#h                 
,sulpho-acid--,amidosulpho-acid--,amidop
henol                                   
and ethers4#f                           
,azobenzene--,benzidine4#g              
,toluidines#g ,sulpho-acids4#g          
,amidoazotoluene#g                      
and sulpho-acid4#g                      
,thiotoluidine and primuline4#g         
,toluene--,nitrotoluenes                
,azotoluene--,tolidine4#g               
,sulpho-acid and ,stilbene-derivative4#g
                                        
,sulpho-acids4#g                        
,xylene-,nitroxylenes-,xylidines#g      
,amidoazoxylene#g and sulpho-acid4#g    
,cumidine4#g  ,carbolic ,oil3           
,phenol--,nitrophenol and ethers        
,azophenol ethers--,diamidic bases#i    
analogous to benzidine4                 

,amidophenol#i and ethers4#i            
,cresols--,nitrocresols and             
ethers--,amidocresols#i and ethers4#i   
,nitronaphthalene                       
,greek3 a-,naphthylamine#iaj,naphthionic
 acid4#iaj                              
,amidoazonaphthalene                    
,magdala red4                           
,sulpho-acid4#i                         
,naphthalene,tetrachloride--,phthalic   
acid and anhydride4                     
,manchester yellow4                     
,greek3 a-,naphthol  ,acid naphthol     
yellow4                                 
,sulpho-acids4#aj                       
,sulpho-acids                           
,greek3 b-,naphthylamine                
and sulpho-acids4#iaj                   
,greek3 b-,naphthol,sulpho-acids        
,greek3 b-naphthylamine                 
sulpho-acids4#iaj                       
,nitrososulpho-acid and                 
naphthol green4  ,the fraction of       
coal-tar succeeding the carbolic oil1   
viz4 the creosote oil1 does not at      

present supply the colour manufacturer  
with any raw materials beyond the small 
proportion of naphthalene which         
separates from it in a very impure      
condition as creosote salts4 ,this oil  
consists of a mixture of the higher     
homologues of phenol with various       
hydrocarbons and basic compounds4 ,it is
 the oil used for creosoting timber in  
the manner already described2 and among 
its other applications may be mentioned 
its use as an illuminating agent and as 
a source of lampblack4 ,in order to burn
 the oil effectively as a source of     
light1 a specially-constructed burner is
 used1 which is fed by a stream of oil  
raised from a reservoir at its foot by  
means of compressed air1 which also aids
 the combustion of the oil4 ,there is   
produced by this means a great body of  
lurid flame1 which is very serviceable  
where building or other operations have 
to be carried on at night 7see ,fig4    
#aj74 ,for lampblack the oil is simply  
burnt in iron pans set in ovens1 and the

 sooty smoke conducted into condensing  
chambers4 ,the creosote oil constitutes 
more than #cj per cent4 by weight of the
 tar--the time may come when this       
fraction1 like the light oil and        
carbolic oil1 may be found to contain   
compounds of value to the colour-maker  
or to other branches of chemical        
manufacture4   ,illustration3 ,,fig4    
#aj4--,,vertical ,,burner ,,for ,,heavy 
,,coal ,,oil ,,by ,,the ,,lucigen       
,,light ,,co4  ,illustration3 ,,fig4    
#aa4--,,the ,,madder ,,plant 7,rubia    
tinctoria74   ,the utilization of the   
next fraction1 anthracene oil1 is one of
 the greatest triumphs which applied    
chemical science can lay claim to since 
the foundation of the coal-tar colour   
industry4 ,this discovery dates from    
#ahfh1 when it was shown by two ,german 
chemists1 ,graebe and ,liebermann1 that 
the colouring-matter of madder was      
derived from the hydrocarbon anthracene4
 ,like indigo1 madder may be regarded as
 one of the most ancient of natural     

dye-stuffs4 ,it consists of the powdered
 roots of certain plants of the genus   
,rubia1 such as ,r4 tinctoria 7see ,fig4
 #aa71 ,r4 peregrina1 and ,r4 munjista1 
which were at one time cultivated on an 
enormous scale in various parts of      
,europe and ,asia4 ,it is estimated that
 at the time of ,graebe and             
,liebermann's discovery1 #gj1jjj tons of
 madder were produced annually in the   
madder-growing countries of the world4  
,at that time we were importing madder  
into this country at the rate of #ae1jjj
 to #af1jjj tons per annum1 at a cost of
 ,l#ej per ton4 ,in ten years the       
importation had fallen to about #afjj   
tons1 and the price to ,l#ah per ton4   
,at the present time the cultivation of 
madder is practically extinct4  ,there  
is no better gauge of the practical     
utility of a scientific discovery than  
the financial effect4 ,in addition to   
madder1 a more concentrated extract     
containing the colouring-matter itself  
was largely used by dyers and cotton    

printers under the name of garancin4 ,in
 #ahfh we were importing1 in addition to
 the #ae1jjj to #af1jjj tons of madder1 
about #bjjj tons of this extract        
annually1 at a cost of ,l#aej per ton4  
,by #ahgh the importation of garancin   
had sunk to about #adj tons1 and the    
price had been lowered to ,l#fe per ton4
 ,the total value of the imports of     
madder and garancin in #ahfh was over   
one million pounds sterling2 in ten     
years the value of these same imports   
had been reduced to about ,l#ch1jjj4    
,concurrently with this falling off in  
the demand for the natural              
colouring-matter1 the cultivation of the
 madder plant had to be abandoned1 and  
the vast tracts of land devoted to this 
purpose became available for other      
crops4 ,a change amounting to a         
revolution was produced in an           
agricultural industry by a discovery in 
chemistry4  ,in the persons of two      
,frenchmen1 ,messrs4 ,robiquet and      
,colin1 science laid hands on the       

colouring-matter of the ,rubia in #ahbf4
 ,these chemists isolated two compounds 
which they named alizarin and purpurin4 
,it is now known that there are at least
 six distinct colouring-matters in the  
madder root1 all of these being         
anthracene derivatives4 ,it is known    
also that the colouring-matters do not  
exist in the free state in the plant1   
but in the form of compounds known as   
glucosides1 i4e4 compounds consisting of
 the colouring-matter combined with the 
sugar known as glucose4 ,it may be      
mentioned incidentally that the         
colouring-matter of the indigo plant    
also exists as a glucoside in the plant4
 ,during a period of more than forty    
years from the date of its isolation1   
alizarin was from time to time submitted
 to examination by chemists1 but its    
composition was not completely          
established till #ahfh1 when ,graebe and
 ,liebermann1 by heating it with        
zinc-dust1 obtained anthracene4 ,this   
was the discovery which gave the        

death-blow to the madder culture1 and   
converted the last fraction of the      
tar-oil from a waste product into a     
material of the greatest value4  ,the   
large quantity of madder consumed for   
tinctorial purposes is indicative of the
 value of this dye-stuff4 ,it produces  
shades of red1 purple1 violet1 black1 or
 deep brown1 according to the mordant   
with which the fabric is impregnated4   
,the colours obtained by the use of     
madder are among the fastest of dyes1   
the brilliant ,turkey red being one of  
the most familiar shades4 ,the discovery
 of the parent hydrocarbon of this      
colouring-matter which had been in use  
for so many ages--a colouring-matter    
capable of furnishing both in dyeing and
 printing many distinct shades1 all     
possessed of great fastness--was        
obviously a step towards the realization
 of an industrial triumph1 viz4 the     
chemical synthesis of alizarin4 ,within 
a year of their original observation1   
this had been accomplished by ,graebe   

and ,liebermann1 and almost             
simultaneously by ,w4 ,h4 ,perkin in    
this country4 ,from that time the       
anthracene1 which had previously been   
burnt or used as lubricating grease1    
rose in value to an extraordinary       
extent4 ,in two years a material which  
could have been bought for a few        
shillings the ton1 rose at the touch of 
chemical magic to more than two hundred 
times its former value4  ,anthracene is 
a white crystalline hydrocarbon1 having 
a bluish fluorescence1 melting at #bac  
deg4 ,c4 and boiling above #cfj deg4 ,c4
 ,it was discovered in coal-tar by      
,dumas and ,laurent in #ahcb1 and its   
composition was determined by ,fritzsche
 in #aheg4 ,it separates in the form of 
crystals from the anthracene oil on     
cooling1 and is removed by filtration4  
,the adhering oil is got rid of by      
submitting the crystals to great        
pressure in hydraulic presses4 ,further 
purification is effected by powdering   
the crude anthracene cake and washing   

with solvent naphtha1 i4e4 the mixture  
of the higher homologues of benzene left
 after the rectification of the light   
oil4 ,another coal-tar product1 viz4 the
 pyridine base referred to in the last  
chapter1 has been recently employed for 
washing anthracene with great success4  
,it is used either by itself or mixed   
with the solvent naphtha4 ,the          
anthracene by washing with these        
solvents is freed from more soluble     
impurities1 and may then contain from   
#cj to #hj per cent4 of the pure        
hydrocarbon4 ,the washing liquid1 which 
is recovered by distillation1 contains1 
among other impurities dissolved out of 
the crude anthracene1 a hydrocarbon     
isomeric with the latter1 and known as  
phenanthrene1 for which there is at     
present but little use1 but which may   
one day be turned to good account4 ,the 
actual amount of anthracene contained in
 coal-tar corresponds to about #a_/b lb4
 per ton of coal distilled1 i4e4 from   
#a_/d to #a_/b per cent4 by weight of   

the tar4 ,owing to the great value of   
alizarin and the large quantity of this 
colouring-matter annually consumed1     
anthracene is now by far the most       
important of the coal-tar hydrocarbons4 
,alizarin1 purpurin1 and the other      
colouring-matters of madder are hydroxyl
 derivatives of a compound derived from 
anthracene by the replacement of two    
atoms of hydrogen by two atoms of       
oxygen4 ,these oxygen derivatives of    
benzenoid hydrocarbons form a special   
group of compounds known as quinones4   
,thus there is quinone itself1 or       
benzoquinone1 which is benzene with two 
atoms of oxygen replacing two atoms of  
hydrogen4 ,there are also isomeric      
quinones of the naphthalene series known
 as naphthaquinones4 ,a dihydroxyl      
derivative of one of the latter is in   
use under the somewhat misappropriate   
name of alizarin black4 ,with this      
exception no other quinone derivative is
 used in the colour industry till we    
come to the hydrocarbons of the         

anthracene oil4 ,phenanthrene forms a   
quinone which has been utilized as a    
source of colouring-matters1 but these  
are comparatively unimportant4 ,the     
quinone with which we are at present    
concerned is anthraquinone4  ,the latter
 is prepared by oxidizing the           
anthracene--previously reduced by       
sublimation to the condition of a very  
finely-divided crystalline powder--with 
sulphuric acid and potassium dichromate4
 ,the quinone is purified1 converted    
into a sulpho-acid1 and the sodium salt 
of the latter on fusion with alkali     
gives alizarin1 which is                
dihydroxy-anthraquinone4 ,it is of      
interest to note that in this case a    
monosulpho-acid gives a                 
dihydroxy-derivative4 ,during the       
process of fusion potassium chlorate is 
added1 by which means the yield of      
alizarin is considerably increased4 ,in 
the original process of ,graebe and     
,liebermann1 dibromanthraquinone was    
fused with alkali2 but this method was  

soon improved upon by the discovery of  
the sulpho-acid by ,caro and ,perkin in 
#ahfi1 and from this period the         
manufacture of artificial alizarin      
became commercially successful4  ,in    
addition to alizarin1 other anthracene  
derivatives are of industrial           
importance4 ,the purpurin1 discovered   
among the colouring-matters of madder in
 #ahbf1 is a trihydroxy-anthraquinone2  
it can be prepared by the oxidation of  
alizarin1 as shown by ,de ,lalande in   
#ahgd4 ,isomeric compounds known as     
flavopurpurin and anthrapurpurin are    
also made from the disulpho-acids of    
anthraquinone by fusion with alkali and 
potassium chlorate4 ,these two          
disulpho-acids are obtained             
simultaneously with the monosulpho-acid 
by the action of fuming sulphuric acid  
on the quinone1 and are separated by the
 fractional crystallization of their    
sodium salts from the monosulpho-acid   
7which gives alizarin7 and from each    
other4 ,the purpurins give somewhat     

yellower shades than alizarin4 ,another 
trihydroxy-anthraquinone1 although not  
obtained directly from anthracene1 must 
be claimed as a tar-product4 ,it is     
prepared by heating gallic acid with    
benzoic and sulphuric acids1 or with    
phthalic anhydride and zinc chloride1   
and is a brown dye known as anthragallol
 or anthracene-brown4 ,the anthracene   
derivative is in this process built up  
synthetically4 ,a sulpho-acid of        
alizarin has been introduced for wool   
dyeing under the name of alizarin       
carmine1 and a nitro-alizarin under the 
name of alizarin orange4 ,the latter on 
heating with glycerin and sulphuric acid
 is transformed into a remarkably fast  
colouring-matter known as alizarin blue1
 which is used for dyeing and printing4 
,by heating alizarin blue with strong   
sulphuric acid1 it is converted into    
alizarin green4  ,the great industry    
arising out of the laboratory work of   
two ,german chemists has influenced     
other branches of chemical manufacture1 

and has reacted upon the coal-tar colour
 industry itself4 ,a new application for
 caustic soda and potassium chlorate    
necessitated an increased production of 
these materials4 ,the first demand for  
fuming sulphuric acid on a large scale  
was created by the alizarin manufacture 
in #ahgc1 when it was found that an acid
 of this strength gave better results in
 the preparation of sulpho-acids from   
anthraquinone4 ,the introduction of this
 acid into commerce no doubt exerted a  
marked influence on the production of   
other valuable sulpho-acids1 such as    
acid magenta in #ahgg1 acid yellow in   
#ahgh1 and acid naphthol yellow in      
#ahgi4 ,the introduction of artificial  
alizarin has also simplified the art of 
colour printing on cotton fabrics to    
such an extent that other               
colouring-matters1 also derived from    
coal-tar1 are largely used in           
combination with the alizarin to produce
 parti-coloured designs4 ,the           
manufacture of one coal-tar             

colouring-matter has thus assisted in   
the consumption of others4  ,artificial 
alizarin is used in the form of a paste1
 which consists of the colouring-matter 
precipitated from its alkaline solution 
by acid1 and mixed with water so as to  
form a mixture containing from #aj to   
#bj per cent4 of alizarin4 ,the         
magnitude of the industry will be       
gathered from the estimate that the     
whole quantity of anthracene annually   
made into alizarin corresponds to a     
daily production of about #fe tons of   
#aj per cent4 paste1 of which only about
 one-eighth is made in this country1 the
 remainder being manufactured on the    
,continent4 ,the total production of    
alizarin corresponds in money value to  
about ,l#b1jjj1jjj per annum4 ,one pound
 of dry alizarin has the tinctorial     
power of #ij pounds of madder4 ,seeing  
therefore that the raw material         
anthracene was at one time a waste      
product1 and that the quantity of       
alizarin produced in the factory        

corresponds to nearly five pounds of #bj
 per cent4 paste for one pound of       
anthracene1 it is not surprising that   
the artificial has been enabled to      
compete successfully with the natural   
product4  ,the industrial history of    
anthracene is thus summarized4 7,see    
opposite47    ,anthracene               
,anthraquinone                          
,sulpho-acid 7,alizarin carmine7        
-,monosulpho-acid--,alizarin----------  
,purpurin                               
,nitro-alizarin--,alizarin blue         
-,greek3                                
a-,disulpho-acid--,flavopurpurin        
-,greek3                                
b-,disulpho-acid--,anthrapurpurin       
,alizarin green4  ,the black1 viscid    
residue left in the tar-still after the 
removal of the anthracene oil is the    
substance known familiarly as pitch4    
,from the latter1 after removal of all  
the volatile constituents1 there is     
prepared asphalte1 which is a solution  
of the pitchy residue in the heavy      

tar-oils from which all the materials   
used in the colour industry have been   
removed4 ,asphalte is used for          
varnish-making1 in the construction of  
hard pavements1 and for other purposes4 
,a considerable quantity of pitch is    
used in an industry which originated in 
,france in #ahcb1 and which is still    
carried out on a large scale in that    
country1 and to a smaller extent in this
 and other tar-producing countries4 ,the
 industry in question is the manufacture
 of fuel from coal-dust by moulding the 
latter in suitable machines with pitch  
so as to form the cakes known as        
briquettes or patent fuel4 ,by this     
means two waste materials are disposed  
of in a useful way--the pitch and the   
finely-divided coal1 which could not    
conveniently be used as fuel by itself4 
,from two to three million tons of this 
artificial fuel are being made annually 
here and on the ,continent4  ,the       
various constituents of coal-tar have   
now been made to tell their story1 so   

far as relates to the colouring-matters 
which they furnish4 ,if the descriptive 
details are devoid of romance to the    
general reader1 the results achieved in 
the short period of thirty-five years1  
dating from the discovery of mauve by   
,perkin1 will assuredly be regarded as  
falling but little short of the         
marvellous4 ,although the most striking 
developments are naturally connected    
with the colouring-matters1 whose       
history has been sketched in the        
foregoing pages1 and whose introduction 
has revolutionized the whole art of     
dyeing1 there are other directions in   
which the coal-tar industry has in      
recent times been undergoing extension4 
,certain tar-products are now rendering 
good service in pharmacy4 ,salicylic    
acid and its salts have long been used  
in medicine4 ,by distilling a mixture of
 the dry lime salts of benzoic and      
acetic acids there is obtained a        
compound known to chemists as           
acetophenone1 which is used for inducing

 sleep under the name of hypnone4 ,the  
acetyl-derivative of aniline and of     
methylaniline are febrifuges known as   
antifebrine and exalgine4 ,ethers of    
salicylic acid and its homologues1      
prepared from these acids and phenol1   
naphthols1 c41 are in use as antiseptics
 under the general designation of       
salols4  ,in #ahha there was introduced 
into medicine the first of a group of   
antipyretics derived from coal-tar bases
 of the pyridine series4 ,it has already
 been explained that this base is       
removed from the light oil by washing   
with acid4 ,chemically considered1 it is
 benzene containing one atom of nitrogen
 in place of a group consisting of an   
atom of carbon and an atom of hydrogen4 
,the quantity of pyridine present in    
coal-tar is very small1 and no use has  
as yet been found for it excepting as a 
solvent for washing anthracene or for   
rendering the alcohol used for          
manufacturing purposes undrinkable1 as  
is done in this country by mixing in    

crude wood-spirit so as to form         
methylated spirit4 ,the salts of        
pyridine were shown by ,mc,kendrick and 
,dewar to act as febrifuges in #ahha1   
but they have not hitherto found their  
way into pharmacy4 ,the chief interest  
of the base for us centres in the fact  
that it is the type of a group of bases 
related to each other in the same way as
 the coal-tar hydrocarbons4 ,thus in    
coal-tar1 in addition to pyridine1 there
 is another base known as quinoline1    
which is related to pyridine in the same
 way that naphthalene is related to     
benzene4 ,similarly there is a coal-tar 
base known as acridine1 which is found  
associated with the anthracene1 and     
which is related to quinoline in the    
same way that anthracene is related to  
naphthalene4 ,the three hydrocarbons are
 comparable with the three bases1 which 
may be regarded as derived from them in 
the same manner that pyridine is derived
 from benzene--    ,benzene    444      
444    444    ,pyridine   ,naphthalene  

444    444    ,quinoline   ,anthracene  
444    444    444    ,acridine  ,some of
 these bases and their homologues are   
found in the evil-smelling oil produced 
by the destructive distillation of bones
 7,dippel's oil1 or bone oil71 and the  
group is frequently spoken of as the    
pyridine group4 ,the colouring-matter   
described as phosphine1 obtained as a   
by-product in the manufacture of magenta
 7p4 #id71 is a derivative of acridine1 
and a yellow colouring-matter discovered
 by ,rudolph in #ahha1 and obtained by  
heating the acetyl derivative of aniline
 with zinc chloride1 is a derivative of 
a homologue of quinoline4 ,this         
dye-stuff1 known as flavaniline1 is no  
longer made2 but it is interesting as   
having led to the discovery of the      
constitution of phosphine by ,o4        
,fischer and ,koerner in #ahhd4  ,the   
antipyretic medicines which we have     
first to consider are derivatives of    
quinoline4 ,this base was discovered in 
coal-tar by ,runge in #ahcd1 and was    

obtained by ,gerhardt in #ahdb by       
distilling cinchonine1 one of the       
cinchona alkaloids1 with alkali4 ,now it
 is of interest to note that the        
quinoline of coal-tar is of no more use 
to the technologist than the aniline2   
these bases are not contained in the tar
 in sufficient quantity to enable them  
to be separated and purified with       
economical advantage4 ,if the colour    
industry had to depend upon this source 
of aniline only1 its development would  
have been impossible4 ,but as chemistry 
enabled the manufacturer to obtain      
aniline in quantity from benzene1 so    
science has placed quinoline at his     
disposal4 ,this important discovery was 
made in #ahhj by the ,dutch chemist     
,skraup1 who found that by heating      
aniline with sulphuric acid and glycerin
 in the presence of nitrobenzene1       
quinoline is produced4 ,the nitrobenzene
 acts only as an oxidizing agent2 the   
amido-group of the aniline is converted 
into a group containing carbon1         

hydrogen1 and nitrogen1 i4e4 the        
pyridine group4 ,the discovery of       
,skraup's method formed the             
starting-point of a series of syntheses1
 which resulted in the formation of many
 products of technical value4 ,in all   
these syntheses the fundamental change  
is the same1 viz4 the conversion of an  
amidic into a pyridine group4 ,we may   
speak of the amido-group as being       
pyridised in such processes4 ,thus      
alizarin blue1 which is formed by       
heating nitro-alizarin with glycerin and
 sulphuric acid1 results from the       
pyridisation of the nitro-group4 ,by an 
analogous method ,doebner and v4 ,miller
 prepared a homologue of quinoline      
7quinaldine7 in #ahha1 by the action of 
sulphuric acid and a certain            
modification of aldehyde known as       
paraldehyde on aniline4  ,quinoline and 
its homologue quinaldine have been      
utilized as sources of                  
colouring-matters4 ,a green dye-stuff1  
known as quinoline green1 was formerly  

made by the same method as that employed
 for producing the phosgene colours by  
,caro and ,kern's process 7p4 #ajf74    
,the phthalein of quinaldine was        
introduced by ,e4 ,jacobsen in #ahhb    
under the name of quinoline yellow1 a   
colouring-matter which forms a soluble  
sulpho-acid by the action of sulphuric  
acid4  ,to return to coal-tar           
pharmaceutical preparations4 ,at the    
present time seven distinct derivatives 
of quinoline1 all formed by pyridising  
the amido-group in aniline1             
amido-phenols1 c41 are known in medicine
 under such names as kairine1 kairoline1
 thalline1 and thermifugine4 ,the mode  
of preparation of these compounds cannot
 be entered into here1 ,kairine1 the    
first of the artificial alkaloids1 is a 
derivative of hydroxy-quinoline1 which  
was discovered in #ahha by ,otto        
,fischer4 ,all these quinoline          
derivatives have the property of        
lowering the temperature of the body in 
certain kinds of fevers1 and may        

therefore be considered as the first    
artificial products coming into         
competition with the natural alkaloid1  
quinine4 ,there is reason for believing 
that the latter alkaloid1 the most      
valuable of all febrifuges1 is related  
to the quinoline bases1 so that if its  
synthesis is accomplished--as may       
certainly be anticipated--we shall have 
to look to coal-tar as a source of the  
raw materials4  ,another valuable       
artificial alkaloid1 discovered in #ahhc
 by ,ludwig ,knorr1 claims aniline as a 
point of departure4 ,when aniline and   
analogous bases are diazotised1 and the 
diazo-salts reduced in the cold with a  
very gentle reducing agent1 such as     
stannous chloride1 there are formed     
certain basic compounds1 containing one 
atom of nitrogen and one atom of        
hydrogen more than the original base4   
,these bases were discovered in #ahgf by
 ,emil ,fischer1 and they are known as  
hydrazines1 the particular compound thus
 obtained from aniline being            

phenylhydrazine4 ,by the action of this 
base on a certain compound ether derived
 from acetic acid1 which is known as    
aceto-acetic ether1 there is formed a   
product termed pyrazole1 and this on    
methylation gives the alkaloid in       
question1 which is now well known in    
pharmacy under the name of antipyrine4  
,while dealing with this first          
industrial application of a hydrazine1  
it must be mentioned that the original  
process by which ,fischer prepared these
 bases was improved upon by ,victor     
,meyer and ,lecco in #ahhc1 who         
discovered the use of a cold solution of
 stannous chloride for reducing the     
diazo-chloride to the hydrazine4 ,by    
this method the manufacture of          
phenylhydrazine and other hydrazines is 
effected on a large scale--all kinds of 
amido-compounds and their sulpho-acids  
can be diazotised and reduced to their  
hydrazines4 ,out of this discovery has  
arisen the manufacture of a new class of
 colouring-matters related to the       

azo-dyes4 ,the hydrazines combine with  
quinones and analogous compounds with   
the elimination of water1 the oxygen    
coming from the quinone1 and the        
hydrogen from the hydrazine4 ,the       
resulting products are coloured         
compounds very similar in properties to 
the azo-dyes1 and one of these was      
introduced in #ahhe by ,ziegler1 under  
the name of tartrazine4 ,the latter is  
obtained by the action of a sulpho-acid 
of phenylhydrazine on dioxytartaric     
acid1 and is a yellow dye1 which is of  
special interest on account of its      
extraordinary fastness towards light4   
,another direction in which coal-tar    
products have been utilized is in the   
formation of certain aromatic compounds 
which occur in the vegetable kingdom4   
,thus the artificial production of      
bitter-almond oil from toluene has      
already been explained4 ,by heating     
phenol with caustic alkali and          
chloroform1 the aldehyde of salicylic   
acid1 i4e4 salicylic aldehyde1 is       

formed1 and this1 on heating with dry   
sodium acetate and acetic anhydride1    
passes into coumarin1 the fragrant      
crystalline substance which is contained
 in the ,tonka bean and the             
sweet-scented woodruff4 ,furthermore1   
the familiar flavour and scent of the   
vanilla bean1 which is due to a         
crystalline substance known as vanillin1
 can be obtained from coal-tar without  
the use of the plant4 ,the researches of
 ,tiemann and ,haarman having shown that
 vanillin is a derivative of benzene    
containing the aldehyde group1 one      
hydroxyl- and one methoxy-group1 the    
synthesis of this compound soon followed
 7,ulrich1 #ahhd74 ,the starting-point  
in this synthesis is nitrobenzoic       
aldehyde1 so that here again we begin   
with toluene as a raw material4 ,a      
mixture of vanillin and benzoic aldehyde
 when attenuated to a state of extreme  
dilution in a spirituous solvent1 gives 
the perfume known as heliotrope4  ,not  
the least romantic chapter of coal-tar  

chemistry is this production of fragrant
 perfumes from the evil-smelling tar4   
,be it remembered that these            
products--which ,nature elaborates by   
obscure physiological processes in the  
living plant--are no more contained in  
the tar than are the hundreds of        
colouring-matters which have been       
prepared from this same source4 ,it is  
by chemical skill that these compounds  
have been built up from their elemental 
groups2 and the artificial products1 as 
in the case of indigo and alizarin1 are 
chemically identical with those obtained
 from the plant4 ,among the late        
achievements in the synthesis of        
vegetable products from coal-tar        
compounds is that of juglone1 a         
crystalline substance found in          
walnut-shell4 ,it was shown by          
,bernthsen in #ahhd that this compound  
was hydroxy-naphthaquinone1 and in #ahhg
 its synthesis from naphthalene was     
accomplished by this same chemist in    
conjunction with ,dr4 ,semper4  ,another

 recent development in the present      
branch of chemistry brings a coal-tar   
product into competition with sugar4 ,in
 #ahgi ,dr4 ,fahlberg discovered a      
certain derivative of toluene which     
possessed an intensely sweet taste4 ,by 
#ahhd the manufacture of this product   
had been improved to a sufficient extent
 to enable it to be introduced into     
commerce as a flavouring material in    
cases where sweetness is wanted without 
the use of sugar1 such as in the food of
 diabetic patients4 ,under the name of  
saccharin1 ,fahlberg thus gave to       
commerce a substance having more than   
three hundred times the sweetening power
 of cane-sugar--a substance not only    
possessed of an intense taste1 but not  
acted upon by ferments1 and possessing  
distinctly antiseptic properties4 ,the  
future of coal-tar saccharin has yet to 
be developed2 but its advantages are so 
numerous that it cannot fail to become  
sooner or later one of the most         
important of coal-tar products4 ,in     

cases where sweetening is required      
without the possibility of the          
subsequent formation of alcohol by      
fermentation1 saccharin has been used   
with great success1 especially in the   
manufacture of aerated waters4 ,its     
value in medicine has been recognized by
 its recent admission into the          
,pharmacopoeia4  ,the remarkable        
achievements of modern chemistry in     
connection with coal-tar products do not
 end with the formation of              
colouring-matters1 medicines1 and       
perfumes4 ,the introduction of the      
beautiful dyes has had an influence in  
other directions1 and has led to results
 quite unsuspected until the restless   
spirit of investigation opened out new  
fields for their application4 ,a few of 
these secondary uses are sufficiently   
important to be chronicled here4 ,in    
sanitary engineering1 for example1 the  
intense colouring power of fluorescein  
is frequently made use of to test the   
soundness of drains1 or to find out     

whether a well receives drainage from   
insanitary sources4 ,in photography also
 coal-tar colouring-matters are playing 
an important part by virtue of a certain
 property which some of these compounds 
possess4  ,the ordinary photographic    
plate is1 as is well known1 much more   
sensitive to blue and violet than to    
yellow or red1 so that in photographing 
coloured objects the picture gives a    
false impression of colour intensity1   
the violets and blues impressing        
themselves too strongly1 and the yellows
 and reds too feebly4 ,it was discovered
 by ,dr4 ,h4 ,w4 ,vogel in #ahgc that if
 the sensitive film is slightly tinted  
with certain colouring-matters1 the     
sensitiveness for yellow and red can be 
much increased1 so that the picture is a
 more natural representation of the     
object4 ,plates thus dyed are said to be
 isochromatic or orthochromatic1 and by 
their use paintings or other coloured   
objects can be photographed with much   
better results than by the use of       

ordinary plates4 ,the boon thus         
conferred upon photographic art is      
therefore to be attributed to coal-tar  
chemistry4 ,among the numerous          
colouring-matters which have been       
experimented with1 the most effective   
special sensitizers are erythrosin1 one 
of the phthaleins1 quinoline red1 a     
compound related to the same group1 and 
cyanin1 a fugitive blue colouring-matter
 obtained from quinoline in #ahfj by    
,greville ,williams4  ,in yet another   
way has photography become indebted to  
the tar chemist4 ,two important         
developers now in common use are        
coal-tar products1 viz4 hydroquinone and
 eikonogen4 ,the history of these       
compounds is worthy of narration as     
showing how a product when once given by
 chemistry to the world may become      
applicable in quite unexpected          
directions4 ,chloroform is a case in    
point4 ,this compound was discovered by 
,liebig in #ahca1 but its use as an     
anaesthetic did not come about till     

seventeen years after its discovery4 ,it
 was ,sir ,james ,simpson who in #ahdh  
first showed the value of chloroform in 
surgical operations4 ,a similar story   
can be told with respect to these       
photographic developers4  ,towards the  
middle of the last century a ,french    
chemist1 the ,count de la ,garaye1      
noticed a crystalline substance         
deposited from the extract of ,peruvian 
bark1 then1 as now1 used in medicine4   
,this substance was the lime salt of an 
acid to which ,vauquelin in #ahjf gave  
the name of quinic acid 7acide          
quinique74 ,in #ahch ,woskresensky1 by  
oxidizing quinic acid with sulphuric    
acid and oxide of manganese1 obtained a 
crystalline substance which he called   
quinoyl4 ,the name was changed to       
quinone by ,woehler1 and1 as we have    
already seen 7p4 #agb71 the term has now
 become generic1 indicating a group of  
similarly constituted oxygen derivatives
 of hydrocarbons4 ,hydroquinone was     
obtained by ,caventou and ,pelletier by 

heating quinic acid1 but these chemists 
did not recognize its true nature4 ,it  
was the illustrious ,woehler who in     
#ahdd first prepared the compound in a  
state of purity1 and established its    
relationship to quinone4 ,this          
relationship1 as the name given by      
,woehler indicates1 is that of the      
nature of a hydrogenised quinone4 ,the  
compound is readily prepared by the     
action of sulphurous acid or any other  
reducing agent on the quinone4  ,it has 
long been known in photography1 that a  
developer must be of the nature of a    
reducing agent1 either inorganic or     
organic1 and many hydroxylic and amidic 
derivatives of hydrocarbons come under  
this category4 ,thus1 pyrogallol1 which 
has already been referred to as a       
trihydroxybenzene 7p4 #adf71 when       
dissolved in alkali rapidly absorbs     
oxygen--it is a strong reducing agent1  
and is thus of value as a developer4    
,but although pyrogallol is a benzene   
derivative1 and could if necessary be   

prepared synthetically1 it can hardly be
 claimed as a tar product1 as it is     
generally made from gallic acid4 ,now   
hydroquinone when dissolved in alkali   
also acts as a reducing agent1 and in   
this we have the first application of a 
true coal-tar product as a photographic 
developer4 ,its use for this purpose was
 suggested by ,captain ,abney in #ahhj1 
and it was found to possess certain     
advantages which caused it to become    
generally adopted4  ,as soon as a       
practical use is found for a chemical   
product its manufacture follows as a    
matter of course4 ,in the case of       
hydroquinone1 the original source1      
quinic acid1 was obviously out of       
question1 for economical reasons4 ,in   
#ahgg1 however1 ,nietzki worked out a   
very good process for the preparation of
 quinone from aniline by oxidation with 
sulphuric acid and bichromate of soda in
 the cold4 ,this placed the production  
of quinone on a manufacturing basis1 so 
that when a demand for hydroquinone     

sprung up1 the wants of the photographer
 were met by the technologist4          
,eikonogen is another organic reducing  
agent1 discovered by the writer in      
#ahhj1 and introduced as a developer by 
,dr4 ,andresen in #ahhi4 ,it is an      
amido-derivative of a sulpho-acid of    
beta-naphthol1 so that naphthalene is   
the generating hydrocarbon of this      
substance4  ,the thio-derivative of     
toluidine described as primuline 7p4    
#afj71 has recently been found by its   
discoverer to possess a most remarkable 
property which enables this compound to 
be used for the photographic            
reproduction of designs in azo-colours4 
,diazotised primuline1 as already       
explained1 combines in the usual way    
with amines and phenols to form         
azo-dyes4 ,under the influence of light1
 however1 the diazotised primuline is   
decomposed with the loss of nitrogen1   
and the formation of a product which    
does not possess the properties of a    
diazo-compound4 ,the product of         

photochemical decomposition no longer   
forms azo-colours with amines or        
phenols4 ,if1 therefore1 a fabric is    
dyed with primuline1 then diazotised by 
immersion in a nitrite bath1 and exposed
 under a photographic negative1 those   
portions of the surface to which the    
light penetrates lose the power of      
giving a colour with amines or phenols4 
,the design can thus be developed by    
dipping the fabric into a solution of   
naphthol1 naphthylamine1 c4 ,by this    
discovery another point of contact has  
been established between photography and
 coal-tar products4 ,nor is this the    
only instance of its kind1 for it has   
also been observed that a               
diazo-sulpho-acid of one of the xylenes 
does not combine with phenols to form   
azo-dyes excepting under the influence  
of light4 ,a fabric can therefore be    
impregnated with the mixture of         
diazo-sulpho-acid and naphthol1 and     
exposed under a design1 when the        
azo-colour is developed only on those   

portions of the surface which are acted 
upon by light4  ,the last indirect      
application of coal-tar                 
colouring-matters to which attention    
must be called is one of great          
importance in biology4 ,the use of these
 dyes as stains for sections of animal  
and vegetable tissue has long been      
familiar to microscopists4 ,owing to the
 different affinities of the various    
components of the tissue for the        
different colouring-matters1 these      
components are capable of being         
differentiated and distinguished by     
microscopical analysis4 ,furthermore1   
the almost invisible organisms which in 
recent times have been shown to play    
such an important part in diseases1 have
 in many cases a special affinity for   
particular colouring-matters1 and their 
presence has been revealed by this      
means4 ,the micro-organism of tubercle1 
for example1 was in this way found by   
,koch to be readily stained by methylene
 blue1 and its detection was thus       

rendered possible with certainty4 ,many 
of the dyes referred to in the previous 
pages have rendered service in a similar
 way4 ,to the pure utilitarian such an  
application of coal-tar products will no
 doubt compensate for any defects which 
they may be supposed to possess from the
 aesthetic point of view4#aa  ,from a   
small beginning there has thus developed
 in a period of five-and-thirty years an
 enormous industry1 the actual value of 
which at the present time it is very    
difficult to estimate4 ,we shall not be 
far out if we put down the value of the 
coal-tar colouring-matters produced     
annually in this country and on the     
,continent at ,l#e1jjj1jjj sterling4    
,the products which half a century or so
 ago were made in the laboratory with   
great difficulty1 and only in very small
 quantities1 are now turned out by the  
hundredweight and the ton4#ab ,to       
achieve these results the most profound 
chemical knowledge has been combined    
with the highest technological skill4   

,the outcome has been to place at the   
service of man1 from the waste products 
of the gas-manufacturer1 a series of    
colouring-matters which can compete with
 the natural dyes1 and which in many    
cases have displaced the latter4 ,from  
this source we have also been provided  
with explosives such as picric acid2    
with perfumes and flavouring materials  
like bitter-almond oil and vanillin2    
with a sweetening principle like        
saccharin--compared with which the      
product of the sugar-cane is but feeble2
 with dyes which tint the photographic  
film1 and enable the most delicate      
gradations of shade to be reproduced2   
with developers such as hydroquinone and
 eikonogen2 with disinfectants which    
contribute to the healthiness of our    
towns2 with potent medicines which rival
 the natural alkaloids2 and with stains 
which reveal the innermost structure of 
the tissues of living things1 or which  
bring to light the hidden source of     
disease4 ,surely if ever a romance was  

woven out of prosaic material it has    
been this industrial development of     
modern chemistry4  ,but although the    
results are striking enough when thus   
summed up1 and although the industrial  
importance of all this work will be     
conceded by those who have the welfare  
of the country in mind1 the paths which 
the pioneers have had to beat out can   
unfortunately be followed but by the    
few4 ,it is not given to our science to 
strike the public mind at once with the 
magnitude of its achievements1 as is the
 case with the great works of the       
engineer4 ,nevertheless the scientific  
skill which enables a ,forth ,bridge to 
be constructed for the use of the       
travelling public of this               
age--marvellous as it may appear to the 
uninstructed--is equalled1 if not       
surpassed1 by the mastery of the        
intricate atomic groupings which has    
enabled the chemist to build up the     
colouring-matters of the madder and     
indigo plants4  ,a great industry needs 

no excuse for its existence provided    
that it supplies something of use to    
man1 and finds employment for many      
hands4 ,the coal-tar industry fulfils   
these conditions1 as will be gathered   
from the foregoing pages4 ,if any       
further justification is required from a
 more exalted standpoint than that of   
pure utilitarianism it can be supplied4 
,it is well known to all who have traced
 the results of applying any scientific 
discovery to industrial purposes1 that  
the practical application invariably    
reacts upon the pure science to the     
lasting benefit of both4 ,in no         
department of applied science is this   
truth more forcibly illustrated than in 
the branch of technology of which ,i    
have here attempted to give a popular   
account4 ,the pure theory of chemical   
structure--the guiding spirit of the    
modern science--has been advanced       
enormously by means of the materials    
supplied by and resulting from the      
coal-tar industry4 ,the fundamental     

notion of the structure of the benzene  
molecule marks an epoch in the history  
of chemical theory of which the         
importance cannot be too highly         
estimated4 ,this idea occurred1 as by   
inspiration1 to ,august ,kekule of ,bonn
 in the year #ahfe1 and its introduction
 has been marked by a quarter century of
 activity in research such as the       
science of chemistry has never          
experienced at any previous period of   
its history4 ,the theory of the atomic  
structure of the benzene molecule has   
been extended and applied to all        
analogous compounds1 and it is in       
coal-tar that we have the most prolific 
source of the compounds of this class4  
,it was scarcely to be wondered at that 
an idea which has been so prolific as a 
stimulator of original investigation    
should have exerted a marked influence  
on the manufacture of tar-products4 ,all
 the brilliant syntheses of             
colouring-matters effected of late years
 are living witnesses of the fertility  

of ,kekule's conception4 ,in the spring 
of #ahij there was held in ,berlin a    
jubilee meeting commemorating the       
twenty-fifth anniversary of the benzene 
theory4 ,at that meeting the            
representative of the ,german coal-tar  
colour industry publicly declared that  
the prosperity of ,germany in this      
branch of manufacture was primarily due 
to this theoretical notion4 ,but if the 
development of the industry has been    
thus advanced by the theory1 it is no   
less true that the latter has been      
helped forward by the industry4  ,the   
verification of a chemical theory       
necessitates investigations for which   
supplies of the requisite materials must
 be forthcoming4 ,inasmuch as the very  
materials wanted were separated from    
coal-tar and purified on a large scale  
for manufacturing purposes1 the science 
was not long kept waiting4 ,the         
laborious series of operations which the
 chemist working on a laboratory scale  
had to go through in order to obtain raw

 materials1 could be dispensed with when
 products which were at one time        
regarded as rare curiosities became     
available by the hundredweight4 ,it is  
perhaps not too much to say that the    
advancement of chemical theory in the   
direction started by ,kekule has been   
accelerated by a century owing to the   
circumstance that coal-tar products have
 become the property of the             
technologist4 ,in other words1 we might 
have had to wait till #aife to reach our
 present state of knowledge concerning  
the theory of benzenoid compounds if the
 coal-tar industry had not been in      
existence4 ,and this is not the only way
 in which the industry has helped the   
science1 for in the course of           
manufacture many new compounds and many 
new chemical transformations have been  
incidentally discovered1 which have     
thrown great light on chemical theory4  
,from the higher standpoint of pure     
science1 the industry has therefore     
deservedly won a most exalted position4 

,with respect to the value of the       
coal-tar dyes as tinctorial agents1     
there is a certain amount of            
misconception which it is desirable to  
remove4 ,there is a widely-spread idea  
that these colours are fugitive--that   
they rub off1 that they fade on exposure
 to light1 that they wash out1 and1 in  
short1 that they are in every way       
inferior to the old wood or vegetable   
dyes4 ,these charges are unfounded4 ,one
 of the best refutations is1 that two of
 the oldest and fastest of natural      
colouring-matters1 viz4 alizarin and    
indigo1 are coal-tar products4 ,there   
are some coal-tar dyes which are not    
fast to light1 and there are many       
vegetable dyes which are equally        
fugitive4 ,if there are natural         
colouring-matters which are fast and    
which are aesthetically orthodox1 these 
are rivalled by tar-products which      
fulfil the same conditions4 ,such dyes  
as aniline black1 alizarin blue1        
anthracene brown1 tartrazine1 some of   

the azo-reds and naphthol green resist  
the influence of light as well as1 if   
not better than1 any natural            
colouring-matter4 ,the artificial yellow
 dyes are as a whole faster than the    
natural yellows4 ,there are at the      
present time some three hundred coal-tar
 colouring-matters made1 and about      
one-tenth of that number of natural dyes
 are in use4 ,of the latter only        
ten--let us say #cc per cent4--are      
really fast4 ,of the artificial dyes1   
thirty are extremely fast1 and thirty   
fast enough for all practical           
requirements1 so that the fast natural  
colours have been largely outnumbered by
 the artificial ones4 ,if ,nature has   
been beaten1 however1 this has been     
rendered possible only by taking        
advantage of ,nature's own resources--by
 studying the chemical properties of    
atoms1 and giving scope to the play of  
the internal forces which they          
inherently possess--    ,yet ,nature is 
made better by no mean1   ,but ,nature  

makes that mean3 so1 o'er that art1     
,which1 you say1 adds to ,nature1 is an 
art   ,that ,nature makes4  ,the story  
told in this chapter is chronologically 
summarized below--    #ahbj4            
,naphthalene discovered in coal-tar by  
,garden4    #ahcb4 ,anthracene          
discovered in coal-tar by ,dumas and    
,laurent4    #ahcd4 ,phenol discovered  
in coal-tar by ,runge4    #ahdb4 ,picric
 acid prepared from phenol by ,laurent2 
manufactured in         ,manchester in  
#ahfb4    #ahde4 ,benzidine discovered  
by ,zinin4    #ahei4 ,corallin and aurin
 discovered by ,kolbe and ,schmitt and  
by ,persoz2         leading to          
manufacture from oxalic acid and phenol4
    #ahfj4 ,synthesis of salicylic acid 
by ,kolbe4    #ahfd4 ,manchester yellow 
discovered by ,martius1 leading to      
manufacture of                          
alpha-naphthylamine and then to         
alpha-naphthol4    #ahfg4 ,magdala red  
discovered by ,schiendl4    #ahfh4      
,synthesis of alizarin by ,graebe and   

,liebermann1 leading to the             
utilization of anthracene1 caustic soda1
 potassium chlorate and                 
bichromate1 and calling into existence  
the manufacture of fuming               
sulphuric acid4    #ahgj4 ,gallein1 the 
first of the phthaleins1 discovered by  
,a4 v4 ,baeyer1         followed in     
#ahga by coerulein1 and in #ahgd by the 
eosin dyes         7,caro74 ,these      
discoveries necessitated the manufacture
 of phthalic         acid and           
resorcinol4    #ahgc4 ,orthochromatic   
photography discovered by ,vogel4       
#ahgf4 ,azo-dyes from the naphthols     
introduced by ,roussin and ,poirrier and
         ,witt1 leading to the          
manufacture of the naphthols1           
sulphanilic         acid1 c4    #ahgg4  
,preparation of quinone from aniline by 
,nietzki1 utilized in                   
photography in #ahhj for manufacture of 
hydroquinone4    #ahgh4 ,disulpho-acids 
of beta-naphthol introduced by ,meister1
 ,lucius1 and         ,bruening1 leading

 to azo-dyes from aniline1 toluidine1   
xylidine1         and cumidine4         
#ahgi4 ,acid naphthol yellow introduced 
by ,caro4         ,biebrich scarlet1 the
 first secondary azo-colour1 introduced 
by         ,nietzki4                    
,nitroso-sulpho acid of beta-naphthol   
discovered by the writer2               
followed in #ahhc by naphthol green 7,o4
 ,hoffmann71 and in #ahhi by            
eikonogen 7,andresen74                  
,beta-naphthol violet1 the first of the 
oxazines1 discovered by the             
writer2 followed in #ahha by            
gallocyanin4         ,coal-tar saccharin
 discovered by ,fahlberg2 manufacture   
made         practicable in #ahhd4      
#ahhj4 ,synthesis of indigo by ,a4 v4   
,baeyer4         ,quinoline synthesised 
by ,skraup's process4    #ahha4 ,kairine
 introduced by ,o4 ,fischer1 the first  
artificial febrifuge4                   
,indophenol discovered by ,koechlin and 
,witt4         ,azo-dyes from new       
sulpho-acid of beta-naphthol introduced 

by ,bayer          ,co4    #ahhc4       
,antipyrine introduced by ,l4 ,knorr1   
leading to manufacture of               
phenylhydrazine4    #ahhd4 ,congo red1  
the first secondary azo-colour from     
benzidine1         introduced by        
,boettiger4 ,beginning of manufacture of
 cotton         azo-dyes1 and leading to
 the production of benzidine and        
tolidine         on a large scale4      
#ahhe4 ,secondary azo-dyes from         
benzidine and tolidine containing two   
dissimilar amines1 phenols1 c41         
introduced by ,pfaff4                   
,tartrazine discovered by ,ziegler2     
manufacture of sulpho-acid of           
phenylhydrazine and of dioxytartaric    
acid4    #ahhe4 ,thiorubin introduced by
 ,dahl  ,co41 leading to manufacture of 
thiotoluidine2 followed by primuline1   
discovered by ,a4 ,g4 ,green in         
#ahhg4    #ahhf4 ,secondary azo-dyes of 
stilbene series introduced by ,leonhardt
  ,co4     ,,addendum4   ,by passing    
steam over red-hot carbon1 a mixture of 

carbon monoxide and hydrogen is formed4 
,this mixture of inflammable gases is   
known as water-gas1 and in the          
preparation of the gas on a large scale1
 coke is used as a source of carbon4    
,if1 therefore1 water-gas became        
generally used1 another use for coke    
would be added to those already referred
 to 7p4 #dg74  ,with reference to the   
consumption of coal in ,london 7p4 #df71
 it appears from the ,report of a       
,committee of the ,corporation of       
,london1 issued at the end of #ahij1    
that the present rate of consumption in 
the ,metropolis is #i1gji1jjj tons per  
annum4 ,this corresponds to #bf1fjj tons
 per diem4 ,it has been proved by       
experiment1 that when coal is burnt in  
an open grate1 from one to three per    
cent4 of the coal escapes in the form of
 unburnt solid particles1 or soot1 and  
about #aj per cent4 is lost in the form 
of volatile compounds of carbon4 ,it has
 been estimated that the total amount of
 coal annually wasted by imperfect      

combustion in this country is           
#de1jjj1jjj tons1 corresponding to about
 ,l#ab1jjj1jjj1 taking the value of coal
 at the pit's mouth4 ,taking the        
unconsumed solid particles at the very  
lowest estimate of #a per cent41 it will
 be seen that1 in ,london alone1 we are 
sending forth carbonaceous and tarry    
matter into the atmosphere at the rate  
of about #bff tons daily2 and volatile  
carbon compounds at the daily rate of   
#bffj tons 7see p4 #cb74 ,at the price  
of coal in ,london this means that1 in  
solid combustibles alone1 we are        
absolutely squandering about ,l#aj1jjj  
annually1 to say nothing of the damage  
caused by the presence of this sooty    
pall4 ,such facts as these require no   
comment2 they speak for themselves in   
sombre gloom1 and in the sickliness of  
our town vegetation--they give a new    
meaning to the term in darkest ,london1 
and they plead eloquently for science   
and legislation to show us the way out4 
,,index4     ,accum1 condensation of    

tar-oils1 #fi    ,acetic acid1 #fd      
,acetophenone1 #agh    ,acid brown1 #aea
    ,acid greens1 #ajf    ,acid magenta1
 #ib    ,acid naphthol yellow1 #adc     
,acid yellow1 #abj    ,acridine1 #ahj   
,air1 composition of1 #bd               
,albo-carbon light1 #adj    ,alizarin   
black1 #agb    ,alizarin blue1 #agd     
,alizarin carmine1 #agd    ,alizarin    
green1 #agd    ,alizarin orange1 #agd   
,alkali blue1 #ic                       
,amidodimethylaniline1 #aab    ,ammonia 
in gas-liquor1 #fd    ,ammonia1 origin  
in gas-liquor1 #fe    ,analyses of coal1
 #bc    ,aniline black1 #aad            
,aniline1 history1 #ge    ,aniline1     
manufacture1 #hg    ,aniline yellow1    
#aaf    ,annual production of ammonia1  
#fh    ,anthracene1 #aga    ,anthracene 
brown1 #agd    ,anthracene oil1 #ha1    
#afg    ,anthragallol1 #agd             
,anthrapurpurin1 #agd    ,anthraquinone1
 #agc    ,antifebrine1 #agi             
,antipyrine1 #ahc    ,archil substitute1
 #aea    ,arctic coal1 #ab    ,arsenic  

acid process1 #ij    ,arsenic acid1     
recovery1 #id    ,artificial alizarin1  
#agc    ,artificial purpurin1 #agc      
,asphalte1 #agf    ,auramine1 #ajf      
,aurin1 #acb    ,azines1 #aji           
,azo-blacks1 #aei    ,azo-colours1 #aah 
,azo-dyes for cotton1 #aeh              
,azobenzene1 #aai    ,azo-dyes from     
salicylic acid1 #ace    ,azotoluene1    
#aai     ,baeyer1 ,a4 v41 indigo1 #abg  
,baeyer1 ,a4 v41 phthaleins1 #adf       
,basle blue1 #aaa    ,becher1 early     
experiments1 #cd    ,beet-sugar         
cultivation1 #fg    ,benzal chloride1   
#ajb    ,benzaldehyde1 #ajc    ,benzene1
 discovery1 #gc    ,benzene1 final      
purification1 #hf    ,benzene in        
tar-oil1 #gc    ,benzene theory1 #aif   
,benzidam1 #ge    ,benzidine1 #acf      
,benzoic acid1 manufacture1 #ajd        
,benzotrichloride1 #ajb    ,benzyl      
chloride1 #ajb    ,bernthsen1 methylene 
blue1 #aac    ,bethell1 timber          
preserving1 #gj    ,biebrich scarlet1   
#aef    ,biology1 dyes used in1 #aib    

,bismarck brown1 #aaf    ,bitter-almond 
oil1 #ajc    ,bone oil1 #ahj            
,boettiger1 ,congo-red1 #aeg    ,breant1
 timber pickling1 #gj    ,briquettes1   
#agh    ,burning naphtha1 #hf           
,calorific value of carbon1 #be         
,calorific value of coal1 #bj           
,carbolic acid1 #abi    ,carbolic oil1  
#bc1 #hj1 #abi    ,carbon dioxide1 #bd  
,carboniferous period1 #aa    ,caro and 
,kern1 phosgene dyes1 #ajf    ,caro and 
,wanklyn1 rosolic acid1 #acc    ,caro1  
fluorescein and eosin1 #adg    ,caro1   
methylene blue1 #aab    ,chemical       
washing1 #hc    ,chlorophyll1 #bi       
,chrysamines1 #acf    ,chrysoidine1 #aaf
    ,cinnamic acid1 #abh    ,clayton1   
,dean1 distils coal1 #ce    ,clegg1     
,samuel1 gas-engineer1 #dj    ,coal1    
amount raised1 #ei    ,coal-fields of   
,united ,kingdom1 #fj    ,coal-gas1     
composition1 #ef    ,coal-gas1          
manufacture1 #db    ,coal-mining1       
history1 #eg    ,coal1 origin1 #i       
,coal1 supply1 #ei    ,coerulein1 #adg  

,coke1 composition of1 #dh    ,coke from
 gas-retorts1 #de    ,coke-oven tar1 #di
    ,coke1 uses of1 #dg    ,combustion1 
#bc    ,composition of coal1 #bc        
,congo red1 #aeg    ,conservation of    
energy1 #ah    ,constitution of         
molecules1 #ie    ,corallin1 #acb       
,cotton dyes1 #acg    ,coumarin1 #ahe   
,coupier's process1 #ia    ,creosote    
oil1 #afc    ,creosoting of timber1 #gj 
,cresols1 #aca    ,cresylic acid1 #aca  
,cretaceous coal1 #ab    ,crocein       
scarlets1 #aef    ,crystal violet1 #ajf 
,cumidine1 #aee    ,cyanin1 #ahh        
,dale and ,caro1 induline1 #abj         
,destructive distillation1 #cc          
,diazo-compounds1 #aaf    ,diazotype1   
#aia    ,dimethylaniline1 #ajj          
,dinitrobenzene1 #abj    ,diphenylamine1
 #aja    ,diphenylamine blue1 #aja      
,distillation1 fractional1 #gh          
,doebner1 malachite green1 #ajb         
,dover1 coal under1 #fj    ,dumas and   
,laurent1 anthracene1 #aga              
,dundonald1 ,earl1 early experiments1   

#ci     ,eikonogen1 #ahi    ,electricity
 as an illuminating agent1 #fb          
,eocene coal1 #ab    ,eosin1 #adg       
,erythrosin1 #ahh    ,essence of        
mirbane1 #gd    ,exalgine1 #agi         
,fahlberg1 saccharin1 #ahf    ,faraday1 
discovers benzene1 #gc    ,fast red1    
#aea    ,fertilization by ammonia1 #ff  
,fire-damp1 #cb    ,first runnings1 #hj 
,fischer1 ,e4 and ,o41 rosaniline1 #ig  
,fischer1 hydrazines1 #ahc    ,fischer1 
malachite green1 #ajc    ,flavaniline1  
#ahj    ,flavopurpurin1 #agd            
,fluorescein1 #adg    ,foot-pound1 #ai  
,fractional distillation1 #gh           
,fritzsche1 aniline1 #ge     ,gallein1  
#adf    ,gallic acid1 #adf              
,gallocyanin1 #afb    ,gambines1 #afa   
,garancin1 #afh    ,garden1 naphthalene1
 #aci    ,gas producers1 #eg    ,gas1   
quantity obtained from coal1 #de        
,girard and ,de ,laire1 rosaniline      
blues1 #ib    ,glucosides1 #afi         
,goethe1 visit to coke-burner1 #dh      
,graebe and ,liebermann1 alizarin1 #agj 

,graphite1 #ab    ,graessler1 acid      
yellow1 #abj    ,green1 ,a4 ,g41        
primuline1 #afj    ,griess1             
diazo-compounds1 #aaf     ,hales1 ,rev4 
,stephen1 distils coal1 #cg    ,hofmann1
 benzene in tar-oil1 #gc    ,hofmann1   
red from aniline1 #hi    ,hofmann's     
violets1 #ic    ,homologous series1 #aeb
    ,horse-power1 #bb    ,hull1 ,prof41 
coal supply1 #ei    ,hydrazines1 #ahc   
,hydrocarbons of benzene series1 #hb    
,hydrogen1 calorific value1 #be         
,hydroquinone1 #ahi    ,hypnone1 #agi   
,indigo plants1 #abd    ,indigo1        
syntheses1 #abf    ,indophenol1 #afb    
,indulines1 #aba    ,ingrain colours1   
#afj    ,iodine green1 #id    ,iron     
smelting1 #af    ,iron swarf1 #hg       
,isochromatic plates1 #ahh              
,isomerism1 #hh     ,joule1 mechanical  
equivalent of heat1 #ai    ,juglone1    
#ahf    ,jurassic coal1 #ab             
,kairine1 #ahb    ,kekule1 benzene      
theory1 #aif    ,kekule and ,hidegh1    
azo-dyes1 #ace    ,koch1 tubercle1 #aic 

,koechlin1 gallocyanin1 #afb            
,koechlin and ,witt1 indophenol1 #afb   
,kolbe1 salicylic acid1 #acd    ,kolbe  
and ,schmitt1 phenol dye1 #acb          
,kyanol1 #ge     ,lampblack1 #aci1 #aff 
,laurent1 phenol1 #aca    ,laurent1     
phthalic acid1 #adc    ,laurent1 picric 
acid1 #acf    ,lauth1 methyl violet1 #ih
    ,lauth's violet1 #aaa    ,leonhardt 
,co41 stilbene dyes1 #acg    ,lightfoot1
 aniline black1 #aad    ,light oil1 #hj 
,light oils1 early uses1 #ga    ,lister1
 antiseptic surgery1 #aca    ,london1   
coal introduced1 #eh    ,london1        
illuminated by gas1 #dj    ,lucigen     
burner1 #afc     ,madder1 #afh          
,magdala red1 #adi    ,magenta1 history1
 #hi    ,malachite green1 #ajb          
,manchester brown1 #aaf    ,manchester  
yellow1 #adb    ,mansfield1 isolation of
 benzene1 #gc    ,mansfield's still1 #gg
    ,manures1 #ff    ,marsh gas1 #cb    
,mauve1 discovery1 #gd    ,mechanical   
value of coal1 #bb    ,medlock1 magenta 
process1 #ij    ,methyl chloride1 #ii   

,methylene green1 #aac    ,methyl green1
 #aja    ,methyl violet1 #ih            
,mirbane1 essence1 #gd    ,murdoch1     
introduces coal-gas1 #dj                
,naphthalene1 annual production1 #ada   
,naphthalene in carbolic oil1 #acj      
,naphthionic acid1 #aea    ,naphthol    
green1 #afa    ,naphthol orange1 #aea   
,naphthols1 #ada    ,naphthylamines1    
#adb    ,natanson1 aniline red1 #hi     
,neutral red1 #aaa    ,neutral violet1  
#aaa    ,new blue1 #afa    ,nicholson   
blue1 #ic    ,nicholson1 magenta        
process1 #ij    ,nietzki1 azines1 #aji  
,nietzki1 ,biebrich scarlet1 #aef       
,nietzki1 quinone1 #aia    ,night blue1 
#ajf    ,nigrosine1 #aba                
,nitrification1 #ff    ,nitrobenzene    
process1 #ia    ,nitrosodimethylaniline1
 #aaa    ,non-,carboniferous coal1 #aa  
,number of compounds in tar1 #ha        
,old ,red ,sandstone1 coal in1 #ab      
,oligocene brown coal1 #ab              
,orthochromatic plates1 #ahh            
,oxazines1 #afb    ,oxide of iron for   

gas purifying1 #dd     ,paraffin oil and
 wax1 #ej    ,patent fuel1 #agh         
,perfumes1 #ahe    ,perkin1 alizarin1   
#agj    ,perkin1 discovers mauve1 #gd   
,permanence of dyes1 #aih    ,permian   
coal1 #ab    ,persoz1 phenol dye1 #acb  
,pharmaceutical preparations1 #agh      
,phenanthrene1 #agb    ,phenols1 #abi   
,phosgene dyes1 #ajf    ,phosphine1 #id1
 #ahj    ,photographic developers1 #ahi 
,phthaleins1 #adf    ,phthalic acid1    
#adc    ,picric acid1 #acf    ,pitch1   
#ha1 #agf    ,plants1 growth of1 #bf    
,ponceaux1 #aea    ,primary azo-dyes1   
#aef    ,primuline1 #afj    ,propiolic  
acid1 #abh    ,purpurin1 #afi           
,pyrazole1 #ahc    ,pyridine1 #hg       
,pyridine bases1 #agi    ,pyrogallol1   
#adf     ,quinaldine1 #ahb    ,quinic   
acid1 #ahi    ,quinoline1 #ahj          
,quinoline green1 #ahb    ,quinoline    
red1 #ahh    ,quinoline yellow1 #ahb    
,quinones1 #agb     ,read ,holliday's   
lamp1 #gb    ,rectification of          
hydrocarbons1 #hd    ,resorcinol1 #ade  

,rhodamines1 #adh    ,roccellin1 #aea   
,roman coal-mining1 #eg    ,rosaniline  
blues1 #ib    ,rosaniline from rosolic  
acid1 #acc    ,rosolic acid1 #acb       
,runge1 kyanol1 #ge    ,runge1 phenol in
 tar1 #aca     ,saccharin1 #ahf         
,saffranine1 #ajh    ,salicylic acid1   
#acd    ,salicylic aldehyde1 #ahe       
,salols1 #agi    ,schiendl1 ,magdala    
red1 #adi    ,scotland1 shale-oil       
industry1 #ec    ,sea coal1 #eh         
,secondary azo-dyes1 #aef    ,shale1    
nature of1 #ea    ,shale-oil industry1  
#ej    ,skraup1 quinoline1 #aha         
,sodium nitrite1 #aai    ,solar energy1 
#bh    ,soluble blue1 #ic    ,solvent   
naphtha1 #hf    ,steam-engines1 #bj     
,stilbene azo-dyes1 #acg    ,structure  
of coal1 #ae    ,sulphanilic acid1 #aej 
,sulphuric acid1 #de    ,sunlight1      
source of energy in coal1 #cj           
,surgery1 antiseptic1 #aca     ,tar     
distilling1 #gg    ,tar1 first          
utilization1 #fi    ,tar from           
coke-ovens1 #di    ,tar1 quantity       

obtained from coal1 #de    ,tartrazine1 
#ahd    ,tertiary coal1 #ab             
,thalline1 #ahb    ,thermifugine1 #ahb  
,thiazines1 #aac    ,thiodiphenylamine1 
#aac    ,thiorubin1 #afj    ,timber     
pickling1 #gj    ,tolidine1 #acf        
,toluene from tar1 #ha    ,torbane ,hill
 coal1 #eb    ,transformation of wood   
into coal1 #ca    ,triassic coal1 #ab   
,trimethylamine1 #ii    ,trinitrophenol1
 #acf    ,triphenylmethane1 #ig         
,tubercle bacillus1 #aic    ,turkey red1
 #agj     ,underclay1 #ac               
,unverdorben1 crystallin1 #ge    ,uses  
of coal1 #af     ,vanillin1 #ahe        
,vegetable deposits1 recent1 #ac        
,verguin1 red from aniline1 #ij         
,victoria blue1 #ajf    ,victoria       
yellow1 #acg    ,vinasse1 #ii           
,vincent1 methyl chloride1 #ajj         
,violaniline1 #aba     ,wasteful use of 
coal1 #cb1 #bjc    ,water1 composition  
of1 #be    ,water gas1 #bjc    ,watson1 
,bishop1 coke-oven tar1 #ej    ,watson1 
,bishop1 distils coal1 #cg    ,wealden  

iron industry1 #ag    ,whitaker1 ,w41   
coal in ,s4-,e4 ,england1 #fj           
,winsor1 promotes introduction of gas1  
#da    ,witt1 azines1 #aji    ,witt1    
chrysoidine1 #aaf    ,witt1 naphthol    
orange1 #aej    ,wood vinegar1 #fd      
,woody fibre1 #bf    ,woulfe1 picric    
acid1 #acf     ,xylenes from tar1 #ha   
,xylidine scarlet1 #aec     ,young1     
,james1 burning-oil1 #ea     ,ziegler1  
tartrazine1 #ahd    ,zinin1 benzidam1   
#ge   ,,the ,,end4   ,richard ,clay     
,sons1 ,limited1 ,london  ,bungay4      
,footnotes3  #a ,an experiment          
concerning the ,spirit of ,coals1 ,phil4
 ,trans4 7abridged71 vol4 viii4 p4 #bie4
  #b ,report of the ,coal ,commissioners
 7#ahff-ga71 vol4 i4  #c ,in a paper    
read before the ,royal ,statistical     
,society by ,mr4 ,price-,williams in    
#ahhi1 this author points out that1     
owing to the introduction of the        
,bessemer process and other economical  
improvements1 the amount of coal used in
 the iron and steel manufacture had     

fallen in #ahfg to about sixteen and a  
half per cent4 of the total quantity    
raised4  #d ,this remark does not apply 
to ,great ,britain2 our ,excise         
regulations have practically killed     
those branches of manufacture requiring 
the use of pure wood-spirit4  #e ,since 
the above was written1 new synthetical  
processes for the production of indigo  
have been made known in ,germany by     
,karl ,heumann4 ,of the commercial      
aspect of these discoveries it is of    
course impossible at present to form an 
opinion4  #f ,with phthalic anhydride   
gives fluorescein and dyes of eosin and 
rhodamin series4  #g ,diazotised and    
combined with naphthylamines1 naphthols1
 or their sulpho-acids give azo-dyes4   
#h ,with naphthols give oxazines and    
indophenol4  #i ,diazotised and combined
 with phenols1 amines1 or sulpho-acids  
to form azo-dyes4  #aj ,combined with   
diazotised amido-compounds to form      
azo-dyes4  #aa ,since the above was     
written the continuation of ,koch's     

researches upon the tubercle bacillus   
has culminated in the discovery of his  
now world-renowned lymph for the        
inoculation of patients suffering from  
tubercular disease4  #ab ,in one large  
factory in ,yorkshire there is a set of 
stills kept constantly at work making   
pure aniline at the rate of two hundred 
tons per month4 ,the monthly consumption
 of coal in this factory is two thousand
 tons1 equal to twenty-four thousand    
tons per annum4     ,,publications ,,of 
,,the  ,society for ,promoting          
,christian ,knowledge4   ,,the ,,romance
 ,,of ,,science4  ,a series of books    
which will show that science has for the
 masses as great interest and more      
edification than the romances of the    
day4  ,small ,post #hvo1 ,cloth boards4 
,the ,birth and ,growth of ,worlds4 ,a  
,lecture by ,professor ,a4 ,h4 ,,green1 
,m4,a41 ,f4,r4,s4 #as4  ,soap-,bubbles1 
and the ,forces which ,mould ,them4 ,a  
course of ,lectures by ,c4 ,v4 ,,boys1  
,a4,r4,s4,m41 ,f4,r4,s4 ,with numerous  

diagrams4 #bs4 #f;d4  ,spinning ,tops4  
,by ,professor ,j4 ,,perry1 ,m4,e41     
,d4,sc41 ,f4,r4,s4 ,with numerous       
diagrams4 #bs4 #f;d4  ,diseases of      
,plants4 ,by ,professor ,,marshall      
,,ward4 ,with ,numerous ,illustrations4 
#bs4 #f;d4  ,the ,story of a            
,tinder-,box4 ,a course of ,lectures by 
,,charles ,,meymott ,,tidy1 ,m4,b41     
,m4,s41 ,f4,c4,s4 ,with ,numerous       
,illustrations4 #bs4  ,time and ,tide4  
,a ,romance of the ,moon4 ,by ,sir      
,,robert ,s4 ,,ball1 ,,ll4,d41 ,royal   
,astronomer of ,ireland4 ,with          
,illustrations4 #bs4 #f;d4   ,,manuals  
,,of ,,health4  ,fcap4 #hvo1 #abh pp41  
limp cloth1 price #as4 each4  ,health   
and ,occupation4 ,by ,b4 ,w4            
,,richardson1 ,esq41 ,f4,r4,s41 ,m4,d4  
,habitation in ,relation to ,health     
7,the74 ,by ,f4 ,s4 ,b4 ,,chaumont1     
,m4,d41 ,f4,r4,s4  ,on ,personal ,care  
of ,health4 ,by the late ,e4 ,a4        
,,parkes1 ,m4,d41 ,f4,r4,s4  ,water1    
,air1 and ,disinfectants4 ,by ,w4 ,,noel

 ,,hartley1 ,esq41 ,king's ,college4    
,,manuals ,,of ,,elementary ,,science4  
,fcap4 #hvo1 #abhpp41 with              
,illustrations1 limp cloth1 #as4 each4  
,physiology4 ,by ,f4 ,,le ,,gros        
,,clarke1 ,f4,r4,s41 ,st4 ,thomas's     
,hospital4  ,geology4 ,by the ,rev4 ,t4 
,g4 ,,bonney1 ,m4,a41 ,f4,g4,s41 ,fellow
 and late ,tutor of ,st4 ,john's        
,college1 ,cambridge4  ,chemistry4 ,by  
,,albert ,j4 ,,bernays4  ,astronomy4 ,by
 ,w4 ,h4 ,m4 ,,christie1 ,m4,a41 the    
,royal ,observatory1 ,greenwich4        
,botany4 ,by ,,robert ,,bentley1        
,professor of ,botany in ,king's        
,college1 ,london4  ,zoology4 ,by       
,,alfred ,,newton1 ,m4,a41 ,f4,r4,s41   
,professor of ,zoology and ,comparative 
,anatomy in the ,university of          
,cambridge4  ,matter and ,motion4 ,by   
the late ,j4 ,,clerk ,,maxwell1 ,m4,a41 
,trinity ,college1 ,cambridge4          
,spectroscope and its ,work 7,the74 ,by 
the late ,,richard ,a4 ,,proctor4       
,crystallography4 ,by ,,henry ,,palin   

,,gurney1 ,m4,a41 ,clare ,college1      
,cambridge4  ,electricity4 ,by the late 
,professor ,,fleeming ,,jenkin4         
,,natural ,,history ,,rambles4  ,fcap4  
#hvo1 with numerous ,woodcuts1 ,cloth   
boards1 #bs4 #f;d4 each4  ,,in ,,search 
,,of ,,minerals4 ,by the late ,d4 ,t4   
,,ansted1 ,m4,a41 ,f4,r4,s4  ,,lakes    
,,and ,,rivers4 ,by ,c4 ,o4 ,,groom     
,,napier1 ,f4,g4,s4  ,,lane ,,and       
,,field4 ,by the late ,rev4 ,j4 ,g4     
,,wood1 ,m4,a4  ,,mountain ,,and ,,moor4
 ,by ,j4 ,e4 ,,taylor1 ,f4,l4,s41       
,f4,g4,s41 ,editor of ,science-,gossip4 
,,ponds ,,and ,,ditches4 ,by ,m4 ,c4    
,,cooke1 ,m4,a41 ,,ll4,d4  ,,the        
,,sea-,,shore4 ,by ,professor ,p4       
,,martin ,,duncan1 ,m4,b4 7,london71    
,f4,r4,s4  ,,the ,,woodlands4 ,by ,m4   
,c4 ,,cooke1 ,m4,a41 ,,ll4,d4           
,,underground4 ,by ,j4 ,e4 ,,taylor1    
,f4,l4,s4   ,,series ,,of               
,,photo-,,relievo ,,maps4  7,patented7  
,size #ai in4 by #ad in4    ,,england   
,,and ,,wales4--,,scotland4--,,europe4  

,names of places and rivers left to be  
filled in by             s4 d4          
scholars                                
each     #j    #f   ,with rivers and    
names of places                         
#j    #i   ,with names of places1 and   
county and country     divisions in     
colours                                 
#a    #j    ,,asia4    ,names of places 
and rivers left to be filled in by      
scholars                                
#j    #f   ,with rivers and names of    
places                                #j
    #i    ,,south ,,london4    ,with    
names of places1 c4                     
#j    #f    ,wall ,map4--,,england ,,and
 ,,wales4    7,size #ef in4 by #df in47 
,mounted on canvas1 roller   and        
varnished                               
#ab    #j  ,these ,maps present each    
country as if in actual relief1 and thus
 afford an accurate picture of the      
configuration of the earth's surface4   
,,miscellaneous ,,publications4         
s4 d4   ,animal ,creation 7,the74 ,a    

popular ,introduction to ,zoology4   ,by
 the late ,,thomas ,,rymer ,,jones1     
,f4,r4,s4 ,with #dhh ,woodcuts4   ,post 
#hvo4 ,cloth boards                     
#g    #f    ,beauty in ,common ,things4 
,illustrated by #ab ,drawings from      
,nature1 by ,mrs4 ,j4 ,w4 ,whymper1 and 
printed in ,colours1 with   descriptions
 by the ,author of ,life ,underground1  
c4 #dto4   ,cloth boards                
#aj    #f    ,birds' ,nests and ,eggs4  
,with #bb coloured plates of ,eggs4     
,square #afmo4 ,cloth boards            
#c    #j    ,british ,birds in their    
,haunts4 ,by the late ,rev4 ,c4 ,a4     
,,johns1 ,b4,a41 ,f4,l4,s4 ,with #aij   
engravings by ,wolf and ,whymper4       
,post #hvo4 ,cloth boards               
#f    #j    ,evenings at the            
,microscope2 or1 ,researches among the  
,minuter ,organs and ,forms of ,animal  
,life4 ,by ,,philip ,h4   ,,gosse1      
,f4,r4,s4 ,with #aab woodcuts4 ,post    
#hvo4 ,cloth boards       #d    #j      
,fern ,portfolio 7,the74 ,by ,,francis  

,g4 ,,heath1 ,author of   ,where to find
 ,ferns1 c4 ,with #ae plates1           
elaborately drawn   life-size1          
exquisitely coloured from ,nature1 and  
accompanied   with descriptive text4    
,cloth boards                           
#h    #j    ,fishes1 ,natural ,history  
of ,british3 their ,structure1          
,economic ,uses1 and ,capture by ,net   
and ,rod4 ,by the late ,,frank          
,,buckland4 ,with numerous              
illustrations4 ,crown #hvo4 ,cloth      
boards                                  
#e    #j    ,flowers of the ,field4 ,by 
the late ,rev4 ,c4 ,a4 ,,johns1 ,b4,a41 
,f4,l4,s4 ,with numerous woodcuts4 ,post
 #hvo4 ,cloth boards         #e    #j   
,forest ,trees 7,the7 of ,great         
,britain4 ,by the late ,rev4   ,c4 ,a4  
,johns1 ,b4,a41 ,f4,l4,s4 ,with #aej    
woodcuts4 ,post #hvo4   ,cloth boards   
#e    #j    ,freaks and ,marvels of     
,plant ,life2 or1 ,curiosities of       
,vegetation4 ,by ,m4 ,c4 ,,cooke1       
,m4,a41 ,,ll4,d4 ,with numerous         

illustrations4 ,post #hvo4 ,cloth boards
                         #f    #j       
,man and his ,handiwork4 ,by the late   
,rev4 ,j4 ,g4 ,,wood1   ,author of ,lane
 and ,field1 c4 ,with about #ejj        
illustrations4 ,large ,post #hvo4 ,cloth
 boards                  #aj    #f      
,natural ,history of the ,bible 7,the74 
,by the ,rev4 ,,canon   ,,tristram1     
,author of ,the ,land of ,israel1 c4    
,with   numerous illustrations4 ,crown  
#hvo4 ,cloth boards               #e    
#j    ,nature and her ,servants2 or1    
,sketches of the ,animal   ,kingdom4 ,by
 the ,rev4 ,,theodore ,,wood4 ,with     
numerous woodcuts4   ,large ,post #hvo4 
,cloth boards                           
#e    #j    ,ocean 7,the74 ,by ,,philip 
,,henry ,,gosse1 ,f4,b4,s41 ,author of  
,evenings at the ,microscope4 ,with #ea 
illustrations and   woodcuts4 ,post     
#hvo4 ,cloth boards                     
#c    #j    ,our ,bird ,allies4 ,by the 
,rev4 ,,theodore ,,wood4 ,with numerous 
illustrations4 ,fcap4 #hvo4 ,cloth      

boards                        #b    #f  
,our ,insect ,allies4 ,by the ,rev4     
,,theodore ,,wood4 ,with   numerous     
illustrations4 ,fcap4 #hvo4 ,cloth      
boards               #b    #f    ,our   
,insect ,enemies4 ,by the ,rev4         
,,theodore ,,wood4 ,with   numerous     
illustrations4 ,fcap4 #hvo4 ,cloth      
boards               #b    #f    ,our   
,island ,continent4 ,a ,naturalist's    
,holiday in   ,australia4 ,by ,j4 ,e4   
,,taylor1 ,f4,l4,s41 ,f4,g4,s4 ,with    
,map4   ,fcap4 #hvo4 ,cloth boards      
#b    #f    ,our ,native ,songsters4 ,by
 ,,anne ,,pratt1 ,author of ,wild       
,flowers4 ,with #gb coloured plates4    
#afmo4 ,cloth boards         #f    #j   
,selborne 7,the ,natural ,history of74  
,by the ,rev4 ,,gilbert   ,,white4 ,with
 ,frontispiece1 ,map1 and #ej woodcuts4 
,post #hvo4   ,cloth boards             
#b    #f    ,toilers in the ,sea4 ,by   
,m4 ,c4 ,,cooke1 ,m4,a41 ,,ll4,d4 ,post 
#hvo4   ,with numerous illustrations4   
,cloth boards                     #e    

#j    ,wayside ,sketches4 ,by ,f4       
,,edward ,,hulme1 ,f4,l4,s41 ,f4,s4,a4  
,with   numerous illustrations4 ,crown  
#hvo4 ,cloth boards               #e    
#j    ,where to find ,ferns4 ,by        
,,francis ,g4 ,,heath1 ,author of ,the  
,fern ,portfolio1 c4 ,with numerous     
illustrations4 ,fcap4   #hvo4 ,cloth    
boards                                  
#a    #f    ,wild ,flowers4 ,by ,,anne  
,,pratt1 ,author of ,our ,native        
,songsters1 c4 ,with #aib coloured      
plates4 ,in two volumes4   #afmo4 ,cloth
 boards                                 
#ab    #j     ,,london3                 
,,northumberland ,,avenue1 ,,charing    
,,cross1 ,w4,c42   #dc1 ,,queen         
,,victoria ,,street1 ,e4,c4             
,,brighton3 #ace1 ,,north ,,street4     
,transcriber's ,notes3  ,passages in    
italics are indicated by italics4       
,punctuation has been corrected without 
note4  ,spelling and hyphenation        
variants have been retained from the    
original4  ,the original text includes  

,greek characters4 ,for this text       
version these letters have been replaced
 with transliterations4  ,the diagrams  
in this text are rough approximations of
 images provided in the html version4