,alembic ,club ,reprints--,no4 #a4      
,,experiments  ,,upon  ,,magnesia       
,,alba1  ,,quicklime1  ,,and ,,some     
,,other  ,,alcaline ,,substances4   ,,by
 ,,joseph ,,black1 ,m4,d41 ,professor of
 ,chemistry in the ,university of       
,edinburgh1 #agff-agig4  7#agee47       
,edinburgh3 ,,published ,,by ,,the      
,,alembic ,,club4  ,edinburgh ,agent3   
,,william ,f4 ,,clay1 #ah ,,teviot      
,,place4  ,london ,agents3 ,,simpkin1   
,,marshall1 ,,hamilton1 ,,kent1  ,,co4  
,,ltd4  #ahih4  ,illustration3 ,insignia
     ,,preface4   ,black's ,paper       
entitled ,experiments upon ,magnesia    
,alba1 ,quicklime1 and some other       
,alcaline ,substances was read in ,june 
#agee1 and was first published in       
,essays and ,observations1 ,physical and
 ,literary4 ,read before a ,society in  
,edinburgh1 and ,published by them1     
,volume ,,ii41 ,edinburgh1 #agef2 pp4   
#aeg-bbe4 ,it was subsequently reprinted
 several times during the life of the   
author1 not only in later editions of   

these ,essays1 but also in a separate   
form4 ,copies of the original ,paper are
 now very difficult to obtain1 and the  
later reprints have also become scarce4 
,the present reprint is a faithful copy 
of the ,paper as it first appeared in   
#agef1 the spelling1 c41 of the original
 having been carefully reproduced4  ,the
 ,paper constitutes a highly important  
step in the laying of the foundations of
 chemistry as an exact science1 and     
furnishes a model of carefully planned  
experimental investigation1 and of clear
 reasoning upon the results of          
experiment4 ,it is neither so widely    
read by the younger chemists nor is it  
so readily accessible as it ought to be1
 and the object of the ,alembic ,club in
 issuing it as the first volume of a    
series of ,reprints of historically     
important contributions to ,chemistry1  
is to place it within easy reach of     
every student of ,chemistry and of the  
,history of ,chemistry4  ,the student's 
attention may be particularly called to 

,black's tacit adoption of the          
quantitative method in a large number of
 his experiments1 and to the way in     
which he bases many of his conclusions  
upon the results obtained in these      
experiments4 ,even yet it is very       
frequently stated that the introduction 
of the quantitative method into         
,chemistry 7which did not by any means  
originate with ,black7 took place at a  
considerably later date4  ,l4 ,d4       
,,experiments  ,,upon  ,,magnesia       
,,alba1 ,,quicklime1  ,,and ,,some      
,,other  ,,alcaline ,,substances2  ,,by 
,,joseph ,,black1 ,m4,d4#a  ,,part ,i4  
,hoffman1 in one of his observations1   
gives the history of a powder called    
magnesia alba1 which had long been used 
and esteemed as a mild and tasteless    
purgative2 but the method of preparing  
it was not generally known before he    
made it public4#b  ,it was originally   
obtained from a liquor called the mother
 of nitre1 which is produced in the     
following manner3  ,salt-petre is       

separated from the brine which first    
affords it1 or from the water with which
 it is washed out of nitrous earths1 by 
the process commonly used in            
crystallizing salts4 ,in this process   
the brine is gradually diminished1 and  
at length reduced to a small quantity of
 an unctuous bitter saline liquor1      
affording no more salt-petre by         
evaporation2 but1 if urged with a brisk 
fire1 drying up into a confused mass    
which attracts water strongly1 and      
becomes fluid again when exposed to the 
open air4  ,to this liquor the workmen  
have given the name of the mother of    
nitre2 and ,hoffman1 finding it composed
 of the magnesia united to an acid1     
obtained a separation of these1 either  
by exposing the compound to a strong    
fire in which the acid was dissipated   
and the magnesia remained behind1 or by 
the addition of an alkali which         
attracted the acid to itself3 and this  
last method he recommends as the best4  
,he likewise makes an inquiry into the  

nature and virtues of the powder thus   
prepared2 and observes1 that it is an   
absorbent earth which joins readily with
 all acids1 and must necessarily destroy
 any acidity it meets in the stomach2   
but that its purgative power is         
uncertain1 for sometimes it has not the 
least effect of that kind4 ,as it is a  
mere insipid earth1 he rationally       
concludes it to be purgative only when  
converted into a sort of neutral salt by
 an acid in the stomach1 and that its   
effect is therefore proportional to the 
quantity of this acid4  ,altho' magnesia
 appears from this history of it to be a
 very innocent medicine1 yet having     
observed1 that some hypochondriacs who  
used it frequently1 were subject to     
flatulencies and spasms1 he seems to    
have suspected it of some noxious       
quality4 ,the circumstances however     
which gave rise to his suspicion1 may   
very possibly have proceeded from the   
imprudence of his patients1 who1        
trusting too much to magnesia1 7which is

 properly a palliative in that disease17
 and neglecting the assistance of other 
remedies1 allowed their disorder to     
increase upon them4 ,it may indeed be   
alledged1 that magnesia1 as a purgative1
 is not the most eligible medicine for  
such constitutions1 as they agree best  
with those that strengthen1 stimulate   
and warm2 which the saline purges       
commonly used are not observed to do4   
,but there seems at least to be no      
objection to its use when children are  
troubled with an acid in their stomach2 
for gentle purging in this case is very 
proper1 and it is often more            
conveniently procured by means of       
magnesia than of any other medicine1 on 
account of its being intirely insipid4  
,the above-mentioned ,author observing1 
some time after1 that a bitter saline   
liquor1 similar to that obtained from   
the brine of salt-petre1 was likewise   
produced by the evaporation of those    
waters which contain common salt1 had   
the curiosity to try if this would also 

yield a magnesia4 ,the experiment       
succeeded3 and he thus found out another
 process for obtaining this powder1 and 
at the same time assured himself by     
experiments1 that the product from both 
was exactly the same4#c  ,my curiosity  
led me some time ago to inquire more    
particularly into the nature of         
magnesia1 and especially to compare its 
properties with those of the other      
absorbent earths1 of which there plainly
 appeared to me to be very different    
kinds1 altho' commonly confounded       
together under one name4 ,i was indeed  
led to this examination of the absorbent
 earths1 partly by the hope of          
discovering a new sort of lime and      
lime-water1 which might possibly be a   
more powerful solvent of the stone than 
that commonly used2 but was disappointed
 in my expectations4  ,i have had no    
opportunity of seeing ,hoffman's first  
magnesia or the liquor from which it is 
prepared1 and have therefore been       
obliged to make my experiments upon the 

second4  ,in order to prepare it1 ,i at 
first employed the bitter saline liquor 
called bittern1 which remains in the    
pans after the evaporation of sea water4
 ,but as that liquor is not always      
easily procured1 ,i afterwards made use 
of a salt called epsom-salt1 which is   
separated from the bittern by           
crystallization1 and is evidently       
composed of magnesia and the vitriolic  
acid4  ,there is likewise a spurious    
kind of ,glauber salt1 which yields     
plenty of magnesia1 and seems to be no  
other than the epsom salt of sea water  
reduced to crystals of a larger size4   
,and common salt also affords a small   
quantity of this powder2 because being  
separated from the bittern by one hasty 
crystallization only1 it necessarily    
contains a portion of that liquor4      
,those who would prepare a magnesia from
 epsom-salt1 may use the following      
process4  ,dissolve equal quantities of 
epsom-salt1 and of pearl ashes          
separately in a sufficient quantity of  

water2 purify each solution from its    
dregs1 and mix them accurately together 
by violent agitation3 then make them    
just to boil over a brisk fire4  ,add   
now to the mixture three or four times  
its quantity of hot water2 after a      
little agitation1 allow the magnesia to 
settle to the bottom1 and decant off as 
much of the water as possible4 ,pour on 
the same quantity of cold water2 and1   
after settling1 decant it off in the    
same manner4 ,repeat this washing with  
the cold water ten or twelve times3 or  
even oftner1 if the magnesia be required
 perfectly pure for chemical            
experiments4  ,when it is sufficiently  
washed1 the water may be strained and   
squeezed from it in a linen cloth2 for  
very little of the magnesia passes      
thro'4  ,the alkali in the mixture      
uniting with the acid1 separates it from
 the magnesia2 which not being of itself
 soluble in water1 must consequently    
appear immediately under a solid form4  
,but the powder which thus appears is   

not intirely magnesia2 part of it is the
 neutral salt1 formed from the union of 
the acid and alkali4 ,this neutral salt 
is found1 upon examination1 to agree in 
all respects with vitriolated tartar1   
and requires a large quantity of hot    
water to dissolve it4 ,as much of it is 
therefore dissolved as the water can    
take up2 the rest is dispersed thro' the
 mixture in the form of a powder4 ,hence
 the necessity of washing the magnesia  
with so much trouble2 for the first     
affusion of hot water is intended to    
dissolve the whole of the salt1 and the 
subsequent additions of cold water to   
wash away this solution4  ,the caution  
given of boiling the mixture is not     
unnecessary2 if it be neglected1 the    
whole of the magnesia is not accurately 
separated at once2 and by allowing it to
 rest for some time1 that powder        
concretes into minute grains1 which1    
when viewed with the microscope1 appear 
to be assemblages of needles diverging  
from a point4 ,this happens more        

especially when the solutions of the    
epsom-salt and of the alkali are diluted
 with too much water before they are    
mixed together4 ,thus1 if a dram of     
epsom-salt and of salt of tartar be     
dissolved each in four ounces of water1 
and be mixed1 and then allowed to rest  
three or four days1 the whole of the    
magnesia will be formed into these      
grains4 ,or if we filtrate the mixture  
soon after it is made1 and heat the     
clear liquor which passes thro'2 it will
 become turbid1 and deposite a magnesia4
  ,i had the curiosity to satisfy myself
 of the purgative power of magnesia1 and
 of ,hoffman's opinion concerning it1 by
 the following easy experiment4 ,i made 
a neutral salt of magnesia and distilled
 vinegar2 choosing this acid as being1  
like that in weak stomachs1 the product 
of fermentation4 ,six drams of this ,i  
dissolved in water1 and gave to a       
middle-aged man1 desiring him to take it
 by degrees4 ,after having taken about a
 third1 he desisted1 and purged four    

times in an easy and gentle manner4 ,a  
woman of a strong constitution got the  
remainder as a brisk purgative1 and it  
operated ten times without causing any  
uneasiness4 ,the taste of this salt is  
not disagreeable1 and it appears to be  
rather of the cooling than of the acrid 
kind4  ,having thus given a short sketch
 of the history and medical virtues of  
magnesia1 ,i now proceed to an account  
of its chemical properties4 ,by my first
 experiments1 ,i intended to learn what 
sort of neutral salts might be obtained 
by joining it to each of the vulgar     
acids2 and the result was as follows4   
,magnesia is quickly dissolved with     
violent effervescence1 or explosion of  
air1 by the acids of vitriol1 nitre1 and
 of common salt1 and by distilled       
vinegar2 the neutral saline liquors     
thence produced having each their       
peculiar properties4  ,that which is    
made with the vitriolic acid1 may be    
condensed into crystals similar in all  
respects to epsom-salt4  ,that which is 

made with the nitrous is of a yellow    
colour1 and yields saline crystals1     
which retain their form in a very dry   
air1 but melt in a moist one4  ,that    
which is produced by means of spirit of 
salt1 yields no crystals2 and if        
evaporated to dryness1 soon melts again 
when exposed to the air4  ,that which is
 obtained from the union of distilled   
vinegar with magnesia1 affords no       
crystals by evaporation1 but is         
condensed into a saline mass1 which1    
while warm1 is extremely tough and      
viscid1 very much resembling a strong   
glue both in colour and consistence1 and
 becomes brittle when cold4  ,by these  
experiments magnesia appears to be a    
substance very different from those of  
the calcarious class2 under which ,i    
would be understood to comprehend all   
those that are converted into a perfect 
quick-lime in a strong fire1 such as    
lime-stone1 marble1 chalk1 those spars  
and marles which effervesce with aqua   
fortis1 all animal shells and the bodies

 called lithophyta4 ,all of these1 by   
being joined with acids1 yield a set of 
compounds which are very different from 
those we have just now described4 ,thus1
 if a small quantity of any calcarious  
matter be reduced to a fine powder and  
thrown into spirit of vitriol1 it is    
attacked by this acid with a brisk      
effervescence2 but little or no         
dissolution ensues4 ,it absorbs the     
acid1 and remains united with it in the 
form of a white powder1 at the bottom of
 the vessel1 while the liquor has hardly
 any taste1 and shews only a very light 
cloud upon the addition of alkali4#d    
,the same white powder is also formed   
when spirit of vitriol is added to a    
calcarious earth dissolved in any other 
acid2 the vitriolic expelling the other 
acid1 and joining itself to the earth by
 a stronger attraction2 and upon this   
account the magnesia of sea-water seems 
to be different from either of those    
described by ,hoffman4 ,he says         
expressly1 that the solutions of each of

 his powders1 or1 what is equivalent1   
that the liquors from which they are    
obtained1 formed a coagulum1 and        
deposited a white powder1 when he added 
the vitriolic acid2#e which experiment  
,i have often tried with the marine     
bittern1 but without success4 ,the      
coagulum thus formed in the mother of   
nitre may be owing to a quantity of     
quick-lime contained in it2 for         
quick-lime is used in extracting the    
salt-petre from its matrix4 ,but it is  
more difficult to account for the       
difference between ,hoffman's bittern   
and ours1 unless we will be satisfied to
 refer it to this1 that he got his from 
the waters of salt springs1 which may   
possibly be different from those of the 
sea4  ,magnesia is not less remarkably  
distinguished from the calcarious       
earths1 by joining it to the nitrous and
 vegetable acids1 than to the vitriolic4
 ,those earths1 when combined with      
spirit of nitre1 cannot be reduced to a 
crystalline form1 and if they are       

dissolved in distilled vinegar1 the     
mixture spontaneously dries up into a   
friable salt4  ,having thus found       
magnesia to differ from the common      
alkaline earths1 the object of my next  
inquiry was its peculiar degree of      
attraction for acids1 or what was the   
place due to it in ,mr4 ,geoffroy's     
table of elective attractions4  ,three  
drams of magnesia in fine powder1 an    
ounce of salt ammoniac1 and six ounces  
of water were mixed together1 and       
digested six days in a retort joined to 
a receiver4  ,during the whole time1 the
 neck of the retort was pointed a little
 upwards1 and the most watery part of   
the vapour1 which was condensed there1  
fell back into its body4 ,in the        
beginning of the experiment1 a volatile 
salt was therefore collected in a dry   
form in the receiver1 and afterwards    
dissolved into spirit4  ,when all was   
cool1 ,i found in the retort a saline   
liquor1 some undissolved magnesia1 and  
some salt ammoniac crystallized4 ,the   

saline liquor was separated from the    
other two1 and then mixed with the      
alkaline spirit4 ,a coagulum was        
immediately formed1 and a magnesia      
precipitated from the mixture4  ,the    
magnesia which had remained in the      
retort1 when well washed and dried1     
weighed two scruples and fifteen grains4
  ,we learn by the latter part of this  
experiment1 that the attraction of the  
volatile alkali for acids is stronger   
than that of magnesia1 since it         
separated this powder from the acid to  
which it was joined4 ,but it also       
appears1 that a gentle heat is capable  
of overcoming this superiority of       
attraction1 and of gradually elevating  
the alkali1 while it leaves the less    
volatile acid with the magnesia4        
,dissolve a dram of any calcarious      
substance in the acid of nitre or of    
common salt1 taking care that the       
solution be rendered perfectly neutral1 
or that no superfluous acid be added4   
,mix with this solution a dram of       

magnesia in fine powder1 and digest it  
in the heat of boiling water about      
twenty four hours2 then dilute the      
mixture with double its quantity of     
water1 and filtrate4 ,the greatest part 
of the earth now left in the filtre is  
calcarious1 and the liquor which passed 
thro'1 if mixed with a dissolved alkali1
 yields a white powder1 the largest     
portion of which is a true magnesia4    
,from this experiment it appears1 that  
an acid quits a calcarious earth to join
 itself to magnesia2 but the exchange   
being performed slowly1 some of the     
magnesia is still undissolved1 and part 
of the calcarious earth remains yet     
joined to the acid4  ,when a small      
quantity of magnesia is thrown into a   
solution of the corrosive sublimate of  
mercury1 it soon separates part of the  
mercury in the form of a dark red       
powder1 and is itself dissolved4        
,imagining that ,i perceived some       
resemblance between the properties of   
magnesia and those of alkalis1 ,i was   

led to try what change this substance   
would suffer from the addition of       
quick-lime1 which alters in such a      
peculiar manner the alkaline salts4     
,twenty seven grains of magnesia in fine
 powder were mixed with eighteen ounces 
of lime-water in a flask1 which was     
corked close and shaken frequently for  
four days4 ,during this time1 ,i        
frequently dipp'd into it little bits of
 paper1 which were coloured with the    
juice of violets2 and these became green
 as soon as they touched the water1     
until the fourth day1 when their colour 
did not seem to be altered4 ,the water  
being now poured off1 was intirely      
insipid1 and agreed in every chemical   
trial with pure water4 ,the powder1     
after being perfectly well dried1       
weighed thirty seven grains4 ,it did not
 dissolve intirely in spirit of vitriol2
 but1 after a brisk effervescence1 part 
of it subsided in the same manner as the
 calcarious earths1 when mixed with this
 acid4  ,when ,i first tried this       

experiment1 ,i was at the trouble of    
digesting the mixture in the heat of    
boiling water1 and did not then know    
that it would succeed in the heat of the
 air4 ,but ,dr4 ,alston1 who has obliged
 the world with many curious and useful 
discoveries on the subject of           
quick-lime1 having had occasion to      
repeat it1 ,i learned from him that heat
 is not necessary2 and he has moreover  
added an useful purpose to which this   
property of magnesia may be applied2 ,i 
mean the sweetening of water at sea1    
with which lime may have been mixed to  
prevent its putrefaction4  ,that part of
 the dried powder which does not        
dissolve in spirit of vitriol1 consists 
of the lime separated from the water4   
,quick-lime itself is also rendered mild
 by magnesia1 if these two are well     
rubbed together and infused with a small
 quantity of water4  ,by the following  
experiments1 ,i proposed to know whether
 this substance could be reduced to a   
quick-lime4  ,an ounce of magnesia was  

exposed in a crucible for about an hour 
to such a heat as is sufficient to melt 
copper4 ,when taken out1 it weighed     
three drams and one scruple1 or had lost
 #g_/ab of its former weight4  ,i       
repeated1 with the magnesia prepared in 
this manner1 most of those experiments  
,i had already made upon it before      
calcination1 and the result was as      
follows4  ,it dissolves in all the      
acids1 and with these composes salts    
exactly similar to those described in   
the first set of experiments3 but what  
is particularly to be remarked1 it is   
dissolved without any the least degree  
of effervescence4  ,it slowly           
precipitates the corrosive sublimate of 
mercury in the form of a black powder4  
,it separates the volatile alkali in    
salt ammoniac from the acid1 when it is 
mixed with a warm solution of that salt4
 ,but it does not separate an acid from 
a calcarious earth1 nor does it induce  
the least change upon lime-water4       
,lastly1 when a dram of it is digested  

with an ounce of water in a bottle for  
some hours1 it does not make any the    
least change in the water4 ,the         
magnesia1 when dried1 is found to have  
gained ten grains2 but it neither       
effervesces with acids1 nor does it     
sensibly affect lime-water4  ,observing 
magnesia to lose such a remarkable      
proportion of its weight in the fire1 my
 next attempts were directed to the     
investigation of this volatile part1    
and1 among other experiments1 the       
following seemed to throw some light    
upon it4  ,three ounces of magnesia were
 distilled in a glass retort and        
receiver1 the fire being gradually      
increased until the magnesia was        
obscurely red hot4 ,when all was cool1  
,i found only five drams of a whitish   
water in the receiver1 which had a faint
 smell of the spirit of hartshorn1 gave 
a green colour to the juice of violets1 
and rendered the solutions of corrosive 
sublimate and of silver very slightly   
turbid4 ,but it did not sensibly        

effervesce with acids4  ,the magnesia1  
when taken out of the retort1 weighed an
 ounce1 three drams1 and thirty grains1 
or had lost more than the half of its   
weight4 ,it still effervesced pretty    
briskly with acids1 tho' not so strongly
 as before this operation4  ,the fire   
should have been raised here to the     
degree requisite for the perfect        
calcination of magnesia4 ,but even from 
this imperfect experiment1 it is        
evident1 that of the volatile parts     
contained in that powder1 a small       
proportion only is water2 the rest      
cannot1 it seems1 be retained in        
vessels1 under a visible form4 ,chemists
 have often observed1 in their          
distillations1 that part of a body has  
vanished from their senses1             
notwithstanding the utmost care to      
retain it2 and they have always found1  
upon further inquiry1 that subtile part 
to be air1 which having been imprisoned 
in the body1 under a solid form1 was set
 free and rendered fluid and elastic by 

the fire4 ,we may therefore safely      
conclude1 that the volatile matter1 lost
 in the calcination of magnesia1 is     
mostly air2 and hence the calcined      
magnesia does not emit air1 or make an  
effervescence1 when mixed with acids4   
,the water1 from its properties1 seems  
to contain a small portion of volatile  
alkali1 which was probably formed from  
the earth1 air1 and water1 or from some 
of these combined together2 and perhaps 
also from a small quantity of           
inflammable matter which adhered        
accidentally to the magnesia4 ,whenever 
,chemists meet with this salt1 they are 
inclined to ascribe its origin to some  
animal1 or putrid vegetable1 substance2 
and this they have always done1 when    
they obtained it from the calcarious    
earths1 all of which afford a small     
quantity of it4 ,there is1 however1 no  
doubt that it can sometimes be produced 
independently of any such mixture1 since
 many fresh vegetables and tartar afford
 a considerable quantity of it4 ,and how

 can it1 in the present instance1 be    
supposed1 that any animal or vegetable  
matter adhered to the magnesia1 while it
 was dissolved by an acid1 separated    
from this by an alkali1 and washed with 
so much water8  ,two drams of magnesia  
were calcined in a crucible1 in the     
manner described above1 and thus reduced
 to two scruples and twelve grains4     
,this calcined magnesia was dissolved in
 a sufficient quantity of spirit of     
vitriol1 and then again separated from  
the acid by the addition of an alkali1  
of which a large quantity is necessary  
for this purpose4 ,the magnesia being   
very well washed and dryed1 weighed one 
dram and fifty grains4 ,it effervesced  
violently1 or emitted a large quantity  
of air1 when thrown into acids1 formed a
 red powder when mixed with a solution  
of sublimate1 separated the calcarious  
earths from an acid1 and sweetened      
lime-water3 and had thus recovered all  
those properties which it had but just  
now lost by calcination3 nor had it only

 recovered its original properties1 but 
acquired besides an addition of weight  
nearly equal to what had been lost in   
the fire2 and1 as it is found to        
effervesce with acids1 part of the      
addition must certainly be air4  ,this  
air seems to have been furnished by the 
alkali from which it was separated by   
the acid2 for ,dr4 ,hales has clearly   
proved1 that alkaline salts contain a   
large quantity of fixed air1 which they 
emit in great abundance when joined to a
 pure acid4 ,in the present case1 the   
alkali is really joined to an acid1 but 
without any visible emission of air2 and
 yet the air is not retained in it3 for 
the neutral salt1 into which it is      
converted1 is the same in quantity1 and 
in every other respect1 as if the acid  
employed had not been previously        
saturated with magnesia1 but offered to 
the alkali in its pure state1 and had   
driven the air out of it in their       
conflict4 ,it seems therefore evident1  
that the air was forced from the alkali 

by the acid1 and lodged itself in the   
magnesia4  ,these considerations led me 
to try a few experiments1 whereby ,i    
might know what quantity of air is      
expelled from an alkali1 or from        
magnesia1 by acids4  ,two drams of a    
pure fixed alkaline salt1 and an ounce  
of water1 were put into a ,florentine   
flask1 which1 together with its         
contents1 weighed two ounces and two    
drams4 ,some oil of vitriol diluted with
 water was dropt in1 until the salt was 
exactly saturated2 which it was found to
 be1 when two drams1 two scruples1 and  
three grains of this acid had been      
added4 ,the vial with its contents now  
weighed two ounces1 four drams1 and     
fifteen grains4 ,one scruple1 therefore1
 and eight grains were lost during the  
ebullition1 of which a trifling portion 
may be water1 or something of the same  
kind4 ,the rest is air4  ,the celebrated
 ,homberg has attempted to estimate the 
quantity of solid salt contained in a   
determined portion of the several acids4

 ,he saturated equal quantities of an   
alkali with each of them2 and1 observing
 the weight which the alkali had gained1
 after being perfectly dryed1 took this 
for the quantity of solid salt contained
 in that share of the acid which        
performed the saturation4 ,but we learn 
from the above experiment1 that his     
estimate was not accurate1 because the  
alkali loses weight as well as gains it4
  ,two drams of magnesia1 treated       
exactly as the alkali in the last       
experiment1 were just dissolved by four 
drams1 one scruple1 and seven grains of 
the same acid liquor1 and lost one      
scruple and sixteen grains by the       
ebullition4  ,two drams of magnesia were
 reduced1 by the action of a violent    
fire1 to two scruples and twelve grains1
 with which the same process was        
repeated1 as in the two last            
experiments2 four drams1 one scruple1   
and two grains of the same acid were    
required to compleat the solution1 and  
no weight was lost in the experiment4   

,as in the separation of the volatile   
from the fixed parts of bodies1 by means
 of heat1 a small quantity of the latter
 is generally raised with the former2 so
 the air and water1 originally contained
 in the magnesia1 and afterwards        
dissipated by the fire1 seem to have    
carried off a small part of the fixed   
earth of this substance4 ,this is       
probably the reason1 why calcined       
magnesia is saturated with a quantity of
 acid1 somewhat less than what is       
required to dissolve it before          
calcination3 and the same may be        
assigned as one cause which hinders us  
from restoring the whole of its original
 weight1 by solution and precipitation4 
,i took care to dilute the vitriolic    
acid1 in order to avoid the heat and    
ebullition which it would otherwise have
 excited in the water2 and ,i chose a   
,florentine flask1 on account of its    
lightness1 capacity1 and shape1 which is
 peculiarly adapted to the experiment2  
for the vapours raised by the ebullition

 circulated for a short time1 thro' the 
wide cavity of the vial1 but were soon  
collected upon its sides1 like dew1 and 
none of them seemed to reach the neck1  
which continued perfectly dry to the end
 of the experiment4  ,we now perceive   
the reason1 why crude and calcined      
magnesia1 which differ in many respects 
from one another1 agree however in      
composing the same kind of salt1 when   
dissolved in any particular acid2 for   
the crude magnesia seems to differ from 
the calcined chiefly by containing a    
considerable quantity of air1 which air 
is unavoidably dissipated and lost      
during the dissolution4  ,from our      
experiments1 it seems probable1 that the
 increase of weight which some metals   
acquire1 by being first dissolved in    
acids1 and then separated from them     
again by alkalis1 proceeds from air     
furnished by the alkalis4 ,and that in  
the aurum fulminans1 which is prepared  
by the same means1 this air adheres to  
the gold in such a peculiar manner1     

that1 in a moderate degree of heat1 the 
whole of it recovers its elasticity in  
the same instant of time2 and thus1 by  
the violent shock which it gives to the 
air around1 produces the loud crack or  
fulmination of this powder4 ,those who  
will imagine the explosion of such a    
minute portion of fixed air1 as can     
reside in the aurum fulminans1 to be    
insufficient for the excessive loudness 
of the noise1 will consider1 that it is 
not a large quantity of motion          
communicated to the air1 but rather a   
smart stroke which produces sound1 and  
that the explosion of but a few         
particles of fixed air may be capable of
 causing a loud noise1 provided they all
 recover their spring suddenly1 and in  
the same instant4  ,the above           
experiments lead us also to conclude1   
that volatile alkalis1 and the common   
absorbent earths1 which lose their air  
by being joined to acids1 but shew      
evident signs of their having recovered 
it1 when separated from them by alkalis1

 received it from these alkalis which   
lost it in the instant of their joining 
with the acid4  ,the following are a few
 experiments upon three of the absorbent
 earths1 made in order to compare them  
with one another1 and with magnesia4    
,suspecting that magnesia might possibly
 be no other than a common calcarious   
earth1 which had changed its nature1 by 
having been previously combined with an 
acid1 ,i saturated a small quantity of  
chalk with the muriatic acid1 separated 
the acid from it again by means of a    
fixed alkali1 and carefully washed away 
the whole of the salt4  ,the chalk when 
dryed was not found to have suffered any
 alteration2 for it effervesced with the
 vitriolic acid1 but did not dissolve in
 it2 and when exposed to a violent fire1
 was converted into a quick-lime1 in all
 respects similar to that obtained from 
common chalk4  ,in another experiment of
 the same kind1 ,i used the vitriolic   
acid with the same event4  ,any         
calcarious matter reduced to a fine     

powder1 and thrown into a warm solution 
of alum1 immediately raises a brisk     
effervescence4 ,but the powder is not   
dissolved2 it is rather increased in    
bulk3 and if the addition be repeated   
until it is no longer accompanied with  
effervescence1 the liquor loses all     
taste of the alum1 and yields only a    
very light cloud upon the admixture of  
an alkali4  ,from this experiment we    
learn1 that acids attract the calcarious
 earths more strongly than they do the  
earth of alum2 and as the acid in this  
salt is exactly the same with the       
vitriolic1 it composes with the         
calcarious earth a neutral substance1   
which is very difficultly soluble in    
water1 and therefore falls down to the  
bottom of the vessel along with the     
earth of alum which is deprived of its  
acid4 ,the light cloud formed by the    
alkali proceeds from the minute portion 
of the calcarious compound which        
saturates the water4  ,the earth of     
animal bones1 when reduced to a fine    

powder and thrown into a diluted        
vitriolic acid1 gradually absorbs the   
acid in the same manner as the          
calcarious earths1 but without any      
remarkable effervescence4 ,when it is   
added to the nitrous or to the muriatic 
acid1 it is slowly dissolved4 ,the      
compound liquor thence produced is      
extremely acrid1 and still changes the  
colour of the juice of violets to a red1
 even after it is fully saturated with  
the absorbent4 ,distilled vinegar has   
little or no effect upon this earth2 for
 after a long digestion it still retains
 its sour taste1 and gives only a light 
cloud upon the addition of an alkali4   
,by dropping a dissolved fixed alkali   
into a warm solution of alum1 ,i        
obtained the earth of this salt1 which1 
after being well washed and dried1 was  
found to have the following properties4 
,it is dissolved in every acid but very 
slowly1 unless assisted by heat4 ,the   
several solutions1 when thoroughly      
saturated1 are all astringent with a    

slight degree of an acid taste1 and they
 also agree with a solution of alum in  
this1 that they give a red colour to the
 infusion of turnsol4  ,neither this    
earth1 nor that of animal bones1 can be 
converted into quick-lime by the        
strongest fire1 nor do they suffer any  
change worth notice4 ,both of them seem 
to attract acids but weakly1 and to     
alter their properties less when united 
to them than the other absorbents4      
,,part ,,ii4   ,in reflecting afterwards
 upon these experiments1 an explication 
of the nature of lime offered itself1   
which seemed to account1 in an easy     
manner1 for most of the properties of   
that substance4  ,it is sufficiently    
clear1 that the calcarious earths in    
their native state1 and that the alkalis
 and magnesia in their ordinary         
condition1 contain a large quantity of  
fixed air1 and this air certainly       
adheres to them with considerable force1
 since a strong fire is necessary to    
separate it from magnesia1 and the      

strongest is not sufficient to expel it 
entirely from fixed alkalis1 or take    
away their power of effervescing with   
acid salts4  ,these considerations led  
me to conclude1 that the relations      
between fixed air and alkaline          
substances was somewhat similar to the  
relation between these and acids2 that  
as the calcarious earths and alkalis    
attract acids strongly and can be       
saturated with them1 so they also       
attract fixed air1 and are in their     
ordinary state saturated with it3 and   
when we mix an acid with an alkali or   
with an absorbent earth1 that the air is
 then set at liberty1 and breaks out    
with violence2 because the alkaline body
 attracts it more weakly than it does   
the acid1 and because the acid and air  
cannot both be joined to the same body  
at the same time4  ,i also imagined1    
that1 when the calcarious earths are    
exposed to the action of a violent fire1
 and are thereby converted into         
quick-lime1 they suffer no other change 

in their composition than the loss of a 
small quantity of water and of their    
fixed air4 ,the remarkable acrimony     
which we perceive in them after this    
process1 was not supposed to proceed    
from any additional matter received in  
the fire1 but seemed to be an essential 
property of the pure earth1 depending on
 an attraction for those several        
substances which it then became capable 
of corroding or dissolving1 which       
attraction had been insensible as long  
as the air adhered to the earth1 but    
discovered itself upon the separation4  
,this supposition was founded upon an   
observation of the most frequent        
consequences of combining bodies in     
chemistry4 ,commonly when we join two   
bodies together1 their acrimony or      
attraction for other substances becomes 
immediately either less perceivable or  
entirely insensible2 altho' it was      
sufficiently strong and remarkable      
before their union1 and may be rendered 
evident again by disjoining them4 ,a    

neutral salt1 which is composed of an   
acid and alkali1 does not possess the   
acrimony of either of its constituent   
parts4 ,it can easily be separated from 
water1 has little or no effect upon     
metals1 is incapable of being joined to 
inflammable bodies1 and of corroding and
 dissolving animals and vegetables2 so  
that the attraction both of the acid and
 alkali for these several substances    
seems to be suspended till they are     
again separated from one another4       
,crude lime was therefore considered as 
a peculiar acrid earth rendered mild by 
its union with fixed air3 and quick-lime
 as the same earth1 in which1 by having 
separated the air1 we discover that     
acrimony or attraction for water1 for   
animal1 vegetable1 and for inflammable  
substances4  ,that the calcarious earths
 really lose a large quantity of air    
when they are burnt to quick-lime1 seems
 sufficiently proved by an experiment of
 ,mr4 ,margraaf1#f an exceedingly       
accurate and judicious ,chemist4 ,he    

subjected eight ounces of osteocolla to 
distillation in an earthen retort1      
finishing his process with the most     
violent fire of a reverberatory1 and    
caught in the receiver only two drams of
 water1 which by its smell and          
properties shewed itself to be slightly 
alkaline4 ,he does not tell us the      
weight of the osteocolla remaining in   
the retort1 and only says1 that it was  
converted into quick-lime2 but as no    
calcarious earth can be converted into  
quick-lime1 or bear the heat which he   
applied without losing above a third of 
its weight1 we may safely conclude1 that
 the loss in his experiment was         
proportional1 and proceeded chiefly from
 the dissipation of fixed air4          
,according to our theory1 the relation  
of the calcarious earth to air and water
 appeared to agree with the relation of 
the same earth to the vitriolic and     
vegetable acids4 ,as chalk for instance 
has a stronger attraction for the       
vitriolic than for the vegetable acid1  

and is dissolved with more difficulty   
when combined with the first1 than when 
joined to the second3 so it also        
attracts air more strongly than water1  
and is dissolved with more difficulty   
when saturated with air than when       
compounded with water only4  ,a         
calcarious earth deprived of its air1 or
 in the state of quick-lime1 greedily   
absorbs a considerable quantity of      
water1 becomes soluble in that fluid1   
and is then said to be slaked2 but as   
soon as it meets with fixed air1 it is  
supposed to quit the water and join     
itself to the air1 for which it has a   
superior attraction1 and is therefore   
restored to its first state of mildness 
and insolubility in water4  ,when slaked
 lime is mixed with water1 the fixed air
 in the water is attracted by the lime1 
and saturates a small portion of it1    
which then becomes again incapable of   
dissolution1 but part of the remaining  
slaked lime is dissolved and composes   
lime-water4  ,if this fluid be exposed  

to the open air1 the particles of       
quick-lime which are nearest the surface
 gradually attract the particles of     
fixed air which float in the atmosphere4
 ,but at the same time that a particle  
of lime is thus saturated with air1 it  
is also restored to its native state of 
mildness and insolubility2 and as the   
whole of this change must happen at the 
surface1 the whole of the lime is       
successively collected there under its  
original form of an insipid calcarious  
earth1 called the cream or crusts of    
lime-water4  ,when quick-lime itself is 
exposed to the open air1 it absorbs the 
particles of water and of fixed air     
which come within its sphere of         
attraction1 as it meets with the first  
of these in greatest plenty1 the        
greatest part of it assumes the form of 
slaked lime2 the rest is restored to its
 original state2 and if it be exposed   
for a sufficient length of time1 the    
whole of it is gradually saturated with 
air1 to which the water as gradually    

yields its place4  ,we have already     
shown by experiment1 that magnesia alba 
is a compound of a peculiar earth and   
fixed air4 ,when this substance is mixed
 with lime-water1 the lime shews a      
stronger attraction for fixed air than  
that of the earth of magnesia2 the air  
leaves this powder to join itself to the
 lime4 ,and as neither the lime when    
saturated with air1 nor the magnesia    
when deprived of it1 are soluble in     
water1 the lime-water becomes perfectly 
pure and insipid1 the lime which it     
contained being mixed with the magnesia4
 ,but if the magnesia be deprived of air
 by calcination before it is mixed with 
the lime-water1 this fluid suffers no   
alteration4  ,if quick-lime be mixed    
with a dissolved alkali1 it likeways    
shews an attraction for fixed air       
superior to that of the alkali4 ,it robs
 this salt of its air1 and thereby      
becomes mild itself1 while the alkali is
 consequently rendered more corrosive1  
or discovers its natural degree of      

acrimony or strong attraction for water1
 and for bodies of the inflammable1 and 
of the animal and vegetable kind2 which 
attraction was less perceivable as long 
as it was saturated with air4 ,and the  
volatile alkali when deprived of its    
air1 besides this attraction for various
 bodies1 discovers likeways its natural 
degree of volatility1 which was formerly
 somewhat repressed by the air adhering 
to it1 in the same manner as it is      
repressed by the addition of an acid4   
,this account of lime and alkalis       
recommended itself by its simplicity1   
and by affording an easy solution of    
many phnomena1 but appeared upon a      
nearer view to be attended with         
consequences that were so very new and  
extraordinary1 as to render suspicious  
the principles from which they were     
drawn4  ,i resolved however to examine1 
in a particular manner1 such of these   
consequences as were the most           
unavoidable1 and found the greatest     
number of them might be reduced to the  

following propositions3       ,i4 ,if we
 only separate a quantity of air from   
lime and alkalis1      when we render   
them caustic they will be found to lose 
part of      their weight in the        
operation1 but will saturate the same   
quantity      of acid as before1 and the
 saturation will be performed without   
effervescence4       ,,ii4 ,if          
quick-lime be no other than a calcarious
 earth deprived of      its air1 and    
whose attraction for fixed air is       
stronger than that      of alkalis1 it  
follows1 that1 by adding to it a        
sufficient quantity      of alkali      
saturated with air1 the lime will       
recover the whole of      its air1 and  
be entirely restored to its original    
weight and      condition3 and it also  
follows1 that the earth separated from  
lime-water by an alkali1 is the lime    
which was dissolved in the      water   
now restored to its original mild and   
insoluble state4       ,,iii4 ,if it be 
supposed that slaked lime does not      

contain any parts      which are more   
firey1 active or subtile than others1   
and by which      chiefly it            
communicates its virtues to water2 but  
that it is an      uniform compound of  
lime and water3 it follows1 that1 as    
part of it      can be dissolved in     
water1 the whole of it is also capable  
of being      dissolved4       ,,iv4 ,if
 the acrimony of the caustic alkali does
 not depend on any      part of the lime
 adhering to it1 a caustic or soap-ley  
will      consequently be found to      
contain no lime1 unless the quantity of 
lime employed in making it were greater 
than what is just      sufficient to    
extract the whole air of the alkali2 for
 then as much      of the superfluous   
quick-lime might possibly be dissolved  
by the      ley as would be dissolved by
 pure water1 or the ley would contain   
as much lime as lime-water does4        
,v4 ,we have shewn in the former        
experiments1 that absorbent earths      
lose their air when they are joined to  

an acid2 but recover it1 if             
separated again from that acid1 by means
 of an ordinary alkali3 the      air    
passing from the alkali to the earth1 at
 the same time that the      acid passes
 from the earth to the alkali4  ,if the 
caustic alkali therefore be destitute of
 air1 it will separate magnesia from an 
acid under the form of a magnesia free  
of air1 or which will not effervesce    
with acids2 and the same caustic alkali 
will also separate a calcarious earth   
from acids under the form of a          
calcarious earth destitute of air1 but  
saturated with water1 or under the form 
of slaked lime4  ,these were all        
necessary conclusions from the above    
suppositions4 ,many of them appeared too
 improbable to deserve any further      
attention3 some however1 ,i found upon  
reflection1 were already seconded by    
experience4 ,thus ,hoffman has observed1
 that quick-lime does not effervesce    
with spirit of vitriol2#g and it is well
 known that the caustic spirit of urine1

 or of salt ammoniac1 does not emit air1
 when mixed with acids4 ,this           
consideration excited my curiosity1 and 
determined me to inquire into the truth 
of them all by way of experiment4 ,i    
therefore engaged myself in a set of    
trials2 the history of which is here    
subjoined4 ,some new facts are likeways 
occasionally mentioned2 and here it will
 be proper to inform the reader1 that ,i
 have never mentioned any without       
satisfying myself of their truth by     
experiment1 tho' ,i have sometimes taken
 the liberty to neglect describing the  
experiments when they seemed            
sufficiently obvious4  ,desiring to know
 how much of an acid a calcarious earth 
will absorb1 and what quantity of air is
 expelled during the dissolution1 ,i    
saturated two drams of chalk with       
diluted spirit of salt1 and used the    
,florentine flask1 as related in a      
similar experiment upon magnesia4 ,seven
 drams and one grain of the acid        
finished the dissolution1 and the chalk 

lost two scruples and eight grains of   
air4  ,this experiment was necessary    
before the following1 by which ,i       
proposed to inquire into the truth of   
the first proposition so far as it      
relates to quick-lime4  ,two drams of   
chalk were converted into a perfect     
quick-lime1 and lost two scruples and   
twelve grains in the fire4 ,this        
quick-lime was slaked or reduced to a   
milky liquor with an ounce of water1 and
 then dissolved in the same manner1 and 
with the same acid1 as the two drams of 
chalk in the preceding experiment4 ,six 
drams1 two scruples and fourteen grains 
of the acid finished the saturation     
without any sensible effervescence or   
loss of weight4  ,it therefore appears  
from these experiments1 that no air is  
separated from quick-lime by an acid1   
and that chalk saturates nearly the same
 quantity of acid after it is converted 
into quick-lime as before4  ,with       
respect to the second proposition1 ,i   
tried the following experiments4  ,a    

piece of perfect quick-lime made from   
two drams of chalk1 and which weighed   
one dram and eight grains1 was reduced  
to a very fine powder1 and thrown into a
 filtrated mixture of an ounce of a     
fixed alkaline salt and two ounces of   
water4 ,after a slight digestion1 the   
powder being well washed and dried1     
weighed one dram and fifty eight grains4
 ,it was similar in every trial to a    
fine powder of ordinary chalk1 and was  
therefore saturated with air which must 
have been furnished by the alkali4  ,a  
dram of pure salt of tartar was         
dissolved in fourteen pounds of         
lime-water1 and the powder thereby      
precipitated1 being carefully collected 
and dried1 weighed one and fifty grains4
 ,when exposed to a violent fire1 it was
 converted into a true quick-lime1 and  
had every other quality of a calcarious 
earth4  ,this experiment was repeated   
with the volatile alkali1 and also with 
the fossil or alkali of sea-salt1 and   
exactly with the same event4  ,the third

 proposition had less appearance of     
probability than the foregoing2 but1 as 
an accurate experiment was the only test
 of its truth1 ,i reduced eight grains  
of perfect quick-lime made of chalk1 to 
an exceedingly subtile powder1 by       
slaking it in two drams of distilled    
water boiling hot1 and immediately threw
 the mixture into eighteen ounces of    
distilled water in a flask4 ,after      
shaking it1 a light sediment1 which     
floated thro' the liquor1 was allowed to
 subside and this1 when collected with  
the greatest care1 and dryed1 weighed1  
as nearly as ,i could guess1 one third  
of a grain4 ,the water tasted strongly  
of the lime1 had all the qualities of   
lime-water1 and yielded twelve grains of
 precipitate1 upon the addition of salt 
of tartar4 ,in repeating this           
experiment1 the quantity of sediment was
 sometimes less than the above1 and     
sometimes amounted to half a grain4 ,it 
consisted partly of an earth which      
effervesced violently with aqua fortis1 

and partly of an ochry powder1 which    
would not dissolve in that acid4 ,the   
ochry powder1 as it usually appears in  
chalk to the eye1 in the form of veins  
running thro' its substance1 must be    
considered only as an accidental or     
foreign admixture2 and1 with respect to 
the minute portion of alkaline earth    
which composed the remainder of the     
sediment1 it cannot be supposed to have 
been originally different from the rest1
 and incapable1 from its nature1 of     
being converted into quick-lime1 or of  
being dissolved in water2 it seems      
rather to have consisted of a small part
 of the chalk in its mild state1 or     
saturated with air1 which had either    
remained1 for want of a sufficient fire 
to drive it out entirely1 or had been   
furnished by the distilled water4  ,i   
indeed expected to see a much larger    
quantity of sediment produced from the  
lime1 on account of the air which water 
constantly contains1 and with a view to 
know whether water retains its air when 

fully saturated with lime1 a lime-water 
was made as strong as possible2 four    
ounces of which were placed under the   
receiver of an air-pump1 together with  
four ounces of common water in a vial of
 the same size2 and1 upon exhausting the
 receiver1 without heating the vials1   
the air arose from each in nearly the   
same quantity3 from whence it is        
evident1 that the air1 which quick-lime 
attracts1 is of a different kind from   
that which is mixed with water4 ,and    
that it is also different from common   
elastic air1 is sufficiently proved by  
daily experience2 for lime-water1 which 
soon attracts air1 and forms a crust    
when exposed in open and shallow        
vessels1 may be preserved1 for any time1
 in bottles which are but slightly      
corked1 or closed in such a manner as   
would allow free access to elastic air1 
were a vacuum formed in the bottle4     
,quick-lime therefore does not attract  
air when in its most ordinary form1 but 
is capable of being joined to one       

particular species only1 which is       
dispersed thro' the atmosphere1 either  
in the shape of an exceedingly subtile  
powder1 or more probably in that of an  
elastic fluid4 ,to this ,i have given   
the name of fixed air1 and perhaps very 
improperly2 but ,i thought it better to 
use a word already familiar in          
philosophy1 than to invent a new name1  
before we be more fully acquainted with 
the nature and properties of this       
substance1 which will probably be the   
subject of my further inquiry4  ,it is1 
perhaps1 needless to mention here1 that 
the calcarious substances used in making
 the above experiments should be of the 
purest kind1 and burnt with the utmost  
violence of heat1 if we would be sure of
 converting them into perfect           
quick-lime4 ,i therefore made use of    
chalk burnt in a small covered crucible 
with the fiercest fire of a             
,black-smith's forge1 for half an hour1 
and found it necessary to employ1 for   
this purpose1 a crucible of the         

,austrian kind1 which resemble black    
lead2 for if any calcarious substance be
 heated to such a degree in an ordinary 
or ,hessian crucible1 the whole of it is
 melted down1 together with part of the 
vessel1 into glass4  ,i now prepared to 
inquire into the properties of the      
caustic alkali2 in order to which1 ,i   
made a caustic or soap ley in the       
following manner4  ,twenty six ounces of
 very strong quick-lime made of chalk1  
were slaked or reduced to a sort of     
fluid paste1 with eleven pounds of      
boiling water1 and then mixed in a glass
 vessel with eighteen ounces of a pure  
fixed alkaline salt1 which had been     
first dissolved in two pounds and a half
 of water4 ,this mixture was shaken     
frequently for two hours1 when the      
action of the lime upon the alkali was  
supposed to be over1 and nothing        
remained but to separate them again from
 one another4 ,i therefore added #ab    
pounds of water1 stirred up the lime1   
and1 after allowing it to settle again1 

poured off as much of the clear ley as  
possible4  ,the lime and alkali were    
mixed together under the form of a very 
thick milky liquor or fluid paste2      
because they are thus kept in perpetual 
contact and equal mixture until they    
have acted sufficiently upon one        
another3 whereas in the common way of   
using a larger quantity of water1 the   
lime lies for the most part at bottom1  
and1 tho' stirred up ever so often1     
cannot exert its influence so fully upon
 the alkali1 which is uniformly diffused
 thro' every part of the liquor4  ,the  
above ley was found upon trial to be    
saturated by acids without the least    
effervescence or diminution of weight4  
,it was now proper to examine whether   
the alkali suffered any loss in becoming
 caustic1 which ,i proposed to attempt  
by ascertaining the strength of the ley1
 or the quantity of salt which a given  
portion of it contained2 from which by  
computation some imperfect knowledge    
might be obtained of the quantity of    

caustic produced from the eighteen      
ounces of mild salt4  ,i therefore      
evaporated some of my ley1 but soon     
perceived that no certain judgment could
 be formed of its strength in this way1 
because it always absorbed a            
considerable quantity of air during the 
evaporation1 and the dried salt made a  
pretty brisk effervescence with acids1  
so that the ley appeared stronger than  
it really was2 and yet1 upon proceeding 
in the estimate from this rude and      
unfair trial1 it appeared that the salt 
had lost above a sixth in becoming      
caustic1 and the quantity of acid       
saturated by two drams of it was to the 
quantity of acid saturated by two drams 
of salt of tartar1 nearly as six to     
five4  ,these experiments are therefore 
agreeable to that part of the second    
proposition which relates to the caustic
 alkali4  ,upon farther examining what  
changes the alkali had undergone1 ,i    
found that the ley gave only an         
exceeding faint milky hue to lime-water2

 because the caustic alkali wants that  
air by which salt of tartar precipitates
 the lime4 ,when a few ounces of it were
 exposed in an open shallow vessel for  
four and twenty hours1 it imbibed a     
small quantity of air1 and made a slight
 effervescence with acids4 ,after a     
fortnight's exposure in the same manner1
 it became entirely mild1 effervesced as
 violently with acids1 and had the same 
effect upon lime-water as a solution of 
an ordinary alkali4 ,it likeways agrees 
with lime-water in this respect1 that it
 may be kept in close vessels1 or even  
in bottles which are but slightly       
covered1 for a considerable time1       
without absorbing a sensible quantity of
 air4  ,in order to know how much lime  
it contained1 ,i evaporated ten ounces  
in a small silver dish over a lamp1 and 
melted the salt1 after having dissipated
 the water4#h  ,the caustic thus        
produced was dissolved again in a small 
quantity of water1 and deposited a      
trifling portion of sediment1 which ,i  

imagined at first to be lime2 but       
finding that it could easily be         
dissolved in a little more water1       
concluded it to be a vitriolated tartar1
 which always accompanies the fixed     
alkali of vegetables4  ,i then saturated
 the solution of the caustic salt with  
spirit of vitriol1 expecting thus to    
detect the lime2 because that acid      
precipitates a calcarious earth from its
 ordinary solutions4 ,during the        
saturation1 a large quantity of white   
powder was formed2 but this likeways    
turned out to be a vitriolated tartar1  
which had appeared in the form of a     
powder1 because there was not enough of 
water in the mixture to dissolve it4    
,lastly1 ,i exposed a few ounces of the 
ley in an open shallow vessel so long1  
that the alkali lost the whole of its   
causticity1 and seemed entirely restored
 to the state of an ordinary fixed      
alkali2 but it did not however deposite 
a single atom of lime4 ,and to assure   
myself that my caustic ley was not of a 

singular kind1 ,i repeated the same     
experiments with an ordinary soap-ley1  
and with one made by mixing one part of 
a pure fixed alkaline salt with three   
parts of common stone lime fresh slaked 
and sifted2 nor could ,i discover any   
lime in either4 ,the first of these     
contained a small quantity of brimstone1
 and was far from being perfectly       
caustic1 for it made a pretty brisk     
effervescence with acids2 but the last  
was so entirely deprived of its air1    
that it did not diminish in the least   
the transparency of lime-water4  ,these 
experiments seem therefore to support   
the fourth proposition1 and to shew that
 the caustic alkali does not contain any
 lime4  ,as it seems probable1 from the 
quickness and ease wherewith the alkali 
was rendered caustic1 that more lime had
 been employed than what was just       
sufficient to extract the whole of its  
air1 we are surprised to find that      
little or none of the superfluous       
quick-lime was dissolved by the water4  

,but this phnomenon will become less    
surprizing1 by comparing it with some   
similar instances in chemistry4 ,water  
may be made to deposite a salt1 by the  
admixture of a substance which it       
attracts more strongly than it does that
 salt2 such as spirit of wine2 and      
quick-lime itself may be separated from 
water upon the same principle2 for if   
that spirit is added to an equal        
quantity of lime-water1 the mixture     
becomes turbid and deposites a sediment1
 which1 when separated and dissolved    
again in distilled water1 composes      
lime-water4 ,we may therefore refer the 
above phnomenon1 with respect to the    
ley1 to the same cause with these1 and  
say1 that the water did not dissolve the
 lime1 because it already contained a   
caustic alkali1 for which it has a      
superior attraction4  ,i also rendered  
the volatile alkali caustic1 in order to
 examine what change it suffered in the 
operation1 and obtained an exceedingly  
volatile and acrid spirit1 which neither

 effervesced with acids1 nor altered in 
the least the transparency of           
lime-water2 and1 altho' very strong1 was
 lighter than water1 and floated upon it
 like spirit of wine4  ,i next inquired 
into the truth of the fifth proposition1
 in the following manner4  ,two drams of
 epsom-salt were dissolved in a small   
quantity of water1 and thrown into two  
ounces of the caustic-ley2 the mixture  
instantly became thick1 like a decoction
 of starch or barley1 by the magnesia1  
which was precipitated4 ,i then added   
spirit of vitriol by degrees1 until the 
mixture became perfectly clear1 or the  
whole of the magnesia was again         
dissolved2 which happened without any   
effervescence or emission of air4  ,half
 an ounce of chalk was dissolved in     
spirit of salt1 the quantity of which   
was so adjusted1 that the mixture was   
not acid in the least degree2 and the   
solution was thrown into twelve ounces  
of the caustic ley2 which quantity ,i   
found1 by experiment1 to be sufficient  

for precipitating almost the whole of   
the chalk4 ,i now filtrated this turbid 
liquor1 and laid the powder remaining in
 the paper upon a chalk-stone1 in order 
to draw as much of the water from it as 
possible1 and thereby reduce it to the  
form of a more dense and heavy powder1  
that it might subside the more perfectly
 in the following part of the           
experiment4 ,i then mixed it with about 
twenty ounces of pure water in a flask1 
and1 after allowing the powder to       
subside1 poured off the water1 which had
 all the qualities of lime-water4 ,and  
,i successively converted eight waters  
more into lime-water1 seven of these in 
the same quantity1 and with the same    
management1 as the first4 ,the eighth   
was likeways in the same quantity2 but  
,i allowed it to remain with the chalk1 
and shook it frequently1 for two days4  
,this1 after being filtrated1 formed a  
cream or crust upon its surface when    
exposed to the air2 changed the colour  
of the juice of violets into green2     

separated an orange-coloured powder from
 a solution of corrosive sublimate2     
became turbid upon the addition of an   
alkali2 was entirely sweetened by       
magnesia2 and appeared so strong to the 
taste1 that ,i could not have           
distinguished it from ordinary          
lime-water4 ,and when ,i threw some salt
 ammoniac into the lime which remained1 
the vapour of the volatile alkali       
immediately arose from the mixture4  ,in
 this experiment therefore the air is   
first driven out of the chalk by an     
acid1 and then1 in order to separate    
this acid from it1 we add an alkali     
which has been previously deprived of   
its air2 by which means1 the chalk      
itself is also obtained free of air1 and
 in an acrid form1 or in the form of    
slaked lime4  ,we have also several     
processes for obtaining the volatile    
alkali in a caustic form1 which seem to 
be only so many methods of obtaining it 
in its pure state1 and free of fixed    
air4 ,the first of these is the         

separation of the alkali from an acid1  
merely by heat2 an instance of which we 
have from ,mr4 ,margraaf4#i ,he prepared
 from urine an ammoniacal salt1 the acid
 of which is the basis of the           
phosphorus1 and is of such a peculiar   
nature1 that it endures a red heat      
without being dissipated4 ,sixteen      
ounces of the neutral salt were         
subjected by him to distillation4 ,the  
acid remained in the retort1 and he     
found in the receiver eight ounces of an
 alkaline spirit1 which1 he tells us1   
was extremely volatile1 very much       
resembling the spirit of salt ammoniac  
distilled with quick-lime2 and no       
crystals were formed in it1 when exposed
 to the cold air4  ,a caustic volatile  
alkali may also be obtained1 by mixing  
salt ammoniac with half its weight of a 
caustic fixed alkali1 or of magnesia    
which has been previously deprived of   
its air by fire2 and then submitting    
these mixtures to distillation3 ,or     
merely by adding any ordinary volatile  

alkali to a proper quantity of a caustic
 ley2 for in this case the air passes   
from the volatile to the fixed alkali1  
by a superior attraction for the last1  
and1 by a gentle heat1 the compound     
yields a spirit similar to that prepared
 from salt ammoniac and quick-lime4  ,it
 is therefore probable1 that1 had we    
also a method of separating the fixed   
alkali from an acid1 without1 at the    
same time1 saturating it with air1 we   
should then obtain it in a caustic form2
 but ,i am not acquainted with an       
instance of this separation in          
chemistry4 ,there are two indeed which1 
at first sight1 appear to be of this    
kind2 these are the separation of the   
fixed alkali from the nitrous acid by   
means of inflamed charcoal1 in the      
process for making nitrum fixatum1 and  
of the same alkali1 from vegetable acids
 merely by heat2 but1 upon examining the
 product of each process1 we find the   
alkali either fully or nearly saturated 
with air4 ,in the first1 either the     

charcoal or the acid1 or both together1 
are almost wholly converted into air2 a 
part of which is probably joined to the 
alkali4 ,in the second1 the acid is not 
properly separated1 but rather destroyed
 by the fire3 a considerable portion of 
it is converted into an inflammable     
substance and we learn from ,dr4 ,hales1
 that the bodies of this class contain a
 large quantity of fixed air4  ,when we 
consider that the attraction of alkalis 
for fixed air is weaker than that of the
 calcarious earths1 and reflect upon the
 effects of heat in chemistry1 we are   
led to imagine1 that alkalis might be   
entirely deprived of their air1 or      
rendered perfectly caustic1 by a fire   
somewhat weaker than that which is      
sufficient to produce the same change   
upon lime2 but this opinion does not    
seem agreeable to experience4  ,the     
alkalis do1 however1 acquire some degree
 of causticity in a strong fire1 as     
appears from their being more easily    
united with spirit of wine after having 

been kept in fusion for some time4 ,for 
that fluid1 which cannot be tinctured by
 a mild salt of tartar1 will soon take a
 very deep colour from a few drops of a 
strong caustic ley4 ,the circumstances  
which hinder us from rendering these    
salts perfectly caustic by heat1 are    
their propensity to dissipation in the  
utmost violence of the fire1 their      
extreme acrimony1 and the imperfection  
of our common vessels4 ,for before the  
heat becomes very intense1 the alkalis  
either evaporate1 or dissolve a part of 
the crucibles in which they are         
contained1 and often escape thro' their 
pores2 which happens1 especially as soon
 as they have already acquired some     
degree of additional acrimony1 by the   
loss of part of their air4  ,the fusion 
also1 which they so readily undergo1 is 
well known by ,chemists1 as a strong    
obstacle to the separation of the       
volatile from the fixed parts of a      
compound by fire2 accordingly1 in       
several processes1 we are directed to   

add to the fusible compound some porous 
substance which is incapable of fusion1 
and will retain the whole in a spongy   
form1 thereby to facilitate the         
dissipation of the volatile parts4  ,in 
order to know whether an alkali would   
lose a part of its air1 and acquire a   
degree of causticity1 when exposed1 with
 this precaution1 to the action of a    
strong fire1 ,i mixed an ounce and a    
half of salt of tartar with three ounces
 of black-lead1 a substance of any the  
most unchangeable by chemical           
operations4 ,this mixture ,i exposed1   
for several hours1 in a covered         
crucible1 to a fire somewhat stronger   
than what is necessary to keep salt of  
tartar in fusion4 ,when allowed to cool1
 ,i found it still in the form of a     
loose powder2 and taking out one half1  
,i diluted it with water1 and by        
filtration obtained a ley1 which1 when  
poured into a solution of white marble  
in aqua fortis1 precipitated the marble 
under the form of a weak quick-lime3 for

 the turbid mixture gave a green colour 
to the juice of violets1 and threw up a 
crust like that of lime-water2 and the  
precipitated powder collected and mixed 
with salt ammoniac immediately yielded  
the scent of the volatile alkali4  ,lest
 it should here be suspected1 that the  
alkaline qualities of this mixture1 and 
of the precipitated marble1 were not    
owing to a lime into which the marble   
was converted1 but to the alkali itself 
which was added1 it is proper to        
observe1 that ,i mixed so small a       
proportion of the ley with the solution 
of marble as made me sure1 from certain 
experiments1 that the whole of the      
alkali was spent in performing the      
precipitation1 and was consequently     
converted into a neutral salt by        
attracting the acid4 ,the properties    
therefore of the mixture can only be    
referred to a lime1 as is indeed        
sufficiently evident from the crust     
which is peculiar to lime-water4  ,i was
 therefore assured by this experiment1  

that an alkali does really lose a part  
of its air1 and acquire a degree of     
causticity1 by the proper application of
 heat2 but finding by several trials1   
that the degree of causticity which it  
had thus acquired was but weak1 and that
 the quick-lime produced in this        
experiment was exhausted and rendered   
mild by a small quantity of water1 ,i   
exposed the crucible together with that 
half of the alkali which remained in it 
to a stronger fire1 in order to expel a 
larger quantity of air1 and render it   
more remarkably caustic2 but the whole  
of it was dissipated by the force of the
 heat1 and the black lead1 which still  
retained the form of a loose and subtile
 powder1 yielded little or nothing to   
water4  ,we learn then from the above   
experiment the reason why the alkali    
newly obtained from the ashes of        
vegetables is generally of the more     
acrid kinds of that salt4 ,it never     
appears until the subject be converted  
into ashes1 and is supposed to be formed

 by the fire1 and to be the result of a 
particular combination of some of the   
principles of the vegetable2 one of     
which principles is air1 which is       
contained in large quantity in all      
vegetable matters whatever4 ,but as soon
 as the smallest part of a vegetable is 
converted into ashes1 and an alkali is  
thus formed1 this salt necessarily      
suffers a calcination1 during which it  
is kept in a spongy form by the ashes1  
and shews a very considerable degree of 
acrimony if immediately applied to the  
body of an animal but if the ashes are  
for any time exposed to the air1 or if  
we separate the alkali from them by the 
addition of a large quantity of water   
and subsequent evaporation1 the salt    
imbibes fixed air from the atmosphere1  
and becomes nearly saturated with it3   
tho' even in this condition it is       
generally more acrid than salt of       
tartar1 when this is prepared with a    
gentle heat4  ,borax has sometimes been 
referred to the class of alkalis1 on    

account of some resemblance it bears to 
those salts3 but it has been            
demonstrated by accurate experiments1   
that we should rather consider it as a  
neutral salt2 that it is composed of an 
alkali and of a particular saline       
substance called the sedative salt1     
which adheres to the alkali in the same 
manner as an acid1 but can be separated 
by the addition of any acid whatever1   
the added acid joining itself to the    
alkali in the place of the sedative     
salt4 ,as this conjunction of an acid   
with the alkali of borax happens without
 the least effervescence1 our principles
 lay us under a necessity of allowing   
that alkali to be perfectly free of air1
 which must proceed from its being      
incapable of union with fixed air and   
with the sedative salt at the same time3
 whence it follows1 that1 were we to mix
 the sedative salt with an alkali       
saturated with air1 the air would       
immediately be expelled1 or the two     
salts in joining would produce an       

effervescence4 ,this ,i found to be     
really the case upon making the trial1  
by mixing a small quantity of the       
sedative salt with an equal quantity of 
each of the three alkalis1 rubbing the  
mixtures well in a mortar1 and adding a 
little water4 ,it is however proper in  
this place to observe1 that1 if the     
experiments be made in a different      
manner1 they are attended with a        
singular circumstance4 ,if a small      
quantity of the sedative salt be thrown 
into a large proportion of a dissolved  
fixed alkali1 the sedative salt         
gradually disappears1 and is united to  
the alkali without any effervescence2   
but if the addition be repeated several 
times1 it will at last be accompanied   
with a brisk effervescence1 which will  
become more and more remarkable1 until  
the alkali be entirely saturated with   
the sedative salt4  ,this phnomenon may 
be explained by considering the fixed   
alkalis as not perfectly saturated with 
air3 and the supposition will appear    

very reasonable1 when we recollect1 that
 those salts are never produced without 
a considerable degree of heat1 which may
 easily be imagined to dissipate a small
 portion of so volatile a body as air4  
,now1 if a small quantity of the        
sedative salt be thrown into an alkaline
 liquor1 as it is very slowly dissolved 
by water1 its particles are very        
gradually mixed with the atoms of the   
alkali4 ,they are most strongly         
attracted by such of these atoms as are 
destitute of air1 and therefore join    
with them without producing an          
effervescence2 or1 if they expel a small
 quantity of air from some of the salt1 
this air is at the same time absorbed by
 such of the contiguous particles as are
 destitute of it1 and no effervescence  
appears until that part of the alkali1  
which was in a caustic form or destitute
 of air1 be nearly saturated with the   
sedative salt4 ,but if1 on the other    
hand1 a large proportion of the sedative
 salt be perfectly and suddenly mixed   

with the alkali1 the whole1 or a large  
part1 of the air is as suddenly         
expelled4  ,in the same manner may we   
also explain a similar phnomenon1 which 
often presents itself in saturating an  
alkali with the different acids3 the    
effervescence is less considerable in   
the first additions of acid1 and becomes
 more violent as the mixture approaches 
the point of saturation4 ,this appears  
most evidently in making the sal        
diureticus or regenerated tartar3 ,the  
particles of the vegetable acid here    
employed being always diffused thro' a  
large quantity of water1 are more       
gradually applied to those of the       
alkali1 and during the first additions  
are chiefly united to those that are    
freest of air4#aj  ,that the fixed      
alkali1 in its ordinary state1 is seldom
 entirely saturated with air1 seems to  
be confirmed by the following           
experiment4  ,i exposed a small quantity
 of a pure vegetable fixed alkali to the
 air1 in a broad and shallow vessel1 for

 the space of two months2 after which ,i
 found a number of solid crystals1 which
 resembled a neutral salt so much as to 
retain their form pretty well in the    
air1 and to produce a considerable      
degree of cold when dissolved in water4 
,their taste was much milder than that  
of ordinary salt of tartar2 and yet they
 seemed to be composed only of the      
alkali1 and of a larger quantity of air 
than is usually contained in that salt1 
and which had been attracted from the   
atmosphere3 for they still joined very  
readily with any acid1 but with a more  
violent effervescence than ordinary2 and
 they could not be mixed with the       
smallest portion of vinegar1 or of the  
sedative salt1 without emitting a       
sensible quantity of air4  ,as it now   
appeared that several alkaline          
substances have an attraction for fixed 
air1 ,i tried a few experiments to learn
 the relative strength of their several 
attractions4  ,twenty four grains of    
magnesia in fine powder were mixed with 

five ounces of the caustic ley in a     
small vial1 which was immediately corked
 and shaken frequently for four hours4  
,the ley was then poured off1 and the   
magnesia washed with repeated affusions 
of water1 and dried4 ,it had lost about 
the half of its weight1 and when reduced
 to a fine powder was readily dissolved 
by acids with an effervescence which was
 hardly perceivable3 the alkali had     
therefore extracted its air4 ,i also    
threw some fresh magnesia into the ley  
which had been poured off1 and thereby  
rendered it perfectly mild and similar  
to a solution of salt of tartar2 so that
 it effervesced briskly with acids4     
,with an ounce of the mild spirit of    
salt ammoniac1 ,i mixed a dram of       
magnesia in very fine powder which had  
been previously deprived of its air by  
fire2 and observing that the magnesia   
had a tendency to concrete into a solid 
mass1 ,i shook the vial very frequently4
 ,after some days the powder was        
increased to more than double its former

 bulk2 and when the vial was opened1 the
 alkaline spirit emitted a most         
intolerably pungent smell4 ,it likewise 
floated upon water1 but was not         
perfectly caustic2 for it still yielded 
some air when mixed with acids1 and also
 rendered lime-water turbid3 neither of 
which would probably have happened if ,i
 had used a greater quantity of         
magnesia1 or had allowed the mixture to 
remain a longer time in the vial4 ,i now
 washed out the whole of the mixture    
into a bowl1 and dryed the magnesia     
until it lost all smell of the alkali4  
,it weighed a dram and fifty eight      
grains1 effervesced violently with      
acids1 and therefore contained a large  
quantity of air1 which had been drawn   
from the alkali by a stronger           
attraction4  ,having formerly shewn1    
that magnesia saturated with air        
separates an acid from a calcarious     
earth1 which it is not able to do after 
being deprived of its air by fire2 ,i   
now suspected that the air was the cause

 of this separation1 because ,i found   
that it was joined to the calcarious    
earth at the same time that the acid was
 joined to the earth of magnesia2 and   
imagined that a pure calcarious earth   
might possibly have a stronger          
attraction for acids than a earth of    
magnesia4  ,i therefore dissolved two   
drams of magnesia in the marine acid1   
and thus obtained a compound of an acid 
and of the pure earth of this substance2
 for the air which was at first attached
 to it1 was expelled during the         
dissolution4 ,i then added thirty grains
 of strong quick-lime in exceeding fine 
powder1 shook the mixture well1 and     
filtrated it4 ,the powder remaining in  
the paper1 after being well washed1 was 
found to be a magnesia1 which1 as ,i    
expected1 was destitute of air2 for it  
was dissolved by the vitriolic acid     
without effervescence4 ,and the         
filtrated liquor contained the lime     
united to the acid2 for upon dropping   
spirit of vitriol into it1 a white      

powder was immediately formed4  ,we must
 therefore acknowledge a stronger       
attraction between the calcarious earths
 and acids than between these and       
magnesia3 but how does it then happen1  
that1 if magnesia saturated with air be 
mixed with a compound of acid and       
calcarious earth1 these two last1 which 
attract one another the most strongly1  
do not remain united2 but the acid is   
joined to the magnesia1 and the         
calcarious earth to the air which it    
attracts much more weakly than it does  
the acid8 ,is it because the sum of the 
forces which tend to join the magnesia  
to the acid and the calcarious earth to 
the air1 is greater than the sum of the 
forces which tend to join the calcarious
 earth to the acid1 and the magnesia to 
the air3 and because there is a         
repulsion between the acid and air1 and 
between the two earths2 or they are     
somehow kept asunder in such a manner as
 hinders any three of them from being   
united together8  ,the first part of    

this supposition is favoured by our     
experiments1 which seem to shew a       
greater difference between the forces   
wherewith the calcarious earth and      
magnesia attract fixed air1 than between
 those which dispose them to unite with 
the acid4 ,the repulsions however hinted
 in the second are perhaps more         
doubtful1 tho' they are suggested in    
many other instances of decomposition2  
but the bounds of my present purpose    
will not allow me to enter upon this    
subject1 which is one of the most       
extensive in chemistry4  ,we meet also  
with a difficulty with respect to the   
volatile alkali similar to the above4   
,thus a calcarious earth that is pure or
 free of air has a much stronger        
attraction for acids than a pure        
volatile alkali1 as is evident when we  
mix quick-lime with salt ammoniac2 for  
the alkali is then immediately detached 
from the acid3 and agreeably to this ,i 
found1 upon trial1 that a pure or       
caustic volatile alkali does not        

separate a calcarious earth from an     
acid4 ,yet1 if we mix a mild volatile   
alkali1 which is a compound of alkali   
and air1 with a compound of acid and    
calcarious earth1 these two last1 which 
attract one another most strongly1 do   
not remain united2 but the acid is      
joined to the alkali and the earth to   
the air1 as happens in the precipitation
 of a calcarious earth from an acid1 by 
means of the common or mild volatile    
alkali4  ,i remember likewise a parallel
 instance with regard to quick-silver4  
,this metal has an attraction for the   
vitriolic acid1 and when joined to it   
appears under the form of turbith       
mineral3 but this attraction is weaker  
than that of the fixed alkali for the   
same acid2 for if we mix a dissolved    
salt of tartar with turbith mineral1 the
 turbith is converted into a brown      
powder1 and the alkali into vitriolated 
tartar2 which change happens the sooner1
 if the pure or caustic alkali is used4 
,yet1 if to a compound of quick-silver  

and the nitrous acid1 we add a compound 
of the fixed alkali and the vitriolic   
acid1 or a vitriolated tartar1 and      
digest the mixture with a strong heat1  
the vitriolic acid does not remain with 
the alkali1 but is joined to the        
quick-silver which it attracts more     
weakly1 composing with it a turbith     
mineral2 while the alkali is joined to  
the nitrous acid which it likeways      
attracts more weakly than it does the   
vitriolic1 and is converted into        
salt-petre4  ,from some of the above    
experiments1 it appears1 that a few     
alterations may be made in the column of
 acids in ,mr4 ,geoffroy's table of     
elective attractions1 and that a new    
column may be added to that table1      
according to the following scheme1 where
 the alkaline substances are all        
considered as in their pure state and   
free of fixed air4                      
,acids4                 ,fixed air4     
------------------------------          
-----------------            ,fixed     

alkali1            ,calcarious earth4   
,calcarious earth1           ,fixed     
alkali4    ,volatile alkali and         
magnesia4       ,magnesia4              
,volatile alkali4                       
----------------------                  
---------------  ,at the foot of the    
first column several of the metals might
 follow1 and after these the earth of   
alum2 but as ,i don't know what number  
of the metals should precede that earth1
 ,i have left it to be determined by    
further experience4  ,the volatile      
alkali and magnesia are placed in the   
same line of this column2 because their 
force of attraction seems pretty equal4 
,when we commit a mixture of magnesia   
and salt ammoniac to distillation1 the  
alkali arises and leaves the acid with  
the magnesia2 because this earth1 by    
attracting the acid1 represses its      
volatility1 and it seems also to        
diminish the cohesion of the acid and   
alkali1 and to render them separable by 
a gentle heat4 ,if the magnesia be      

saturated with air1 this likewise1 on   
account of its volatile nature and      
attraction for the alkali1 is driven up 
along with it1 and makes it appear under
 a mild form1 and in the same manner do 
the alkali and air arise from a mixture 
of salt ammoniac and of a crude         
calcarious earth4   ,footnotes3  #a     
,june #e4 #agee4  #b ,hoff4 ,op4 ,t4 iv4
 p4 #dgi4  #c ,hoff4 ,op4 ,t4 iv4 p4    
#ejj4  #d ,mr4 ,margraaf has lately     
demonstrated1 by a set of curious and   
accurate experiments1 that this powder  
is of the nature1 and possesses the     
properties1 of the gypseous or selenitic
 substances4 ,that such substances can  
be resolved into vitriolic acid and     
calcarious earth1 and can be again      
composed by joining these two           
ingredients together4 ,mem4 de l',acad4 
de ,berlin4 an4 #agej1 p4 #add4  #e     
,hoff4 ,op4 ,t4 iv4 p4 #dhj  #ejj4  #f  
,mem4 de l',acad4 de ,berlin4 an4 #agdh1
 p4 #eg4  #g ,hoff4 ,op4 ,t4 iv4 p4     
#dhj4  #h ,this evaporation was         

performed in a silver dish1 on account  
of the acrimony of the salt2 which is so
 very great1 that1 having once          
evaporated a part of the same ley in a  
bowl of ,english earthen or stone ware1 
and melted the caustic with a gentle    
heat1 it corroded and dissolved a part  
of the bowl1 and left the inside of it  
pitted with small holes4  #i ,mem4 de   
l',acad4 de ,berlin4 an4 #agdf1 p4 #hg4 
#aj ,boerh4 ,operat4 ,chem4 process4    
,,lxxvi4   ,transcribers ,notes3  #a4   
,author's spelling has been retained4   
#b4 ,minor punctuation issues have been 
corrected without note4