,transcrib]'s ,notes3 ,und]scores 80 be=e & aft] a ^w or phrase indicate italics 9 ! orig9al text4 ,c>at symbol 80 designates a sup]script4 ,a s+le und]score betwe5 two *>act]s indicates a subscript4 ,equal signs 80 be=e & aft] a ^w or phrase indicate bold 9 ! orig9al text4 ,small capitals h be5 conv]t$ to ,,solid capitals4 ,illu/rations h be5 mov$ s !y d n break up p>agraphs4 ,typographical errors h be5 sil5tly correct$ b o!r v>iations 9 spell+ & punctuation rema9 unalt]$4 ,,pyrometry ,,by ,,! ,,same ,,au?or ,,heat ,,= ,,eng9e]s ,a ,,treatise ,,on ,,heat ,,) ,,special ,,reg>d ,,to ,,its ,,practical ,,applications ,?ird ,edition1 revis$1 ) #aaj illu/rations1 xiv #dcj pp4 ,demy #hvo4 ,price #abs4 #f;d4 net4 ,,liquid ,,drops ,,& ,,globules ,,_! ,,=mation ,,& ,,movem5t ,,?ree ,,lectures ,,deliv]$ ,,to ,,popul> ,,audi5ces ,) #dc illu/rations1 x #hd pp4 ,cr[n #hvo1 clo?4 ,price #cs4 net4 ,e4 ,f4 ,n4 ,,spon1 ,,ltd41 ,,haym>ket1 ,,london1 ,s4,w4 #a ,,pyrometry ,a ,,practical ,,treatise ,,on ,,! ,,measurem5t ,,( ,,high ,,temp]atures ,,by ,,*as4 ,r4 ,,d>l+ ,,associate ,,( ,,! ,,royal ,,college ,,( ,,sci5ce1 ,,dubl92 ,,:itwor? ,,exhibition]2 ,,fell[ ,,( ,,! ,,in/itute ,,( ,,*emi/ry2 ,,fell[ ,,( ,,! ,,physical ,,society1 ,,etc4 ,,lectur] ,,9 ,,physics ,,at ,,! ,,city ,,& ,,guilds ,,te*nical ,,college1 ,,f9sbury1 ,e4,c4 ,,au?or ,,( 8,,heat ,,= ,,eng9e]s0 ,,second ,,edition1 ,,revis$ ,,& ,,enl>g$ ,,sixty-,,n9e ,,illu/rations ,illu/ration ,london ,e4 ,f4 ,n4 ,,spon1 ,ltd41 #eg ,,haym>ket1 ,s4,w4 #a ,new ,york ,,spon ,,*amb]la91 #abj ,,lib]ty ,,/reet #aibj ,cont5ts ,,page ,,preface ,,to ,,second ,,edition ix ,,preface ,,to ,,fir/ ,,edition xi ,,*ap4 ,i4 ,,introduction #a ,,ii4 ,,/&>ds ,,( ,,temp]ature #i ,absolute or ,!rmodynamic ,scale--,con/ant ,volume ,gas ,!rmomet]--,fix$ ,po9ts = ,calibration--,national ,physical ,laboratory ,scale--,temp]atures above ! ,pres5t ,limit ( ! ,gas ,!rmomet]4 ,,iii4 ,,!rmo-,,electric ,,pyromet]s #bj ,g5]al ,pr9ciples--,metals us$ = ,!rmal ,junctions-- ,*anges 9 ,!rmal ,junctions :5 con/antly us$--,electromotive ,=ce develop$ by ,typical ,junctions--,practical ,=ms ( ,!rmoc\ples-- ,liquid ,elem5t ,!rmoc\ples--,indicators = ,!rmo-electric ,pyromet]s--,special ,features ( ,indicators--,/&>diz+( ,indicators to read ,temp]atures directly--,/&>dization by ,fix$ ,po9ts-- ,/&>dization by ,measurem5t ( ,e4,m4,f4--,cold-,junction ,comp5sators--,con/ant ,temp]ature ,cold ,junctions-- ,special-,range ,indicators--,potentiometer,indicators-- ,record]s = ,!rmo-electric ,pyromet]s--,! ,?read ,record]--,! ,siem5s ,record]--,fo/]'s ,record]-- ,paul's ,record]--,! ,le$s-,nor?rup ,record]-- ,control ( ,furnace ,temp]atures--,contact-,p5 ,record]s-- ,in/allations ( ,!rmo-electric ,pyromet]s--,managem5t ( ,!rmo-electric ,pyromet]s--,laboratory ,uses ( ,temp]atures ,!rmo-electric ,pyromet]s--,measurem5t ( ,l[] by ! ,!rmo-electric ,me?od--,measurem5t ( ,surface ( ,surface ,temp]atures--,measurem5t ( ,l[ ,temp]atures-- ,temp]ature ( ,/eam1 ,exhau/ ,gases--,measurem5t ( ,diff]5ces ( ,temp]ature--,advantages ( ! ,!rmo-electric ,me?od ( ,measur+ ,temp]atures4 ,,iv4 ,,resi/ance ,,pyromet]s #aja ,g5]al ,pr9ciples--,measurem5t ( ,resi/ance by ! ,diff]5tial ,galvanomet]--,measurem5t ( ,resi/ance by ! ,:eat/one ,bridge--,relation betwe5 ,resi/ance ( ,plat9um & ,temp]ature--,*anges 9 ,resi/ance ( ,plat9um :5 con/antly ,heat$--,t]ms us$ 9 ,resi/ance ,pyrometry--,practical ,=ms ( ,resi/ance ,pyromet]s--,indicators--,siem5s' ,indicator--,:ipple's ,indicator--,! ,h>ris ,indicator-- ,! ,le$s-,nor?rup ,indicator--,siem5s' ,diff]5tial ,indicator--,record]s = ,resi/ance ,pyromet]s--,! ,le$s-,nor?rup ,record]--,paul's ,record]--,in/allation ( ,resi/ance ,pyromet]s--,managem5t ( ,resi/ance ,pyromet]s--,special ,uses ( ,resi/ance ,pyromet]s4 ,v4 ,,radiation ,,pyromet]s #acd ,g5]al ,pr9ciples--,practical ,=ms ( ,radiation ,pyromet]s--,fry's ,mirror ,pyromet]--,fry's ,spiral ,radiation ,pyromet]--,fo/]'s ,fix$-,focus ,radiation ,pyromet]--,paul's ,radiation ,pyromet]--,indicators = ,radiation ,pyromet]s--,calibration ( ,indicators-- ,record]s--,managem5t ( ,radiation ,pyromet]s--,special ,uses ( ,radiation ,pyromet]s4 ,,vi4 ,,optical ,,pyromet]s #afg ,g5]al ,pr9ciples--,wi5's ,law--,practical ,=ms ( ,optical ,pyromet]s--,fry's ,optical ,pyromet]--,le ,*ateli]'s ,optical ,pyromet]--,wann]'s ,pyromet]-- ,cambridge ,optical ,pyromet]--,holborn-,kurlbaum ,pyromet]--,lovibond's ,pyromet]--,mesur & ,n\el's ,pyromet]--,col\r-ext9ction ,pyromet]s-- ,managem5t ( ,optical ,pyromet]s--,special ,uses ( ,optical ,pyromet]s4 ,,vii4 ,,calorimetric ,,pyromet]s #aie ,g5]al ,pr9ciples--,practical ,=ms--,siem5s' ,calorimetric or 8,wat]0 ,pyromet]--,special ,uses4 ,,viii4 ,,fusion ,,pyromet]s #bjd ,g5]al ,pr9ciples--,seg] ,pyramids or 8,cones0-- ,watk9's ,heat ,record]--8,s5t9el0 ,pyromet]s-- ,/one's ,pyromet]--,fusible ,metals--,fusible ,pa/es4 ,,ix4 ,,miscellane\s ,,appliances #baa ,expansion & ,contraction ,pyromet]s--,w$gwood's ,pyromet]--,daniell's ,pyromet]--,nor?rup's ,molt5 ,t9 ,pyromet]--,vap\r-,pressure ,pyromet]s--,wat]-,jet ,pyromet]s--,pneumatic ,pyromet]s--,conduction ,pyromet]s--,gas ,pyromet]s--,wiborgh's ,!rmophones-- ,joly's ,meldomet]--,bre>ley's ,curve ,trac]4 ,,index #bbb ,preface to ! ,second ,edition ,s9ce ! publication ( ! fir/ edition 9 #aiaa1 a great ext5sion has be5 witness$ 9 ! use ( pyromet]s 9 indu/rial processes & laboratory "w1 to :i* developm5t ! au?or hopes 8 book has contribut$ 9 "s measure4 ,dur+ ! /ress occasion$ by ! w>1 pyromet]s h prov$ invaluable 9 _m processes1 & ,briti% mak]s 7 fully able to meet ! dem&s1 ow+ to ! /atus atta9$ 9 pre-w> days4 ,! increas+ use ( pyrometric appliances r5d]s necess>y "s book ( ref]5ce :i* w provide ! us] ) in=mation to enable him to get ! be/ results out ( 8 in/rum5ts1 & x is hop$ t ! pres5t treatise meets ?is ne$4 ,9 prep>+ ! second edition1 c]ta9 p>ts h be5 revis$ 9 con=mity ) mod]n practice1 & ! lat] developm5ts includ$4 ,! scope ( ! book rema9s z be=e4 ,! au?or desires to ackn[l$ge ! assi/ance he has receiv$ f ! ,briti% mak]s ( pyromet]s1 all ( :om h lib]ally provid$ him ) in=mation ( a mo/ useful k9d1 ( :i* he has avail$ himself 9 ! production ( ! pres5t edition4 ,,*as4 ,r4 ,,d>l+4 ,,woolwi*1 #aibj4 ,preface to ! ,fir/ ,edition ,! pres5t treatise has be5 f\nd$ on a c\rse ( ,cantor ,lectures on 8,indu/rial ,pyrometry10 deliv]$ by ! au?or be=e ! ,royal ,society ( ,arts 9 ! autumn ( #aiaj4 ,! practice ( pyrometry 9 rec5t ye>s has progress$ at a great] rate ?an ! lit]ature be>+ ^u x2 & ! au?or is n aw>e ( ! exi/5ce ( any o!r book writt5 9 ,engli% :i* treats ! subject f ! /&po9t ( ! actual daily use ( ! in/rum5ts4 ,9 ! succe$+ pages ! exact measurem5t ( temp]ature1 z an end 9 itself1 is made subord9ate to ! practical utility ( pyromet]s 9 controll+ v>i\s op]ations2 & consequ5tly descriptions ( appliances ( int]e/ only !oretically h ei!r be5 omitt$1 or at ! mo/ briefly describ$4 ,nev]!less1 ! fundam5tal pr9ciples are 9 all cases fully expla9$1 z an und]/&+ ( ^! is ess5tial to ! intellig5t use ( ! appliances dealt ) 9 ! book4 ,:5 necess>y1 num]ical examples are giv5 to illu/rate ! applications ( ! pr9ciples2 & ! read] :o f9ds any difficulty 9 foll[+ ! v>i\s explanations--:i* ( necessity involve an und]/&+ ( _m portions ( ! subject ( heat--is ref]r$ to ! au?or's treatise on 8,heat = ,eng9e]s10 issu$ by ! publi%]s ( ! pres5t volume4 ,) reg>d to temp]ature scales1 ! au?or has 9 ! ma9 employ$ ,c5tigrade degrees1 b has recognis$ t ! ,fahr5heit degree is /ill l>gely us$1 & has !re=e frequ5tly express$ temp]atures 9 t]ms ( bo? scales4 ,! numb] ( ^? :o f9d x an advantage 9 _! call+ to measure & control high temp]atures is con/antly increas+2 & ! manufacture ( pyrometric appliances n[ gives employm5t to consid]able numb]s4 ,! au?or tru/s t ! pres5t treatise w prove ( s]vice to all ?us conc]n$1 & also to ^? :o pursue ! fasc9at+ /udy ( high temp]ature measurem5t f ! purely sci5tific /&po9t4 ,9 conclusion1 ! au?or expresses 8 ?anks to ! v>i\s firms1 m5tion$ 9 ! text1 :o h loan$ blocks = ! purpose ( illu/ration1 & :o h furni%$ him ) mu* valuable in=mation4 ,,*as4 ,r4 ,,d>l+4 ,,woolwi*1 #aibj4 ,,pyrometry ,,*apt] ,i ,,introduction ,! t]m 8pyromet]0--=m]ly appli$ to in/rum5ts design$ to measure ! expansion ( solids--is n[ us$ to describe any device = det]m9+ temp]atures beyond ! upp] limit ( a m]cury !rmomet]4 ,?is limit1 9 ! common =m1 is ! boil+ po9t ( m]cury3 #ceg ,c4 or #fgb ,f4 ,by leav+ ! bore ( ! tube full ( nitrog5 or c>bon dioxide prior to seal+1 ! pressure ex]t$ by ! enclos$ gas :5 ! m]cury exp&s prev5ts boil+2 & ) a /rong bulb ( h>d glass ! read+s may be ext5d$ to #eej ,c4 or #ajbj ,f4 ,above ?is temp]ature ! h>de/ glass is di/ort$ by ! high int]nal pressure1 b1 by sub/itut+ silica = glass1 read+s z high z #gjj ,c4 or #abij ,f4 may be secur$4 ,:il/ su* !rmomet]s are useful 9 laboratory processes !y are too fragile = work%op use2 & if made ( ! l5g? necess>y 9 _m cases 9 :i* ! temp]ature ( furnaces is s\ght1 ! co/ w\ld be z great z t ( m durable & conv5i5t appliances4 ,no o!r in/rum5t1 h[ev]1 is s simple to read z ! !rmomet]2 & = ?is reason x is us$ :5ev] ! conditions are fav\rable4 ,! late/ proposal 9 ?is direction is due to ,nor?rup1 :o has con/ruct$ a !rmomet] conta9+ t9 enclos$ 9 a graphite envelope1 :i* is capable ( read+ up to #aejj ,c4 or high]4 ,?is in/rum5t is describ$ on page #baf4 ,! orig9 & developm5t ( ! sci5ce ( pyrometry furni% a notable example ( ! value ( ! application ( sci5tific pr9ciples to indu/ry4 ,sir ,isaac ,newton 0 ! fir/ to attempt to measure ! temp]ature ( a fire by obs]v+ ! "t tak5 to cool by a b> ( iron )drawn f ! fire2 b1 al?\gh ,newton's results 7 publi%$ 9 #agja1 x 0 n until #aghb t a practical in/rum5t = measur+ high temp]atures 0 design$4 ,9 t ye> ,josiah ,w$gwood1 ! fam\s pott]1 introduc$ an in/rum5t bas$ on ! progressive contraction und]gone by clay :5 bak$ at increas+ temp]atures1 :i* he us$ 9 controll+ 8 furnaces1 f9d+ x mu* m reliable ?an ! eye ( ! mo/ exp]i5c$ workman4 ,?is app>atus 7describ$ on page #baa7 rema9$ )\t a s]i\s rival = =ty ye>s1 & its use has n yet be5 entirely ab&on$4 ,! next /ep 9 advance 0 ! introduction ( ! expansion pyromet] by ,john ,daniell 9 #ahbb4 ,! elongation ( a plat9um rod1 encas$ 9 plumbago1 0 made to op]ate a magnify+ device1 :i* mov$ a po9t] ov] a scale divid$ s z to read temp]atures directly4 ,al?\gh inaccurate z comp>$ ) mod]n in/rum5ts1 ?is pyromet] 0 ! fir/ to give a cont9u\s read+1 & requir$ no p]sonal att5tion4 ,! expansion pyromet]--) diff]5t exp&+ sub/ances--is /ill us$ to a limit$ ext5t4 ,! ye> #ahbb 0 also m>k$ by ,seebeck's discov]y ( !rmo-electricity4 ,! g5]ation ( a curr5t ( electricity by a heat$ junction ( two metals1 increas+ ) ! temp]ature1 appe>$ to af=d a simple & satisfactory basis = a pyromet]1 & ,becqu]el con/ruct$ an in/rum5t on ^! l9es 9 #ahbf4 ,p\illet & o!rs also endeav\r$ to measure temp]atures by ! !rmo-electric me?od1 b p>tly ow+ to ! use ( unsuitable junctions1 & p>tly to ! lack ( reliable galvanomet]s1 ^! work]s fail$ to obta9 concordant results4 ,! me?od 0 = all practical purposes ab&on$ until #ahhf1 :5 its revival 9 reliable =m l$ to ! enorm\s ext5sion ( ! use ( pyromet]s witness$ dur+ rec5t ye>s4 ,9 #ahbh ,pr9sep initiat$ ! use ( gas pyromet]s1 & enclos$ ! gas 9 a gold bulb4 ,lat] work]s us$ porcela9 bulbs1 on acc\nt ( great] infusibility1 b mod]n rese>* has %[n t porcela9 is q unsuitable = accurate measurem5ts1 be+ por\s to c]ta9 gases at high temp]atures1 ev5 :5 glaz$4 ,gas pyromet]s are ( little use indu/rially1 b are n[ us$ z /&>ds = ! calibration ( o!r pyromet]s1 ! bulb be+ made ( an alloy ( plat9um & rhodium4 ,calorimetric pyromet]s1 bas$ on ,regnault's 8me?od ( mixtures10 7 fir/ made = indu/rial purposes by ,by/rm1 :o pat5t$ an in/rum5t ( ?is type 9 #ahfb4 ,?is me?od has be5 widely appli$1 & a simplifi$ =m ( 8wat]0 pyromet]1 made by ,siem5s1 is at pres5t 9 daily use = indu/rial purposes4 ,x is n capable1 h[ev]1 ( giv+ results ( ! degree ( accuracy dem&$ by _m mod]n processes4 ,! resi/ance pyromet] 0 fir/ describ$ by ,sir ,w4 ,siem5s 9 #ahga1 & 0 made by him = ev]yday use 9 furnaces4 ,_m difficulties 7 enc\nt]$ be=e ?is me?od 0 plac$ on a satisfactory foot+1 b cont9u\s inve/igation by ! firm ( ,siem5s ,co41 & also ! valuable rese>*es ( ,call5d> & ,griffi?s1 h result$ 9 ! production ( reliable resi/ance pyromet]s1 :i* are ext5sively us$ at ! pres5t "t4 ,9 #ahgb ,sir ,william ,b>rett made a discov]y :i* indirectly l$ to ! pres5t developm5t ( ! sci5ce ( pyrometry4 ,b>rett obs]v$ t iron & /eel1 on cool+ d[n f a :ite heat1 sudd5ly became hott] at a def9ite po9t1 ow+ to an int]nal molecul> *ange2 & gave ! "n ( 8recalesc5ce0 to ! ph5om5on4 ,work]s 9 /eel subsequ5tly discov]$ t ?is prop]ty 0 intimately connect$ ) ! h>d5+ ( ! metal2 ?us ,hadfield notic$ t a sample ( /eel conta9+ #aaf p] c5t4 ( c>bon1 :5 qu5*$ j bel[ ! *ange-po9t 0 n h>d5$1 b :5 treat$ simil>ly at #ae ,c4 high] x became totally h>d4 ,! dem& = accurate pyromet]s 9 ! /eel indu/ry foll[$ imm$iately on ^! discov]ies1 = ev5 ! be/-tra9$ workman c\ld n detect ) ! eye a diff]5ce 9 temp]ature s small1 & yet productive ( su* pr(\nd modification ( ! prop]ties ( ! f9i%$ /eel4 ,9 ?is in/ance1 z 9 _m o!rs1 ! in/rum5ts 7 =?com+ to meet ! dem&4 ,! rese>*es ( ,le ,*ateli]1 publi%$ 9 #ahhf1 m>k$ a great advance 9 ! progress ( pyrometry4 ,he discov]$ t a !rmo-electric pyromet]1 satisfactory 9 all respects1 c\ld be made by us+ a junction ( pure plat9um ) a rhodioplat9um alloy1 conta9+ #aj p] c5t4 ( rhodium2 a d',arsonval mov+-coil galvanomet] be+ us$ z indicator4 ,?is type ( galvanomet]1 :i* p]mits ( an ev5ly-divid$ scale1 is n[ univ]sally employ$ = ?is purpose1 & has made !rmo-electric pyromet]s n only practicable1 b m conv5i5t = g5]al purposes ?an any o!r type4 ,cont9u\s progress has s9ce be5 made 9 connection ) ?is me?od1 :i* is n[ m ext5sively us$ ?an any o!r4 ,attempts to d$uce temp]ature f ! lum9osity ( ! heat$ body 7 fir/ made by ,ed4 ,becqu]el 9 #ahfc1 b ! me?od 0 n successfully develop$ until #ahib1 :5 ,le ,*ateli] introduc$ 8 optical pyromet]4 ,?is in/rum5t1 be+ entirely ext]nal to ! hot s\rce1 enabl$ read+s to be tak5 at temp]atures f> beyond ! melt+ po9t ( plat9um1 :i* w\ld obvi\sly be ! extreme limit ( a pyromet] 9 :i* plat9um 0 us$4 ,! quantitative di/ribution ( en]gy 9 ! spectrum has s9ce be5 work$ out by ,wi5 & ,planck1 :o h furni%$ =mula bas$ on !rmodynamic reason+1 by ! use ( :i* optical pyromet]s may n[ be calibrat$ 9 t]ms ( ! !rmodynamic scale ( temp]ature4 ,o!r optical pyromet]s1 ref]r$ to 9 ! text1 h be5 devis$ by ,wann]1 ,holborn & ,kurlbaum1 ,fry1 & o!rs2 & ! highe/ atta9able temp]atures c n[ be measur$ satisfactorily by optical means4 ,! inv5tion ( ! total-radiation pyromet] by ,fry 9 #aijb add$ ano!r valuable in/rum5t to ^? already available4 ,bas$ on ! f\r?-p[] radiation law1 discov]$ by ,/efan & confirm$ by ! ma!matical inve/igations ( ,boltzmann1 ?is pyromet] is ( great s]vice 9 indu/rial op]ations at v high temp]atures1 be+ entirely ext]nal1 & capable ( giv+ p]man5t records4 ,modifications h be5 introduc$ by ,fo/] & o!rs1 & ! me?od is n[ widely appli$4 ,record]s1 = obta9+ p]man5t evid5ce ( ! temp]ature ( a furnace at any "t1 7 fir/ made = !rmo-electric pyromet]s by ,hold5 & ,rob]ts-,au/51 & = resi/ance pyromet]s by ,call5d>4 ,num]\s =ms are n[ 9 use1 & ! value ( ! records obta9$ has be5 abundantly prov$4 ,= sci5tific purposes1 all pyromet]s are made to indicate ,c5tigrade degrees1 #ajj ( :i* repres5t ! temp]ature int]val betwe5 ! melt+-po9t ( ice & ! boil+ po9t ( wat] at #gfj mm4 pressure1 ! ice-po9t be+ m>k$ #j & ! /eam-po9t #ajj4 ,9 indu/rial life1 h[ev]1 ! ,fahr5heit scale is (t5 us$ 9 ,engli%-speak+ c\ntries1 ! ice-po9t 9 ?is case be+ numb]$ #cb & ! /eam-po9t #bab2 ! int]val be+ #ahj4 ,a s+le degree on ! ,c5tigrade scale is !re=e #ah times z l>ge z a ,fahr5heit degree1 b 9 f9d+ ! numb]s on ea* scale :i* designate a giv5 temp]ature1 ! diff]5ce 9 ! z]o position on ! two scales mu/ be tak5 into acc\nt4 ,:5 x is desir$ to translate read+s on "o scale into ! correspond+ numb]s on ! o!r1 ! foll[+ =mula may be us$3-- 7,c4 read+7 7,f4 read+ - #cb7 ------------------------ ---------------------------------- 4 #e #i ,?us by sub/itut+ 9 ! above expression1 #ffj ,c4 w be f\nd to correspond to #abbj ,f4 & #aecj ,f4 to #hcb ,c4 ,x is greatly to be regrett$ t all pyromet]s are n made to indicate 9 ,c5tigrade degrees1 z confusion (t5 arises ?r\gh ! use ( ! two scales4 ,an agreem5t on ?is po9t betwe5 in/rum5t mak]s w\ld ov]come ! difficulty at once1 z ! ,c5tigrade scale is n[ s widely us$ t few pur*as]s w\ld insi/ on ,fahr5heit m>k+s4 ,x may be po9t$ out "h t no s+le pyromet] is suit$ to e purpose1 & ! *oice ( an in/rum5t mu/ be decid$ by ! nature ( ! "w 9 h&4 ,a pyromet] requir+ skill$ att5tion %\ld n be entru/$ to an untra9$ man2 & x may be tak5 = grant$ t to obta9 ! mo/ useful results intellig5t sup]vision is necess>y4 ,9 ! ensu+ pages ! advantages & drawbacks ( ea* type w be consid]$2 b 9 all cases x is desirable1 be=e mak+ any l>ge outlay on pyromet]s1 to obta9 a compet5t & imp>tial op9ion z to ! k9d be/ suit$ to ! processes to be controll$4 ,catalogue descriptions are n always tru/wor?y1 & in/ances are n want+ 9 :i* a l>ge sum has be5 exp5d$ on in/rum5ts :i*1 ow+ to wrong *oice1 h prov$ practically useless4 ,an in/rum5t suit$ to laboratory measurem5ts is (t5 a failure 9 ! work%op1 & all possibilities ( ?is k9d %\ld be consid]$ be=e decid+ ^u ! type ( pyromet] to be us$4 ,,*apt] ,,ii ,,/&>ds ,,( ,,temp]ature ,! ,absolute or ,!rmodynamic ,scale ( ,temp]atures4--,all practical in/rum5ts = measur+ temp]atures are bas$ on "s progressive physical *ange on ! "p ( a sub/ance or sub/ances4 ,9 a m]cury !rmomet]1 ! alt]ation 9 ! volume ( ! liquid is us$ z a measure ( hotness2 & simil>ly ! *ange 9 volume or pressure on ! "p ( a gas1 or ! v>iation 9 resi/ance to electricity %[n by a metal1 & _m o!r physical *anges1 may be employ$ = ?is purpose4 ,9 connection ) ! measurem5t ( high temp]atures1 _m diff]5t physical pr9ciples are reli$ ^u 9 ! v>i\s in/rum5ts 9 use1 & x is ( ! greate/ importance t all %\ld read alike "u ! same conditions4 ,?is result w\ld n be atta9$ if ea* in/rum5t 7 judg$ by its own p]=mances4 ,9 ! case ( a m]cury !rmomet]1 = example1 we may indicate ! am\nt ( expansion betwe5 ! temp]atures ( ice & /eam at #gf c5timetres pressure1 repres5t+ #ajj ,c5tigrade1 by a2 & !n assume t an expansion ( #b;a w signify a temp]ature ( #bjj1 & s on 9 proportion4 ,simil>ly1 we may f9d ! increase 9 resi/ance manife/$ by plat9um betwe5 ! same two fix$ po9ts1 & indicate x by r1 & !n assume t an increase ( #br w correspond to #bjj4 ,if n[ we comp>e ! two in/rum5ts1 we f9d t !y d n agree1 = on plac+ bo? 9 a space 9 :i* ! plat9um in/rum5t regi/]$ #bjj1 ! m]cury !rmomet] w\ld %[ #bjc4 ,a simil>1 or ev5 great]1 discrepancy w\ld be obs]v$ if o!r physical *anges 7 reli$ ^u to furni% temp]ature scales on ^! l9es1 & x is !re=e highly desirable t a /&>d indep5d5t ( any physical prop]ty ( matt] %\ld be us$4 ,su* a /&>d is to be f\nd 9 ! !rmodynamic scale ( temp]atures1 orig9ally sugge/$ by ,"l ,kelv94 ,?is scale is bas$ ^u ! conv]sion ( heat into "w 9 a heat eng9e1 a process :i* is indep5d5t ( ! nature ( ! m$ium us$4 ,a temp]ature scale f\nd$ on ?is conv]sion is !re=e n connect$ ) any physical prop]ty ( matt]1 & furni%es a /&>d ( ref]5ce to :i* all practical appliances = measur+ temp]atures may be comp>$4#a ,:5 read+s are express$ 9 t]ms ( ?is scale1 x is cu/om>y to use ! lett] ,k 9 conjunction ) ! numb]3 ?us #hej ,k w\ld mean #hej degrees on ! !rmodynamic scale4 ,:5 exi/+ in/rum5ts are comp>$ ) ?is /&>d1 x is f\nd t a scale bas$ on ! assumption t ! volume ( a gas free to exp&1 or ! pressure ( a conf9$ gas1 increases directly z ! temp]ature is 9 close agreem5t ) ! !rmodynamic scale4 ,x may be prov$ t if ! gas employ$ 7 8p]fect10 a scale 9 exact con=mity ) ! /&>d describ$ w\ld be secur$2 & gases :i* approa* ne>e/ 9 prop]ties to a p]fect gas1 su* z hydrog51 nitrog51 & air1 may !re=e be us$ to produce a practical /&>d1 ! indications ( :i* are ne>ly id5tical ) ! !rmodynamic scale4 ,if any o!r physical *ange be *os51 su* z ! expansion ( a solid1 or ! increase 9 resi/ance ( a metal1 & a temp]ature scale be bas$ on ! supposition t ! *ange 9 "q v>ies directly z ! temp]ature1 ! results obta9$ w\ld diff] consid]ably f ! absolute /&>d4 ,= ?is reason ! practical /&>d ( temp]ature n[ univ]sally adopt$ is an in/rum5t bas$ on ! prop]ties ( a suitable gas4 ,! ,con/ant ,volume ,gas ,!rmomet]4--,9 apply+ ! prop]ties ( a gas to practical temp]ature measurem5t1 we may devise "s means ( det]m9+ ! increase 9 volume :5 ! gas is all[$ to exp&1 or ! increase 9 pressure ( a conf9$ gas may be obs]v$4 ,! latt] proc$ure is m conv5i5t 9 practice1 & ! in/rum5t us$ = ?is purpose is kn[n z ! con/ant volume gas !rmomet]1 "o =m ( :i* is %[n 9 fig4 #a4 ,! gas is enclos$ 9 a bulb ,b1 connect$ to a tube b5t into a p>allel bran*1 into ! b5d ( :i* is seal$ a tap ,c1 furni%$ ) a dry+ cup4 ,! extremity ( ! p>allel bran* is connect$ to a piece ( flexible tub+ ,t1 :i* communicates ) a m]cury ci/]n :i* may be mov$ ov] a scale1 ! rod ,g s]v+ z a guide4 ,9 us+ ?is in/rum5t ! bulb ,b is imm]s$ 9 ice1 & ! tap ,c op5$4 ,:5 ! temp]ature has fall5 to #j ,c41 ! m]cury is br\ght to ! m>k ,a by adju/+ ! ci/]n1 & ! tap ,c !n clos$4 ,! bulb ,b is n[ plac$ 9 ! space or m$ium ( :i* ! temp]ature is to be det]m9$1 & expansion prev5t$ by rais+ ! ci/]n s z to keep ! m]cury at ,a4 ,:5 /eady1 ! height ( ! m]cury 9 ! ci/]n above ! level ( ,a is read (f1 & furni%es a clue to ! temp]ature ( ,b4 ,if ! coeffici5t ( pressure ( ! gas us$ 79 ?is case1 air7 be kn[n1 ! temp]ature may be calculat$ f ! equation ,p#a ,p#j7a bt71 :]e ,p#a is ! pressure at t2 ,p#j ! pressure at #j2 & b ! coeffici5t ( pressure2 t is1 ! increase 9 unit pressure at #j = a rise 9 temp]ature ( #a4 ,?us if ,p#j #gf cms42 b #jjjcfg2 height ( m]cury 9 ci/]n above ,a #eeh cms42 !n ,p#a 7#gf #eeh7 #acah cms41 & by ins]t+ ^! values 9 ! above equation t is f\nd to be #bjj4 ,9 ! in/rum5t describ$1 ,p#j is equal to ! height ( ! b>omet]1 s9ce ! tap ,c is op5 :il/ ! bulb is imm]s$ 9 ice4 ,! coeffici5t ( pressure may be det]m9$ by plac+ ! bulb 9 /eam at a kn[n temp]ature1 & not+ ! increas$ pressure4 ,9 ! equation giv51 ,p#a1 ,p#j1 & t are !n kn[n1 & ! value ( b may be calculat$4 ,illu/ration3 ,,fig4 #a4--;,,con/ant ,,volume ,,air ,,!rmomet]4 ,9 us+ ?is in/rum5t = exact det]m9ations ( temp]ature1 all[ance mu/ be made = ! expansion ( ! bulb1 :i* causes a l[] pressure to be regi/]$ ?an w\ld be not$ if ! bulb 7 non-expansive4 ,aga91 ! gas 9 ! connect+ tube is n at ! same temp]ature z t 9 ! bulb2 an error :i* may be practically elim9at$ by mak+ ! bulb l>ge & ! bore ( ! tube small4 ,! temp]ature ( ! m]cury column mu/ also be all[$ =1 z ! d5sity v>ies ) ! temp]ature4 ,:5 ! v>i\s corrections h be5 made1 read+s ( great accuracy may be secur$4 ,:5 appli$ to ! measurem5t ( high temp]atures1 ! bulb mu/ be made ( a m infusible mat]ial ?an glass4 ,gold1 porcela91 plat9um1 & qu>tz h be5 us$ by diff]5t inve/igators1 b ! mo/ reliable mat]ial = temp]atures exce$+ #ijj ,c4 has be5 f\nd to be an alloy ( plat9um ) #bj p] c5t4 ( rhodium4 ,! mo/ suitable gas to use inside ! bulb is nitrog51 :i* is *emically in]t t[>ds ! mat]ials ( ! bulb1 & is n absorb$ by ! metals me*anically4 ,:5 measur+ high temp]atures ) ?is in/rum5t1 a consid]able pressure1 am\nt+ to #a atmosph]e = e increase ( #bgc degrees above ! ice po9t1 is requisite to prev5t expansion ( ! nitrog52 & ?is pressure t5ds to di/ort ! bulb & s to falsify ! indications4 ,?is tr\ble has be5 ov]come by ,day1 :o surr\nd$ ! bulb by a second l>g] bulb1 & =c$ air or nitrog5 into ! int]v5+ space until ! pressure on ! ext]ior ( ! !rmomet] bulb 0 equal to t prevail+ 9 ! int]ior4 ,ev5 !n x 0 n f\nd possible to secure high] read+s ?an #aeej ,c41 z ! bulb comm5c$ to alt] 9 %ape ow+ to ! s(t5+ ( ! mat]ial4 ,?is temp]ature repres5ts ! highe/ yet measur$ on ! gas scale2 b by us+ a m refractory mat]ial1 su* z fus$ zirconia1 x may be f\nd possible to ext5d ?is range to #bjjj ,c4 or m4 ,exp]im5ts 9 ?is direction are v desirable1 9 ord] t high-read+ pyromet]s may be *eck$ directly aga9/ ! gas scale4 ,fix$ ,po9ts = ,calibration ( ,pyromet]s4--,x is evid5t t ! gas !rmomet] is totally unsuit$ = use 9 work%ops or laboratories :5 a rapid det]m9ation ( a high temp]ature is requir$4 ,its function is to e/abli% fix$ po9ts or temp]ature /&>ds1 by means ( :i* o!r in/rum5ts1 m conv5i5t to use1 may be graduat$ s z to agree ) ea* o!r & ) ! gas scale itself4 ,! temp]ature scales ( all mod]n pyromet]s are ?us d]iv$1 directly or indirectly1 f ! gas !rmomet]4 ,9 ! table on next page1 a numb] ( fix$ po9ts1 det]m9$ by v>i\s obs]v]s1 is giv52 ! error1 ev5 at ! highe/ temp]atures1 probably n exce$+ #b ,c4 ,9 prep>+ ! temp]ature scale ( a pyromet] = practical use1 ! in/rum5t is subject$ successively to a numb] ( ! temp]atures indicat$ 9 ! table1 & 9 ?is mann] sev]al fix$ po9ts are e/abli%$ on its scale4 ,! space betwe5 ^! po9ts is !n suitably subdivid$ to repres5t int]m$iate temp]atures4 ,,table ,,( ,,fix$ ,,po9ts4 ,sub/ance4 ,physical ,condition4 ,deg4 ,deg4 ,c5t4 ,fahr4 ,wat] 7ice7 ,at ,melt+ ,po9t #j #cb ,wat] 0 ,boil+ 0 #ajj #bab ,anil9e 0 0 0 #ahd #cfc ,naph?al5e 0 0 0 #bah #dbd ,t9 0 ,melt+ 0 #bcb #ddi ,lead 0 0 0 #cbg #fbj ,z9c 0 0 0 #dai #ghf ,sulphur 0 ,boil+ 0 #dde #hcc ,antimony 0 ,melt+ 0 #fca #aafg ,alum9ium 0 0 0 #feg #abad ,common ,salt 0 0 0 #hjj #adgb ,silv] 79 air7 0 0 0 #iee #agea ,silv] 7free f oxyg57 0 0 0 #ifb #agfc ,gold 0 0 0 #ajfd #aidg ,copp] 79 air7 0 0 0 #ajfd #aidg ,copp] 7,graphite cov]$7 0 0 0 #ajhd #aihc ,iron 7pure7 0 0 0 #aebj #bgfh ,palladium 0 0 0 #aedi #bhbj ,plat9um 0 0 0 #agee #caij ,x is necess>y to po9t out t ! figures giv5 9 ! table ref] only to pure sub/ances1 & t relatively small quantities ( impurities may give rise to s]i\s errors4 ,! me?ods by :i* ! physical condition to :i* ! temp]atures ref] may be realis$ 9 practice w be describ$ 9 ! succe$+ *apt]4 ,national ,physical ,laboratory ,scale4--,exact agreem5t ) reg>d to fix$ po9ts has n yet be5 arriv$ at 9 diff]5t c\ntries1 & an ef=t to co-ord9ate ! "w ( ! ,national ,physical ,laboratory1 ! ,unit$ ,/ates ,bureau ( ,/&>ds1 & ! ,rei*san/alt1 ) a view to ! =mation ( an int]national scale1 0 int]rupt$ by ! w>4 ,9 #aiaf ! ,national ,physical ,laboratory adopt$ a set ( fix$ po9ts on ! ,c5tigrade !rmodynamic scale1 9 con=mity ) :i* all ,briti% pyromet]s h s9ce be5 /&>dis$4 ,x w be se5 t ! figures diff] v slightly f ^? giv5 9 ! previ\s table1 :i* repres5t ! av]age results ( sep>ate det]m9ations 9 diff]5t c\ntries4 ,,national ,,physical ,,laboratory ,,scale 7#aiaf74 ,sub/ance4 ,physical ,condition4 ,deg4 ,deg4 ,c5t4 ,fahr4 ,wat] 7ice7 ,at ,melt+ ,po9t #j #cb ,wat] 0 ,boil+ 0 7#gfj mm47 #ajj #bab ,naph?al5e 0 0 0 0 #bagi #dbd ,b5zoph5one 0 0 0 0 #cjei #ehb ,z9c 0 ,melt+ 0 #daid #ghg ,antimony 0 0 0 #fcj #aaff ,common ,salt 0 0 0 #hja #adgd ,silv] 79 r$uc+ atmosph]e7 0 0 0 #ifa #agfa ,gold 0 0 0 #ajfc #aide ,copp] 79 r$uc+ atmosph]e7 0 0 0 #ajhc #aihb ,= high] temp]atures ! melt+ po9ts ( nickel 7#adeb ,c47 & palladium 7#aedi ,c47 are employ$1 b ! accuracy 9 ^! cases is n s c]ta9 z ) ! sub/ances nam$ 9 ! table4 ,a useful po9t1 int]m$iate betwe5 copp] & nickel1 has be5 e/abli%$ by ,e4 ,griffi?s1 & is obta9$ by heat+ nickel ) an excess ( graphite1 :5 a well-def9$ eutectic is =m$ :i* freezes at #accj ,c41 or #bdbf ,f4 ,temp]atures above ! ,pres5t ,limit ( ! ,gas ,!rmomet]4--,z x is n yet possible to comp>e an in/rum5t directly ) ! gas !rmomet] above #aeej ,c41 all high] temp]atures mu/ be arriv$ at by a process ( extrapolation4 ,by c>eful obs]vation ( a physical *ange at temp]atures up to ! limit ( #aeej ,c41 ! law gov]n+ su* *ange may be discov]$2 & assum+ ! law to hold indef9itely1 high] temp]atures may be d$uc$ by calculation4 ,an am\nt ( unc]ta9ty always atta*es to ?is proc$ure1 & 9 ! pa/ "s ludicr\s figures h be5 giv5 z ! result ( indef9ite extrapolation4 ,w$gwood1 = example1 by assum+ ! uni=m contraction ( clay1 gave #abjja ,c41 or #bafcg ,f41 z ! melt+ po9t ( wr\ght iron1 :]eas ! correct figure is #aebj ,c41 accord+ to ! gas scale4 ,ev5 9 rec5t times1 ! extrapolation ( ! law connect+ ! temp]ature ( a !rmal junction ) ! electromotive =ce develop$1 obta9$ by comp>ison ) ! gas scale up to #aajj ,c41 l$ ,h>k] to ! conclusion t ! melt+ po9t ( plat9um 0 #agaj ,c41 a figure #de degrees l[] ?an t n[ accept$4 ,! laws gov]n+ ! radiation ( en]gy at diff]5t temp]atures1 h[ev]1 appe> to be capable ( ma!matical pro( f !rmodynamic pr9ciples1 & temp]atures d]iv$ f ^! laws are 9 reality express$ on ! absolute or !rmodynamic scale4 ,extrapolation ( ^! laws1 :5 us$ to d$uce temp]atures by means ( radiation pyromet]s1 appe>s to be ju/ifi$2 b x is /ill desirable to ext5d ! gas scale z f> z possible to *eck su* in/rum5ts4 ,assum+ ! radiation laws to hold1 x is possible to det]m9e ! highe/ temp]atures procurable1 su* z t ( ! electric arc1 ) a reasonable degree ( c]ta9ty4 #a ,= a full] acc\nt ( ! !rmodynamic scale1 see ! au?or's treatise ,heat = ,eng9e]s1 pp4 #cia-b4 ,,*apt] ,,iii ,,!rmo-,,electric ,,pyromet]s ,g5]al ,pr9ciples4--,seebeck1 9 #ahbb1 made ! discov]y t :5 a junction ( two dissimil> metals is heat$ an electromotive =ce is set up at ! junction1 :i* gives rise to a curr5t ( electricity :5 ! heat$ junction =ms "p ( a clos$ circuit4 ,becqu]el1 9 #ahbf1 attempt$ to apply ?is discov]y to ! measurem5t ( high temp]atures1 x hav+ be5 obs]v$ t 9 g5]al ! ,e4,m4,f4 increas$ z ! temp]ature ( ! junction 0 rais$4 ,no concordant results 7 obta9$1 & ! same fate befell ! inve/igations ( o!rs :o subsequ5tly attempt$ to produce pyromet]s bas$ on ! ,seebeck effect4 ,^! failures 7 due to sev]al causes1 b *iefly to ! non-exi/5ce ( reliable galvanomet]s1 su* z we n[ possess4 ,x 0 n until #ahhf t ! problem 0 satisfactorily solv$ by ,le ,*ateli] ( ,p>is4 ,al?\gh any heat$ junction ( metals w give rise to an electromotive =ce1 x does n foll[ t any pair1 tak5 at r&om1 w be suit$ to ! purposes ( a pyromet]4 ,a junction ( iron & copp]1 = example1 gives rise to an ,e4,m4,f4 :i* increases ) ! temp]ature up to a c]ta9 po9t1 beyond :i* ! ,e4,m4,f4 falls (f al?\gh ! temp]ature rises1 & f9ally rev]ses 9 direction--a ph5om5on to :i* ! "n ( 8!rmo-electric inv]sion0 has be5 appli$4 ,evid5tly1 x w\ld be impossible to measure temp]atures 9 ?is case f obs]vations ( ! electromotive =ce produc$1 & any c\ple *os5 mu/ be free f ?is det]r5t prop]ty4 ,moreov]1 ! metals us$ mu/ n und]go det]ioration1 or alt]ation 9 !rmo-electric prop]ties1 :5 subject$ = a prolong$ p]iod to ! temp]ature x is desir$ to measure4 ,^! & o!r consid]ations greatly re/rict ! *oice ( a suitable pair ( metals1 :i*1 to give satisfaction1 %\ld con=m to ! foll[+ conditions3-- #a4 ,! ,e4,m4,f4 develop$ by ! junction %\ld increase uni=mly z ! temp]ature rises4 #b4 ,! melt+ po9t ( ei!r compon5t %\ld be well above ! highe/ temp]ature to be measur$4 ,an exception to ?is rule occurs :5 ! ,e4,m4,f4 ( fus$ mat]ials is employ$4 #c4 ,! !rmo-electric value ( ! c\ple %\ld n be alt]$ by prolong$ heat+4 #d4 ,! metals %\ld be capable ( be+ drawn into homog5e\s wires1 s t a junction1 :]ev] =m$1 may always give rise to ! same ,e4,m4,f4 "u giv5 conditions4 ,x is a fur!r advantage if ! metals :i* fulfil ! above conditions are *eap & durable4 ,! exact+ "* ( ^! requirem5ts delay$ ! production ( a reliable !rmo-electric pyromet] until #ahhf1 :5 ,le ,*ateli] discov]$ t a junction =m$ ( plat9um z "o metal1 & an alloy ( #ij p] c5t4 ( plat9um & #aj p] c5t4 ( rhodium z ! o!r1 gave concordant results4 ,9 measur+ ! ,e4,m4,f4 produc$1 ,le ,*ateli] took advantage ( ! mov+-coil galvanomet] introduc$ by d',arsonval1 :i* possess$ ! advantages ( an ev5ly-divid$ scale & a dead-beat action4 ,?is happy comb9ation ( a suitable junction ) a simple & satisfactory indicator imm$iately e/abli%$ ! reliability ( ! !rmo-electric me?od ( measur+ temp]atures4 ,z plat9um melts at #agee ,c41 & ! rhodium alloy at a /ill high] temp]ature1 a means 0 ?us provid$ ( controll+ mo/ ( ! indu/rial op]ations c>ri$ out 9 furnaces4 ,s f>1 ! effect ( heat+ ! junction has be5 consid]$ )\t reg>d to ! temp]ature ( ! rema9d] ( ! circuit1 & x is necess>y1 be=e describ+ ! con/ruction ( practical in/rum5ts1 to consid] ! laws gov]n+ ! !rmo-electric circuit1 ! simple/ =m ( :i* is repres5t$ 9 fig4 #b4 ,"o ( ! wires is connect$ at bo? ends to sep>ate pieces ( ! o!r wire1 ! free ends ( :i* are tak5 to ! galvanomet] ,two junctions1 ,a & ,b1 are ?us =m$1 :i* evid5tly act 9 opposition2 = if on heat+ ,a ! direction ( curr5t be f ,a to ,b1 !n on heat+ ,b ! direction w be f ,b to ,a4 ,h5ce if ,a & ,b 7 equally heat$ no curr5t w\ld fl[ 9 ! circuit1 ! arrangem5t be+ equival5t to two cells ( equal ,e4,m4,f4 9 opposition4 ,!rmal junctions are =m$ at ea* ( ! galvanomet] t]m9als1 b ! curr5ts to :i* !y give rise1 :5 ! temp]ature *anges1 are oppos$ & cancel ea* o!r4 ,! law :i* holds = ?is circuit may be express$ ?us3-- 8,if 9 a !rmo-electric circuit !re be two junctions1 ,a & ,b1 ! electromotive =ce develop$ is proportional to ! diff]5ce 9 temp]ature betwe5 ,a & ,b40 ,illu/ration3 ,,fig4 #b4--,,two-,,junction ,,!rmo-,,electric ,,circuit4 ,x is cu/om>y to ref] to ! two junctions z ! 8hot0 & 8cold0 junctions2 b x is important to rememb] t fluctuations 9 ! temp]ature ( ei!r w alt] ! read+ on ! galvanomet] or indicator4 ,a second law1 :i* applies to all !rmo-electric circuits1 is t 8! ,e4,m4,f4 develop$ is indep5d5t ( ! ?ickness ( ! wire40 ,?is does n mean t ! deflection ( ! galvanomet] is ! same :e!r ?9 or ?ick wires are us$ to =m ! junction4 ,! deflection dep5ds ^u ! curr5t fl[+ ?r\gh ! circuit1 & ?is1 accord+ to ,ohm's law1 v>ies inv]sely z ! total resi/ance ( ! circuit4 ,consequ5tly1 ! use ( ?9 wires ( a giv5 k9d w t5d to give a less deflection ?an 9 ! case ( ?ick wires1 z ! resi/ance ( ! =m] w be great]1 & unless ! resi/ance ( ! galvanomet] be great comp>$ ) t ( ! junction1 ! diff]5ce 9 deflection w be conspicu\s4 ,! ,e4,m4,f41 h[ev]1 is ! same "u giv5 conditions1 :atev] ?ickness ( wire be us$4 ,ref]5ce to fig4 #b w %[ t 9 ord] to realise ?is circuit 9 practice1 "o ( ! wires =m+ ! c\ple mu/ be us$ 9 ! =m ( leads to ! galvanomet]4 ,?is c readily be done if ! mat]ial ( ! wire is *eap2 b if plat9um or o!r exp5sive metal be us$1 & ! galvanomet] be "s y>ds di/ant1 ! "q ( co/ necessitates a compromise1 & ! circuit is !n arrang$ z 9 fig4 #c4 ,! wires =m+ ! hot junction are br\ght to brass t]m9als ,t ,t1 f :i* copp] wires lead to ! galvanomet] ,g4 ,?is arrangem5t results 9 ?ree effective junctions1 viz4 ! hot junction ,a to ,b2 ! junction ,a to brass1 & ! junction ,b to brass4 ,x w be se5 t ! two junctions ( copp] to brass are 9 opposition1 & cancel ea* o!r = equal heat+2 & ! same applies to ! galvanomet] connections4 ,a circuit ?us compos$ ( ?ree sep>ate junctions does n p]mit ( a simple expression = ! net ,e4,m4,f4 "u v>y+ temp]ature conditions1 & to avoid errors 9 read+s c>e mu/ be tak5 to prev5t any notable *ange ( temp]ature at ! t]m9als ,t ,t 9 a practical in/rum5t arrang$ z 9 ! diagram4 ,illu/ration3 ,,fig4 #c4--,,?ree-,,junction ,,!rmo-,,electric ,,circuit4 ,a po9t ( practical utility 9 !rmo-electric "w is ! fact t if a wire be int]rupt$ by a l5g? ( o!r metal1 z indicat$ at ,c 9 fig4 #c1 no curr5t w be set up 9 a circuit if bo? jo9ts are equally heat$1 z ! electromotive =ces g5]at$ at ea* junction are 9 opposition4 ,x is ?us possible to int]rupt a circuit by a plug-key or swit*1 )\t introduc+ an error2 always provid$ t an ev5 temp]ature prevails ov] ! region conta9+ ! jo9ts4 ,ano!r useful fact is t if two wires be br\ght into contact1 !y may be fa/5$ ov] ! jo9t by sold]+ or us+ a ?ird metal1 )\t alt]ation ( !rmo-electric value1 except 9 r>e cases4 ,?us a copp]-con/antan or iron-con/antan junction may suitably be unit$ by silv] sold]1 us+ borax z a flux1 ?us avoid+ ! unc]ta9ty ( contact :i* mu/ always occur :5 ! wires are m]ely twi/$ toge!r4 ,weld+1 h[ev]1 is pref]able to sold]+4 ,metals us$ = ,!rmal ,junctions4--,until rec5t ye>s x 0 cu/om>y to employ a plat9um-rhodioplat9um or plat9um-iridioplat9um junction = all temp]atures beyond ! scope ( ! m]cury !rmomet]4 ,! almo/ prohibitive price ( ^! metals has caus$ inve/igations to be made ) a view to discov]+ *eap] sub/itutes1 ) successful results up to #ajjj ,c4 or #ahjj ,f41 ?us compreh5d+ ! range ( temp]atures employ$ 9 _m indu/rial processes4 ,above ?is temp]ature ! plat9um s]ies ( metals are /ill us$ = accurate work+1 b x w be ( great advantage if ! range measurable by *eap or 8base0 metals c be fur!r ext5d$4 ,promise 9 ?is direction is af=d$ by ! prop]ties ( fus$ metals :5 us$ 9 !rmal junctions4 ,an inve/igation by ! au?or has %[n t 9 g5]al ! ,e4,m4,f4 develop$ by a junction does n und]go any sudd5 *ange :5 "o or bo? metals melt1 b cont9ues z if fusion _h n occurr$4 ,by mak+ arrangem5ts to ma9ta9 ! cont9uity ( ! circuit aft] fusion1 x may be possible to read temp]atures approximat+ to ! boil+ po9ts ( metals su* z copp] & t91 bo? ( :i* are ov] #bjjj ,c4 ,! base metals are n s durable z plat9um & k9dr$ metals1 b z ! co/ ( replacem5t is negligible1 ?is drawback is ( little importance4 ,moreov]1 base-metal junctions usually develop a mu* high] ,e4,m4,f4 ?an ! plat9um metals1 :i* enables /rong] & *eap] galvanomet]s to be us$ z indicators4 ,,!rmal ,,junctions ,,us$ ,,9 ,,pyromet]s4 ,upp] limit to :i* ,junction may be us$4 ,c\ple4 ,deg4 ,deg4 ,c5t4 ,fahr4 ,plat9um & rhodioplat9um 7#aj p] c5t4 ,rh7 #adjj #beej #b ,rhodioplat9um alloys ( diff]5t composition #afjj #bijj ,plat9um & iridioplat9um 7#aj p] c5t4 ,ir7 #aajj #bjjj ,nickel & con/antan #ijj #afej ,nickel & copp] #hjj #adge ,nickel & c>bon #ajjj #ahej ,nickel & iron #ajjj #ahej ,iron & con/antan #ijj #afej ,copp] & con/antan #hjj #adge ,silv] & con/antan #hjj #adge #b ,nickel *rome alloys ( diff]5t composition 7,hosk9's alloys7 #aajj #bjaj ,nickel-*rome alloy & nickel-alum9ium alloy #aajj #bjaj #b ,iron-nickel alloys ( diff]5t composition #ajjj #ahej ,! electromotive =ce develop$ by a junction ( any giv5 pair ( metals :5 heat$ to a giv5 temp]ature v>ies accord+ to ! orig9 ( ! metals4 ,x is n unusual1 = example1 = two samples ( #aj p] c5t4 rhodioplat9um1 obta9$ f diff]5t s\rces1 to %[ a diff]5ce 9 ?is respect ( #dj p] c5t4 :5 c\pl$ ) ! same piece ( plat9um4 ,equal or great] div]g5ces may be not$ ) o!r metals2 & h5ce ! replacem5t ( a junction c only be effect$1 ) accuracy1 by wires f ! same l5g?s ( :i* ! junction =m$ a "p4 ,z %[+ h[ plat9um itself is n uni=m1 x may be m5tion$ t almo/ any two pieces ( plat9um wire1 if n f ! same l5g?1 w cause a deflection on a s5sitive galvanomet] :5 made into a junction & heat$4 ,x is !re=e cu/om>y = mak]s to obta9 consid]able quantities ( wire ( a giv5 k9d1 homog5e\s z f> z possible1 9 ord] t a numb] ( id5tical in/rum5ts may be made1 & ! junctions replac$1 :5 necess>y1 )\t alt]ation ( ! scale ( ! indicator4 ,! alloy kn[n z 8con/antan10 :i* figures l>gely 9 ! =ego+ table1 is compos$ ( nickel & copp]1 & is practically id5tical ) ! alloy sold z 8,eureka0 or 8,advance40 ,x has a high specific resi/ance1 & a v small temp]ature coeffici5t1 & is mu* us$ = w9d+ resi/ances4 ,c\ples =m$ ( con/antan & o!r metals furni% on heat+ an ,e4,m4,f4 sev]al times great] ?an t yield$ by c\ples ( ! plat9um s]ies1 & %[ an equally /eady rise ( ,e4,m4,f4 ) temp]ature4 ,?is alloy has prov$ ( great s]vice 9 connection ) ! !rmo-electric me?od ( measur+ temp]atures4 ,c\ples =m$ ( nickel-*rome alloys1 kn[n z 8,hosk9's alloys10 h be5 introduc$ into ,brita9 by ! ,fo/] ,in/rum5t ,company1 :i* may be us$ cont9u\sly to #aajj ,c41 & = occasional read+s up to #acjj ,c4 ,ano!r c\ple1 mu* us$ 9 ,am]ica1 consi/s ( an alloy ( #ij p] c5t4 nickel & #aj p] c5t4 *romium1 & an alloy ( #ih p] c5t4 nickel & #b p] c5t4 alum9ium1 :i* may be us$ up to #aajj ,c4 ,o!r c\ples1 =m$ ( alloys ( nickel1 *romium1 iron1 alum9ium1 etc41 h be5 introduc$ by diff]5t mak]s1 b h n prov$ s satisfactory z ^? m5tion$ above4 ,*anges 9 ,!rmal ,junctions :5 con/antly us$4--,no metal appe>s to be able to )/& a high temp]ature cont9u\sly )\t und]go+ "s physical alt]ation2 & = ?is reason ! ,e4,m4,f4 develop$ by a giv5 junction is liable to *ange aft] a p]iod ( con/ant use4 ,at temp]atures above #aajj ,c41 plat9um1 = example1 und]goes a notable *ange 9 a comp>atively %ort p]iod1 b bel[ #ajjj ,c41 ! *ange is v slight1 & if ?is range be n exce$$1 a plat9um-rhodioplat9um or iridioplat9um junction may be us$ = ye>s )\t s]i\s error aris+ f ?is cause4 ,?is liability to *ange is "o ( ! factors :i* re/ricts ! range ( !rmal junctions1 :i* %\ld nev] be us$ cont9u\sly beyond ! temp]ature at :i* ! alt]ation comm5ces to become l>ge4 ,a second cause ( discrepancy is ! possible alt]ation 9 ! composition ( an alloy1 due to "o ( ! con/itu5ts leav+ 9 ! =m ( vap\r1 z is not$ ) iridioplat9um alloys1 f :i* ! iridium volatilises 9 tangible quantities above #aajj ,c41 caus+ a fall ( #aj p] c5t4 or m 9 ! !rmo-electric value ( ! junction ( ^! alloys ) plat9um4 ,con/antan appe>s to be v /able 9 its !rmo-electric prop]ties1 & ! v>i\s junctions 9 :i* x plays a "p %[ a high degree ( /ability if n ov]heat$4 ,rhodioplat9um alloys are v /able1 & = temp]atures exce$+ #aajj ,c4 a junction ( two ( ^! alloys1 ( diff]5t composition1 is m durable ?an "o 9 :i* pure plat9um is us$4 ,an ext5d$ s]ies ( te/s on base-metal junctions made 9 ,am]ica by ,k[alke %[$ t cont9u\s heat+ ( c\ples z receiv$ f ! mak]s alt]$ ! ,e4,m4,f4 consid]ably1 ! *ange 9 "s cases repres5t+ ov] #ajj ,c4 on ! indicator4 ,a /able condition1 due to ! relief ( /ra9s or o!r *ange1 0 f9ally rea*$1 & ! conclusion drawn t ! mat]ials %\ld be ?or\ghly anneal$ be=e calibration4 ,x is desirable 9 all cases p]iodically to te/ ! junctions at "s /&>d temp]ature1 & if any conspicu\s error be not$1 to replace ! old junction by a new "o4 ,9 addition to ! errors due to sl[ physical *anges1 a junction may be alt]$ consid]ably1 if imp]fectly protect$1 ow+ to ! *emical action ( furnace gases1 or ( solids ) :i* ! junction may come into contact4 ,! vap\rs ( metals su* z lead or antimony are v injuri\s2 & plat9um 9 p>ticul> is s]i\sly affect$ by vap\rs conta9+ phosphorus1 if 9 a r$uc+ atmosph]e4 ,s se>*+ is ! corrosive action ( furnace gases t adequate protection ( ! junction is ess5tial if errors & damage are to be avoid$4 ,:5 a wire has once be5 corrod$1 a junction made ) x w n develop ! same ,e4,m4,f4 z be=e4 ,electromotive ,=ce develop$ by ,typical ,junctions4--,! foll[+ table exhibits ! ,e4,m4,f4 g5]at$ by sev]al junctions = a range ( #ajj ,c41 tak5 at ! middle "p ( ! work+ range 9 ea* case4 ,^! figures are subject to consid]able v>iation1 accord+ to ! orig9 ( ! metals4 ,e4,m4,f4 9 millivolts = ,c\ple4 a rise ( #ajj at middle ( work+ range4 ,plat9um-rhodioplat9um 7#aj p] c5t4 ,rh7 #aa ,plat9um-iridioplat9um 7#aj p] c5t4 ,ir7 #ab ,nickel-con/antan #bc ,copp]-con/antan #eh ,nickel-copp] #fa ,iron-con/antan #fg ,hosk9's alloys #gd ,x w be not$ t ! base-metal junctions give mu* high] values ?an ! plat9um s]ies1 & h5ce c be us$ ) a less s5sitive1 & !re=e *eap]1 indicator4 ,base-metal junctions are also1 9 consequ5ce ( ! great] ,e4,m4,f4 furni%$1 capable ( yield+ m s5sitive read+s ov] a select$ range ( temp]ature4 ,illu/ration3 ,,fig4 #d4--,,practical ,,=m ,,( ,,!rmo-,,electric ,,pyromet]4 ,practical ,=ms ( ,!rmoc\ples4--,:5 exp5sive junctions are employ$1 wires ( ! m9imum ?ickness consi/5t ) /r5g? & conv5i5ce ( con/ruction are us$1 a diamet] ( ,no4 #be /&>d wire gauge be+ suitable4 ,a common arrangem5t is %[n 9 fig4 #d1 9 :i* ,j is ! hot junction1 ! wires f :i* are pass$ ?r\gh ?9 fireclay tubes :i* s]ve z insulators 7or ?r\gh tw9-bore fireclay7 to ! reels ,r ,r1 9 ! head ( ! pyromet]1 ^u :i* a quantity ( sp>e wire is w\nd to enable new junctions to be made :5 requir$4 ,two brass /rips1 ,s1 are screw$ d[n on to ! wires at "o end1 & are furni%$ ) screw t]m9als at ! o!r end1 f :i* wires are tak5 to ! galvanomet] or indicator4 ,a protect+-tube1 ,t1 surr\nds ! wires & hot junction4 ,! head1 ,h1 may be con/ruct$ ( wood1 fibre1 or porcela91 & %\ld be an insulator = electricity & heat4 ,!re are v>i\s modifications 9 use1 b ! g5]al me?od describ$ is adopt$ by mo/ mak]s4 ,9 ord] to gu>d aga9/ errors aris+ f alt]ations 9 ! temp]ature ( ! cold junctions 9 ! end ( ! pyromet]1 "s firms con/ruct ! head s z to leave a holl[ space1 ?r\gh :i* cold wat] is con/antly circulat$ 7fig4 #e71 ! arrangem5t be+ kn[n z a 8wat]-cool$ head40 ,9 "s =ms ! supply ( sp>e wires is made to take ! =m ( two spiral spr+s 9 a holl[ head1 ! upp] ends ( ! spr+s be+ tak5 to t]m9als4 ,illu/ration3 ,,fig4 #e4--,,pyromet] ,,) ,,wat]-,,cool$ ,,head4 ,! *oice ( a protect+-tube is a matt] ( consid]able importance4 ,obvi\sly1 su* a tube %\ld n s(t5 at ! highe/ temp]ature atta9$1 & :5 exp5sive metals are us$ to =m ! junction ! %ea? %\ld n be p]meable to gases or vap\rs4 ,x %\ld also1 if possible1 be a good conductor ( heat1 s t ! junction may respond quickly to a *ange ( temp]ature 9 its surr\nd+s1 & %\ld be me*anically /rong4 ,x is difficult to secure all ^! prop]ties 9 any s+le mat]ial1 & ! *oice ( a %ea? is decid$ by ! conditions "u :i* ! c\ple is to be us$4 ,! sub/ances employ$1 & _! prop]ties & special uses1 may be enum]at$ z foll[s3-- #a4 ,iron or ,mild ,/eel4--,= temp]atures n exce$+ #aajj ,c4 iron or mild /eel cov]s are *eap & effici5t f ! /&po9t ( conductivity1 al?\gh liable to det]iorate ow+ to oxidation4 ,! t5d5cy to oxidise is greatly dim9i%$ by 8caloris+0 ! ext]ior by ,rud]'s process1 9 :i* ! iron is heat$ 9 a mixture ( metallic alum9ium & oxide ( alum9ium1 a surface alloy be+ =m$ :i* resi/s oxidation4 ,a result ne>ly z good may be obta9$ by sme>+ ! surface ) f9e alum9ium p[d]1 & br++ to a :ite heat4 ,?is treatm5t greatly prolongs ! life ( an iron %ea?4 ,"s mak]s employ an inn] /eel tube r\nd ! wires1 & an out] tube :i* comes into contact ) ! furnace gases1 corrosion ( ! latt] be+ detect$ be=e ! inn] tube has giv5 way & expos$ ! junction4 ,"s mak]s d n consid] x safe to expose heat$ plat9um to an iron surface1 ) only air int]v5+1 & h5ce use an inn] cov] ( silica or porcela91 :i* ! out] iron or /eel tube protects f me*anical damage4 ,= ord9>y "w seamless /eam or hydraulic /eel tub+1 ) a weld$ end1 is satisfactory2 b = dipp+ into molt5 lead or o!r metals ! tube %\ld be bor$ f ! solid4 ,! great advantage ( an iron or /eel %ea? is its me*anical /r5g?1 :i* protects ! c\ple f damage 9 case ( r\gh usage4 #b4 ,ni*rom4--,c]ta9 alloys ( nickel & *romium1 & especially t kn[n z ,ni*rom ,,ii1 may be kept at #aajj ,c4 )\t oxidis+ to any appreciable ext5t2 & h5ce %ea?s ( ?is mat]ial may be us$ up to ! temp]ature nam$4 ,9 addition to be+ m durable ?an iron1 ni*rom possesses ! same advantages ( /r5g? & good conductivity2 on ! o!r h&1 x is m co/ly4 #c4 ,molybd5um4--,?is metal1 :i* possesses a melt+ po9t ( ab\t #bejj ,c41 may be dipp$ 9 molt5 brass1 bronze1 copp]1 etc41 )\t be+ attack$1 & has be5 us$ to =m ! tip ( a protect+-tube design$ to measure ! temp]ature ( molt5 alloys4 ,a junction cov]$ only by a ?9 tube ( molybd5um quickly atta9s ! temp]ature ( its surr\nd+s4 #d4 ,graphite & ,graphite ,compositions4--,c>bon has ! highe/ melt+ po9t ( all kn[n sub/ances1 & 9 ! =m ( artificial or ,a*eson graphite may be easily ma*9$ to any desir$ %ape4 ,graphite %ea?s are sometimes us$ = imm]sion 9 molt5 metals1 b at #ajjj ,c4 & high] ,a*eson graphite oxidises easily & becomes friable4 ,x is a good conductor ( heat1 b is easily brok54 ,compositions ( natural graphite & refractory e>?s1 su* z ,morgan's 8,salam&]10 are inf]ior to pure graphite 9 conductivity1 b are /rong] & n readily oxidis$1 & may be us$ to =m %ea?s = temp]atures up to #adjj ,c4 or possibly high]1 :5 p5etration ( furnace gases to ! junction is n ( mom5t4 #e4 ,porcela94--,?is mat]ial1 9 its be/ =ms1 may be us$ up to #adjj ,c41 b mu/ be effici5tly glaz$ to prev5t ! +ress ( furnace gases to ! junction4 ,x is easily brok5 by a bl[1 & :5 circum/ances p]mit %\ld be protect$ by an iron cov]+-%ea?4 ,! v>iety kn[n z 8,m>qu>dt0 has be5 f\nd v satisfactory = high-read+ !rmal c\ples4 ,porcela9 is n a good conductor ( heat1 & a junction encas$ 9 x does n respond quickly to ext]nal *anges 9 temp]ature4 #f4 ,vitrifi$ ,silica4--,?is sub/ance1 :i* may be work$ 9 ! oxy-hydrog5 bl[pipe1 is l>gely us$ z a protect+-tube4 ,x is n advisable1 h[ev]1 to use x = cont9u\s "w above #aajj ,c41 z beyond ?is temp]ature devitrification occurs1 & ! tube becomes por\s4 ,x is a fairly good conductor ( heat1 & )/&s rapid *anges 9 temp]ature )\t crack+4 ,x is v brittle1 & = ?is reason is g5]ally encas$ 9 iron4 #g4 ,alundum4--,?is mat]ial is made f fus$ bauxite1 & has a melt+ po9t ( #bjej ,c4 ,a special =m ( alundum1 us$ = protect+-tubes1 is non-por\s up to #acjj ,c41 & =ms a satisfactory cov]+4 ,alundum is a mod]ately good conductor ( heat1 b is easily brok54 #h4 ,c>borundum4--,?is is an electric furnace product1 :i* may be heat$ above #bjjj ,c4 )\t damage4 ,= mak+ into pyromet] tubes1 x is bond$ ) a suitable mat]ial1 & bak$ aft] %ap+4 ,c>borundum1 & ! amorph\s v>iety kn[n z 8silfrax10 h prov$ useful = protect+ junctions at temp]atures z high z #afjj ,c4 ,! !rmal conductivity is relatively good1 b ! tubes are easily brok54 #i4 ,magnesia4--,tubes ( ?is mat]ial1 :i* melts at a temp]ature consid]ably above #bjjj ,c41 h be5 us$ = special "w4 ,magnesia is a poor conductor ( heat1 & has little me*anical /r5g?4 #aj4 ,zirconia4--,?is is a v refractory mat]ial1 its melt+ po9t exce$+ #bejj ,c4 ,x may be made into a vitre\s v>iety1 :i* is non-por\s & pro( aga9/ sudd5 temp]ature *anges4 ,at pres5t1 only a m\ld$ =m ( pyromet] tube1 made f zirconia p[d]1 is available1 ! mat]ial work$ 9 ?is mann] be+ t]m$ 8zirkite40 ,al?\gh zirconia is a bad conductor ( heat1 its o!r qualities are su* t x =ms an excell5t mat]ial = "w at ! highe/ temp]atures possible = !rmal junctions2 & :5 ! vitre\s v>iety is available1 may come into ext5d$ use4 ,illu/ration3 ,,fig4 #f4 ,,pyromet] ,,) ,,special ,,cold ,,junction ,,9 ,,head4 ,x w be se5 f ! =ego+ t ! ideal protect+-tube has yet to be f\nd1 & ! us] mu/ *oose ! "o :i* comes ne>e/ to 8 requirem5ts4 ,special consid]ation mu/ be giv5 9 cases :5 *emical fumes are pres5t1 & a %ea? select$ :i* is n attack$ or p5etrat$ by !m4 ,return+ to ! junction1 x is advisable always to weld ! wires1 & n to rely ^u ! contact result+ f twi/+ !m toge!r4 ,plat9um & ! plat9um alloys may be weld$ readily by plac+ ! junction 9 a coal-gas bl[pipe f$ ) oxyg5 in/ead ( air4 ,= "w at l[] temp]atures ! plat9um metals may be sold]$ by means ( a small quantity ( gold1 9 ! flame ( a ,buns5 burn]4 ,:5 *eap metals are us$ = ! junction ! con/ruction may be consid]ably modifi$1 & (t5 ) advantage4 ,9 fig4 #f1 = example1 :i* repres5ts a !rmoc\ple made by ,a4 ,gall5kamp ,co41 ! metals us$ are copp] & con/antan1 & ! hot junction1 fa/5$ by silv] sold]1 is supplem5t$ by a cold junction ( ! same metals locat$ 9 ! head4 ,! copp] wire f ! hot junction passes directly to a copp] t]m9al1 f :5ce a copp] wire lead is c>ri$ to ! galvanomet]2 & ! same proc$ure is c>ri$ out ) ! copp] wire f ! cold junction1 ?us realis+ ! circuit %[n 9 fig4 #b4 ,! cold junction is kept 9 oil1 ! temp]ature ( :i* is regi/]$ by a %ort !rmomet]1 ?us enabl+ 7z w be expla9$ lat]7 ! correct temp]ature ( ! hot junction to be d$uc$ "u any circum/ances4 ,9 ?is in/rum5t tw9-bore fireclay is us$ to insulate ! wires1 & ! protect+-tube is ( iron--:i* suffices = ! upp] limit 7#hjj ,c47 to :i* ! junction may be us$4 ,iron & con/antan c\ld be us$ 9 ?is mann] by employ+ iron leads to ! galvanomet]4 ,ano!r type ( in/rum5t1 r5d]$ practicable by ! use ( *eap metals1 & :i* may be t]m$ ! 8heavy type10 is con/ruct$ ( ?ick pieces ( ! metals weld$ toge!r in/ead ( wires1 ?us ensur+ great] /r5g? & long] life4 ,messrs ,crompton ,co4 7 ! fir/ to introduce !rmoc\ples ( ?is type1 consi/+ ( a heavy /eel tube1 to "o end ( :i* a nickel rod is weld$1 ! o!r end be+ free1 & ! l5g? ( ! rod suitably insulat$ f ! /eel tube2 leads = ! rod & tube be+ tak5 to ! galvanomet]4 ,fig4 #g %[s a c\ple ( ?is k9d1 made by ,paul1 consi/+ ( an iron tube d[n ! middle ( :i* a con/antan rod is pass$1 insulat$ f ! tube by magnesia4 ,at ! tap]$ end ! two metals are weld$ toge!r1 & at ! free end a special cap1 fitt$ ov] ! tube & rod1 ! contact p>ts be+ insulat$ f "o ano!r1 s]ves to enable leads to be tak5 to ! galvanomet]4 ,simil> !rmoc\ples are made by ! ,fo/] ,in/rum5t ,company 7fig4 #h71 & are simple1 *eap1 & reliable up to #ijj ,c4 ) an iron-con/antan c\ple1 & to #aajj ,c4 ) ni*rom c\ples4 ,:5 worn out !y may be replac$1 at a trifl+ co/1 by o!rs made f ! same bat* ( metal4 ,illu/ration3 ,,fig4 #g4--;,,heavy ,,type1 ,,*eap-,,metal ,,pyromet]4 ,! drawback to ! use ( c>bon z "o ( ! mat]ials = a junction is ! difficulty exp]i5c$ 9 secur+ a good contact ) ! metal ) :i* x is c\pl$4 ,9 nickel-c>bon junctions ! contact is sometimes ensur$ by ! aid ( a spr+1 :i* presses ! two sub/ances toge!r4 ,su* an arrangem5t is evid5tly n s reliable z "o 9 :i* ! mat]ials are weld$1 & a defective contact1 aris+ f any cause1 w\ld lead to s]i\s error4 ,a pref]able plan is to screw bo? ! nickel & c>bon rods into a cross-piece ( ei!r elem5t4 ,illu/ration3 ,,fig4 #h4--;,,fo/]',s ,,*eap-,,metal ,,pyromet]4 ,:5 apply+ a !rmal junction to ! measurem5t ( surface temp]atures1 su* z /eam-pipes or ! ext]ior ( furnaces1 ! wires may be pass$ ?r\gh a ?9 disc ( metal1 ab\t 94 9 diamet]1 & sold]$ at ! back4 ,suitable mat]ials are copp] & con/antan1 sold]$ to a ?9 copp] disc ) silv] sold]1 & br\ght to a cold junction 9 ! head ( ! in/rum5t z %[n 9 fig4 #f4 ,! t]m9al piece ( ! insulation may be made ( h>d wood1 ) ! holes c\nt]sunk s z to cov] ! sold] & enable ! wood to t\* ! disc1 :i*1 :5 press$ on ! hot surface1 w !n rapidly acquire ! temp]ature4 ,! au?or has f\nd1 by trials "u v>y+ circum/ances1 t ?is me?od ( measur+ surface temp]atures gives reliable & concordant results4 ,= v high surface temp]atures a plat9um disc1 ) "o ( ! usual plat9um metal c\ples sold]$ to ! disc ) pure silv]1 & a piece ( tw9-bore fireclay br\ght to ! back ( ! disc1 w be f\nd to suffice = mo/ cases aris+ 9 practice4 ,a small bl[pipe flame is be/ = sold]+ ! wires to ! disc1 borax be+ us$ z flux 9 ! fir/ case2 b no flux is necess>y 9 sold]+ ! plat9um metals ) pure silv]4 ,9 decid+ ^u ! l5g? ( a !rmoc\ple x mu/ be rememb]$ t ! temp]ature record$ is t prevail+ 9 ! region ( ! hot junction4 ,:5 ! temp]ature ( a furnace is uni=m x is suffici5t to all[ ! end ( ! !rmoc\ple to protrude ab\t #ab in*es into ! int]ior1 b :5 foll[+ ! *ange ( temp]ature und]gone by objects 9 a furnace ! end mu/ be locat$ ne> ! objects4 ,if ! di/ance f ! ext]ior ( ! furnace to ! objects exce$ #b feet1 ! !rmoc\ple %\ld be ins]t$ ?r\gh ! ro( s z to hang v]tically1 z if plac$ ?r\gh ! side x w\ld droop by its own weight at high temp]atures4 ,! di/ance betwe5 ! ext]ior ( ! furnace & ! cold junctions %\ld be at lea/ #ae in*es 9 all cases 9 :i* ! heat+ ( ! cold junction is n automatically comp5sat$4 ,aft] ins]t+ ! c\ple ! op5+ ?r\gh ! furnace wall %\ld be clos$ by means ( suitable lut+-clay4 ,9 c]ta9 in/ances1 su* z flues1 x is necess>y to use a long in/rum5t 9 a horizontal position4 ,a rail may !n be plac$ across ! flue1 at a suitable place1 to s]ve z a support & s to prev5t droop+4 ,liquid ,elem5t ,!rmoc\ples4--,an inve/igation by ! au?or & ,a4 ,w4 ,grace has %[n t ! cont9uity ( ! ,e4,m4,f4 produc$ by a ris+ temp]ature is n int]rupt$ by fusion1 except 9 ! cases ( bismu? & antimony1 :i* bo? %[ an abrupt *ange 9 !rmo-electric prop]ties at ! melt+ po9t4 ,x w\ld !re=e appe> feasible to measure temp]atures by con/ruct+ a !rmoc\ple s z to reta9 ! circuit aft] fusion1 ! advantage ga9$ be+ t ! range is re/rict$ by ! boil+ po9t ( ! metals in/ead ( ! melt+ po9t & high] read+s are r5d]$ possible4 ,! boil+ po9ts ( "s ( ! common metals are app5d$3-- ,metal4 ,boil+ ,po9t4 ,deg4 ,c4 ,deg4 ,f4 ,alum9ium #ahjj #cbgj ,silv] #aiee #ceej ,t9 #bbgj #dabj ,copp] #bcaj #daij ,nickel #bccj #dbbe ,iron #bdej #dddj ,f inspection ( ^! figures1 x w be se5 t if a suitable c\ple c\ld be obta9$1 common metals might be us$ to measure temp]atures equall+ or ev5 exce$+ ! limit ( ! range cov]$ by wire junctions ( metals ( ! plat9um s]ies4 ,in/ead ( us+ two metals1 graphite might =m "o memb] ( ! c\ple1 provid$ t no objection to its use exi/$ on o!r gr\nds4 ,illu/ration3 ,,fig4 #i4--,,liquid-,,elem5t ,,!rmoc\ple4 ,! =m ( !rmoc\ple design$ by ! au?or to p]mit ( ! use ( molt5 elem5ts is %[n 9 fig4 #i4 ,a rod ( refractory mat]ial1 ,r1 is p]=at$ longitud9ally by two holes1 d[n :i* are pass$ rods ( ! !rmo-elem5ts1 ,a & ,b4 ,! l[] ends ( ,a & ,b are ins]t$ 9 a graphite block ,g1 :i* is jo9t$ on its upp] face to ,r2 ! :ole be+ surr\nd$ by ! refractory cov] ,c4 ,on ei!r or bo? ( ! elem5ts melt+1 ! circuit is ma9ta9$ ?r\gh ,g1 :i* s]ves also to prev5t ! mix+ ( ,a & ,b :5 molt51 :il/ n affect+ ! ,e4,m4,f4 develop$4 ,9 ord] to all[ = ! expansion ( ! metals on melt+1 ,a & ,b are made to fit loosely 9 ,r4 ,:5 ins]t$ 9 a furnace to a dep? repres5t$ by ,,ef1 only ! portion ( ! metals adjac5t to ! clos$ end w melt1 ! out] p>ts rema9+ solid4 ,at pres5t x has n be5 f\nd possible to procure ! refractory p>ts 9 a =m suit$ to comm]cial use1 b :5 ?is ob/acle is ov]come ?is type ( !rmoc\ple %\ld prove ( s]vice = measur+ temp]atures beyond ! scope ( ord9>y base-metal junctions4 ,indicators = ,!rmo-electric ,pyromet]s4--,z ! electromotive =ce develop$ by a s+le junction :5 heat$ is small1 a s5sitive galvanomet] is requir$ to indicate ! m9ute curr5t fl[+ ?r\gh ! circuit4 ,delicate millivoltmet]s1 ( ! mov+-coil type1 are univ]sally employ$1 z !y possess ! advantage ( an ev5ly-divid$ scale comb9$ ) ! requisite degree ( s5sitiv5ess4 ,! orig9al d',arsonval galvanomet]1 consi/+ ( a coil susp5d$ by a metallic /rip betwe5 ! poles ( a horse-%oe magnet1 0 us$ by ,le ,*ateli]1 :o1 by its aid1 0 enabl$ to lay ! f\ndations ( ?is bran* ( pyrometry4 ,?ree =ms ( ?is in/rum5t are n[ 9 use1 viz4 7a7 ! susp5d$ coil 8mirror0 type2 7b7 ! susp5d$ coil 8po9t]0 type2 & 7c7 ! pivot$ type4 ,examples ( ea* w n[ be describ$4 ,illu/ration3 ,,fig4 #aj4--;,,hold5-,d',,arsonval ,,mirror ,,galvanomet]4 ,fig4 #aj repres5ts a mirror galvanomet] work+ on ! d',arsonval pr9ciple1 design$ by ,g54 ,hold51 ,f4,r4,s4 ,! horse-%oe magnet is lam9at$1 & an iron core1 support$ by a pill>1 is plac$ betwe5 ! poles4 ,! coil1 :i* moves 9 ! space betwe5 ! core & ! poles ( ! magnet1 is susp5d$ by a ?91 flat /rip ( phosphor-bronze1 :i* c>ries a small circul> mirror4 ,a simil> phosphor-bronze /rip is fa/5$ to ! l[] "p ( ! coil1 & is cont9u$ to an adju/+-screw 9 ! base4 ,! ends ( ! susp5sion /rips communicate ) ! t]m9als ( ! galvanomet]1 & a curr5t ent]+ at "o t]m9al passes ?r\gh ! metallic susp5sions & ! coil to ! o!r4 ,! effect ( pass+ a curr5t ?r\gh ! coil1 :i* is locat$ 9 a p[]ful magnetic field is to produce an axial movem5t t5d+ to twi/ ! susp5sion /rips1 :i* movem5t is greatly magnifi$ by a spot ( light reflect$ f ! mirror on to a di/ant scale4 ,:5 ! curr5t ceases1 ! untwi/+ ( ! /rip re/ores ! coil to its =m] position4 ,galvanomet]s ( ?is type are rem>kably 8dead-beat0 9 action1 t is1 ! movem5t & re/oration ( ! coil are accompli%$ )\t vibration4 ,a semi-transp>5t scale1 plac$ at #a metre di/ance1 & #ej c5timetres long1 is suitable = use ) ?is galvanomet]4 ,:5 us$ 9 work%ops1 x is necess>y to protect a mirror galvanomet] f ! vibrations produc$ by ma*9]y1 :i* w\ld cause ! spot ( light to become un/eady4 ,! be/ me?od ( effect+ ?is is %[n 9 fig4 #aa1 :i* repres5ts ! mode ( susp5sion devis$ by ,w4 ,j4 ,lamb]t = use 9 ! ,royal ,gun ,factory1 ,woolwi* ,ars5al4 ,! usual supports ( ! galvanomet] are aboli%$1 & ! in/rum5t susp5d$ f ! r+ ( a brass tripod1 s z to keep ?ree spr+s p>tly 9 compression4 ,:5 susp5d$ 9 ?is mann]1 a mirror galvanomet] is q suit$ to comm]cial use2 9 ! quiet ( ! laboratory ! ord9>y supports may be employ$4 ,! advantage ga9$ by us+ ! mirror type is t a mu* long] scale is possible ?an ) in/rum5ts furni%$ ) a po9t]1 & h5ce great] accuracy 9 det]m9+ temp]ature read+s may be secur$4 ,illu/ration3 ,,fig4 #aa4--,,lamb]t',s ,,anti-,,vibration ,,/& ,,= ,,galvanomet]s4 ,illu/ration3 ,,fig4 #ab4--,,siem5s' ,,!rmo-,,electric ,,indicator4 ,9 susp5d$ coil in/rum5ts furni%$ ) a po9t]1 ! con/ruction diff]s only 9 detail f ! =ego+4 ,9 place ( ! mirror1 a light po9t] is atta*$ to ! susp5sion s z to re/ on ! coil & a scale is furni%$ ov] :i* ! po9t] moves4 ,fig4 #ab is an example ( ?is type1 made by ,messrs ,siem5s1 ! susp5sion be+ conta9$ 9 ! tube :i* rises f ! body ( ! in/rum5t4 ,! maximum l5g? ( scale mov$ ov] by ! extremity ( ! po9t] is ab\t #f in*es1 z a long] & !re=e heavi] po9t] w\ld r$uce ! s5sitiv5ess bel[ ! po9t requisite = !rmo-electric "w4 ,9 ! d\ble-pivot$ type1 ! susp5sion is elim9at$1 & pivots are fa/5$ to ea* end ( ! mov+ coil :i* re/ 9 be>+s4 ,! turn+ ( ! coil is made to compress a hair spr+1 made ( phosphor-bronze2 & :5 ! curr5t ceases ! unw9d+ ( ?is spr+ re/ores ! coil to its =m] position4 ,! coil c>ries a po9t] :i* moves ov] a scale4 ,^! in/rum5ts are n s s5sitive z ^? 9 :i* ! coil is susp5d$1 b c be made suffici5tly s5sitive to "w ) any k9d ( junction 9 practical use4 ,! pivot$ =m is *eap] & /rong] ?an ! susp5d$ type1 & is us$ :5ev] suffici5tly s5sitive4 ,! 8,uni-pivot0 galvanomet]1 made by ,r4 ,w4 ,paul1 is %[n 9 figs4 #ac & #ag4 ,! coil1 :i* c>ries ! po9t]1 is circul>1 & moves r\nd a sph]ical core ( iron plac$ betwe5 ! poles ( ! magnet4 ,a hole is drill$ 9 ! iron core1 & ! coil re/s on a s+le be>+ at ! bottom ( ?is hole4 ,a phosphor-bronze control-spr+ s]ves to re/ore ! coil to ! z]o position4 ,! less5$ friction due to ! use ( a s+le pivot enables ?is in/rum5t to be made v s5sitive :5 ne$$1 s t a relatively small rise 9 ! temp]ature ( a junction may cause ! po9t] to trav]se ! :ole l5g? ( ! scale4 ,illu/ration3 ,,fig4 #ac4--,,pr9ciple ,,( ,,uni-,,pivot ,,galvanomet]4 ,special ,features ( ,indicators4--,all mov+-coil in/rum5ts1 :e!r susp5d$ or pivot$1 are liable to alt]ation ( ! z]o po9t ow+ to :at is t]m$ 8creep40 ,! susp5sion /rip1 :5 fir/ fix$ 9 position1 g5]ally possesses a c]ta9 am\nt ( initial torsion1 :i* comes into op]ation gradually & causes a slight movem5t ( ! coil4 ,simil>ly1 9 a pivot$ in/rum5t1 ! /r5g? or %ape ( ! control-spr+ und]goes a gradual alt]ation at fir/1 caus+ ! po9t] to move away f ! z]o position4 ,= ?is reason adju/+ arrangem5ts are fitt$ by means ( :i* ! spot ( light or po9t] may be br\ght back to ! z]o4 ,?is creep+ ceases aft] a "t--(t5 requir+ twelve mon?s--& if n subject$ to any /ra91 error f ?is cause does n recur to any notable ext5t4 ,) a mirror galvanomet] x is bett] to move ! scale1 or turn ! galvanomet] r\nd on its axis to re/ore ! correct z]o1 r ?an to twi/ ! coil back2 b ) a fix$ scale & po9t] ! only rem$y is to turn ! coil bodily r\nd4 ,9 a s+le-pivot indicator con/antly us$ 9 ! au?or's laboratory1 ! creep am\nt$ to a movem5t ( ! end ( ! po9t] ?r\gh an angle ( #b degrees 9 ! fir/ few mon?s1 s9ce :51 aft] ! lapse ( sev]al ye>s1 no fur!r alt]ation has occurr$4 ,x is advisable to te/ ! z]o po9t ( an indicator f "t to "t by break+ ! circuit1 & if an error be discov]$ ! po9t] %\ld be re-set1 or an all[ance made 9 tak+ a read+4 ,! resi/ance ( an indicator %\ld be s high t ! read+s %\ld n be p]ceptibly alt]$ by any fluctuations 9 ! resi/ance ( ! circuit :i* may arise 9 practice4 ,if leads ( consid]able l5g? 7 us$ to connect ! pyromet] ) ! indicator1 & 7 subject to fairly l>ge alt]ations ( temp]ature1 ! consequ5t *anges 9 ! resi/ance ( su* leads w\ld be noticeable on a l[-resi/ance indicator2 & simil>ly1 if a pyromet] 7 ins]t$ at diff]5t dep?s 9 a furnace at sep>ate times1 ?us heat+ up v>y+ l5g?s ( ! junction wires1 a discrepancy w\ld arise = ! same reason4 ,! resi/ance ( an indicator1 h[ev]1 _c be rais$ beyond a c]ta9 po9t )\t r$uc+ ! s5sitiv5ess bel[ ! requir$ limit4 ,a mirror galvanomet] ( ! type describ$ may h a resi/ance--p>tly 9 ! coil & p>tly 9 an add$ s]ies resi/ance--( #ajjj ohms or m1 & /ill be suffici5tly s5sitive2 & 9 ! late/ types ( in/rum5ts provid$ ) po9t]s ! resi/ance may be made z high z #ajjj ohms1 al?\gh x is m usually #djj to #ejj ohms4 ,_m indicators are 9 use1 h[ev]1 9 :i* ! resi/ance is #ajj ohms or less4 ,z1 f ,ohm's law1 ! curr5t v>ies inv]sely z ! total resi/ance 9 ! circuit1 any alt]ation 9 resi/ance %\ld be small relatively to ! total to r5d] ! error negligible4 ,?is po9t is made cle> 9 ! foll[+ example3-- ,example4--,a !rmoc\ple & leads h a resi/ance ( #e ohms & are subject to alt]ations am\nt+ to #a ohm4 ,to f9d ! errors result+ :5 indicators ( resi/ances #hjj1 #djj1 & #ej ohms respectively are us$4 ,f ,ohm's law1 ,c ,e_/,r1 ! v>iation 9 ,c1 ) ,e con/ant1 w be #a 9 #hje1 #a 9 #dje1 & #a 9 #ee respectively4 ,z ! indications are proportional to ! curr5t1 ! alt]ations caus$ w be approximately p] c5t41 p] c5t41 & #b p] c5t4 ,! fir/ two may be ignor$2 ! la/ may be q s]i\s & lead to ! failure ( an op]ation4 ,x w be se5 f ! =ego+ t l[-resi/ance indicators %\ld only be us$ = fix$ !rmoc\ples & %ort leads n subject to temp]ature *anges1 or1 9 o!r words1 9 a circuit ( fix$ resi/ance4 ,! resi/ance ( an indicator1 :5 unkn[n1 may be f\nd by ! foll[+ me?od1 sugge/$ by ! au?or3--,a resi/ance box is jo9$ at "o end to "o t]m9al ( ! indicator4 ,to ! o!r t]m9al a fairly /\t iron wire1 #ah in*es long1 is connect$1 & a simil> l5g? ( con/antan wire is c\pl$ to ! o!r end ( ! resi/ance box4 ,! free ends ( ! wires are twi/$ into a junction :i* is dipp$ into boil+ wat]4 ,! deflection obta9$ ) no resi/ance 9 ! box 7,d#a7 is not$1 & resi/ances 7,r7 are !n unplugg$ until ! deflection 7,d#b7 is approximately "o-half ( ,d#a4 ,! resi/ance 7,g7 ( ! indicator1 ignor+ t ( ! wires1 is !n giv5 by ! =mula ,d#b,r ,g 7,d#a - ,d#b7 z may readily be prov$ f ,ohm's law1 ,e be+ con/ant4 ,?is me?od is extremely simple & reasonably accurate4 ,reliable indicators are n[ procurable f _m in/rum5t-mak]s at a comp>atively small co/1 progress 9 ?is direction hav+ be5 mo/ m>k$ 9 rec5t ye>s1 p>ticul>ly 9 ! case ( pivot$ in/rum5ts4 ,! mo/ conv5i5t =m = work%op use is made ) an edgewise scale 7fig4 #ad7 & may be plac$ 9 a suitable position fix$ to a bracket4 ,! flat-scale patt]n is pref]able = use on a laboratory table1 or = a portable pyromet]4 ,! sector patt]n is also good = work%op use1 ! dial be+ visible f a di/ance4 ,illu/ration3 ,,fig4 #ad4--;,,indicator ,,) ,,edgewise ,,scale4 ,/&>diz+ ( ,indicators to read ,temp]atures directly4--,! temp]ature scale ( an indicator1 = use ) a giv5 !rmal c\ple1 is always m>k$ by ! mak] 9 ! case ( in/rum5ts furni%$ ) a po9t]1 &1 g5]ally speak+1 is correct )9 reasonable limits4 ,x is cu/om>y & necess>y to s5d ) ! in/rum5t a /atem5t ( ! cold-junction temp]ature = :i* ! m>k+s are correct2 say #bj ,c4 or #fj ,f4 ,! us] %\ld !n endeav\r to ma9ta9 ! cold junction at ?is specifi$ temp]ature :5 tak+ a read+1 or o!rwise a consid]able error may be introduc$4 ,x is highly desirable1 h[ev]1 t ! us] %\ld be able to p]=m ! /&>diz+ himself1 if only = *eck+ purposes2 & :5 us+ a mirror galvanomet] z indicator x is necess>y to /&>dize on ! spot at :i* ! in/rum5t is fix$4 ,ability to prep>e a temp]ature scale is fur!r useful1 inasmu* z any good millivoltmet]1 ( range #j to #bj millivolts1 may be us$ = !rmo-electric "w ( all k9ds1 & may be calibrat$ = diff]5t junctions1 a suitable s]ies resi/ance be+ add$ to enable ,e4,m4,f4's high] ?an #bj millivolts to be measur$4 ,su* an in/rum5t may ?us be made extremely useful1 bo? 9 ! work%op & laboratory4 ,/&>dization may be effect$ ei!r by subject+ ! hot junction to sev]al kn[n temp]atures1 & notic+ ! deflections correspond+ !reto2 or by measur+ ! electromotive =ce develop$ by ! junction1 & calculat+ ! correspond+ temp]ature f a =mula :i* is kn[n to hold = ! range compreh5d$ by ! in/rum5t4 ,! =m] me?od is simpl]2 & if c>efully conduct$ is q accurate4 ,! latt] me?od possesses ! advantage t read+s 9 millivolts may be translat$ directly into temp]atures :5 ! con/ants ( a giv5 !rmal c\ple are kn[n4 ,x is n[ usual to m>k indicators ) a d\ble scale1 "o read+ millivolts & ! o!r temp]atures4 ,/&>dization by ,fix$ ,po9ts4--,tak+ any millivoltmet] :i*1 ) a maximum ( #bj millivolts at ! t]m9als1 w give a full scale deflection1 ! fir/ /ep is to arrange t ! po9t] 7or spot ( light7 %all j rema9 on ! scale at ! highe/ temp]ature to be atta9$ by ! junction4 ,?is may be done by plac+ ! hot junction 9 boil+ wat] & not+ ! deflection obta9$1 ei!r 9 millivolts or equal arbitr>y divisions1 & also ! temp]ature ( ! cold junction4 ,! deflection obs]v$ is due to a diff]5ce ( temp]ature 7#ajj-t7 deg4 ,c1 :]e t is ! temp]ature ( ! cold junction4 ,if ! highe/ temp]ature to be measur$ is #aj times 7#ajj-t71 ! deflection %\ld be r less ?an #a_/aj ( ! scale1 & simil>ly = any o!r requir$ temp]ature limit4 ,if ! obs]v$ deflection exce$ ?is proportion1 a s]ies resi/ance %\ld be add$ until ! correct value is obta9$4 ,?is resi/ance is !n p]man5tly in/all$ 9 ! circuit = use ) ! junction "u trial4 ,be=e proce$+ fur!r x is necess>y to consid] :e!r ! pyromet] is to possess a s+le cold junction ( asc]ta9able temp]ature 7z 9 fig4 #f71 or :e!r x w be arrang$ ) two cold junctions 9 ! head1 z 9 fig4 #d4 ,9 ! =m] case x is simpl] to prep>e a 8diff]5ce0 scale2 t is1 "o :i* reads diff]5ces ( temp]ature betwe5 ! hot & cold junctions1 f :i* ! temp]ature ( ! hot end may be obta9$ by add+ to ! diff]5ce t ( ! cold junction4 ,9 ! latt] case ! cold end %\ld be kept by artificial means at ! temp]ature likely to be atta9$ 9 practice--say #be ,c4--a wat]-ba? be+ suitable = ?is purpose4 ,x is advisable to remove ! %ield ( ! pyromet] :5 /&>diz+1 s z to expose ! hot junction1 z clos] read+s c !n be tak54 ,a numb] ( mat]ials--pref]ably *eap--( kn[n boil+ po9ts or melt+ po9ts are !n select$ f a table ( fix$ po9ts 7page #af7 s z to give ab\t six po9ts1 di/ribut$ fairly ev5ly ov] ! scale4 ,z an example1 if x 7 desir$ to prep>e a temp]ature scale f #j to #ajjj ,c41 ! foll[+ might be *os53-- ,sub/ance & ,condition4 ,temp]ature4 ,wat] at boil+ po9t #ajj ,c4 #bab ,f4 ,t9 at melt+ po9t #bcb #ddi ,z9c at melt+ po9t #dai #ghf ,antimony at melt+ po9t #fca #aafg ,common salt at melt+ po9t #hjj #adgb ,copp] at melt+ po9t 7cov]$ ) graphite7 #ajhd #aihc ,! hot junction is all[$ to atta9 ^! temp]atures successively1 & ! correspond+ deflection 9 ea* case is not$4 ,x is !n possible to divide up ! :ole ( ! scale to read temp]atures directly4 ,! fir/ read+ is tak5 by plac+ ! junction 9 a vessel ( boil+ wat]1 & = a locality ne> sea level x is n necess>y 9 ord9>y "w to take acc\nt ( fluctuations 9 ! boil+ po9t due to alt]ations ( atmosph]ic pressure4 ,to ensure t ! o!r read+s are tak5 :5 ! sub/ances are exactly at ! melt+ po9t1 ! proc$ure is z foll[s3 ab\t #b-c lb4 ( ! sub/ance are melt$ 9 a salam&] crucible1 & a small fireclay tube1 clos$ at "o end1 is ins]t$ 9 ! molt5 mass4 ,! hot junction is plac$ 9 ! fireclay tube1 & ! int]v5+ space fill$ ) asbe/os fibre4 ,great c>e mu/ be tak5 n to let ! junction t\* ! fus$ sub/ance4 ,! crucible is n[ all[$ to cool1 & a read+ ( ! deflection tak5 e half-m9ute4 ,:5 ! sub/ance is exactly at its solidify+ po9t--id5tical 9 g5]al ) ! melt+ po9t--! deflection rema9s /ation>y = sev]al consecutive read+s1 ow+ to ! lib]ation ( lat5t heat ( fusion 9 suffici5t quantity to balance ! loss by radiation4 ,?is /ation>y read+ is not$ = ea* sub/ance1 & repres5ts ! deflection giv5 :5 ! hot junction is at ! temp]ature correspond+ to ! melt+ po9t1 & ! cold junction or junctions at ! temp]ature exi/+ :5 ! obs]vation is made4 ,= melt+ ! mat]ials1 a ,davies furnace ) a l>ge ,teclu or ,mek] burn] is conv5i5t up to #hej ,c42 b to melt ! copp] a bla/ lamp is requisite4 ,! molt5 mass may be all[$ to cool 9 ! furnace4 ,f ^! obs]vations a calibration curve may be drawn ei!r = diff]5ces betwe5 hot & cold junctions1 or = a /eady temp]ature ( ! cold junctions4 ,two sets ( data are app5d$ to illu/rate ! proc$ure4 ,temp]ature ,pyromet] #a4 ,iron-con/antan4 ,pyromet] #b4 ( ,hot 7,s]ies resi/ance 9 ,plat9um- ,junction4 galvanomet] circuit47 iridioplat9um4 ,deflection4 ,cold ,diff]5ce4,deflection4 ,cold ,junction4 ,junction4 #ajj ,c4 #hi #ae ,c4 #he ,c4 #ee #bcb #bah #ag #bae #aef ,con/ant #dai #djf #ai #djj #bid at #fca #fch #ai #fab #dee #be ,c4 #hjj #hcj #bj #ghj #eij #ajhd 444 444 444 #hbj ,illu/ration3 ,,fig4 #ae4--;,,calibration ,,curves ,,= ,,two ,,!rmo-,,electric ,,pyromet]s4 ,fig4 #ae1 ,a1 is a calibration curve = !rmoc\ple #a1 connect+ deflections ) correspond+ diff]5ces betwe5 ! temp]atures ( ! hot & cold junctions4 ,9 ord] to read f ?is curve ! temp]ature ( ! hot end1 ! read+ correspond+ to ! obs]v$ deflection is add$ to ! exi/+ temp]ature ( ! cold junction4 ,?us if a deflection ( #ef divisions 7 obta9$ ) ! cold junction at #be1 ! temp]ature ( ! hot junction w\ld be 7#edj #be7 #efe ,c4 ,! advantage ( ?is me?od ( calibration is t x is unnecess>y to take precautions to keep ! cold junction at a /eady temp]ature2 & :5 a s+le cold junction is us$1 z 9 fig4 #f1 ?is plan %\ld always be foll[$4 ,x w be not$ t ?is curve passes ?r\gh z]o1 z no deflection repres5ts no diff]5ce ( temp]ature4 ,fig4 #ae1 ,b1 repres5ts ! calibration curve = pyromet] #b1 & is su* t direct read+s may be obta9$ correspond+ to any giv5 deflection1 = a cold junction temp]ature ( #be4 ,?is curve1 !re=e1 cuts ! axis ( z]o deflection at #be1 z no deflection corresponds to ! condition :5 bo? hot & cold junctions are at #be4 ,?is me?od ( calibration may be us$ ) advantage = c\ples ( ! type %[n 9 fig4 #d1 :]e two cold junctions exi/ 9 ! head1 & ! simple rule ( add+ ! cold junction temp]ature does n apply4 ,_m sugge/ions h be5 made = correct+ = alt]ations 9 ! temp]ature ( ! cold end ( su* a c\ple1 b none are accurate1 & x is necess>y to keep ?is "p at ! temp]ature ( /&>dization to secure correct read+s4 ,9 bo? ( ! above calibrations ! galvanomet] us$ possess$ a scale divid$ into #ajj equal arbitr>y divisions4 ,9 mak+ p]man5t temp]ature scales f ^! curves to atta* to ! exi/+ galvanomet] scale1 int]vals ( #ajj may be tak5 & m>k$ opposite to ! correspond+ divisions on ! exi/+ scale4 ,ea* #ajj may !n be equally subdivid$ into z _m p>ts z ! l5g? ( scale p]mits1 & numb]$ at suitable int]vals4 ,if ! junction us$ yield a calibration curve dep>t+ greatly f a /raight l9e1 e #ej int]val %\ld be tak51 or1 if necess>y1 e #be4 ,9 ! examples giv5 bo? curves are ne>ly /raight l9es 9 ! work+ region1 viz4 #djj to #hjj = ! iron-con/antan junction1 & #ejj to #aajj = ! plat9um-iridioplat9um4 ,"o precaution necess>y 9 /&>diz+ an indicator by ?is me?od is to ensure t ! metals us$ are pure1 z impurities l[] ! melt+ po9ts4 ,if ord]$ z 8pure0 f any deal] ( repute1 ! metals w g5]ally be f\nd satisfactory4 ,! common salt us$ %\ld be ! ord9>y salt sold 9 blocks1 & n a prep>$ table salt4 ,a second precaution1 :5 obs]v+ melt+ po9ts1 is to gu>d aga9/ a possible error due to ! sub/ance becom+ 8surfus$0 or 8ov]cool$02 9 :i* case ! temp]ature falls bel[ ! ord9>y freez+ po9t be=e solidification comm5ces4 ,:5 freez+ occurs1 h[ev]1 ! temp]ature rises to & rema9s at ! true melt+ po9t1 & an increase ( deflection foll[+ a gradual fall always indicates ov]cool+4 ,! high] deflection !n atta9$ is ! true freez+ po9t4 ,antimony frequ5tly ov]cools to #fjj be=e freez+1 b on sett+ rises to ! correct figure--#fca4 ,all metals & salts are liable to ov]cool+ occasionally4 ,/&>dization by ,measurem5t ( ,e4,m4,f4--,x has be5 f\nd1 z ! result ( exp]im5ts1 t ! relation betwe5 ! ,e4,m4,f4 develop$ by a junction & its temp]ature--"u con/ant conditions ( ! cold junction--may be express$ approximately by a =mula z "u3-- log ,e ,a log t ,b 7,holman's =mula71 :]e ,e electromotive =ce 9 microvolts1 t temp]ature 9 ,c5tigrade degrees1 & ,a & ,b are con/ants dep5d+ ^u ! junction4 ,) c]ta9 junctions ?is =mula may be appli$ ov] ! work+ "p ( ! scale ) an error n exce$+ #b ,c41 b ) o!rs ! discrepancy is great]4 ,9 ord] to det]m9e ! con/ants ,a & ,b1 x is necess>y to measure ! ,e4,m4,f4 at two kn[n temp]atures1 :i* %\ld be *os5 z f> ap>t z possible 9 ! work+ region4 ,:5 ^! con/ants are kn[n1 a measurem5t ( ,e enables ! temp]ature t to be f\nd by calculation4 ,example4--,le ,*ateli] f\nd t a junction at ! temp]ature ( melt$ alum9ium 7#feg ,c47 gave #fbjj microvolts2 at ! melt+ po9t ( copp] 9 air 7#ajfb ,c47 ! figure 0 #ajehj4 ,apply+ 9 ! above =mula log #fbjj ,a log #feg ,b & log #ajehj ,a log #ajfb ,b1 ! value ( ,a is #abaif & ( ,b #jcjb1 z may be f\nd by tak+ log>i?ms & solv+ = ,a & ,b4 ,! values ( ! con/ants ,a & ,b v>y = diff]5t junctions1 & also = diff]5t melts ( :at are reput$ to be ! same mat]ials4 ,:5 once det]m9$ = a quantity ( homog5e\s wires1 to :i* ! =mula applies ) suffici5t accuracy1 x is evid5t t an indicator ) a millivolt scale may be made to read temp]atures directly )\t any necessity = fur!r exp]im5t1 al?\gh x is always advisable to take "o *eck read+ at a fix$ po9t 9 ! work+ range4 ,illu/ration3 ,,fig4 #af4--,,pot5tiomet] ,,me?od ,,( ,,measur+ ,e4,m4,f4 ,9 ord] to det]m9e ! ,e4,m4,f4 ( a junction at diff]5t temp]atures1 ! pot5tiomet] me?od is us$1 9 :i* ! ,e4,m4,f4 ( ! te/-c\ple is balanc$ aga9/ ! kn[n ,e4,m4,f4 furni%$ by a con/ant cell4 ,! circuit is %[n 9 fig4 #af1 9 :i* ,b is an accumulator :i* s5ds a curr5t ?r\gh ! resi/ances ,r#a1 ,r#b1 & ! calibrat$ wire ,,de4 ,! cold ends ( ! c\ple are atta*$ at ,p s z to be 9 opposition to ,b1 & 9 ?is bran* ( ! circuit are includ$ a s5sitive galvanomet] ,g & a portion ( ! wire ,,de4 ,a /&>d cadmium cell1 ,s1 is connect$ betwe5 ,r#a & ,r#b at "o end1 & may be put 9 circuit ) ! galvanomet] ?r\gh ! swit* ,a4 ,9 comm5c+1 ,s is connect$ to ! galvanomet] & ,r#a adju/$ until no deflection is obta9$ on ,g4 ,! swit* ,a is n[ mov$ ov] to ! circuit ( ! c\ple1 & ! t]m9al ,f mov$ along ! wire until z]o deflection is aga9 obta9$4 ,! ,e4,m4,f4 ( ! c\ple is det]m9$ f ! relation ,e ( junction ,resi/ance ( ,,df 4 ,e ( /&>d cell ,r#b ,by expos+ ! hot end ( ! junction to successive /&>d temp]atures1 & ma9ta9+ ! cold ends at a kn[n con/ant temp]ature1 ! necess>y data = inclusion 9 a =mula may be obta9$4 ,9 fix+ a p]man5t temp]ature scale1 calculat$ f ! =mula1 to a millivoltmet]1 x mu/ be rememb]$ t ! values giv5 by ! exp]im5t are absolute1 & indep5d5t ( ! resi/ance ( ! circuit compos$ ( ! !rmo-elem5t & galvanomet]4 ,on ! o!r h&1 a millivoltmet] is m>k$ to read diff]5ce ( pot5tial at its t]m9als2 & if 9 s]ies ) a junction & leads ( notable resi/ance1 its indications w n be ! ,e4,m4,f4 ( ! junction4 ,an example w make ?is po9t cle>4 ,example4--,a millivoltmet] has a resi/ance ( #ajj ohms1 & is m>k$ to read ,p4,d4 at its t]m9als4 ,a !rmoc\ple & leads connect$ to ! millivoltmet] h a resi/ance ( #e ohms4 ,to f9d ! relation betwe5 ! true ,e4,m4,f4 ( ! junction & ! read+s ( ! indicator4 ,if ,e ! ,e4,m4,f4 develop$ by ! junction1 & ,v1 ! read+ ( ! millivoltmet]1 ,p4,d4 at its t]m9als1 !n ! curr5t 9 ! circuit ,e_/#aje ,v_/#ajj2 & ,v 7#ajj_/aje7;,e4 ,t is1 ! read+s are l[] by #e p] c5t4 ?an ! true ,e4,m4,f4 ( ! junction4 ,9 ! same way a l[ resi/ance voltmet]1 if appli$ to a cell ( high resi/ance1 %[s a l[] read+ ?an ! ,e4,m4,f4 ( ! cell4 ,?is example indicates h[ a table connect+ true ,e4,m4,f4's ) read+ 9 millivolts may be calculat$ :5 ! resi/ances conc]n$ are kn[n4 ,x is presum$1 9 prep>+ a scale 9 ?is mann]1 t ! resi/ance ( ! c\ple w n be subject to su* alt]ations z to affect ! read+4 ,! advantages ( ?is me?od ( calibration are manife/ :5 a numb] ( junctions are be+ made f a giv5 bat* ( wires1 z x is only necess>y to divide ! scale ( ! indicator s z to repres5t millivolts--a simple op]ation--& !n to atta* a temp]ature scale4 ,?is proc$ure is mu* m exp$iti\s ?an /&>diz+ ea* indicator at sev]al fix$ po9ts :5 a numb] are conc]n$1 b = a s+le junction ! fix$ po9t me?od is easi]4 ,! pot5tiomet] me?od ( measur+ ,e4,m4,f4 may also be us$ to det]m9e temp]atures 9 place ( an indicator1 & is ( great s]vice 9 cases :]e v accurate read+s are specially requir$1 be+ f> m delicate 9 detect+ small diff]5ces ( temp]ature ?an an indicator4 ,special pot5tiomet]s = !rmo-electric "w are made by ! ,cambridge & ,paul ,in/rum5t ,company1 ,siem5s1 & o!rs1 & are useful 9 conduct+ accurate rese>*1 b are too elaborate = work%op or ord9>y laboratory practice4 ,cold ,junction ,comp5sators4--,! necessity = pay+ att5tion to ! cold junction has l$ to v>i\s attempts to comp5sate automatically = *anges ( temp]ature at ?is "p ( ! pyromet]4 ,a !rmomet] locat$ ne> ! cold junction1 z 9 fig4 #f1 is all t is ne$$ to correct a two-junction circuit2 b :5 a ?ree-junction circuit is us$ a correct read+ is n secur$ by add+ ! excess temp]ature ( ! !rmomet] ov] ! calibration temp]ature to ! read+ on ! indicator4 ,9 ,bri/ol's arrangem5t a m]cury !rmomet]1 ) a l>ge bulb & wide /em1 is /ation$ at ! cold junction1 & p>ticipates 9 any temp]ature *ange4 ,9 ! /em is plac$ a loop ( ?9 plat9um wire1 :i* =ms "p ( ! pyromet] circuit4 ,:5 ! m]cury is heat$ x exp&s up ! /em & %ort-circuits a portion ( ! loop1 !reby dim9i%+ ! resi/ance ( ! pyromet] circuit1 & t5d+ to increase ! deflection on ! indicator4 ,simultane\sly ! cold junction w be heat$1 t5d+ to dim9i% ! curr5t1 & s to cause a less deflection4 ,by adju/m5t ^! two t5d5cies may be c\nt]balanc$1 s t ! read+ is unaffect$1 b su* adju/m5t w only apply to a giv5 ,e4,m4,f41 & !re=e to "o temp]ature ( ! hot junction4 ,h5ce ?is me?od fails 9 g5]al application4 ,peake's comp5sat$ leads are int5d$ to rem$y cold-junction errors by transf]r+ ?is junction1 9 effect1 to ! galvanomet]4 ,!y are us$ = pyromet]s 9 :i* ! plat9um metals are employ$1 & consi/ ( wires ( two diff]5t alloys ( copp] & nickel1 :i* connect ! cold end to ! indicator4 ,^! alloys are su* t ! electromotive =ces set up at ! junctions 9 ! head--,pt & ,cu-,ni #a1 & ,pt-,ir ) ,cu-,ni #b--;are equal & opposite at all work+ temp]atures1 & h5ce *anges at ! cold junctions d n affect ! read+4 ,at ! indicator1 h[ev]1 temp]ature *anges w\ld cause an alt]ation 9 deflection2 b z ! indicator is g5]ally plac$ well away f ! furnace1 & is n liable to notable heat+ or cool+1 ! possible errors are greatly r$uc$ by ! use ( ^! leads4 ,!y are obvi\sly ( no value = use ) base-metal pyromet]s1 z ! wires us$ 9 su* may be prolong$ to ! indicator1 ) an id5tical result4 ,illu/ration3 ,,fig4 #ag4--;,,d>l+',s ,,comp5sator1 ,,fitt$ ,,to ,,galvanomet]4 ,an automatic comp5sator = use ) base-metal pyromet]s has be5 devis$ by ! au?or1 & is illu/rat$ 9 figs4 #ag & #ah4 ,a spiral made ( a comp\nd /rip ( two metals is atta*$ to ! ne$le ( ! indicator1 & coils or uncoils :5 cool$ or heat$1 !reby mov+ ! po9t] ov] ! scale4 ,! l5g? ( ! spiral is su* t an alt]ation ( a giv5 numb] ( degrees 9 its temp]ature moves ! po9t] by ! same numb] ( degrees on ! scale--or1 9 o!r words1 ! temp]ature scale ( ! pyromet] is id5tical ) t ( ! spiral4 ,! metals =m+ ! junction are cont9u$1 9 ! =m ( wires1 to ! int]ior ( ! galvanomet]1 :]e a cold junction is =m$1 :i* w always possess ! same temp]ature z ! spiral4 ,! scale is con/ruct$ to repres5t diff]5ces ( temp]ature betwe5 ! hot & cold junctions1 & be=e c\pl+ up ! pyromet] ! po9t] indicates ! temp]ature ( ! spiral2 t is1 ( ! cold junction4 ,on connect+ ! !rmoc\ple ! po9t] is mov$ by ! coil ( ! indicator ?r\gh an am\nt repres5t$ by ! diff]5ce 9 temp]ature betwe5 ! two junctions1 & !re=e f9ally indicates ! temp]ature ( ! hot junction4 ,illu/ration3 ,,fig4 #ah4--;,,indicator ,,fitt$ ,,) ,,d>l+',s ,,comp5sator4 ,example4--,if ! cold junction 7 at #bj1 ! po9t]1 be=e connect+ ! c\ple1 w\ld indicate #bj on ! scale4 ,if ! hot junction 7 #ehj hott] ?an ! cold1 !n on complet+ ! circuit ! po9t] w\ld move #ehj additional degrees along ! scale1 s t ! figure indicat$ w\ld be 7#bj #ehj7 #fjj1 ! temp]ature ( ! hot junction4 ,if n[ ! indicator 7 heat$ by #aj1 ! spiral w\ld t5d to augm5t ! deflection by #aj1 b simultane\sly ! deflection due to ! junctions w\ld fall (f by #aj1 & ! read+ w\ld /ill be #fjj4 ,?is me?od ( comp5sation r5d]s ! read+s indep5d5t ( ! cold junction1 &1 9 addition to its use = high temp]atures1 enables ord9>y & l[ temp]atures to be read simply & correctly1 z w be %[n lat]4 ,! spiral is locat$ 9 ! t[] ris+ f ! top ( ! indicator 9 fig4 #ah4 ,9 ,paul's me?od ( comp5sation ! !rmoc\ple & indicator are plac$ across a ,:eat/one bridge1 two arms ( :i* conta9 resi/ances ( copp]1 :il/ ! resi/ances 9 ! o!r two arms are ( mangan94 ,any *ange 9 temp]ature at ! cold junction is %>$ by ^! f\r resi/ances1 &1 :il/ affect+ ! resi/ance ( ! copp] p>ts1 no *ange is caus$ 9 ! mangan9 p>ts1 z ?is alloy has a negligible temp]ature coeffici5t4 ,if1 !re=e1 ! bridge 7 initially balanc$ at #bj ,c41 & ! temp]ature rose to #cj1 ! increas$ resi/ance ( ! copp] w\ld de/roy ! balance1 & p]mit ( a small curr5t pass+ ?r\gh ! indicator4 ,a fall to #aj1 by dim9i%+ ! resi/ance ( ! copp]1 w\ld cause an equal curr5t to pass ?r\gh ! indicator 9 ! opposite direction4 ,! am\nt ( ?is curr5t is arrang$ s z to add ! rise 9 temp]ature ( ! cold junction to ! read+ ( ! indicator 9 ! "o case1 & to subtract ! fall 9 ! o!r1 ?us reta9+ true read+s = ! cold-junction temp]ature at :i* ! c\ple 0 /&>diz$4 ,con/ant ,temp]ature ,cold ,junctions4--,if ! cold junction c be kept at a /eady temp]ature1 comp5sators are unnecess>y1 b no good practical means ( a*iev+ ?is end has yet be5 devis$4 ,wat]-cool$ heads h already be5 ref]r$ to2 b 9 _m situations ! connect+-pipes entail$ w\ld be objectionable1 & h5ce ?is arrangem5t is n greatly us$4 ,an alt]native me?od1 sugge/$ by ,pr(4 ,a4 ,zel5y1 is to bury ! cold junction 9 ! gr\nd4 ,rec5t exp]im5ts1 conduct$ at ,cambridge by ,r4 ,s4 ,:ipple1 %[$ t a junction buri$ #aj feet deep did n v>y 9 temp]ature by m ?an #b ,c4 ov] a p]iod ( ?ree ye>s4 ,?is has l$ to ! adoption ( buri$ junctions 9 special cases2 b x is probable t mu* great] v>iations w\ld be exp]i5c$ 9 ! gr\nd b5ea? l>ge furnaces1 9 :i* case ! advantages ( ?is proc$ure w\ld be lo/4 ,a common work%op me?od is to locate ! cold junction 9 a !rmos flask fill$ ) oil1 :5 a temp]ature con/ant to #b ,c4 may be secur$1 al?\gh ! *anges 9 ! temp]ature ( ! surr\nd+ atmosph]e may be z great z #aej ,c4 ,= special "w1 ice may be us$ 9 ! !rmos flask1 ?us secur+ absolute con/ancy2 b ?is proc$ure is n feasible 9 ord9>y works practice4 ,special-,range ,indicators4--,:5 ! work+ range ( a pyromet] is f #fjj ,c4 upw>ds1 x is evid5t t ! "p ( ! scale occupi$ by ! fir/ #fjj is useless1 & t x w\ld be an advantage if ! :ole scale c\ld be utilis$ = ! special work+ range1 s z to secure m exact read+s4 ,?is may be accompli%$ by a 8set-up0 aga9/ ! movem5t ( ! po9t] caus$ by ! !rmoc\ple1 s z to prev5t any motion ov] ! scale until an assign$ temp]ature is rea*$4 ,= example1 a junction develop+ #ab millivolts at #ajjj ,c4 may be c\pl$ to an indicator 9 :i* ! full-scale deflection ( ! po9t] is produc$ by #f millivolts4 ,if an ,e4,m4,f4 ( #f millivolts be oppos$ to ! junction1 no deflection w occur until ! temp]ature at :i* ! c\ple develops #f millivolts is rea*$--:5 ! oppos+ ,e4,m4,f4 w be ov]come4 ,?is temp]ature may be #ejj ,c41 s t ! :ole scale may be divid$ up betwe5 #ejj & #ajjj4 ,! l5g? ( ! indicator scale is ?us effectively d\bl$2 & by us+ diff]5t values = ! set-up1 x is evid5t t any desir$ range may be obta9$ )9 ! limits ( s5sitivity ( ! indicator4 ,! me?od ( procur+ ! oppos+ ,e4,m4,f4 v>ies ) diff]5t mak]s4 ,! ,cambridge & ,paul ,in/rum5t ,company employ a dry cell & a s]ies resi/ance1 connect$ s z to oppose ! !rmoc\ple2 & by adju/+ ! resi/ance any desir$ set-up may be obta9$1 ! value ( :i*1 9 degrees1 may be read (f by connect+ ! cell & resi/ance to ! indicator1 ! c\ple hav+ be5 swit*$ out ( ! circuit4 ,?us1 to adju/ = a range ( #ejj-ajjj on an indicator giv+ full-scale deflection = #ejj1 ! resi/ance is regulat$ s t ! cell alone causes ! po9t] to move to ! end ( ! scale4 ,! me?od adopt$ by ,paul consi/s ( suitable resi/ances ins]t$ 9 a ,:eat/one bridge1 :i* may be ?r[n (f ! balance1 & ?us cause an oppos+ ,e4,m4,f4 ( ! correct am\nt at ! t]m9als ( ! indicator4 ,a me*anical set-up has be5 introduc$ by ! ,cambridge & ,paul ,in/rum5t ,company1 ! indicator 9 ?is case hav+ a susp5d$ coil4 ,by turn+ a mill$-head a twi/ may be giv5 to ! susp5d+ /rip1 & by ! turn+ ( a second head ! po9t] may be br\ght back to z]o1 reta9+ ! initial twi/1 :i* is oppos$ to t produc$ by ! curr5t due to ! c\ple4 ,?us1 if ! impos$ twi/ 7 su* z to move ! po9t] to ! #djj m>k on ! scale1 ! temp]ature indicat$ by ! junction w\ld be ! obs]v$ read+ plus #djj4 ,by ?is me?od x is possible to obta9 any desir$ range )9 ! limits ( ! indicator4 ,! dang] ( produc+ errors due to 8creep+0 is said to be negligible4 ,illu/ration3 ,,fig4 #ai4--;,,circuit ,,( ,,nor?rup',s 8,,pyrovolt]40 ,pot5tiomet] ,indicators4--,! advantage ( measur+ ,e4,m4,f4 by ! pot5tiomet] me?od is t ! result is indep5d5t ( ! resi/ance ( ! circuit "u te/1 :]eas an indicator is affect$ by *anges 9 ! resi/ance ( ! circuit 9 :i* x is ins]t$4 ,:5 long leads are us$ to connect a c\ple to its indicator1 notable errors may be caus$ by ! v>y+ resi/ance ( ! leads1 due to *ang+ temp]ature2 &1 9 addition1 ! resi/ance ( ! c\ple-wires v>ies accord+ to temp]ature & dep? ( ins]tion 9 ! furnace4 ,attempts h !re=e be5 made to produce indicators bas$ on ! pot5tiomet] pr9ciple1 suitable = work%op use1 & "o =m1 kn[n z ,nor?rup's 8,pyrovolt]10 is arrang$ z %[n 9 fig4 #ai1 ,a4 ,a cell ,d s5ds a curr5t ?r\gh a rheo/at ,r1 a copp] coil ,c1 & a mangan9 coil ,s4 ,! copp] coil has ! same resi/ance z ! copp] w9d+ ( ! indicator ,g4 ,! c\ple is connect$1 ) ,g 9 circuit1 across ! mangan9 coil ,s1 ! resi/ance ( ?is mat]ial be+ unaffect$ by temp]ature4 ,by adju/+ ,r until no deflection is %[n on ,g1 ! drop ( volts across ,s is made equal to ! ,e4,m4,f4 ( ! c\ple4 ,to measure ?is drop1 a key is press$1 alt]+ ! circuit z %[n 9 ,b1 ! indicator be+ n[ 9 s]ies ) ,s & ! c\ple deta*$4 ,! value ( ! curr5t pass+ ?r\gh ,s is un*ang$1 z ! indicator coil has ! same resi/ance z ! copp] coil ,c1 :i* x n[ replaces4 ,! deflection on ,g indicates ! value ( ?is curr5t1 &1 z ! drop ( volts across ,s is proportional to ! curr5t1 ,g may be m>k$ (f to read ,e4,m4,f4 & ! correspond+ temp]ature ( ! junction4 ,! advantages claim$ are t ! indicator may be us$ ) any type ( junction1 & is unaffect$ by temp]ature *anges 9 ! circuit4 ,a simil> in/rum5t is made by ! ,br[n ,company ( ,philadelphia4 ,up to ! pres5t pot5tiomet] indicators h n be5 adopt$ to any ext5t 9 ,brita91 & ! adju/m5ts necess>y to obta9 a read+ mu/ be acc\nt$ a di/9ct drawback f a work%op /&po9t4 ,record]s = ,!rmo-electric ,pyromet]s4--,x is frequ5tly ( importance to "k n only ! exi/+ temp]ature ( a furnace1 b also ! fluctuations to :i* x is subject4 ,cont9u\s obs]vation ( a pyromet] w\ld involve too mu* lab\r1 & x is !re=e evid5t t an automatic record] w\ld possess _m advantages 9 su* cases4 ,a cont9u\s record %[s :e!r ! att5dant has ma9ta9$ ! temp]ature betwe5 ! prescrib$ limits1 & furni%es a p]man5t hi/ory ( a giv5 op]ation1 :i* (t5 s]ves z a guide to future proc$ure4 ,! fir/ successful record]1 sugge/$ by ,sir ,w4 ,rob]ts-,au/5 & design$ by ,g54 ,hold51 ,f4,r4,s41 0 us$ 9 conjunction ) a mirror galvanomet]4 ,9 its orig9al =m1 ! spot ( light f ! mirror 0 made to fall on a s5sitiz$ plate1 to :i* a gradual v]tical motion 0 convey$ by connect+ ! d>k slide to a wat]-float by means ( a *a9 & pulley4 ,! float 0 plac$ 9 a tank ( wat]1 :i* 0 gradually empti$ ?r\gh a tap1 caus+ ! float to s9k & ! plate to rise4 ,if ! deflection ( ! spot ( light rema9$ /eady1 a v]tical /raight l9e 0 trac$ on ! plate1 fluctuations produc+ a s9u\s l9e4 ,trials at kn[n temp]atures enabl$ a /&>d plate to be obta9$1 divid$ into degrees1 :i* c\ld be sup]pos$ on a trial plate1 & ! temp]atures ?us det]m9$4 ,mu* valuable "w 0 accompli%$ ) ?is record] by ,rob]ts-,au/5 = ! ,alloys ,rese>* ,committee ( ! ,in/itution ( ,me*anical ,eng9e]s4 ,illu/ration3 ,,fig4 #bj4--,,rob]ts-,,au/5 ,,record]4 ,9 its mod]n =m 7fig4 #bj7 ! photographic plate is replac$ by a %eet ( s5sitiz$ pap] w\nd r\nd a drum :i* rotates at a kn[n rate--say1 once 9 #ab h\rs--by means ( int]nal clockwork1 %[n to ! left ( ! figure4 ,! galvanomet] is plac$ at ! opposite end1 & ! mirror is illum9at$ by means ( an electric lamp plac$ ext]nally1 ! rays f :i* are reflect$ f a prism 9 ! int]ior on to ! mirror4 ,! ray ( light leav+ ! mirror is brok5 into two portions1 "o ( :i* passes ?r\gh a n>r[ slit on to ! s5sitiz$ pap]1 :il/ ! o!r portion is reflect$ on to a gr\nd-glass scale on ! lid1 divid$ s z to read temp]atures4 ,9 ?is mann] ! arrangem5t s]ves n only z a record]1 b also indicates ! exi/+ temp]ature )\t necessitat+ ! exam9ation ( ! s5sitiz$ pap]4 ,! :ole arrangem5t is made imp]vi\s to light1 s t x may be us$ 9 daylight4 ,a d>k room is necess>y = fix+ ! records4 ,:5 desir$1 records ( two or m pyromet]s may be tak5 on ! same %eet1 a clockwork device be+ us$ to swit* ea* in/rum5t 9 turn on to ! galvanomet] = a giv5 p]iod1 an ext]nal dial indicat+ :i* pyromet] is = ! "t be+ 9 circuit4 ,:il/ x is a drawback to ! use ( ?is record] t ! record is n visible1 ! use ( a mirror galvanomet] conf]s a high degree ( s5sitiv5ess to ! in/rum5t1 n possess$ by ! record]s to be describ$ subsequ5tly4 ,illu/ration3 ,,fig4 #ba4--,,pr9ciple ,,( ,,?read ,,record]4 ,! ,?read ,record]4--,9 ?is in/rum5t an int]mitt5t record is secur$ 9 ink1 possess+ ! advantages ( visibility dur+ ! p]iod ov] :i* read+s are tak51 & ( p]man5ce )\t subsequ5t treatm5t ( ! *>t4 ,! pr9ciple is %[n 9 fig4 #ba1 :]e ,a is a boom t]m9at+ 9 a ,v-%ap$ piece ( ivory1 & atta*$ to ! galvanomet] susp5sion ,b4 ,by means ( a cam ,e1 rotat$ by clockwork1 a b> ,d is made to desc5d at /at$ int]vals1 press+ ! end ( ,a on to an ink$ ?read ,g1 & caus+ ! ?read to t\* a pap] w\nd r\nd ! drum ,c4 ,?is drum rotates on its axis once 9 #be h\rs by ! action ( int]nal clockwork4 ,! cont9u$ rotation ( ! cam ,e alt]nately raises & depresses ! boom ,a1 leav+ x free = a suffici5t "t to enable x to atta9 ! position x w\ld occupy if ! me*anism 7 abs5t4 ,! ?read ,g is pass$ ov] pulleys1 & is w\nd r\nd ?r\gh an ink-well1 s t ! portion opposite ,a is always moi/4 ,) ! b> ,d desc5d+ e two m9utes1 ! successive dots =m a ne>ly cont9u\s l9e4 ,! pap] on ,c is divid$ horizontally into temp]atures1 & v]tically into "t units1 s t ! temp]ature exi/+ at any giv5 "t may readily be asc]ta9$4 ,! front ( ! b> ,d1 or a sep>ate /rip p>allel to x1 is divid$ s z to enable temp]atures to be read )\t ref]5ce to ! *>t4 ,! actual in/rum5t is %[n 9 fig4 #bb4 ,:5 sev]al simultane\s records are requir$1 ! drum ,c is ext5d$1 & o!r galvanomet]s introduc$1 to :i* ! sep>ate pyromet]s are connect$4 ,sev]al records c be tak5 on "o *>t by introduc+ a clockwork me*anism to c\ple ea* pyromet] 9 turn to ! "o galvanomet]4 ,illu/ration3 ,,fig4 #bb4--,,?read ,,record]4 ,illu/ration3 ,,fig4 #bc4--,,siem5s' ,,record]4 ,! ,siem5s ,record]4--,9 ?is in/rum5t 7fig4 #bc7 ! boom f ! galvanomet] t]m9ates 9 a knife-edge1 & moves ov] a ?9 horizontal rail1 ! top ( :i* is r\nd$4 ,betwe5 ! rail & ! boom are plac$ an ink+ ribbon & a pap] *>t1 :i* is mov$ =w>d by clockwork4 ,a *opp]-b>1 also actuat$ by clockwork1 desc5ds at ab\t half-m9ute int]vals1 & depresses ! end ( ! galvanomet] boom1 ?us produc+ a small dot on ! *>t4 ,! pap] is #ab cms4 wide & #dj y>ds long2 x is divid$ into "t & temp]ature units1 & moves =w>d at ! rate ( #b cms4 p] h\r4 ,levell+ screws are fix$ to ! base ( ! record]4 ,illu/ration3 ,,fig4 #bd4--;,,fo/]',s ,,record]4 ,fo/]'s ,record]4--,fo/]'s record] 7fig4 #bd7 is design$ = use ) base-metal c\ples ( ! nickel-*romium type1 kn[n z ,hosk9's alloys1 :i* yield an ,e4,m4,f4 ab\t five times z l>ge z a plat9um-rhodioplat9um c\ple4 ,! =ce available 9 ?is case enables ! coil ( ! galvanomet] to be pivot$ 9 a horizontal position1 ! po9t] be+ v]tical1 & yet to be suffici5tly s5sitive4 ,! *>t is m\nt$ on a v]tical plate :i* rotates on its axis1 ! "t ord9ates tak+ ! =m ( conc5tric circles1 :i* are cut at an angle by ! temp]ature ord9ates4 ,at ! t]m9us ( ! po9t] is plac$ a small capill>y tube1 fitt$ ) an ink$ wick1 :i*1 :5 press$ ^u ! *>t1 makes a m>k4 ,! press]-b> is curv$ to ! same radius z ! po9t]1 & c>ries a pad wett$ ) ink1 s t at ea* depression ! supply ( ink to ! wick is repl5i%$ by an am\nt equal to t imp>t$ to ! *>t4 ,?is record] is sometimes fitt$ ) special contacts1 s t :5 ! correct temp]ature exi/s an electric lamp ) a :ite bulb rema9s light$2 :]eas :5 too l[ or too high a gre5 or r$ lamp is lit up1 & an al>m ?us giv54 ,su* an addition involves ! use ( a relay circuit1 b is advisable 9 cases :]e exp5sive articles might suff] if ov]heat$4 ,x c be modifi$ to p]mit ( sev]al simultane\s records be+ tak51 & possesses ! advantage t ! :ole *>t is visible at any "t4 ,on ! o!r h&1 ! circul> coord9ates may be acc\nt$ a drawback by "s1 z n be+ q s famili> to read z *>ts 9 :i* ! l9es are /raight4 ,robu/ con/ruction is a feature ( ?is record]4 ,illu/ration3 ,,fig4 #be4 ,,paul',s ,,record]4 ,paul's ,record]4--,9 ! record]s previ\sly describ$1 ! motive p[] is furni%$ by clockwork4 ,r4 ,w4 ,paul has introduc$ an in/rum5t 9 :i* all ! mov+ p>ts are actuat$ by a motor driv5 ) p[] f ! ma9s4 ,?is record] is %[n 9 fig4 #be4 ,! motor is furni%$ ) a special type ( gov]nor to ensure con/ant spe$1 & is connect$ by suitable ge>+ to ! me*anisms mov+ ! *>t1 press]-b>1 & ink+ ribbon1 provision be+ made to v>y ! spe$s ( ^! movem5ts by *ang+ ! ge>4 ,! galvanomet] is ( uni-pivot patt]n1 & ! po9t] is press$ at int]vals on to a typewrit] ribbon :i* lies above ! *>t4 ,imm$iately b5ea? ! ribbon is plac$ a ?9 metal rod ov] :i* ! pap] passes1 & ! result ( ! contact is to produce a small dot4 ,z 9 ! ?read record]1 ! *>t is divid$ into rectil9e> coord9ates1 ! ribbon 9 ?is case s]v+ ! same purpose z ! ?read 9 ! =m] in/rum5t4 ,! l[] "p ( ! record] is prolong$ s z to display a consid]able l5g? ( ! *>t1 :i* is 9 ! =m ( a roll1 & is drawn =w>d by ! me*anism4 ,:5 two records are tak5 simultane\sly ! ribbon consi/s ( two /rips1 "o moi/5$ ) black ink1 & ! o!r ) r$2 & x is arrang$ t ea* /rip 9 turn is ov] ! ?9 rod on to :i* ! po9t] is press$1 s t ! records appe> 9 sep>ate col\rs4 ,?is record] c also be arrang$ = multiple records1 or fitt$ ) a scale-control4 ,) a view to work%op use1 all ! cov]s are fitt$ ) fac$ metal jo9ts1 :i* are mu* bett] = keep+ out du/ ?an wood5 ones4 ,a fur!r useful feature is t ! v>i\s units 9 ! record]--galvanomet]1 motor1 fe$ & record me*anism1 & r$uc+ ge>--are all sep>ate & int]*angeable4 ,by introduc+ a suitably divid$ *>t ?is record] w also s]ve = a radiation pyromet]1 or1 z w be %[n lat]1 = a resi/ance pyromet]4 ,illu/ration3 ,,fig4 #bf4--,,le$s-,,nor?rup ,,record]4 ,! ,le$s-,nor?rup ,record]4--,! ,le$s & ,nor?rup ,company1 ( ,philadelphia1 manufacture a record] :i* is l>gely us$ 9 ! ,unit$ ,/ates4 ,z 9 ,paul's record]1 all ! me*anism is motor driv52 b ! o!r arrangem5ts are entirely di/9ct4 ,in/ead ( measur+ ! deflection ( ! po9t]1 a z]o deflection me?od is us$4 ,! pyromet] =ms "p ( a pot5tiomet] circuit1 & ! function ( ! me*anism is to oppose an ,e4,m4,f4 equal to t ( ! pyromet]1 f :i* ! temp]ature is kn[n4 ,?is has ! advantage t ! measurem5t is indep5d5t ( ! resi/ance ( ! leads1 & is capable ( great accuracy4 ,! mann] 9 :i* ! adju/m5t ( ! oppos+ ,e4,m4,f4 is controll$ may be und]/ood f fig4 #bf1 9 :i* ! galvanomet] coil is %[n at ! top ( ! figure4 ,! %aft f ! motor c>ries f\r cams1 ,b1 ,c1 ,d1 ,d1 & at ea* revolution ! cam ,b raises ! b> 7#e7 s z to press x aga9/ an arm atta*$ to ! galvanomet] coil4 ,at ! same mom5t ! cam ,c pu%es aga9/ ! b> 7#c71 & !reby releases a clut* 7#b7 f ! disc b5ea?4 ,z %[n1 ! boom f ! coil is to ! "r ( ! c5tral position1 & is gripp$ betwe5 a b> 7#e7 & ! lev] 7#d7 :5 ! =m] rises1 caus+ an angul> movem5t ( ! clut*-arm 7#b74 ,z ! rotation cont9ues ! cam ,c leaves ! b> 7#c71 :i* !n spr+s back & engages ! clut* on ! disc4 ,! cam ,d !n desc5ds & presses on ! projection ( ! clut*-arm to ! left1 caus+ ! disc to rotate4 ,! movem5t ( ! disc is convey$ to an arm :i* moves ov] ! slide wire ( ! pot5tiomet]2 & ?is movem5t cont9ues until ! galvanomet] boom is 9 ! c5tral or z]o position1 :5 nei!r ( ! lev]s #d1 #d is gripp$1 & consequ5tly ! disc is n f$ 9 ei!r direction4 ,if ! boom sw+ to ! left1 ! movem5t ( ! disc w evid5tly be 9 ! conv]se direction to t describ$4 ,9 ?is record] consid]able p[] is available to drive pr9t+ or o!r me*anisms4 ,! arm mov+ ov] ! pot5tiomet] wire c>ries a p5 :i* m>ks ! mov+ *>t1 or1 :5 sev]al records are tak5 simultane\sly1 a /amp+ ma*9e is us$ :i* impresses ! numb] ( ! pyromet] on ! *>t4 ,! same galvanomet] me*anism s]ves also = use ) resi/ance pyromet]s1 z w be expla9$ lat]4 ,control ( ,furnace ,temp]atures4--,_m attempts h be5 made to secure ! automatic regulation ( furnace temp]atures by means ( me*anisms controll$ by an indicator or record]4 ,9 ! arrangem5t employ$ by ! ,br[n ,company ( ,philadelphia1 movable /ops are provid$1 :i* may be br\ght to any "p ( ! scale1 ! m>k betwe5 ! /ops repres5t+ ! temp]ature x is desir$ to ma9ta94 ,! indicator 7or record]7 is provid$ ) a press]-b> :i* desc5ds p]iodically2 & if ! temp]ature be too l[ ! depress$ po9t] completes a circuit ?r\gh ! inn] /op1 :il/ if too high ! circuit is ?r\gh ! out] /op4 ,bo? circuits conta9 a relay :i* br+s a me*anism into op]ation1 ! result be+ to increase ! supply ( electricity or gas if ! temp]ature be too l[1 or to dim9i% ! supply :5 too high4 ,:5 correct1 ! depression ( ! po9t] fails to complete ei!r circuit1 & 9 ?is mann] control betwe5 small limits may be ensur$4 ,9 ! case ( l>ge furnaces ! relay circuits are employ$ to light lamps ( diff]5t col\rs1 ! adju/m5t !n be+ made by ! man 9 *>ge ( ! furnace4 ,arrangem5ts ( ?is k9d effect a consid]able sav+ 9 fuel by prev5t+ unnecess>y heat+1 & are p>ticul>ly valuable 9 cases :]e ov]heat+ w\ld be delet]i\s to ! articles 9 ! furnace4 ,! future w probably witness consid]able developm5ts along ^! l9es4 ,contact-,p5 ,record]s4--,! =ce ) :i* ! po9t] ( an indicator is urg$ ov] ! scale is relatively small1 p>ticul>ly 9 ! case ( pyromet]s 9 :i* ! plat9um s]ies ( metals are us$1 z ^! furni% only a l[ ,e4,m4,f4 ,if1 !re=e1 ! po9t] t]m9ate 9 a p5 :i* is 9 cont9u\s contact ) ! record-pap]1 ! friction ?us occasion$ int]f]es consid]ably ) ! free movem5t ( ! po9t]4 ,:5 *eap-metal pyromet]s are us$1 :i* yield a mu* high] ,e4,m4,f41 ! use ( ! po9t] z contact-p5 becomes m feasible1 & if uni=m friction at all p>ts ( ! pap] c be ensur$1 records may be tak5 9 ?is mann]2 & a record] s con/ruct$ is simpl] & *eap] ?an ^? ( ! int]mitt5t type4 ,contact-p5 record]s are us$ 9 ,am]ica to "s ext5t1 be+ made by ,bri/ol1 ,br[n1 & o!rs2 b s f> ,briti% mak]s h n develop$ ! manufacture ( ^! in/rum5ts4 ,at pres5t1 contact-p5 record]s mu/ be consid]$ less accurate & reliable ?an ^? 9 :i* ! contact is int]mitt5t4 ,in/allations ( ,!rmo-electric ,pyromet]s4--,:5 a numb] ( furnaces 9 ! same e/abli%m5t are to be controll$1 consid]able economy may be effect$ by mak+ "o indicator s]ve = all ! c\ples1 :i* 9 ?is case mu/ necess>ily be made up ( wires id5tical 9 !rmo-electric value4 ,su* an arrangem5t is %[n 9 fig4 #bg1 9 :i* ,h#a & ,h#b repres5t two c\ples1 "o wire f ea* be+ connect$ to "o ( ! t]m9als ( ! galvanomet] ,g4 ,! o!r t]m9al ( ! galvanomet] is connect$ to ! arm ,d ( a swit*1 & ! rema9+ !rmoc\ple leads are connect$ to ! po9ts #a & #b respectively on ! circumf]5ce4 ,z %[n1 ,h#a is connect$ to ! galvanomet]1 & by turn+ ! arm ,d to ! po9t #b ! o!r c\ple w\ld !n be connect$4 ,any numb] ( junctions may ?us be arrang$ ) a s+le indicator4 ,:5 ?is arrangem5t is adopt$ 9 a work%op1 x is advisable to con/ruct a small wood5 build+ at a spot conv5i5t = mo/ ( ! furnaces1 9 :i* ! indicator & swit*bo>d are kept1 & :i* c\ld also conta9 a record] if necess>y2 a spot z free z possible f vibration be+ pref]able4 ,sep>ate indicators are only necess>y :5 a furnace is us$ = special "w4 ,illu/ration3 ,,fig4 #bg4--;,,connections ,,= ,,an ,,in/allation ,,( ,,pyromet]s4 ,9 "s in/ances a second indicator is kept 9 ! %op (fice1 to :i* all ! pyromet]s are wir$1 & :i* s]ves z a /&>d4 ,! scale ( ! (fice indicator is *eck$ daily at "o po9t2 & by connect+ a giv5 c\ple fir/ ) ! %op indicator1 & imm$iately aft]w>ds ) ! (fice /&>d1 any errors c be detect$4 ,x is also possible to asc]ta9 ! temp]ature ( any giv5 furnace 9 ! (fice at any "t1 & s to control ! :ole4 ,9 fix+ up su* an arrangem5t x is necess>y t ea* c\ple & its leads1 up to ! indicator1 %\ld possess ! same resi/ance1 or %\ld n diff] by an am\nt suffici5t to affect ! read+s4 ,! g5]al exp]i5ce ( a prop]ly manag$ in/allation is t ! co/ is sav$ 9 a few mon?s 9 fuel alone2 &1 9 addition1 ! "w is c>ri$ out to mu* bett] advantage ow+ to complete control f ! (fice4 ,managem5t ( ,!rmo-electric ,pyromet]s4--,g5]ally speak+1 !rmo-electric pyromet]s give little tr\ble 9 practice1 b ! managem5t %\ld always be plac$ 9 skill$ h&s4 ,x is advisable to te/ ea* in/rum5t p]iodically at a fix$ po9t ne> ! work+ temp]ature1 by ! me?od expla9$ on page #eg2 & if two or ?ree p\nds ( mat]ial be us$1 ! protect+ %ield ne$ n be remov$4 ,a useful mat]ial = *eck+ pyromet]s ne> ! critical range ( /eel is an alloy ( #fj p] c5t4 ( copp] & #dj p] c5t4 ( t91 :i* gives a well-def9$ freez+ po9t at #gch ,c41 & :i* may be us$ indef9itely 9 a r$uc+ atmosph]e ,any s]i\s error is easily detect$ by obs]v+ t ! indications diff] widely f ^? g5]ally obta9$ "u ! same work+ conditions4 ,if an error ( #bj ,c4 or m is not$1 x is advisable to =m a new junction1 z ! discrepancy w probably become great]1 be+ due to a *ange at ! hot junction4 ,a small error1 ( ! nature ( #e or #aj ,c41 may be due to 8creep0 9 ! indicator1 :i* may be adju/$ accord+ly1 or a num]ical correction may be made :5 tak+ a read+4 ,an iron protect+ %ea? may be sav$ f rapid oxidation by black-lead+ once p] week1 :i* greatly prolongs its useful life1 b %\ld be replac$ imm$iately x becomes dang]\sly ?9 9 any "p4 ,coat+ ) alum9ium p[d] also greatly prolongs ! life ( an iron %ea?4 ,:5 us$ 9 lead ba?s1 ! imm]s$ "p1 if ( iron or /eel1 %\ld be bor$ f ! solid1 & left ?ick at ! portion opposite ! surface ( ! lead1 :]e mo/ corrosion occurs4 ,a graphite tube1 or "o made ( a composition conta9+ graphite1 is (t5 useful 9 cases :]e iron is readily corrod$1 & c be us$ to mu* high] temp]atures4 ,:5 a numb] ( in/rum5ts are 9 use1 x is advisable to keep a /&>d pyromet] = *eck+ purposes1 pref]ably "o :i* has be5 c]tifi$ by ! ,national ,physical ,laboratory4 ,9 conduct+ a te/1 ! c\ples1 ) protect+-tubes remov$1 may be plac$ 9 ! tube ( an electric furnace ( ! type %[n 9 fig4 #bi1 9 close proximity ) ! /&>d junction4 ,on rais+ ! temp]ature gradually1 ! read+s ( ea* work+ in/rum5t may be comp>$ ) ! /&>d1 & ! necess>y corrections discov]$4 ,c>e mu/ be tak5 to prev5t contact ) ! furnace tube1 & ?is may be accompli%$ by pass+ ! wires ?r\gh an asbe/os /opp] fitt$ into ! end ( ! tube4 ,:5 record]s are us$ ! att5dant %\ld make himself ?or\ghly conv]sant ) ! details ( ! me*anism1 s z to be able to rem$y any m9or ailm5ts1 :i* are1 z a rule1 easily cur$4 ,on no acc\nt %\ld an unskill$ workman be tru/$ ) record]s2 x is bett] & saf] to keep ^! 9 ! (fice1 :]e !y w n be likely to be damag$ or tamp]$ )4 ,all records %\ld be kept = future ref]5ce1 prop]ly dat$1 & labell$ accord+ to ! op]ations repres5t$4 ,laboratory ,uses ( ,!rmo-electric ,pyromet]s4--,num]\s op]ations c>ri$ out 9 muffle furnaces at prescrib$ temp]atures require no special precautions beyond ^? previ\sly giv54 ,9 det]m9+ ! melt+ po9ts ( metals or alloys1 h[ev]1 a porcela9 or silica %ea? is inadvisable1 z !y are easily corrod$4 ,an iron %ea? is pro( aga9/ "s metals1 b n aga9/ o!rs1 & x is always saf] to fix a ?9 fireclay sleeve1 clos$ at ! end1 ov] ! "p imm]s$4 ,a %ea? ( graphite or graphite composition may be us$ = temp]atures above #aajj ,c42 & occasionally a %ea? bor$ f a ?ick arc-lamp c>bon1 c\pl$ to an iron tube beyond ! heat$ "p1 w be f\nd useful at high temp]atures4 ,alundum is useful up to #afjj ,c1 & = temp]atures ( ?is ord] ! high] refractories su* z silfrax & zirkite may also be us$ to advantage4 ,illu/ration3 ,,fig4 #bh4--;,,diff]5tial ,,me?od ,,= ,,det]m9+ ,,critical ,,po9ts ,,( ,,/eel4 ,! det]m9ation ( ! 8critical0 po9ts ( /eel call = special m5tion4 ,9 cool+ d[n a mass ( /eel ! fall ( temp]ature is arre/$ at "o or m po9ts1 obs]vations ( :i* are frequ5tly ( s]vice 9 decid+ ! subsequ5t treatm5t ( ! /eel4 ,a me?od commonly employ$ is kn[n z ! 8diff]5tial me?od10 & is indicat$ 9 fig4 #bh4 ,! sample ( /eel1 ,a1 is plac$ side by side ) a piece ( nickel1 ,b1 ( equal dim5sions1 9 ! tube ( an electric furnace4 ,a nak$ junction1 ,c1 is plac$ 9 a hole drill$ 9 ,a1 & is connect$ to ! galvanomet] ,g1 :i* is calibrat$ to read temp]atures4 ,a two-junction circuit1 =m$ ( a junction ,d plac$ 9 ! hole 9 ,a1 & ano!r junction ,e locat$ 9 ! hole 9 ,b1 are connect$ to a delicate galvanomet] ,h4 ,! furnace is heat$ until ! galvanomet] ,g indicates #ijj ,c41 :5 ! arrangem5t is all[$ to cool4 ,z ,a & ,b1 "u normal circum/ances1 cool at an equal rate1 ! junctions ,d & ,e w be at ! same temp]ature1 & no deflection w be obs]v$ on ,h4 ,:51 ow+ to recalesc5ce1 ! cool+ ( ,a is arre/$1 ,b1 n be+ ?us affect$1 w cont9ue to cool1 ?us produc+ a diff]5ce betwe5 ! temp]atures ( ,d & ,e1 & consequ5tly a deflection on ,h4 ,! temp]ature ( ,a at ! "t ?is occurs is read (f on ,g4 ,illu/ration3 ,,fig4 #bi4--;,,electric ,,tube-,,furnace4 ,! furnace illu/rat$ 9 fig4 #bi is suit$ to ?is det]m9ation4 ,x consi/s ( a silica tube #a foot long1 w\nd ) a special resi/ance wire & effici5tly lagg$1 & may be heat$ 9 safety to #ajjj ,c4 = long p]iods1 & to #abjj = a %ort "t4 ,x may be plac$ across ! electric ma9s directly1 & rea*es #ijj ,c4 9 less ?an half an h\r4 ,x consumes #fjj to #gjj watts at ! highe/ temp]atures1 & ! co/ ( re-w9d+ is small4 ,?is furnace is useful z a g5]al laboratory appliance1 & may be kept at a giv5 /eady temp]ature by ! use ( an ext]nal resi/ance4 ,! wires 9 ?is exp]im5t %\ld be plat9um & iridioplat9um or rhodioplat9um1 or a good pair ( base metals1 & ! junctions 9 ,a %\ld be sep>at$ f ea* o!r & f ! specim5 by asbe/os2 ! same precaution be+ tak5 to prev5t ! junction ,e f t\*+ ,b4 ,a ?9 lay] ( mica %\ld be us$ b5ea? ,a & ,b1 to avoid contact ) ! furnace tube1 :i*1 :5 hot1 all[s ( leakage ( curr5t f ! heat+ coil4 ,bo? ,a & ,b may be #a 94 long1 94 diamet]1 ) a hole 94 diamet] drill$ to a dep? ( in*4 ,an alt]native me?od is to ins]t a junction 9 a hole 9 ! specim51 & to take direct read+s z ! temp]ature sl[ly rises or falls1 :5 an arre/ 9 ! movem5t ( ! po9t] ( ! indicator %[s t ! *ange-po9t has be5 rea*$4 ,special sets are made = ?is purpose4 ,measurem5t ( ,l[] ,temp]atures by ! ,!rmo-electric ,me?od4--,_m cases arise 9 practice 9 :i* a !rmal junction & a s5sitive galvanomet] are pref]able to a m]cury !rmomet]2 & bel[ -#ci ,c41 at :i* temp]ature m]cury freezes1 a !rmal junction is frequ5tly bett] to employ ?an an alcohol or p5tane !rmomet]4 ,a numb] ( practical examples ( ! use ( !rmal junctions = ord9>y & l[ temp]atures w n[ be consid]$4 ,measurem5t ( ,surface ,temp]atures4--,a m]cury !rmomet]1 :5 laid on a hot surface1 only t\*es along a l9e1 & does n %[ ! true surface temp]ature4 ,! con/ruction ( a !rmal junction suitable = ?is purpose is describ$ on page #da1 & = /eam-pipe surfaces1 hot plates1 & ! ext]ior ( furnaces1 a specially calibrat$ millivoltmet]1 giv+ a full-scale deflection ) #bj millivolts1 may be us$4 ,9 mak+ ! temp]ature scale1 boil+ wat] 7#ajj;,c471 boil+ anil9e 7#ahd ,c471 & melt+ t9 7#bcb ,c47 are conv5i5t /&>ds4 ,if ! surface temp]ature be less ?an #ajj ,c4 a mirror galvanomet] %\ld be us$1 & ! junction /&>diz$ 9 p>aff9 wax 7freez+ po9t usually ab\t #ej ,c41 b %\ld previ\sly be det]m9$ ) an accurate !rmomet]71 absolute alcohol at boil+ po9t 7#gi ,c47 & boil+ wat]4 ,! au?or has f\nd t ?is me?od yields excell5t results 9 ! case ( /eam-pipes1 ! ext]ior ( rot>y cem5t kilns1 & hot surfaces g5]ally4 ,measurem5t ( ,l[ ,temp]atures4--,junctions ( iron & con/antan1 ,hosk9's alloys1 copp] & ,g]man silv]1 or copp] & con/antan1 are suit$ to ^! measurem5ts4 ,9 a laboratory ! cold junction may be kept 9 ice 9 a ,dew> vessel1 ! me*anically protect$ =m kn[n z ! 8,!rmos0 flask be+ v useful = ?is purpose4 ,) a good mirror galvanomet] precise read+s may be secur$1 #a_/aj ( a degree ,c4 be+ easily detect$4 ,calibration betwe5 -#dj & #dj;,c4 may be effect$ by comp>ison ) a /&>d m]cury !rmomet]1 a wat]-ba? be+ us$ above #j1 & alcohol surr\nd$ by a freez+ mixture ( ice & calcium *loride cry/als bel[ z]o4 ,= v l[ temp]atures 7-#bjj;,c4 or less7 ! junction maybe calibrat$ 9 solid c>bon dioxide 7-#gh;,c47 & liquid air 7-#ahd;,c474 ,dew> has f\nd t copp] & ,g]man silv] =m a reliable junction = v l[ temp]atures1 & ! au?or has successfully us$ a c\ple ( ,hosk9's alloys = special "w d[n to -#bjj;,c41 a pivot$ indicator be+ employ$4 ,no c\ples te/$ %[ a l9e> relation betwe5 ,e4,m4,f4 & temp]ature at ^! l[ ranges4 ,ow+ to ! magnitude ( ! error caus$ by *anges 9 ! cold junction1 ! !rmo-electric me?od is n suit$ to ! measurem5t ( atmosph]ic temp]atures1 or = explosive magaz9es or cold /ores4 ,9 su* cases in/rum5ts ( ! resi/ance type1 to be describ$ lat]1 are us$4 ,temp]ature ( ,/eam1 ,exhau/ ,gases1 etc4--,= measur+ ! temp]ature ( ord9>y or sup]heat$ /eam1 ! exhau/ gases f int]nal combu/ion eng9es1 etc41 iron-con/antan junctions1 ) suitable indicators1 are satisfactory4 ,:5 plac$ 9 a pipe ! junction %\ld be z ne>ly z possible 9 ! c5tre1 s z to avoid ! cool+ effect ( ! walls4 ,sev]al junctions1 situat$ 9 diff]5t p>ts ( ! pipe1 may be us$ ) a s+le indicator & suitable swit*bo>d4 ,! above rem>ks also apply to ! hot-bla/ = bla/ furnaces1 & simil> in/ances :]e ! temp]ature does n exce$ #ijj ,c4 ,measurem5t ( ,diff]5ces ( ,temp]ature4--,cases frequ5tly arise 9 practice 9 :i* ! diff]5ce 9 temp]ature betwe5 two po9ts is requir$1 & if ?is diff]5ce be subject to rapid *anges1 a m]cury !rmomet]1 f its l>ge mass1 w\ld n respond ) suffici5t rapidity to indicate ^! *anges4 ,9 su* cases a circuit is made aft] ! mann] ( fig4 #b1 "o junction be+ locat$ at ea* po9t2 ?9 wires ( iron & con/antan be+ us$4 ,= small diff]5ces--#a ,c4 or less--a mirror galvanomet] %\ld be us$4 ,calibration may be p]=m$ by plac+ "o junction 9 hot wat] & ! o!r 9 cold1 ! wat] temp]atures be+ read ) an accurate !rmomet]4 ,advantages ( ! ,!rmo-electric ,me?od ( ,measur+ ,temp]atures4--,comp>$ ) o!r me?ods1 ! !rmo-electric possesses ! foll[+ po9ts ( sup]iority3--7#a7 ,simplicity1 no special exp]im5t be+ necess>y to obta9 a read+2 7#b7 *eapness ( outfit2 7#c7 adaptability to a v>iety ( purposes2 7#d7 ease ( repair 9 case ( damage2 7#e7 robu/ness1 n be+ liable to get out ( ord] "u work%op conditions2 & 7#f7 suitability to ! purpose ( a c5trally controll$ in/allation4 ,! drawbacks are3--7#a7 ,liability to error ow+ to fluctuations 9 ! cold junction 7:i* may be avoid$ ) c>e72 & 7#b7 lack ( s5sitiv5ess at v high temp]atures comp>$ ) ! resi/ance me?od--a po9t seldom ( great practical importance1 z ! limit ( accuracy is usually )9 ! am\nt by :i* an ord9>y furnace fluctuates 9 temp]ature "u work+ conditions4 ,,*apt] ,,iv ,,resi/ance ,,pyromet]s ,g5]al ,pr9ciples4--,:5 a pure metal is heat$1 its resi/ance to electricity increases progressively ) ! temp]ature4 ,c]ta9 alloys1 on ! o!r h&1 %[ a practically con/ant resi/ance at all temp]atures1 examples ( su* alloys be+ con/antan1 mangan91 & plat9oid4 ,all ! elem5t>y metals1 h[ev]1 exhibit a tangible rise 9 resi/ance :5 ! temp]ature is augm5t$2 & ,sir ,w4 ,siem5s1 9 #ahga1 propos$ to apply ?is pr9ciple to ! measurem5t ( high temp]atures by det]m9+ ! resi/ance1 & d$uc+ ! correspond+ temp]ature f a table prep>$ "u kn[n conditions4 ,! *oice ( a metal is 9 ?is case m greatly re/rict$ ?an 9 ! selection ( mat]ials = a !rmal junction4 ,a c]ta9 am\nt ( ext]nal corrosion does n alt] ! ,e4,m4,f4 ( a junction2 b an alt]ation 9 size produces a m>k$ diff]5ce 9 ! resi/ance ( a wire1 :i* v>ies directly z ! l5g? & inv]sely z ! area ( cross-section4 ,to ! necessity = ! abs5ce ( any int]nal physical *ange affect+ ! resi/ance is !re=e add$ ! fur!r condition ( p]man5ce ( ext]nal dim5sions4 ,= temp]atures above a r$ heat ! only feasible metals to use are plat9um or ! m exp5sive metals ( ! plat9um s]ies--& h5ce plat9um is univ]sally employ$ = ?is purpose4 ,! orig9al ,siem5s pyromet] consi/$ ( #a metre ( plat9um wire1 #a millimetre 9 diamet]1 wrapp$ r\nd a porcela9 rod1 & protect$ f furnace gases by an iron %ea? ,an elaborate me?od ( measur+ ! resi/ance1 involv+ ! electrolysis ( acidulat$ wat]1 0 adopt$ = work%op use1 b 0 too involv$ to become popul>4 ,lat]1 ,siem5s employ$ ! diff]5tial galvanomet] me?od1 & f9ally ! ,:eat/one bridge1 to measure ! resi/ance4 ,bo? me?ods are /ill 9 use 9 connection ) resi/ance pyromet]s1 & ! pr9ciple ( ea* w n[ be expla9$4 ,measurem5t ( ,resi/ance by ! ,diff]5tial ,galvanomet]4--,a diff]5tial galvanomet] is "o :i* possesses two w9d+s1 arrang$ s t a curr5t pass+ ?r\gh ! "o t5ds to turn ! po9t] 9 "o direction1 & ?r\gh ! o!r to cause a movem5t 9 ! opposite direction4 ,if ! curr5ts 9 ea* w9d+ simultane\sly be equal1 ! po9t] rema9s at re/ "u ! action ( two equal & opposite =ces4 ,! exp]im5tal atta9m5t ( ! condition ( re/ s]ves z a means ( measur+ resi/ance1 ! circuit be+ arrang$ z 9 fig4 #cj4 ,curr5t f a batt]y ,b passes ?r\gh a divid$ circuit1 "o bran* conta9+ ! adju/able resi/ance ,r & "o coil ( ! galvanomet] ,g2 & ! o!r ! unkn[n resi/ance ,p & ! opposite coil4 ,! resi/ance ,r is adju/$ until on tapp+ ! key ,k no deflection on ! galvanomet] is not$1 :5 ! curr5t 9 ea* bran* ( ! circuit w be ! same4 ,! resi/ances ( ea* coil ( ! galvanomet] be+ equal1 x foll[s f ,ohm's law t ,p is equal to ,r :5 no deflection is obta9$4 ,illu/ration3 ,,fig4 #cj4--;,,diff]5tial ,,galvanomet] ,,me?od ,,( ,,measur+ ,,resi/ance4 ,! accuracy ( ?is me?od dep5ds ^u ! s5sitiv5ess ( ! galvanomet]1 & also ^u ! ext5t to :i* ! two coils may be reg>d$ z truly diff]5tial1 z ! measurem5t evid5tly assumes complete equality 9 resi/ance & effect on ! mov+ "p4 ,) mod]n galvanomet]s ( ?is patt]n1 x is possible to secure read+s ( suffici5t accuracy = ! purposes ( pyrometry4 ,! me?od1 h[ev]1 is less s5sitive ?an ! ,:eat/one bridge1 n[ to be describ$4 ,illu/ration3 ,,fig4 #ca4--,,pr9ciple ,,( ,,:eat/one ,,bridge4 ,measurem5t ( ,resi/ance by ! ,:eat/one ,bridge4--,! pr9ciple ( ?is me?od is %[n 9 fig4 #ca1 :]e a & b are two fix$ resi/ances ( kn[n value2 d is an adju/able resi/ance2 x ! resi/ance to be measur$2 ,b a batt]y2 & ,g a s5sitive galvanomet]4 ,if1 9 ?is circuit1 d be adju/$ until no deflection is %[n on ! galvanomet]1 !n a_/b x_/d2 or x 7a d7_/b4 ,h5ce1 if a b1 !n x w be equal to d4 ,x is n difficult to con/ruct a portable app>atus1 suitable = work%op use1 by means ( :i* ! value ( x may be det]m9$ to #jja ohm2 & 9 ! laboratory1 ) a v delicate galvanomet]1 #jjja ohm may readily be detect$4 ,! ,:eat/one bridge me?od is ! be/ = ! accurate measurem5t ( resi/ance2 b 9 resi/ance pyromet]s x is sometimes advisable to sacrifice extreme accuracy 9 ord] to ga9 advantages 9 o!r directions1 z w be %[n subsequ5tly4 ,relation betwe5 ! ,resi/ance ( ,plat9um & ,temp]ature4--,z plat9um is ! only feasible metal to use 9 ! con/ruction ( resi/ance pyromet]s1 x is ess5tial t ! effect ( temp]ature on ! resi/ance ( ?is metal %\ld be kn[n4 ,difficulties 7 exp]i5c$1 9 ! e>ly days ( resi/ance pyromet]s1 f ! fact t diff]5t samples ( plat9um wire1 ( v>y+ degrees ( purity1 gave widely diff]+ results 9 ?is connection2 & no c]ta9ty 0 atta9$ until #ahhf1 :5 ,pr(essor ,call5d> ?or\ghly inve/igat$ ! subject1 & evolv$ a =mula f :i* ! temp]ature ( a giv5 k9d ( plat9um c\ld be d$uc$ ) great accuracy f ! resi/ance4 ,9 ord] to und]/& ?is =mula & its application1 x w be necess>y to consid] ! und]ly+ pr9ciples ^u :i* x is f\nd$4 ,if ! resi/ance ( a plat9um wire be measur$ at a numb] ( /&>d gas-scale temp]atures1 & ! results depict$ graphically by plott+ resi/ances aga9/ correspond+ temp]atures1 ! curve obta9$ is "p ( a p>abola1 exhibit+ a decrease 9 ! rate at :i* ! resi/ance increases at ! high] temp]atures4 ,a second plat9um wire1 ( diff]5t orig9 & purity1 & ( ! same initial resi/ance z ! =ego+1 w\ld furni% a curve :i*1 al?\gh p>abolic1 w\ld n ov]lap t obta9$ ) ! fir/ wire4 ,! advance made by ,call5d> 0 to d$uce a =mula f :i* ! temp]ature ( any k9d ( plat9um wire c\ld be d$uc$ f its resi/ance1 aft] ?ree measurem5ts at kn[n gas-scale temp]atures _h be5 det]m9$4 ,! calibration ( a resi/ance pyromet] 0 !reby r$uc$ to ?ree exact obs]vations1 in/ead ( a l>ge numb] di/ribut$ ov] ! scale2 &1 moreov]1 ! =mula 9 "q 0 f\nd to give results ( great accuracy ov] a wide range ( temp]ature = any k9d ( plat9um wire4 ,be=e deal+ ) ,call5d>'s =mula1 ! t]m 8degrees on ! plat9um scale0 w be expla9$4 ,su* degrees are obta9$ by assum+ t ! increase ( resi/ance ( plat9um is uni=m at all temp]atures2 t is1 t ! temp]ature-resi/ance curve is a /raight l9e1 & n a p>abola4 ,= example1 a piece ( plat9um wire ( #bf ohms resi/ance at #j ,c4 w %[ an increase to #cf ohms at #ajj ,c4--an addition ( #a ohm = #ajj4 ,we n[ assume t a fur!r augm5tation ( #a ohm1 br++ ! total to #df ohms1 w repres5t an increase ( #ajj1 or a temp]ature ( #bjj4 ,simil>ly1 a total resi/ance ( #ef ohms w\ld indicate #cjj1 & #abf ohms #ajjj4 ,! temp]ature scale obta9$ by ?is process ( extrapolation is call$ ! 8plat9um scale10 & diff]s consid]ably f ! true or gas scale1 ! diff]5ce becom+ great] z ! temp]ature rises4 ,?is is indicat$ 9 fig4 #cb1 9 :i* ,a repres5ts ! true p>abolic relation betwe5 resi/ance & temp]ature1 & ,b ! assum$ /raight-l9e relation4 ,read+ f curve ,a1 ! temp]ature correspond+ to #h ohms resi/ance is #fjj ,c42 b f ,b ! same resi/ance is se5 to repres5t only #ede ,c41 :i* is ! 8temp]ature on ! plat9um scale0 to :i* ?is resi/ance ref]s4 ,an inspection ( fig4 #cb %[s t at all temp]atures1 except betwe5 #j & #ajj1 ! plat9um-scale read+s = giv5 resi/ances are less ?an ^? indicat$ on ! gas scale4 ,call5d>'s =mula is express$ 9 t]ms ( ! diff]5ce betwe5 ! gas-scale & plat9um-scale read+s1 & takes ! =m t - p 7t_/#ajj7b - 7t_/#ajj71 :]e t temp]ature on ! gas scale1 p temp]ature on ! plat9um scale4 a con/ant1 dep5d+ ^u ! purity ( ! wire4 ,illu/ration3 ,,fig4 #cb4--;,,connection ,,betwe5 ,,resi/ance ,,( ,,plat9um ,,& ,,temp]ature3 ,a1 ,,on ,,gas ,,scale2 ,b1 ,,on ,,plat9um ,,scale4 ,9 ord] to det]m9e ! value ( 1 x is necess>y to measure ! resi/ance ( ! wire at #j1 #ajj1 & a ?ird temp]ature1 :i* %\ld be consid]ably above #ajj4 ,! read+s at #j & #ajj are requisite to e/abli% ! plat9um scale ( temp]atures2 ! ?ird read+ is requir$ to calculate ! value ( 1 z p & t are equal at #j & #ajj1 ^! po9ts =m+ ! basis ( bo? scales4 ,an example is app5d$ to make ?is matt] cle>4 ,example4--,a plat9um wire has a resi/ance 9 ice ( #bf ohms2 9 /eam1 #cf ohms2 9 boil+ sulphur1 #fhae ohms4 ,to f9d ! value ( 1 ! boil+ po9t ( sulphur be+ #ddde on ! gas scale4 ,s9ce an increase ( 7#cf - #bf7 #a ohm is produc$ by #ajj1 ! increase obs]v$ 9 boil+ sulphur1 7#fhae - #bf7 #dbae ohms1 w repres5t a temp]ature1 on ! plat9um scale1 ( 7#dbae #ajj7_/a #dbae p4 ,apply+ ,call5d>'s =mula1 7#ddde - #dbae7 7#ddde_/ajj7b - 7#ddde_/ajj7 ! value ( is f\nd to be #ae4 ,call5d>1 9 8 exp]im5ts1 employ$ ! boil+ po9t ( sulphur = ! ?ird po9t1 & det]m9$ ?is temp]ature on ! gas scale ) great accuracy1 ,! necessity = extreme precision 9 apply+ ?is =mula is made cle> by not+ ! effects on ! value ( result+ f small diff]5ces 9 ! figures *os5 9 ! above example4 ,if1 = in/ance1 ! boil+ po9t ( sulphur on ! gas scale 7 tak5 at #b l[]1 or #ddbe1 ! value ( w\ld "w out to #acg2 & ! error at #abjj ,c4 ?us caus$ w\ld am\nt to #ag4 ,! same discrepancy w\ld be obs]v$ if ! resi/ance 9 boil+ sulphur 7 tak5 z #fhce ohms1 an error ( #jjb ohm2 & a /ill great] error w\ld result if ! diff]5ce 9 resi/ance at #j & #ajj 7 measur$ z #jii ohm in/ead ( #a ohm4 ,f an ext5sive exp]i5ce ( ! difficulties att5dant on correctly det]m9+ ! value ( 1 ! au?or has f\nd t no reliable result c be obta9$ unless measur+ in/rum5ts ( ! highe/ precision are us$1 & elaborate precautions tak5 to ensure ! exact correction = alt]ations 9 ! boil+ po9ts ( wat] & sulphur occasion$ by *anges 9 atmosph]ic pressure4 ,unless ! necess>y facilities are at h&1 an op]ator w\ld be well advis$ to /&>dize a resi/ance pyromet] by tak+ sev]al fix$ po9ts & draw+ a calibration curve1 aft] ! mann] recomm5d$ = a !rmo-electric pyromet]4 ,if a resi/ance pyromet] be calibrat$ s z to read 9 plat9um-scale degrees1 & ! value ( be kn[n = ! wire1 ! correct gas-scale temp]atures may be calculat$ f ,call5d>'s =mula4 ,! table on next page gives ! results ( a numb] ( calculations made 9 ?is mann]4 ,*anges 9 ,resi/ance ( ,plat9um :5 con/antly ,heat$4--,! resi/ance ( plat9um und]goes a gradual *ange :5 ! wire is kept cont9u\sly above a r$ heat2 & if ! temp]ature exce$ #ajjj ,c4 ! *ange becomes v m>k$ aft] a "t1 lead+ to s]i\s errors 9 temp]ature indications :5 us$ 9 a pyromet]4 ,! alt]ation "u notice is due1 z %[n by ,sir ,william ,crookes1 to ! fact t plat9um is di/9ctly volatile above #ajjj ,c41 & h5ce ! diamet] ( ! wire dim9i%es4 ,?is v>iation con/itutes a s]i\s drawback to ! use ( resi/ance pyromet]s = temp]atures exce$+ #ajjj ,c4 ,,comp>ison ,,( ,,gas ,,& ,,plat9um ,,scales4 #ae4 ,plat9um ,!rmomet],air ,!rmomet] ,read+ ,diff]5ce ,read+ 7,pt474 t 7deg4 ,c474 7t ,pt474 -#ajj -#iga #bi #j #j #j #ej #dif -#jjd #ajj #ajj #j #bjj #bjca #ca #cjj #cjih #ih #djj #dbjb #bjb #ejj #ecdi #cdi #fjj #fedd #edd #gjj #ggid #gid #hjj #iajg #aajg #ijj #ajdid #adid #ajjj #aaigj #aigj #aajj #aceej #beej #abjj #aebfg #cbfg #acjj #agafj #dafj ,t]ms us$ 9 ,resi/ance ,pyrometry4--,foll[+ on ! rese>*es ( ,call5d> & o!rs1 c]ta9 t]ms relat+ to resi/ance pyromet]s h come into use1 & w n[ be def9$4 7#a7 ,! ,fundam5tal ,int]val is ! increase 9 resi/ance betwe5 #j ,c4 & #ajj ,c1 or ,r#ajj-,r#j4 ,x %\ld be rememb]$ t ! increases betwe5 #bjj & #cjj1 or #hjj & #ijj1 all temp]atures be+ tak5 on ! gas scale1 diff] f ! fundam5tal increase4 7#b7 ,! ,fundam5tal ,coeffici5t is t fraction ( ! resi/ance at #j ,c4 by :i* x increases p] degree betwe5 #j & #ajj1 on ! av]age1 or 7,r#ajj - ,r#j7 4 7,r#j #ajj7 ,?is figure is 9 reality ! av]age temp]ature coeffici5t betwe5 #j & #ajj4 ,= pure plat9um ! value is or #a_/bfj or #jjjchdf4 7#c7 ,! ,fundam5tal ,z]o is ! temp]ature1 on ! plat9um scale1 at :i* ! resi/ance w\ld vani%2 x is evid5tly ! reciprocal ( 7#b71 prefac$ by a m9us sign1 or 7,r#j #ajj7 4 7,r#ajj - ,r#j7 ,= pure plat9um ?is temp]ature w\ld be -#bfjp1 s9ce x is assum$ t ! av]age increase or decrease p] degree holds ?r\gh\t2 t is1 = e degree ! metal is cool$ ! loss ( resi/ance is tak5 to be #a_/bfj ! resi/ance at #j4 ,h5ce at -#bfjp ! resi/ance1 on ?is assumption1 w\ld vani%4 7#d7 ,! ,diff]5ce ,=mula is ! expression :i* gives ! relation betwe5 gas-scale & plat9um-scale temp]atures1 or t - p 7t_/#ajj7b - 7t_/#ajj7 ,?is =mula has already be5 fully dealt )4 7#e7 ,! ,plat9um ,con/ant is 9 ! above expression4 ,! value = pure plat9um is ab\t #ae1 b small quantities ( impurities may alt] ! figure consid]ably4 ,! tru? ( ! =mula 7#d71 h[ev]1 is unaffect$ by *anges 9 1 z p w\ld be correspond+ly alt]$4 ,illu/ration3 ,,fig4 #cc4--,,plat9um ,,resi/ance ,,pyromet]4 ,practical ,=ms ( ,resi/ance ,pyromet]s4--,a typical =m ( resi/ance pyromet]1 made by ! ,cambridge & ,paul ,in/rum5t ,company1 is illu/rat$ 9 fig4 #cc4 ,! coil ( plat9um wire is w\nd r\nd ! edges ( a mica framework1 made ( two /rips ( mica fa/5$ at "r angles s z to =m a 9 section4 ,?is me?od ( w9d+ is due to ,call5d>1 :o discov]$ t mica 0 *emically in]t t[>ds plat9um1 ev5 at high temp]atures4 ,! leads1 also ( plat9um wire1 pass f ! coil ?r\gh mica wa%]s to t]m9als fa/5$ to ! boxwood head4 ,a second wire1 n connect$ ) ! coil1 b id5tical 9 l5g? & diamet] ) ! ord9>y leads1 is b5t into two p>allel bran*es1 :i* are pass$ ?r\gh ! mica wa%]s side by side ) ! leads1 & are br\ght to a second pair ( t]m9als 9 ! head4 ,! function ( ?is wire is to comp5sate = *anges 9 ! resi/ance ( ! leads :5 heat$1 by oppos+ ! comp5sat+ wire to ! pyromet] 9 ! measur+ arrangem5t1 :5 ! resi/ance ( ! leads & wire1 be+ equal1 w cancel1 ! resi/ance actually measur$ be+ 9 consequ5ce t ( ! coil only4 ,fig4 #cd %[s ! connections = a ,:eat/one bridge :5 ?is me?od ( comp5sation is employ$1 a & b repres5t+ two equal fix$ resi/ances1 ,p ! pyromet] coil1 x ! leads1 ,l ! comp5sat+ wire1 & d ! adju/able resi/ance4 ,:5 no deflection is obs]v$ on ! galvanomet]1 a x ,p 1 b ,l d & s9ce a b & x ,l1 x foll[s t ,p d4 ,! protect+ tube us$ by ! ,cambridge & ,paul ,in/rum5t ,company is made ( porcela91 :i* is f\nd to %ield ! plat9um completely f ! furnace gases1 b is extremely fragile1 & = work%op use %\ld be protect$ by an out] iron %ea?4 ,illu/ration3 ,,fig4 #cd4--,,:eat/one ,,bridge ,,z ,,us$ ,,) ,a ,,resi/ance ,,pyromet]4 ,resi/ance pyromet]s made by o!r firms diff] 9 detail f ! =ego+4 ,9 ! ,siem5s pyromet] ! coil is w\nd on special fireclay1 & protect$ by an iron %ea?1 ! space betwe5 ! coil & ! %ea? be+ fill$ ) magnesia1 :i* effectively prev5ts ! corrosion ( ! plat9um2 & comp5sation is effect$ by means ( a s+le wire pass+ d[n ! c5tre & connect$ to "o end ( ! coil1 a special =m ( ,:eat/one bridge be+ us$ to take ! measurem5t4 ,9 ! in/rum5ts made by ,r4 ,w4 ,paul ! coil is made ( flat /rip roll$ out f wire1 w\nd on mica1 & protect$ by a silica tube & out] iron %ea?4 ,! ,le$s-,nor?rup ,company ( ,philadelphia employ a rod ( obsidian on :i* to w9d ! coil1 & also make a =m 9 :i* ! coil is w\nd s z to be self-su/a9+1 ?us disp5s+ ) ! support4 ,9 all cases ! coil is w\nd non-inductively1 i4e4 ! wire is d\bl$ be=e mak+ into a spiral4 ,! z]o resi/ance ( a giv5 in/rum5t dep5ds ^u ! accuracy ( ! measur+ appliances us$1 & ^u ! degree ( precision x is desir$ to atta94 ,if1 = example1 x is int5d$ to read to #a;,c41 ) appliances capable ( measur+ to #a_/ajj ( an ohm1 a conv5i5t z]o resi/ance is #bf ohms2 x be+ f\nd t ) pure plat9um ! resi/ance rises f #bf ohms at #j to #cf ohms at #ajj ,c41 an increase ( #a_/ajj ( an ohm = #a ,c4 ,) co>s] measur+ arrangem5ts1 = ! same degree ( precision1 a correspond+ly high] z]o resi/ance w be requir$2 ?us if #a_/be ohm be ! lea/ am\nt detectable by ! measur+ device1 a z]o resi/ance ( #ajd ohms w\ld enable #a ,c4 to be obs]v$4 ,x is evid5t t a suitable z]o resi/ance may be calculat$ simil>ly 9 all cases :5 ! limit ( ! measur+ appliance is kn[n1 & ! m9imum temp]ature int]val specifi$4 ,= "w above a r$ heat1 ! leads f ! coil %\ld always be made ( plat9um4 ,copp] leads1 :5 heat$1 give (f vap\r 9 suffici5t quantity to attack ! plat9um2 & ! same applies to a great] degree to all k9ds ( sold]4 ,= l[ temp]ature "w1 h[ev]1 copp] leads may be us$1 ?us r$uc+ ! co/ ( ! in/rum5t4 ,mica1 above #ajjj ,c41 t5ds to crumble2 & mo/ =ms melt at #acjj ,c4 or l[]2 h5ce a mica-w\nd in/rum5t %\ld n be us$ cont9u\sly above #ajjj ,c4 ,! fireclay w9d+ us$ by ,siem5s p]mits ( occasional read+s be+ tak5 up to #adjj ,c41 & ! same applies to wires w\nd on obsidian 7melt+ po9t #aeej ,c471 or ^? 9 :i* ! coil is self-su/a9+4 ,z previ\sly m5tion$1 h[ev]1 alt]ations 9 ! plat9um itself r5d] cont9u\s read+s above #ajjj ,c4 inaccurate aft] a %ort "t4 ,x has be5 po9t$ out t ) accurate measur+ devices1 a resi/ance correspond+ to a *ange ( #a ,c4 c be measur$2 & x might appe> at fir/ sight t ! resi/ance me?od is consid]ably m accurate 9 practice ?an ! !rmo-electric4 ,if a p]fectly con/ant temp]ature 7 to be measur$1 a resi/ance pyromet] w\ld und\bt$ly give a clos] indication2 b con/ancy to #aj ,c4 is seldom possible ) gas-fir$ or coal furnaces or o!r hot spaces 9 :i* pyromet]s are us$4 ,! accuracy ( a pyromet] "u work%op conditions !re=e dep5ds ^u ! rapidity ) :i* x responds to temp]ature fluctuations1 :i* condition w evid5tly be influ5c$ by ! !rmal conductivity ( ! %ea?4 ,z x is necess>y to protect a resi/ance pyromet] ) a porcela9 or silica %ea?1 bo? ( :i* are poor conductors ( heat1 ?is in/rum5t is 9 consequ5ce n capable ( foll[+ a rapidly *ang+ temp]ature4 ,! same applies to ! magnesia pack+ us$ 9 ! ,siem5s =m2 :]eas a !rmo-electric pyromet] is (t5 suffici5tly %ield$ by an iron tube1 :i* transmits heat ) a fair degree ( fre$om4 ,! sup]ior delicacy ( ! resi/ance me?od is !re=e nullifi$ by ! sluggi%ness ( its indications2 & = read+ *ang+ temp]atures ! !rmo-electric pyromet] is at lea/ equally accurate4 ,if1 h[ev]1 a con/ant temp]ature c be obta9$1 z 9 ! det]m9ation ( melt+ po9ts1 or :5 us+ exp]im5tal furnaces capable ( exact regulation1 ! /eady temp]ature read+ may be secur$ ) great] precision by us+ ! resi/ance pyromet]4 ,indicators = ,resi/ance ,pyromet]s4--,all exi/+ indicators = resi/ance pyromet]s are 9 reality outfits = measur+ resi/ance1 ei!r by ! ,:eat/one bridge1 diff]5tial galvanomet]1 or o!r me?od1 ! resi/ance be+ translat$ on ! dial into correspond+ temp]atures4 ,typical examples w n[ be describ$4 ,illu/ration3 ,,fig4 #ce4--,,siem5s' ,,dial ,,indicator4 ,siem5s' ,indicator4--,?is in/rum5t is bas$ ^u ! ,:eat/one bridge pr9ciple1 & is %[n 9 fig4 #ce4 ,! galvanomet] is m\nt$ 9 ! c5tre ( ! dial1 r\nd ! edge ( :i* is fix$ a r+ on :i* ! adju/able resi/ance is w\nd 9 spiral =m4 ,suitable t]m9als are provid$1 duly labell$1 to :i* ! batt]y1 pyromet] leads1 & comp5sator are atta*$4 ,a brass arm1 movable ab\t ! c5tre ( ! dial1 t]m9ates 9 a tapp+-key :i* moves ov] ! adju/able resi/ance2 ! key be+ plac$ 9 ! batt]y circuit4 ,! fix$ kn[n resi/ances are locat$ 9 ! int]ior ( ! indicator4 ,! adju/m5t consi/s 9 mov+ ! key r\nd ! circumf]5ce until1 on tapp+1 no deflection is obta9$ on ! galvanomet]4 ,! po9t$ end ( ! movable arm !n indicates ! temp]ature ( ! pyromet] on ! dial1 :i* is m>k$ 9 temp]atures correspond+ to ! resi/ance oppos$ to ! pyromet] = diff]5t positions ( ! key4 ,9 tak+ a read+1 ! op]ator is guid$ by ! fact t :5 ! temp]ature indicat$ is too high1 ! movem5t ( ! galvanomet] ne$le w be 9 "o direction2 :]eas if too l[ an opposite deflection w be giv54 ,! int]m$iate position ( no deflection mu/ !n be f\nd by trial2 & ! proc$ure %\ld n occupy m ?an two m9utes if ! obs]v] possess an approximate notion ( ! temp]ature to be measur$4 ,illu/ration3 ,,fig4 #cf--,,:ipple',s ,,indicator4 ,:ipple's ,indicator4--,?is in/rum5t 7fig4 #cf7 is employ$ by ! ,cambridge & ,paul ,in/rum5t ,company1 & is also a =m ( ,:eat/one bridge4 ,! pyromet] leads & comp5sator are connect$ to prop]ly labell$ t]m9als ,t1 & ! batt]y to o!r t]m9als at ! opposite side ( ! box4 ,! po9t] ( ! galvanomet] is visible ?r\gh ! small w9d[ ,b1 & a batt]y ( two dry cells is plac$ at ! side ( ! box4 ,! fix$ resi/ances are conta9$ 9 ! int]ior1 & ! adju/able resi/ance consi/s ( a cont9u\s wire w\nd on a drum1 :i* may be rotat$ by ! h&le ,h4 ,! %aft connect+ ,h ) ! drum is screw$1 & works 9 a nut1 s t ! turn+ ( ,h produces a spiral movem5t ( ! drum4 ,! adju/m5t consi/s 9 rotat+ ,h until1 on tapp+ ! key ,f1 no deflection ( ! galvanomet] po9t] is obs]v$4 ,! temp]ature ( ! pyromet] is !n read (f directly f a pap] scale w\nd r\nd ! drum & rotat+ ) x1 visible ?r\gh ! w9d[ ,a1 ! read+ be+ indicat$ by a fix$ po9t]4 ,?is arrangem5t =ms a compact & conv5i5t indicator4 ,illu/ration3 ,,fig4 #cg4--,,! ,,h>ris ,,indicator4 ,! ,h>ris ,indicator4--,9 ! ,siem5s & ,:ipple indicators x is necess>y1 be=e a read+ c be tak51 to adju/ a resi/ance until ! galvanomet] %[s no deflection--an op]ation :i* takes up "t & requires a fair am\nt ( skill4 ,?is is obviat$ 9 ! ,h>ris indicator1 made by ,r4 ,w4 ,paul1 & %[n 9 fig4 #cg4 ,?is in/rum5t is a special =m ( ohmmet]1 :i* automatically indicates ! resi/ance ( ! pyromet] by ! movem5t ( ! po9t]2 ! scale1 h[ev]1 be+ divid$ s z to read correspond+ temp]atures4 ,9 ?is indicator ! scale may be made to notify an excess temp]ature--say #ajj--;above a giv5 fix$ numb]1 & h5ce is capable ( yield+ an exact read+ ov] ! work+ range = :i* x is us$4 ,x may also be connect$ s t ! :ole scale repres5ts ! complete range--say #j to #ajjj ,c4--or o!r specifi$ int]val4 ,! advantage possess$ by ?is in/rum5t is t ! manipulation is mu* simpl] ?an 9 ! indicators previ\sly describ$4 ,! ,le$s-,nor?rup ,indicator4--,9 ?is app>atus ! ,:eat/one bridge pr9ciple is employ$1 b ! galvanomet] is provid$ ) a scale divid$ or temp]atures4 ,coils are provid$ :i* correspond to an increase ( resi/ance due to a rise ( #ajj ,c4 on ! "p ( ! pyromet]1 & by ins]t+ ^! coils 9 ! circuit ! temp]ature is obta9$ to ! ne>e/ #ajj4 ,if ! temp]ature 7 exactly at an ev5 hundr$--say #gjj--! po9t] ( ! galvanomet] w\ld be at z]o on its scale2 b if n[ ! temp]ature rose1 ! sy/em w\ld no long] be balanc$1 & ! galvanomet] po9t] w\ld move ov] its scale by an am\nt dep5d+ ^u ! pot5tial diff]5ce at its t]m9als4 ,a v s5sitive galvanomet] w\ld give a movem5t to ! end ( its scale ) a slight alt]ation f ! correct balance ( ! sy/em2 b by us+ a co>s] in/rum5t ! po9t] w\ld rema9 )9 b\nds2 & ! great] ! increase ( resi/ance1 ! l>g] w\ld be ! deflection4 ,x is possible1 9 su* a case1 to divide ! galvanomet] scale to read temp]atures correspond+ to a giv5 increase above t ( ! coils plac$ 9 ! circuit4 ,9 "o =m ( ! ,le$s-,nor?rup indicator1 ! :ole scale is ?us divid$ to read #ajj1 & ! read+ is obta9$ by add+ ! figure %[n on ! galvanomet] to ! hundr$s repres5t$ by ! coils ins]t$4 ,9 ano!r =m ! galvanomet] has a c5tral z]o1 & its scale is divid$ bo? "r & left1 "o side giv+ ! numb] ( degrees above1 & ! o!r bel[1 ! ne>e/ hundr$4 ,! obs]vations are ?us mu* simpl] ?an 9 ! case :]e adju/m5t to ! condition ( no deflection is requisite4 ,siem5s' ,diff]5tial ,indicator4--,?is =m ( indicator is /ill 9 use1 & consi/s ( a diff]5tial galvanomet] & box ( resi/ance coils1 connect$ z %[n 9 fig4 #cj4 ,by adju/+ ! coils until no deflection is produc$1 ! resi/ance ( ! pyromet] is obta9$1 & ! correspond+ temp]ature read (f f tables provid$4 ,?is =m ( indicator is pref]r$ by "s us]s1 b x is less s5sitive ?an ! m rec5t ,:eat/one bridge indicator made by ?is firm 7fig4 #ce71 & equally difficult to manipulate4 ,record]s = ,resi/ance ,pyromet]s4--,! value ( records 9 high-temp]ature "w has l$ to ! inv5tion ( record+ me*anisms = use ) resi/ance pyromet]s4 ,! =m 9 common use 9 ,brita9 is t devis$ by ,call5d>1 %[n 9 fig4 #ch1 & consi/s ( a me*anism = re/or+ automatically ! balance ( ! resi/ances 9 a ,:eat/one bridge circuit1 9 su* a mann] z to indicate ! exi/+ resi/ance on a *>t4 ,to ?is end ! mov+ coil ( ! galvanomet] c>ries a boom1 or contact-arm1 :i*1 on sw++ to ! "r or left1 completes "o ( two electric circuits4 ,! clos+ ( ei!r circuit br+s into action a clockwork me*anism1 :i* causes a slid] c>ry+ a p5 to move ov] ! bridge wire until ! balance is re/or$1 & incid5tally to produce a m>k 9 ink on a pap] w\nd on a drum1 :i* rotates at a kn[n spe$4 ,:5 ! resi/ance ( ! pyromet] is balanc$1 ! galvanomet] boom w be 9 a c5tral position1 & ! slid] at re/2 :]eas a rise 9 temp]ature caus+ an increase 9 ! resi/ance ( ! pyromet]1 w result 9 ! boom sw++ ov] & complet+ ! circuit1 :i* introduces m resi/ance 9 opposition to ! pyromet]4 ,a fall 9 temp]ature w simil>ly result 9 ! lib]ation ( ! second me*anism1 ow+ to ! boom sw++ 9 ! opposite direction1 ) ! result t ! slid] moves s z to oppose a less resi/ance to ! pyromet]4 ,if ! *>t be divid$ horizontally into equal spaces1 repres5t+ equal increm5ts or decrem5ts ( resi/ance1 !y may be m>k$ to repres5t degrees on ! plat9um scale1 :i* may be translat$ into ord9>y degrees by ref]5ce to a conv]sion table4 ,9 c>eful & skill$ h&s ?is record] gives excell5t results1 & ! value ( ! records obta9$ is cle>ly %[n by an inspection ( ! example %[n 9 fig4 #ci1 :i* repres5ts ! fluctuations ( an anneal+ furnace dur+ a p]iod ( n9e h\rs4 ,x w be not$ t dur+ ! p]iod cov]$ by workman ,a ! furnace has receiv$ con/ant & c>eful att5tion2 b workman ,b has evid5tly neglect$ 8 duty conspicu\sly at two sep>ate times4 ,illu/ration3 ,,fig4 #ch4--;,,call5d>',s ,,record]4 ,illu/ration3 ,,fig4 #ci4--,,record ,,obta9$ ,,) ,,call5d>',s ,,record]4 ,! ,le$s-,nor?rup ,record]4--,9 ! ,call5d> record] ! boom :i* completes ! electric circuits is press$ aga9/ ! contact-surface m]ely by ! small =ce due to ! axial twi/ ( ! galvanomet] coil1 :i* necessitates ! use ( delicate me*anism if c]ta9ty ( action is to be secur$4 ,a sur] contact is secur$ 9 ! in/rum5t made by ! ,le$s-,nor?rup ,company ( ,philadelphia1 by means ( an int]mitt5t action :i* w be und]/ood f ! annex$ draw+ 7fig4 #dj74 ,! boom f ! galvanomet] t]m9ates 9 a plat9um tip1 ,p1 :i* moves betwe5 two blocks1 ! upp] ( :i* consi/s ( two pieces ( silv]1 ,a & ,b1 sep>at$ by a /rip ( ivory1 ,i1 :il/ ! l[] block1 ,c1 is ano!r piece ( silv]1 :i* is mov$ p]iodically up & d[n by an electro-magnetic contrivance n %[n 9 ! draw+4 ,:5 ! galvanomet] is at ! position ( balance1 ! tip ( ! boom is b5ea? ! ivory piece ,i2 & :5 ,c asc5ds ! tip ,p is !n squeez$ on to ! ivory1 & no curr5t w !n pass f ! batt]y ?r\gh ei!r ( ! circuits ,e or ,f4 ,if1 h[ev]1 ! po9t ( ! boom be b5ea? ,a1 ow+ to an alt]ation 9 ! temp]ature ( ! pyromet]1 !n on ,c ris+ ! circuit ?r\gh ,e w be complet$2 &1 simil>ly1 if b5ea? ,b ! circuit ?r\gh ,f w be e/abli%$4 ,! result 9 ei!r case is to br+ into action a me*anism :i* moves a slid]1 c>ry+ a p51 ov] a resi/ance wire oppos$ to ! pyromet] 9 su* a mann] z to re/ore ! balance4 ,c]ta9ty ( contact is ?us secur$1 :i* enables all ! p>ts to be /rongly made4 ,! actual record] is %[n 9 fig4 #da1 9 :i* x w be se5 t ! slid] c>ries an ord9>y /ylographic p5 9 contact ) ! *>t4 ,?is record] is work$ on ! diff]5tial galvanomet] me?od2 & ! adju/+ resi/ance1 ov] :i* ! slid] moves1 consi/s ( a mangan9 wire w\nd on a tap]$ core1 su* t horizontal movem5ts repres5t equal *anges ( temp]ature1 & n ( resi/ance1 ?us obviat+ ! necessity ( translat+ plat9um-scale read+s into ord9>y degrees4 ,concordant & accurate results1 c\pl$ ) robu/ con/ruction1 are claim$ = ?is in/rum5t by ! mak]s4 ,! o!r type ( record] made by ?is firm 7fig4 #bf7 may also be us$ 9 conjunction ) a resi/ance pyromet]4 ,9 ?is case ! movem5ts describ$ introduce or cut out resi/ance oppos$ to ! pyromet] 9 a ,:eat/one bridge circuit1 until ! balance is re/or$4 ,illu/ration3 ,,fig4 #dj4--,,pr9ciple ,,( ,,le$s-,,nor?rup ,,record]4 ,illu/ration3 ,,fig4 #da4--,,le$s-,,nor?rup ,,record]4 ,paul's ,record]4--,?is in/rum5t1 z us$ = !rmo-electric pyromet]s1 has already be5 describ$4 ,by replac+ ! galvanomet] by a ,h>ris indicator1 & us+ a suitable *>t1 ! same me*anism s]ves to record ! indications ( a resi/ance pyromet]4 ,in/allations ( ,resi/ance ,pyromet]s4--,! resi/ance me?od _c be s readily appli$ to ! purpose ( a c5trally controll$ in/allation z ! !rmo-electric1 ow+ to ! difficulty ( produc+ a set ( pyromet]s exactly equal 9 resi/ance4 ,! introduction ( ! ohmmet] me?od ( measur+ resi/ances1 z 9 ! ,h>ris indicator 7page #abb71 has1 h[ev]1 r5d]$ ?is project feasible1 z x is possible 9 ?is arrangem5t to br+ a set ( pyromet]s to a common resi/ance by add+ ! requisite am\nt 9 ! =m ( a wire ( negligible temp]ature coeffici5t4 ,sev]al in/rum5ts1 br\ght ?us to a z]o resi/ance ( #c ohms1 = example1 may !n be wir$ up to a ,h>ris record]1 & w give closely id5tical results4 ,= v>i\s reasons1 h[ev]1 a !rmo-electric in/allation is pref]able4 ,managem5t ( ,resi/ance ,pyromet]s4--,x is n advisable to use resi/ance pyromet]s cont9u\sly above #ijj ,c4 7#afej ,f471 al?\gh an occasional read+ may be tak5 up to #abjj ,c4 7#baij ,f474 ,great c>e mu/ be tak5 t metallic vap\rs or furnace gases d n f9d access to ! int]ior1 & = ?is reason a crack$ or defective %ea? %\ld imm$iately be replac$4 ,z ! resi/ance gradually *anges1 ev5 :5 #ijj ,c4 is n exce$$1 a read+ %\ld be *eck$ at a fix$ po9t 9 ! neighb\rhood ( ! work+ temp]ature1 & all[ance made = ! obs]v$ error4 ,ano!r me?od ( correction recomm5d$ by "s mak]s is to measure ! resi/ance 9 ice1 & to note h[ mu* ?is diff]s f ! z]o resi/ance not$ :5 ! indicator 0 m>k$1 & to correct by simple proportion4 ,?us1 if ! obs]v$ resi/ance 9 ice 7 #ajb ohms1 ! orig9al hav+ be5 #ajj ! read+ on ! indicator w\ld be multipli$ by #ajj_/ajb #jih1 a correction :i* assumes a l9e> relation betwe5 resi/ance & temp]ature1 & is !re=e only approximate4 ,g5]ally speak+1 any s]i\s defect entails ! s5d+ ( ! in/rum5t to ! mak]1 z a special degree ( skill is requir$ to execute ! necess>y repairs4 ,z ! indicators are usually n automatic 9 action1 c>e %\ld be tak5 9 ! manipulation n to damage any "p1 p>ticul>ly ! galvanomet]2 & x is advisable n to tru/ ! in/rum5ts to unskill$ obs]v]s4 ,! rem>ks apply+ to record]s & protect+ %ea?s 9 relation to !rmo-electric pyromet]s 7page #ib7 apply equally 9 ?is case4 ,special ,uses ( ,resi/ance ,pyromet]s4--,9 all cases 9 :i* an exact read+ is requir$1 & a /eady temp]ature c be secur$1 ! resi/ance pyromet] c be us$ to advantage4 ,?us = accurate det]m9ations ( melt+ po9ts & boil+ po9ts1 or = exact read+s ( temp]atures 9 exp]im5tal furnaces1 a resi/ance pyromet] is sup]ior to appliances ( o!r k9ds4 ,on ! o!r h&1 x is n capable ( respond+ to *anges ) ! same rapidity z a !rmal junction1 & is !re=e inf]ior = su* purposes z ! det]m9ation ( recalesc5ce po9ts1 or ! temp]ature ( exhau/ gases f an int]nal combu/ion eng9e4 ,! resi/ance me?od may be appli$ to atmosph]ic & v l[ temp]atures 7liquefi$ gases1 etc471 to measure /eady conditions ) accuracy1 nickel wire be+ sometimes us$ in/ead ( plat9um bel[ #djj ,c4 ,_m cold /ores are fitt$ ) resi/ance !rmomet]s1 ! temp]ature be+ read directly on ! galvanomet]1 :i* is plac$ across a ,:eat/one bridge1 & %[s a deflection :i* dep5ds ^u ! am\nt by :i* ! bridge is ?r[n out ( balance4 ,*anges 9 ! temp]ature ( ! resi/ance elem5t may ?us be read accurately4 ,:e!r ! resi/ance me?od is suitable to a giv5 purpose mu/ be decid$ by ! ?ree factors3 7#a7 temp]ature to be measur$1 :i* mu/ n exce$ #ajjj ,c4 cont9u\sly2 7#b7 degree ( accuracy requir$ 7a !rmo-electric pyromet] giv+ results to #aj ,c472 7#c7 /ability ( ! temp]ature measur$1 rapid *anges n be+ readily %[n by resi/ance pyromet]s4 ,"o advantage ( resi/ance pyromet]s is t ! read+s are indep5d5t ( ! resi/ance ( ! wires us$ to connect ! pyromet] ) ! indicator1 z su* wires are duplicat$ & oppos$ to ea* o!r 9 ! measur+ device1 _! resi/ance be+ !reby cancell$4 ,h5ce ! same read+ is obta9$ at any di/ance1 &1 9 addition1 ! head ( ! pyromet] may v>y 9 temp]ature to any ext5t )\t alt]+ ! read+4 ,^! are po9ts ( sup]iority ov] ! !rmo-electric me?od2 b1 on ! o!r h&1 resi/ance pyromet]s & indicators are m co/ly1 m fragile1 m difficult to repair1 require m skill$ att5tion1 & are m liable to get out ( ord] :5 us$ = indu/rial purposes4 ,^! drawbacks h result$ 9 re/rict+ ! use ( resi/ance pyromet]s to special purposes1 ! g5]al run ( obs]vations be+ conduct$ by means ( !rmo-electric pyromet]s4 ,,*apt] ,v ,,radiation ,,pyromet]s ,g5]al ,pr9ciples4--,x is a common exp]i5ce t ! heat radiat$ by a sub/ance increases z its temp]ature rises2 & x w\ld obvi\sly be an advantage if ! temp]ature ( a hot body c\ld be d$uc$ f ! int5sity ( its radiations1 z ! measurem5t c\ld !n be made f a di/ance1 )\t ! necessity ( plac+ a pyromet] 9 contact ) ! heat$ sub/ance4 ,at temp]atures above #ajjj ,c41 :5 difficulties are exp]i5c$ ei!r ) ! metals or protect+ %ea?s ( !rmo-electric or resi/ance pyromet]s1 ! advantage ga9$ w\ld become m conspicu\s z ! temp]ature increas$4 ,a brief survey ( our k ( ! relations betwe5 radiant en]gy & temp]ature w indicate h[ ?is desir$ end may be a*iev$4 ,any sub/ance at a temp]ature above absolute z]o 7-#bgc ,c47 radiates en]gy to its surr\nd+s by means ( e!r waves4 ,bel[ #djj ,c4 ^! waves produce no impression on ! ret9a ( ! eye1 & ! radiat+ body is !re=e invisible 9 a d>k room4 ,above #djj ,c41 h[ev]1 a proportion ( visible waves are emitt$2 & z ! temp]ature rises ! effect on ! ret9a is enhanc$1 & ! body increases 9 brightness4 ,! diff]5ce betwe5 ! non-lum9\s & lum9\s waves is m]ely "o ( wave-l5g?1 ! %ort] wave-l5g?s be+ visible to ! eye2 & bo? repres5t radiant en]gy4 ,9 addition to giv+ out radiant en]gy1 a sub/ance receives waves f its surr\nd+s1 :i* x absorbs 9 great] or less degree1 & :i* :5 absorb$ t5d to raise ! temp]ature ( ! receiv+ sub/ance4 ,a numb] ( objects 9 a room1 all at ! same temp]ature1 are !re=e radiat+ en]gy to "o ano!r1 & equality ( temp]ature is e/abli%$ :5 ea* object receives f its surr\nd+s an am\nt ( en]gy equal to t :i* x radiates4 ,a hot sub/ance radiates m en]gy ?an a cold "o2 ?us if a hot iron ball be hung 9 a room x w radiate m en]gy to its surr\nd+s ?an x receives f !m1 & w !re=e cool until ! outgo+ en]gy is balanc$ by ! incom+1 :5 its temp]ature w be equal to t ( ! o!r objects 9 ! room4 ,! rate at :i* a sub/ance emits or takes up radiant en]gy dep5ds ^u ! nature ( its surface4 ,a r\gh1 black surface1 su* z may be obta9$ by hold+ an object 9 ! smoke f burn+ camphor1 radiates & absorbs heat ) great] fre$om ?an any o!r2 :il/ a poli%$1 metallic surface1 :i* acts z a reflector1 is wor/ ( all 9 ^! respects4 ,ev5 a surface ( f9ely divid$ soot1 h[ev]1 does n completely absorb all ! radiations :i* fall ^u x1 b exhibits a small degree ( reflection4 ,an 8absolute black surface10 if su* c\ld be f\nd1 w\ld be totally devoid ( reflect+ p[]1 & w\ld absorb all ! radiant en]gy incid5t ^u x2 & conv]sely w\ld radiate all en]gy rea*+ x f its "u side1 )\t reflect+ any back1 or all[+ any to pass ?r\gh 9 ! mann] t light waves are transmitt$ ?r\gh a transp>5t sub/ance4 ,no su* p]fect surface is kn[n2 b1 z ,kir*(f %[$1 x is possible to make a radiat+ arrangem5t :i* w give ! same num]ical result = ! en]gy radiat$ z w\ld be obta9$ by a p]fect surface at ! same temp]ature4 ,su* an arrangem5t is t]m$ a 8black body10 & radiations f x are designat$ 8black-body radiations40 ,illu/ration3 ,,fig4 #db4--;,,black-,,body ,,radiations4 ,any enclosure1 if opaque to radiant en]gy1 & kept at a con/ant temp]ature1 con/itutes a black body1 & radiations receiv$ f ! int]ior ?r\gh a small op5+ 9 ! side are black-body radiations4 ,fig4 #db repres5ts su* an enclosure2 9 :i*1 to %[ ! application to pyrometry1 a body ,a is indicat$ opposite to an op5+ 9 ! side1 ?r\gh :i* radiations escape f ! surface ( ,a4 ,if ?is surface 7 8p]fect10 all ! waves fall+ ^u x w\ld be completely absorb$ & completely radiat$2 b to prev5t *ange ( temp]ature ! en]gy radiat$ mu/ balance ! en]gy receiv$4 ,if1 on ! o!r h&1 ! surface ( ,a 7 a poli%$ metal1 ! waves fall+ ^u x f ! sides ( ! enclosure w\ld 9 ! ma9 be reflect$2 b "h aga9 ! en]gy leav+ ! surface mu/ equal ! am\nt receiv$ if ! temp]ature be con/ant4 ,x foll[s1 !re=e1 t if no alt]ation 9 temp]ature occur1 ! en]gy leav+ ! surface ( ,a is indep5d5t ( ! nature ( t surface2 & ! am\nt escap+ ?r\gh ! op5+ w !re=e be ! same1 :atev] be ! "* ( ! surface opposite ! op5+4 ,) a good radiat+ surface ! rays f ! enclosure w fir/ be absorb$ & !n radiat$ ?r\gh ! op5+2 9 ! case ( a poor radiat+ surface1 ! rays w be directly reflect$ ?r\gh ! op5+2 ! total en]gy escap+ be+ ! same 9 ei!r case4 ,x w be se5 lat] t radiation pyromet]s are bas$ ^u black-body radiations2 & x is important to note t ! arrangem5t "u discussion is realis$ 9 a furnace at a con/ant temp]ature1 9 :i* ,a might repres5t an object su* z a block ( /eel4 ,x happ5s1 !re=e1 t ! condition ( p]fect radiation is atta9$ by ! appliances 9 ev]yday use2 &1 moreov]1 black-body radiations c always be secur$ by plac+ a tube1 clos$ at "o end1 9 ! heat$ space1 & receiv+ ! radiations ?r\gh ! op5 end2 = ?is aga9 repres5ts an enclosure at a con/ant temp]ature4 ,simil>ly1 radiations f a solid 9 ! int]ior ( ! tube ( ! electric furnace %[n 9 fig4 #bi w be ( ! same description1 & we c !re=e apply ) accuracy any in/rum5t bas$ ^u black-body radiations1 kn[+ t ! same may be readily realis$ 9 practice4 ,! law connect+ ! en]gy radiat$ by a sub/ance1 "u giv5 conditions1 ) its temp]ature1 0 v>i\sly /at$ by diff]5t obs]v]s until ,/efan1 9 #ahgi1 d$uc$ ! true relation f c]ta9 exp]im5tal data obta9$ by ,tyndall4 ,/efan conclud$ t ! figures giv5 by ,tyndall indicat$ t ! en]gy radiat$ by a giv5 solid v>i$ z ! f\r? p[] ( its absolute temp]ature4 ,num]\s exp]im5ts1 "u diff]5t conditions1 %[$ t ! f\r?-p[] law did n apply to all k9ds ( surfaces or circum/ances2 b a /rong confirmation ( its tru? :5 appli$ to black-body radiations 0 =?com+ 9 #ahhd1 :5 ,boltzmann %[$1 f !rmodynamic consid]ations1 t ! quantity ( en]gy radiat$ 9 a giv5 "t f a p]fect radiator mu/ v>y z ! f\r? p[] ( its absolute !rmodynamic temp]ature4 ,c]ta9 assumptions made by ,boltzmann 9 ?is inve/igation 7 subsequ5tly ju/ifi$ by exp]im5t2 & num]\s te/s "u black-body conditions h s9ce amply v]ifi$ ! law4 ,x is ^u ! ,/efan-,boltzmann law t radiation pyromet]s are bas$2 ! en]gy receiv$ by radiation f ! heat$ sub/ance1 "u black-body conditions1 be+ measur$ by ! in/rum5t1 & translat$ into correspond+ temp]atures on its scale4 ,express$ 9 symbols1 ! f\r?-p[] law takes ! =m-- ,e ,k7,t#ad - ,t#bd71 :]e ,e is ! total en]gy radiat$2 ,t#a ! absolute temp]ature ( ! black body2 ,t#b ! absolute temp]ature ( ! receiv+ sub/ance1 & ,k a con/ant dep5d+ ^u ! units *os54 ,if ,e be express$ z watts p] squ>e c5timetre1 ! value ( ,k is #ef #aj-ab2 if 9 calories p] squ>e c5timetre p] second1 ! value is #acd #aj-ab4 ,! introduction ( ! temp]ature ( ! receiv+ sub/ance1 ,t#b1 is r5d]$ necess>y by ! fact1 previ\sly cit$1 t en]gy w be radiat$ back to ! hot body1 & ! net loss ( en]gy w evid5tly be ! diff]5ce betwe5 t :i* leaves x & t :i* returns to x f ! receiv+ sub/ance4 ,if ,t#b 7 absolute z]o1 ! en]gy leav+ ! black body w\ld be ,,kt#ad2 :]eas if ,t#b 7 equal to ,t#a1 ! loss ( en]gy w\ld be nil1 z a sub/ance _c cool by radiation to a l[] temp]ature ?an its surr\nd+s4 ,! temp]atures ,t#a & ,t#b ref] to ! !rmodynamic scale 7page #i71 b z ! gas scale is practically id5tical1 ,c5tigrade degrees may be us$1 measur$ f absolute z]o1 or -#bgc4 ,an example is app5d$ to illu/rate ! application ( ! law3-- ,example4--,to comp>e ! en]gy radiat$ ?r\gh an op5+ 9 ! side ( a furnace at temp]atures ( #ebg1 #gbg1 & #ibg ,c4 respectively1 to surr\nd+s at #bg ,c4 ,! quantities w be z ,k7#hjjd - #cjjd7 3 ,k7#ajjjd - #cjjd7 3 ,k7#abjjd - #cjjd74 s9ce #bgc mu/ be add$ to ea* temp]ature to conv]t into absolute degrees4 ,divid+ ea* by ,k1 & exp&+ 9 ea* case1 ! ratio becomes 7#djif - #ha7 #ajh 3 7#ajjjj - #ha7 #ajh 3 7#bjgcf - #ha7 #ajh4 ,divid+ ea* by #ajh & subtract+1 ! result is #djae 3 #iiai 3 #bjfee1 or #a 3 #bdg 3 #eab4 ,x w be not$ 9 ! above example t ! effect ( ! surr\nd+ temp]ature1 tak5 z #bg ,c41 is small 9 quantity1 & becomes proportionately less z ! temp]ature ( ! furnace increases4 ,if ,t#b _h be5 ignor$ 9 ! calculation1 ! am\nts ( en]gy radiat$ w\ld h appe>$ z #a 3 #bdd 3 #ejf4 ,x w be se5 lat]1 t 9 calculat+ ! temp]ature scale ( a radiation pyromet]1 ! temp]ature ( ! surr\nd+s is = ?is reason n tak5 into acc\nt4 ,fig4 #dc is a graphic illu/ration ( ! f\r?-p[] law4 ,illu/ration3 ,,fig4 #dc4--;,,en]gy ,,radiat$ ,,by ,a ,,black ,,body ,,at ,,diff]5t ,,temp]atures4 ,:5 ! relation betwe5 temp]ature & quantity ( en]gy radiat$ is kn[n1 any in/rum5t :i* w indicate ! am\nt ( ! radiations x receives may be us$ to measure temp]atures4 ,! ray1 = example1 may be focus$ on a !rmal junction1 :i* w be heat$ 9 proportion to ! am\nt ( en]gy incid5t ^u x1 & :5 connect$ to a millivoltmet] w cause deflections proportional to ! en]gy x receives4 ,a ?9 /rip ( metal might be us$ 9 place ( a junction1 & by measur+ its resi/ance ! heat+ effect ( ! radiations1 & h5ce ! am\nt !re(1 may be d$uc$4 ,a ?ird me?od w\ld be to focus ! rays on to a comp\nd /rip ( two metals1 :i* by alt]+ 9 %ape c\ld be made to furni% a clue to ! quantity ( en]gy receiv$ by x4 ,9 !ory1 x is only necess>y to all[ ! radiations to fall on ! work+ "p ( any in/rum5t = measur+ l[ temp]atures1 :5 ! rise 9 temp]ature produc$ may be tak5 z proportional to ! en]gy receiv$1 & ! !rmal condition ( ! radiat+ body d$uc$ f ! f\r?-p[] law4 ,9 practice1 h[ev]1 x is desirable t ! receiv+ !rmomet] %\ld be small 9 size2 ( l[ !rmal capacity1 s z to respond rapidly2 & capable ( giv+ a s5sitive indication--h5ce an ord9>y m]cury !rmomet] w\ld be unsuitable = ?is purpose4 ,a !rmopile1 plac$ at a fix$ di/ance1 w\ld fail ow+ to ! cold junctions gradually w>m+ up by conduction ?r\gh ! pile4 ,! "p receiv+ ! radiations %\ld be coat$ ) lamp-black1 s t practically all ! waves imp++ ^u x1 :e!r lum9\s or non-lum9\s1 may be absorb$1 & ! en]gy !y repres5t utilis$ 9 produc+ a rise 9 temp]ature4 ,practical ,=ms ( ,radiation ,pyromet]s3 ,fry's ,in/rum5ts4--,9 ! ye> #aijb ,fry introduc$ a pyromet] 9 :i* ! rays 7 focus$ by ! aid ( a l5s ^u a small1 black5$ !rmal junction1 9 ! same way t ! rays ( ! sun may be focus$ by a burn+-l5s4 ,! junction 0 connect$ to a special =m ( d',arsonval galvanomet]1 :i* record$ ! ,e4,m4,f4 develop$4 ,by tak+ ! read+s ( ! galvanomet] z proportional to ! temp]ature ( ! junction--t is1 to ! radiant en]gy imp++ ^u x--! temp]ature ( ! s\rce c\ld be calculat$ f ! f\r?-p[] law4 ,! drawback to ! use ( ?is in/rum5t 0 ! fact t a proportion ( ! rays 0 absorb$ by ! glass1 ?is proportion1 moreov]1 v>y+ at diff]5t temp]atures1 s t ! f\r?-p[] law c\ld n be appli$ ) accuracy4 ,by us+ a fluorsp> l5s 9 place ( glass1 ?is error 0 ov]come1 b ! co/ ( a good l5s ( ?is mat]ial be+ high1 its use 9 ord9>y work%op practice 0 r5d]$ prohibitive on acc\nt ( ! price4 ,a numb] ( ^! pyromet]s1 furni%$ ) glass l5ses1 & calibrat$ by comp>ison ) a /&>d possess+ a fluorsp> l5s1 7 plac$ on ! m>ket1 b 7 sup]s$$ 9 #aijd1 :5 ,fry hit ^u ! plan ( focus+ ! rays by means ( a concave mirror1 ?us ov]com+ ! error due to absorption by ! glass l5s4 ,?is plan1 :i* s]ves admirably1 has s9ce be5 adopt$ 9 mo/ radiation pyromet]s4 ,fry's ,mirror ,pyromet]4--,?is in/rum5t is %[n 9 longitud9al & also 9 cross section 9 fig4 #dd4 ,a concave mirror1 ,m1 :i* has a gilt reflect+ surface1 is plac$ at "o end ( a metal tube1 & is fa/5$ to a rack :i* engages 9 a p9ion mov$ by ! mill$-head1 ,p1 s t on turn+ ,p1 a longitud9al movem5t is imp>t$ to ! mirror4 ,a small1 black5$ !rmal junction1 %[n at ! c5tre ( ! cross section1 & consi/+ ( a copp] disc to :i* wires ( copp] or iron & con/antan are fa/5$1 receives ! rays aft] reflection1 & may be br\ght into focus by suitably mov+ ! mirror4 ,illu/ration3 ,,fig4 #dd4--;,f,,ry',s ,,mirror ,,pyromet]4 ,,section4 ,illu/ration3 ,,fig4 #de4--;,f,,ry',s ,,mirror ,,pyromet]4 ,,end ,,view4 ,! wires pass to t]m9als b & b on ! outside ( ! tube1 f :i* leads are tak5 to ! indicator4 ,9 ord] to discov] :5 ! junction is 9 ! focus ( ! mirror1 an eye-piece1 ,o1 is fitt$ 9 ! end ( ! tube1 :i* enables ! junction to be se51 magnifi$1 ?r\gh a hole 9 ! c5tre ( ,m4 ,by means ( an optical device plac$ ne> ! junction1 ! image ( ! sight$ object1 produc$ by ,m1 is reflect$ 9 two portions to ! eye-piece ,o4 ,:5 ! junction is exactly 9 ! focus ( ,m1 a circul> image is se5 r\nd ! junction2 :5 out ( focus1 ! appe>ance pres5t$ is t ( two semi-circles n co9cid+ lat]ally4 ,! adju/m5t consi/s 9 mov+ ! mirror until ! sep>ate semi-circles produce a cont9u\s circle2 a me?od at once simple & def9ite4 ,! front end ( ! pyromet] is %[n 9 fig4 #de1 9 :i* x w be se5 t ! entrance may be p>tially clos$ by a diaphragm1 or left entirely op51 z requir$4 ,! diaphragm is us$ to cut (f a def9ite proportion ( ! radiations1 & is us$ = v high temp]atures1 at :i*1 ) full ap]ture1 ! indicator ne$le w\ld be urg$ beyond ! limits ( ! scale4 ,on ! indicator two sep>ate temp]ature scales are provid$1 "o ref]r+ to full1 & ! o!r to p>tial ap]ture4 ,! same end might be a*iev$ by ins]t+ a suitable resi/ance 9 s]ies ) ! indicator3 b 9 ?is case ! junction might be unduly heat$1 & possibly damag$ !reby4 ,! proportions ( ! pyromet] are su* t at ! highe/ temp]atures measur$ ! heat incid5t on ! junction nev] raises x above #aaj ,c4 ,al?\gh ! int5sity ( radiations dim9i%es z ! squ>e ( ! di/ance1 ! quantity imp++ on ! junction is1 )9 limits1 indep5d5t ( ! di/ance3 ,?is arises f ! prop]ty ( concave mirrors ) respect to ! relation betwe5 ! size ( an image & ! di/ance ( ! object produc+ x4 ,if r ! radius ( ! mirror1 u ! di/ance ( ! object1 & v ! di/ance ( ! image1 bo? measur$ f ! c5tre ( ! mirror1 ! relation #a_/u #a_/v #b_/r holds = a concave mirror1 & :5 two ( ^! are kn[n ! ?ird may be calculat$4 ,fur!r1 if d be ! l9e> dim5sion ( an object1 & d#a t ( its image1 ! relation d_/d#a u_/v also holds1 & f ^! two expressions all ! po9ts aris+ 9 connection ) ! ,fry pyromet] may be det]m9$1 z w be/ be made cle> by examples4 ,example ,i4--,to f9d ! position ( ! image ( an object =m$ by a mirror ( #f in*es radius1 ) object at di/ance 7a7 #aj feet1 7b7 #bj feet4 ,r$uc+ to in*es1 & apply+ 9 ! =mula #a #a #b #a #a #a 1 u v r #abj v #c & #a #a #a #bdj v #c f :i* ! values ( v are #c-a_/ac in*es & #c-a_/bf in*es respectively1 a diff]5ce ( only #a_/bf ( an in*4 ,if u 7 #f in*es1 v w\ld also be #f in*es2 if u 7 inf9ity1 v w\ld be #c in*es4 ,! movem5t ( ! image1 :5 an object is br\ght t[>ds x f a great di/ance1 w\ld 9 ! mirror "u notice be f #c in*es away to #f in*es away1 & at di/ances ( #aj feet & upw>ds w\ld only diff] 9 position by small fractions ( an in*4 ,example ,,ii4--,to f9d ! area ( ! image ( a circul> op5+1 #a foot 9 diamet]1 =m$ by a mirror ( #f in*es radius di/ant f ! op5+ 7a7 #aj feet2 7b7 #bj feet4 ,s9ce d u 2 !n1 f ! results ( d#a v ,example #ab #abj at #aj feet di/ance1 d#a 7#c-a_/ac7 & #ab #bdj at #bj feet4 d#a 7#c-a_/bf7 ,h5ce ! l9e> dim5sions1 i4e4 ! diamet]s ( ! circul> images1 w be #jcjh & #jaeb in* respectively2 & ! areas #jjgd & #jjahb squ>e in*4 ,^! areas are to ea* o!r practically z #d 3 #a4 ,t is1 ! area ( ! image decreases 9 size directly z ! squ>e ( ! di/ance ( ! object2 ! squ>es ( ! di/ances be+ #ajj & #djj1 or z #a 3 #d2 :]eas ! areas ( ! images are z #d 3 #a4 ,example ,,iii4--,to f9d1 = a #f-;in* mirror1 & a junction ( #a_/aj? ( an in* 9 diamet]1 ! greate/ di/ance at :i* ! mirror may be plac$ f an op5+ #a foot 9 diamet]1 s z to give an image n less ?an ! junction4 ,f ,example ,i x is evid5t t at any di/ance exce$+ #bj feet ! position ( ! image w only be a m9ute & negligible fraction ov] #c in*es2 h5ce v may be tak5 z #c4 ,apply+ values 9 ! =mula d u & d#a v tak+ d#a z equal to ! diamet] ( ! junction1 #ja in*1 #ab u 1 & u #cfj in*es1 or #cj feet4 #ja #c ,beyond ?is di/ance ! image w\ld be less ?an ! junction4 ,! conclusions to be drawn f ! =ego+ examples are3 7#a7 t ! am\nt ( en]gy receiv$ by ! junction does n v>y1 provid$ ! image ov]laps x2 & 7#b7 t ! limit+ di/ance at :i* a correct read+ c be secur$ is t at :i* ! size ( ! image is equal to t ( ! junction4 ,?us1 tak+ di/ances ( #aj & #bj feet1 z 9 ,example ,,ii2 at ! =m] di/ance ! en]gy /rik+ ! mirror is f\r times z great z ) ! latt]2 b1 on ! o!r h&1 ! area ( ! image at #aj feet di/ance is f\r times z great z t obta9$ at #bj feet4 ,h5ce1 at ! great] di/ance1 ! proportion ( ! image imp++ on ! junction is f\r times z great1 & ! fact t only ! am\nt ( en]gy /rikes ! mirror is ?us c\nt]balanc$4 ,all ! reflect$ rays :i* fail to /rike ! junction are ineffective1 & pass out ?r\gh ! entrance ( ! tube4 ,illu/ration3 ,,fig4 #df4--;,f,,ry',s ,,spiral4 ,! two-scale =m ( in/rum5t describ$ above is extremely useful = g5]al purposes1 b :5 all ! temp]atures to be controll$ fall )9 ! limit ( "o ( ! scales1 x is simpl] & *eap] to disp5se ) ! diaphragm1 & to use an indicator furni%$ ) "o scale only4 ,! s+le-scale mirror pyromet] is = ?is reason m g5]ally employ$ = indu/rial purposes2 & ! ,cambridge & ,paul ,in/rum5t ,company n[ make a pivot$ indicator = use ) full ap]ture1 :i* is less liable to damage ?an "o :i* possesses a susp5d$ coil4 ,illu/ration3 ,,fig4 #dg4--;,f,,ry',s ,,spiral ,,pyromet]4 ,,section4 ,fry's 8,spiral0 ,radiation ,pyromet]4--,?is in/rum5t diff]s f ! prec$+ m]ely 9 ! fact t ! rays are focus$ on a small spiral1 =m$ ( a comp\nd /rip ( two metals1 fix$ at "o end & furni%$ ) a po9t] at ! free-mov+ end 7fig4 #df74 ,! effect ( alt]ations ( temp]ature on ?is spiral are to cause x to coil up or uncoil1 accord+ to :e!r ! temp]ature rises or falls4 ,?is movem5t is magnifi$ by ! po9t]1 ! end ( :i* moves ov] a dial graduat$ to read temp]atures directly4 ,?is arrangem5t is %[n 9 section 9 fig4 #dg1 :]e ,c is ! mirror1 ,e ! eye-piece1 ,s ! spiral1 ,p ! po9t]1 & ,d ! dial1 view$ ?r\gh ! w9d[ ,w4 ,! appe>ance ( ! app>atus :5 view$ f ! front is %[n 9 fig4 #dh4 ,! advantage ga9$ by ! use ( ! spiral is t ! in/rum5t is self-conta9$1 no galvanomet] be+ necess>y2 b1 on ! o!r h&1 ! indications are n s exact1 an error ( #bj ,c4 be+ probable at temp]atures ov] #ajjj ,c4 ,9 us+ ?is pyromet]1 x is obs]v$ t aft] focus+ ! hot sub/ance1 ! po9t] moves rapidly = a "t & !n pauses1 aft] :i* x aga9 comm5ces to creep along ! scale4 ,! temp]ature indicat$ at ! mom5t ! pause occurs is g5]ally tak5 z ! read+1 b ?is is n always correct4 ,illu/ration3 ,,fig4 #dh4--;,f,,ry',s ,,spiral ,,pyromet]4 ,,front ,,view4 ,! creep+ movem5t is probably due to ! :ole in/rum5t1 & ! air 9 ! int]ior1 becom+ heat$ by ! ent]+ rays1 & by proximity to ! hot s\rce4 ,9 a numb] ( trials made by ! au?or1 x 0 notic$ t :5 ! in/rum5t 0 all[$ to /& ne> ! furnace = "s "t be=e us+1 !reby atta9+ ! temp]ature exi/+ 9 ! vic9ity1 ! 8creep0 almo/ entirely vani%$4 ,all ?+s consid]$1 ! spiral =m ( ,fry's pyromet] mu/ be reg>d$ z m portable b less accurate ?an t 9 :i* ! rays are receiv$ on a !rmal junction4 ,fo/]'s ,fix$-,focus ,radiation ,pyromet]4--,! necessity = focus+1 common to all ,fry's radiation pyromet]s1 is obviat$ 9 ,fo/]'s pyromet]1 :i*1 h[ev]1 _c be us$ f s great a di/ance4 ,! pr9ciple involv$ 9 ! fix$-focus pyromet] is t ! am\nt ( en]gy receiv$ by a concave mirror & focus$ on a !rmal junction w n v>y s long z ! area ( ! surface s5d+ rays to ! mirror1 ?r\gh a fix$ op5+1 increases z ! squ>e ( ! di/ance4 ,?is w be und]/ood f fig4 #di1 9 :i* ,c is ! mirror1 ,d a !rmal junction fix$ s z to be 9 ! focus ( ! op5+ ,e ,f1 & ,a ,b ! heat$ surface4 ,! l9es jo9+ ,e & ,f to ! edge ( ! mirror int]sect 9 a po9t ,g1 & provid$ ! l9es ,g ,e & ,g ,f1 if produc$1 fall )9 ! heat$ surface ,a ,b1 ! quantity ( en]gy fall+ on ,d w always be ! same4 ,a cross section ( ! cone ,g ,a ,b is a circle2 & if ,a ,b be twice z f> away f ,g z ,e ,f1 ! areas ( ! circles ( :i* ,a ,b & ,e ,f are diamet]s w be 9 ! ratio #d3 #a4 ,b z ,a ,b is twice z f> f ,g z ,e ,f1 ! int5sity ( its radiations w be z #a3 #d2 & h5ce loss ( radiat+ p[] is exactly balanc$ by increase 9 area4 ,illu/ration3 ,,fig4 #di4--,,pr9ciple ,,( ,,fo/]',s ,,fix$-,,focus ,,pyromet]4 ,9 ! actual in/rum5t ! tube 9 :i* ! mirror is plac$ is black5$ int]nally1 s t no rays rea* ! mirror by reflection f x4 ,! diamet]s ( ! op5+ ,e ,f & ! mirror ,c are su* t ! p]p5dicul> f ,g on to ,a ,b is t5 times ! l5g? ( ,a ,b4 ,h5ce1 if ! heat$ object be #f in*es 9 diamet]1 ! limit+ di/ance ( ,g is #aj #f #fj in*es4 ,! position ( ! po9t ,g is indicat$ by a r+ on ! outside ( ! tube1 & 9 tak+ a measurem5t ! tube is br\ght well )9 ! di/ance prescrib$1 :i* is 9 all cases t5 times ! diamet] ( ! heat$ object4 ,temp]atures are read f a galvanomet] connect$ to ! !rmal junction1 ! :ole arrangem5t be+ portable1 z %[n 9 figs4 #ej & #ea1 :i* repres5t ! in/rum5t 9 use4 ,illu/ration3 ,,fig4 #ej4--;,,fo/]',s ,,pyromet]1 ,,m\nt$ ,,on ,,/&4 ,! advantages d]iv$ f ! use ( a fix$ focus in/rum5t are simplicity & *eapness2 b1 z _m occasions arise 9 practice 9 :i* focus+ on an object is a necessity1 ,fo/]'s pyromet] mu/ be reg>d$ z a simplifi$ app>atus n capable ( ! wid] applications ( ,fry's in/rum5ts1 b ( great s]vice 9 _m cases4 ,:ipple has rec5tly adapt$ ! ,fry spiral pyromet] to produce an in/rum5t ) a fix$ focus1 by fa/5+ ! in/rum5t to a fireclay tube1 on ! clos$ end ( :i* ! pyromet] is p]man5tly focus$4 ,?is =m is specially useful = det]m9+ ! temp]ature ( molt5 metals1 into :i* ! end ( ! fireclay tube is plung$1 ?us giv+ true black-body conditions4 ,illu/ration3 ,,fig4 #ea4--;,,fo/]',s ,,pyromet]1 ,,9 ,,use4 ,paul's ,radiation ,pyromet]4--,?w+1 9 ,am]ica1 has introduc$ a radiation pyromet] 9 :i* ! rays f ! furnace ent] ! wide end ( a cone1 & by int]nal reflection are br\ght to ! apex1 at :i* a !rmal junction is locat$4 ,paul1 9 ?is c\ntry1 has m>ket$ a simil> in/rum5t1 ! action ( :i* is %[n 9 fig4 #eb1 :]e ,e is a tube conta9+ a poli%$ cone1 ,c1 at ! apex ( :i* is fix$ a !rmal junction1 ,t4 ,rays f ! hot s\rce ,a ,a ent] ! tube at ,d1 & pass into ! cone1 be+ f9ally reflect$ on to ,t1 :i* is connect$ to ! indicator4 ,s long z ! l9es jo9+ ! outside ( ! cone ) ! extremities ( ! entrance ,d1 cross+ at ,o1 fall )9 ! hot s\rce1 ,a ,a1 ! read+ w be ! same at all di/ances4 ,fig4 #ec %[s ! actual pyromet]1 m\nt$ on a tripod4 ,illu/ration3 ,,fig4 #eb4--,,pr9ciple ,,( ,,paul',s ,,radiation ,,pyromet]4 ,indicators = ,radiation ,pyromet]s4--,:5 ! radiations are focus$ on a !rmal junction1 ! temp]ature ( :i* is rais$ 9 consequ5ce1 ! ,e4,m4,f4 develop$ is 9 accordance ) ! laws discuss$ 9 ,*apt] ,,ii1 & any !rmo-electric indicator1 if suffici5tly s5sitive1 w s]ve = ! purposes ( a radiation pyromet]4 ,! effect on ! galvanomet] is influ5c$ by3 7#a7 ! nature ( ! junction2 7#b7 ! size ( ! mirror or cone2 & 7#c7 ! highe/ temp]ature atta9$ by ! junction4 ,! indicators us$ 9 connection ) radiation pyromet]s are ( ! pivot$ type1 :i* c n[ be made suffici5tly s5sitive to give full-scale deflection = a rise ( #ajj ,c4 9 ! temp]ature ( ! junction4 ,= ! junction itself1 ,heil's alloy 7z9c & antimony 9 atomic proportions7 p>tn]$ ) con/antan has be5 us$1 ow+ to ! high ,e4,m4,f4 develop$2 b cases ( det]ioration ( ?is alloy h be5 not$1 caus+ x to be replac$ by "s mak]s by iron4 ,two iron or copp] con/antan junctions 9 s]ies give an ,e4,m4,f4 = a rise ( #ajj ,c41 suffici5t to "w a pivot$ indicator1 & are pref]able to ,heil's c\ple = a radiation pyromet]4 ,illu/ration3 ,,fig4 #ec4--,,paul',s ,,radiation ,,pyromet]4 ,calibration ( ,indicators = ,radiation ,pyromet]s4--,! deflections on ! indicators are due to ! ,e4,m4,f4 g5]at$1 :i* is proportional to ! diff]5ce 9 temp]ature betwe5 ! hot & cold junctions4 ,if bo? ^! are at ! same temp]ature--say1 #bj ,c4--! deflection is z]o2 & on all[+ ! radiations to fall on ! hot junction its temp]ature is rais$ by an am\nt dep5d+ ^u ! int5sity ( ! radiations--say1 to #ij ,c4 ,! deflection produc$ is !n due to a diff]5ce ( 7#ij-bj7 #gj1 ! radiations hav+ rais$ ! temp]ature ( ! hot junction #gj above its surr\nd+s4 ,if ! surr\nd+s 7includ+ ! cold junction or junctions7 _h be5 at #ae to comm5ce )1 ! hot junction "u ! same conditions w\ld h ris5 to #he1 giv+ aga9 a diff]5ce ( #gj1 & ?us caus+ ! same deflection z be=e4 ,provid$ bo? hot & cold junctions are locat$ s z to atta9 ! same atmosph]ic temp]ature 9 ! abs5ce ( radiations1 a giv5 quantity ( en]gy imp++ on ! hot junction w always produce 9 x ! same excess temp]ature1 & w !re=e give rise to ! same deflection at all ord9>y atmosph]ic temp]atures4 ,z ! junctions are s arrang$ 9 radiation pyromet]s z to fulfill ?is condition1 no correction = fluctuations 9 ! cold junctions is necess>y4 ,! deflections1 !re=e1 correspond to excess temp]atures ( ! hot junction1 :i* 9 turn are directly proportional to ! en]gy receiv$ by ! junction4 ,read+s 9 millivolts on ! indicator ?us repres5t directly ! proportions ( en]gy receiv$ by ! hot junction1 #d millivolts correspond+ to twice ! en]gy1 :i* produces #b millivolts1 & s on2 & h5ce ! millivolt scale becomes an en]gy scale4 ,9 ord] to translate en]gy into correspond+ temp]atures1 ! f\r?-p[] law mu/ be appli$4 ,if ,e#a correspond to an absolute temp]ature ,t#a on ! "p ( ! black body f :i* radiations are receiv$1 & ,e#b correspond to ano!r temp]ature ,t#b1 ! foll[+ relations w hold good3 ,e#a ,k7,t#ad - x#d71 & ,e#b ,k7,t#bd - x#d71 :]e x is ! temp]ature ( ! surr\nd+s receiv+ ! radiations4 ,z previ\sly po9t$ out 7see ,example on page #adj71 ! t]m x#d may be ignor$ = ! range ( high temp]atures measur$ by a radiation pyromet]1 h5ce ,e#a ,,kt#ad1 & ,e#b ,,kt#bd2 & !re=e ,e#a_/;,e#b ,t#ad_/,t#bd4 ,b1 z %[n above1 read+s 9 millivolts on ! indicator are directly proportional to ! en]gy receiv$1 & if ,r#a & ,r#b millivolts due to ,e#a & ,e#b1 ! relation ,r#a_/,r#b ,t#ad_/,t#bd is !n obta9$4 ,9 ord] to prep>e a temp]ature scale f ?is relation1 x is necess>y to take "o correct read+ at a kn[n temp]ature1 aft] :i* ! rema9d] ( ! scale may be m>k$ by calculation1 z %[n 9 ! example app5d$3-- ,example4--,a tube clos$ at "o end is at #ibg ,c4 7#abjj abs471 & gives a deflection correspond+ to #b millivolts on ! indicator4 ,to f9d ! temp]atures :i* w\ld yield deflections due to #a1 #c1 #d1 & #e millivolts4 ,tak+ ! case ( #a millivolt & apply+ 9 ! =mula ,r#a ,t#ad #b #abjjd 1 2 ,r#b ,t#bd #a ,t#bd #abjjd f :i* ,t#bd & ,t#b #ajji abs4 #b #gcf ,c4 ,simil>ly1 #c millivolts repres5t #ajee ,c42 #d millivolts #aaed ,c42 & #e millivolts #abcf ,c4 ,^! values are readily obta9$ by ! use ( f\r-figure log>i?ms4 ,hav+ calculat$ ! temp]ature correspond+ to ea* :ole millivolt1 a curve may be plott$ to repres5t millivolts aga9/ correspond+ temp]atures1 & int]m$iate values d$uc$ f x4 ,evid5tly1 ! /&>d read+ mu/ be tak5 ) great accuracy1 z ! :ole scale h+es ^u x2 & = ?is purpose an accurate resi/ance or !rmo-electric pyromet] may be us$1 plac$ inside ! tube ( an electric furnace1 & ! radiation pyromet] sight$ on a ?9 %eet ( iron plac$ j 9 front ( ! nak$ junction4 ,a *eck at ! high] read+s ( ! scale is necess>y1 z an exact realisation ( ! f\r?-p[] law is seldom obta9$ 9 practice4 ,?is may be tak5 9 ! same mann]1 z !rmoc\ples may n[ be calibrat$ directly aga9/ ! gas scale up to #aeej ,c41 ?us enabl+ ! gas-scale read+ to be transf]r$ to ! radiation pyromet]4 ,= delicate read+s ov] a giv5 range1 ! scale ( a mirror galvanomet] may be calibrat$ 9 ?is mann]1 suffici5t resi/ance hav+ fir/ be5 add$ 9 s]ies to ensure t at ! highe/ temp]ature employ$ ! spot ( light w rema9 on ! scale4 ,illu/ration3 ,,fig4 #ed4--,,record ,,obta9$ ,,) ,,radiation ,,pyromet]4 ,record]s = ,radiation ,pyromet]s4--,any ( ! !rmo-electric record]s describ$ 9 ,*apt] ,,ii may be appli$ to radiation pyromet]s1 ! *>t be+ suitably divid$ accord+ to ! f\r?-p[] law4 ,:5 tak+ a record1 ! pyromet] is fix$ on a /& or bracket & focus$ on ! desir$ spot4 ,fig4 #ed is an example ( a record tak5 ) a ,?read record] & ,fry pyromet]1 9 :i* ! division ( ! temp]ature scale accord+ to ! f\r?-p[] law w be notic$4 ,x is possible to arrange t ! work+ temp]ature %all lie on ! op5 "p ( ! scale1 by adju/+ ! s5sitiv5ess ( ! galvanomet] accord+ly be=e calibrat+4 ,managem5t ( ,radiation ,pyromet]s4--,x is n advisable to place a radiation pyromet] 9 ! h&s ( an unskill$ obs]v]1 z intellig5t ov]sight is requir$ if good results are to be secur$4 ,c>e mu/ be tak5 to adju/ ! galvanomet] ne$le to z]o be=e tak+ a read+1 & ! ne$le %\ld always be lock$ dur+ transit4 ,:5 focus+ on an object 9 a furnace x is necess>y to make c]ta9 t ! r$ image se5 is actually t ( ! object1 :i* may be done by mov+ ! pyromet] until ! side ( ! object1 or "s special feature1 is visible 9 ! eye-piece1 :5 ! pyromet] may be mov$ until ! image surr\nds ! junction4 ,occasions may arise1 z 9 tak+ ! temp]atures ( v>i\s zones ( a rot>y cem5t-kiln or o!r furnace1 9 :i* x is requir$ to focus ! mirror = a specifi$ di/ance2 9 :i* case ! au?or has adopt$ ! plan ( plac+ a fix$ po9t] opposite ! mill$ head :i* controls ! mirror 7,p1 fig4 #dd7 & focus+ ! b>s ( a w9d[ at measur$ di/ances1 m>k+ ! same on ! mill$ head opposite ! po9t]2 & x w\ld be a conv5i5ce if all radiation pyromet]s 7 ?us m>k$ initially4 ,a good *eck to correct focus+ 9 ! case ( a heat$ object is to alt] ! focus 9 bo? directions1 & f9ally to adju/ to ! maximum read+1 :i* %\ld correspond to ! true focus4 ,great c>e %\ld be tak5 n to damage ! mirror4 ,if1 9 a work%op1 ! surface become cov]$ ) dirt1 ?is %\ld be remov$ by g5tle bru%+ ) a camel-hair bru% or by bl[+ air ov] ! mirror4 ,! focus+ device %\ld nev] be /ra9$ beyond its work+ limits2 :5 ^! are rea*$1 ! pyromet] %\ld be mov$ bodily until ! object c be correctly sight$ )9 ! ord9>y limits ( ! movem5t ( ! mill$ head4 ,if metallic fumes or d5se smoke int]v5e betwe5 ! furnace & ! pyromet]1 ! radiations w be imp$$ & ! temp]ature record$ w be too l[2 & 9 su* cases ! pyromet] %\ld be plac$ at ! op5 end ( a tube & sight$ ^u ! clos$ end1 :i* %\ld t]m9ate at ! spot "u obs]vation4 ,9 all cases x mu/ be borne 9 m9d t ! indications only apply to black-body conditions4 ,if a block ( /eel be sight$ inside a furnace1 & !n be remov$ to ! ext]ior & aga9 sight$1 ! ext]nal read+ w be mu* less ?an ! int]nal1 ow+ to ! inf]ior radiat+ p[] ( ! surface1 :i* n[ d]ives no assi/ance f ! furnace4 ,all read+s %\ld !re=e be tak5 :il/ ! object is /ill 9 ! furnace1 or 7z 9 tak+ ! temp]ature ( molt5 metal 9 a ladle7 a fireclay tube ) a clos$ end ins]t$ 9 ! mass may be us$1 & read+s tak5 ?r\gh ! op5 end4 ,/atem5ts are sometimes made t ! diff]5ce betwe5 ext]nal read+s & black-body read+s is con/ant = a giv5 surface1 & t ! "o may be translat$ into ! o!r2 b ?is is true only = un*ang+ surfaces1 su* z plat9um1 & seldom applies to ord9>y work+ surfaces4 ,z black-body conditions are s easy to ensure1 x is simpl] & saf] always to arrange to take obs]vations "u su* conditions1 r ?an to tru/ a relation seldom con/ant 9 practice4 ,:5 us+ a radiation pyromet] = a numb] ( furnaces1 fireclay tubes1 clos$ at "o end1 may be ins]t$ 9 ea*1 s t ! clos$ end t]m9ates at ! work+ spot1 ! op5 end be+ left flu% ) ! ext]ior ( ! furnace4 ,! diamet] ( su* tubes w dep5d ^u ! l5g? & also ^u ! make ( ! pyromet]2 9 all cases ! image ( ! clos$ end mu/ be l>ge en\gh to ov]lap ! receiv+ junction or spiral4 ,in=mation on ?is po9t c always be obta9$ f ! mak]s1 or c be discov]$ by trial ) op5+s ( kn[n diamet]4 ,:5 us+ ! pyromet] to obta9 temp]atures 9 ! int]ior ( ! tube ( an electric furnace1 su* z t illu/rat$ 9 fig4 #bi1 a solid object1 su* z a %ort fireclay cyl9d]1 or a piece ( graphite1 %\ld be plac$ 9 ! middle ( ! tube1 & focus$ on ! junction4 ,special ,uses ( ,radiation ,pyromet]s4--,= regul> use at temp]atures above #ajjj ,c4 or #ahej ,f4 ! radiation pyromet] w be f\nd to be m useful ?an in/rum5ts ( ! !rmo-electric or resi/ance type z ! latt] und]go det]ioration ow+ to ! cont9u\s action ( ! furnace gases1 :i* becomes m m>k$ z ! temp]ature increases4 ,examples ( indu/rial processes 9 :i* #ajjj ,c4 is consid]ably exce$$ are ! manufacture ( glass1 pott]y1 & cem5t1 ! treatm5t ( special /eels1 & ! ca/+ ( metals & alloys4 ,ev5 = temp]atures betwe5 #gej & #ajjj ,c4 a radiation pyromet] may be us$1 b is n s conv5i5t = ?is range z a !rmo-electric in/rum5t4 ,!re is no upp] limit to ! in/rum5t1 :i* may be calibrat$ by ! f\r?-p[] law to ! highe/ temp]ature atta9able1 t ( ! electric arc1 :i* has be5 f\nd to be #cgbj ,c4 by ! use ( a ,fry radiation pyromet]4 ,measurem5ts may !re=e be made beyond ! limits ( !rmal junctions1 su* z ! temp]ature ( electric furnaces & ( !rmit 9 ! m\ld1 & ( molt5 /eel be=e p\r+1 ?us op5+ out ! possibility ( accurate control at extremely high temp]atures4 ,!re is always a dang]1 h[ev]1 ( ! cold junction becom+ unduly heat$ :5 ne> to l>ge masses at v high temp]atures1 & s]i\s errors may arise f ?is cause4 ,two examples may be cit$ to illu/rate ! usefulness ( ! radiation pyromet] 9 practice3 7#a7 ! h>d5+ ( /eel projectiles2 & 7#b7 ! det]m9ation ( ! temp]ature ( ! cl9k]+ zone 9 a rot>y cem5t kiln4 ,9 7#a7 ! projectile is br\ght to a giv5 spot ne> ! br9k ( ! furnace1 :]e x is 9 ! focus ( a radiation pyromet]1 & :5 at ! specifi$ temp]ature is rak$ out ( ! furnace & drops into an oil-tr\gh4 ,x has be5 f\nd t a diff]5ce ( #aj ,c4 f ! /&>d temp]ature at :i* ! projectiles %\ld be qu5*$ may cause a s]i\s l[]+ ( ! p5etrative p[] ( ! f9i%$ projectile2 & h5ce a radiation pyromet]1 :i* may readily be sight$ on ea* individual %ell1 is ! be/ to use = ?is purpose4 ,9 7#b7 ! hotte/ spot may be f\nd by focus+ ! pyromet] to diff]5t di/ances up ! kiln1 &1 by tak+ a record1 any fall 9 temp]ature due to defect ( coal or air supplies1 or to excessive fe$ ( raw mat]ial1 may be detect$1 ?us furni%+ in=mation f :i* ! process may be regulat$ to ! be/ advantage4 ,at ! temp]atures prevail+ 9 su* kilns--#acjj to #adej ,c41 or #bcgj to #bfdj ,f41 accord+ to ! nature ( ! kiln--a ,fry radiation pyromet] is q s5sitive to *anges ( #aj ,c4 or #ah ,f41 & ! au?or has f\nd x to be entirely satisfactory 9 ?is connection4 ,! adaptability ( radiation pyromet]s to all temp]atures above a r$ heat1 comb9$ ) ! abs5ce ( det]ioration1 r5d]s ^! in/rum5ts ( great value1 & ! possibility ( obta9+ records is a fur!r recomm5dation4 ,! radiation me?od1 h[ev]1 is n suit$ to ! purposes ( an in/allation1 z ev5 if mirrors & junctions c\ld be con/ruct$ s z to be id5tical1 ! arrangem5t w\ld be v co/ly4 ,a *eap adaptation ( ! radiation pr9ciple1 by means ( :i* a numb] ( furnaces1 su* z a set ( cem5t-kilns1 c\ld be controll$ f a c5tre1 w\ld be ( great advantage1 & w\ld add fur!r to ! g5]al utility ( ?is class ( pyromet]4 ,,*apt] ,,vi ,,optical ,,pyromet]s ,g5]al ,pr9ciples4--,:5 a solid is heat$ to #dej ,c41 x comm5ces to s5d out lum9\s radiations & appe>s a dull-r$ col\r 9 a d>k5$ room4 ,z ! temp]ature rises1 ! lum9\s radiations become m int5se2 ! col\r *anges to a light] r$1 !n to orange1 yell[1 :ite1 & f9ally to a dazzl+ :ite4 ,attempts h be5 made to assign temp]atures to specifi$ col\rs1 & ,p\illet1 9 #ahcf1 introduc$ a table :i* purport$ to give ! relation betwe5 col\r & temp]ature4 ,! foll[+ table1 publi%$ by ,h[e 9 #aijj1 diff]s consid]ably f t ( ,p\illet1 :o _h no accurate means ( measur+ ! temp]atures he assign$ to ! col\rs3-- ,,h[e',s ,,table4 ,description4 ,temp4 ,deg4 ,c4 ,temp4 ,deg4 ,f4 ,l[e/ r$ visible 9 d>kness #dgj #hgh 0 0 0 daylight #dge #hhg ,dull r$ #eej to #fbe #ajbb to #aaeg ,full *]ry #gjj #abib ,light r$ #hej #aefb ,full yell[ #iej to #ajjj #agdb to #ahcb ,light yell[ #ajej #aibb ,:ite #aaej #bajh ,if x 7 possible = all obs]v]s to detect exactly ! col\rs to :i* ^! temp]atures ref]1 ! table w\ld be ( great utility2 b 9 practice any two p]sons might diff] 9 judgm5t to ! ext5t ( #ej ,c4 bel[ a yell[2 & :5 ! :ite is rea*$1 & becomes dazzl+1 accurate discrim9ation is impossible4 ,at ! same "t1 a tra9$ workman1 us$ to qu5*+ /eel at a fix$ temp]ature1 say #hej ,c41 acquires a high degree ( judgm5t ) con/ant practice1 & may n v>y by m ?an #bj ,c4 at temp]atures bel[ a light yell[4 ,! p]sonal equation1 h[ev]1 is too great = col\r judgm5t by ! unaid$ eye to be tak5 z an accurate guide to temp]ature4 ,a fairly close approximation1 h[ev]1 may be obta9$ by mat*+ ! col\rs aga9/ prep>$ /&>ds1 z w be ref]r$ to lat]4 ,! det]m9ation ( ! intr9sic brightness ( ! heat$ sub/ance by a photometric me?od naturally sugge/s itself z a possible means ( asc]ta9+ temp]atures by optical means1 & x w be f\nd t all ! optical pyromet]s us$ = indu/rial purposes are bas$ on ?is proc$ure4 ,! law connect+ ! int5sity ( ! :ole ( ! light waves emitt$ ) temp]ature1 = a giv5 solid1 is approximately giv5 by ,ras*'s =mula3-- x ,i#a ,t#a ,i#b ,t#b :]e ,i#a & ,i#b are ! int5sities correspond+ to absolute temp]atures ,t#a & ,t#b2 & ! expon5t #bejjj x 4 ,t#a ,h5ce at #abej abs4 ! brightness increases z ! #bj? p[]1 & at #bejj abs4 z ! #aj? p[] ( ! temp]ature4 ,?is rapid increase 9 brightness = a small rise 9 temp]ature enables small increm5ts to be readily obs]v$2 b a difficulty arises 9 practice ow+ to va/ diff]5ces 9 brightness display$ by diff]5t sub/ances at ! same temp]ature4 ,= example1 ! light emitt$ by an inc&esc5t gas-mantle1 :i* consi/s ( ?orium oxide1 is va/ly great] ?an t giv5 out by a metal1 su* z plat9um1 at ! same temp]ature2 & x is !re=e evid5t t ! lum9osity ( a sub/ance dep5ds n m]ely ^u its temp]ature1 b also ^u its nature4 ,x is possible1 h[ev]1 to obta9 indications = any sub/ance 9 t]ms ( a black body2 ?us if a heat$ solid possess$ ! same intr9sic brightness z a black body at a temp]ature ( ,t1 ! 8app>5t0 or 8black-body0 temp]ature ( ! solid w\ld also be call$ ,t4 ,all t ?is w\ld signify w\ld be t ! condition ( ! solid 0 su* t ! light radiat$ 0 equal 9 int5sity to t emitt$ by a black body at temp]ature ,t2 & to obta9 ! true temp]ature ( ! solid1 ,t mu/ be multipli$ by a factor :i* expresses ! ratio ( its emissive p[] to t ( a black body4 ,9 all photometric me?ods a /&>d light is employ$1 :i* %\ld n v>y 9 brightness1 & ) :i* ! light f ! s\rce is comp>$4 ,9 optical pyromet]s no attempt is made to measure ! illum9ation 9 t]ms ( c&le-p[]2 all t is necess>y is to br+ ! /&>d & ! s\rce to ! same degree ( brightness by suitable adju/m5ts4 ,among/ ! /&>ds employ$ are c>bon-filam5t electric lamps1 amyl-acetate lamps1 & = high] temp]atures ! c5tre ( an acetyl5e gas-flame2 ea* ( :i* is capable ( produc+ a fix$ degree ( brightness :5 us$ "u specifi$ conditions4 ,a black body1 at kn[n temp]atures1 is comp>$ ) ! /&>d us$1 ?us furni%+ a scale ( 8black-body0 temp]atures to :i* ! indications ( a giv5 s\rce may be ref]r$1 z expla9$ 9 ! previ\s p>agraph4 ,above #ajjj ,c41 h[ev]1 ! light becomes too dazzl+ to enable a prop] comp>ison ( ! /&>d & s\rce to be made1 & absorb+ glasses mu/ !n be us$ to r$uce ! brightness4 ,any col\r$ glass1 tak5 at r&om1 might n r$uce ! /&>d & s\rce equally2 b if a mono*romatic glass be us$--t is1 a glass :i* transmits light ( "o wave-l5g? only--a well-def9$ relation is f\nd to exi/ betwe5 ! int5sity ( ! transmitt$ light & ! temp]ature ( ! s\rce4 ,z optical pyromet]s are us$ = temp]atures above #ajjj ,c4 9 mo/ cases1 involv+ ! use ( su* glass1 x w be necess>y briefly to consid] ! relations betwe5 ! wave-l5g?s ( light & ! temp]ature ( ! radiat+ sub/ance1 :i* 9 all cases w be assum$ to be a black body4 ,wi5's ,law4--,:5 ! temp]ature ( a sub/ance increases1 ! enhanc$ brightness :i* results is %>$ by all p>ts ( its spectrum2 & if ! sub/ance 7 view$ ?r\gh a glass prism1 x w\ld be notic$ t e portion 0 bright] ?an be=e4 ,tak+ a ray ( wave-l5g? 1 ! relation betwe5 its int5sity & ! temp]ature ( ! 7black-body7 s\rce is giv5 by ,wi5's =mula3-- ,j c#a-e e-c#b_/,t 7#a7 :]e ,j en]gy correspond+ to wave-l5g? 2 e ! base ( ! natural sy/em ( log>i?ms2 ,t absolute 7!rmodynamic7 temp]ature ( ! black-body s\rce1 & c#a & c#b are con/ants1 ! values ( :i* may be f\nd by measur+ ,j at two kn[n temp]atures = light ( a kn[n wave-l5g?4 ,exp]im5t has %[n t ?is =mula is correct = wave-l5g?s :i* lie 9 ! visible spectrum1 b does n hold = long] waves2 & modifications ( ,wi5's equation h be5 giv5 by ,planck & o!rs :i* are ( m ext5d$ application4 ,= ! purposes ( optical pyrometry1 h[ev]1 us+ r$ light ( wave-l5g? ab\t #fe million?s ( a c5timetre1 ,wi5's law may be appli$ ) great accuracy2 & a calibration bas$ ^u ?is law agrees closely ) ! values obta9$ by o!r pyrometric me?ods4 ,wi5's =mula may be writt5 9 ! =m-- log#aj;,j ,k#a ,k#b7a_/,t7 7#b7 :]e ,k#a log c#a-e log & ,k#b c#b7log e_/74 ,?is simplifi$ expression %[s a l9e> relation betwe5 log ,j & #a_/,t2 & h5ce if ! temp]atures correspond+ to two int5sities be kn[n1 ! results may be plott$ on squ>$ pap] 9 ! =m ( a /raight l9e connect+ ,t & ,j1 f :i* l9e int]m$iate or extrane\s read+s ( temp]atures may be obta9$ = any giv5 int5sity4 ,ano!r useful =m ( ,wi5's equation1 ref]r+ to ! ratio ( two int5sities ,j#a & ,j#b1 is z "u3-- ,j#a c#b log e #a #a log - 7#c7 ,j#b ,t#b ,t#a :]e ,t#b & ,t#a are ! absolute temp]atures correspond+ to ,j#b & ,j#a ,! value ( c#b is #adejjjj1 :5 is express$ 9 million?s ( a c5timetre4 ,evid5tly1 if ! ratio ,j#a_/;,j#b & ! value ( c#b1 1 & ,t#b be kn[n1 ,t#a may be calculat$4 ,:5 is n kn[n1 z 9 ! case ( a piece ( r$ glass = :i* its value has n be5 det]m9$1 two read+s at kn[n temp]atures w e/abli% ! value ( 7c#b log e7_/1 & all o!r results may !n be calculat$4 ,examples illu/rat+ ! application ( ! =mula w n[ be giv54 ,example ,i4--,a black body at an absolute temp]ature ,t#a is f\nd to give twice ! int5sity obs]v$ at #abjj abs41 ! comp>ison be+ made ) r$ glass transmitt+ wave-l5g? #fe #aj-f cms4 ,to f9d ! value ( ,t#a4 ,apply+ values to =mula 7#c7 #adejjjj #a #a log #b log #bgahc - #fe #abjj ,t#a & #adejjjj #jdcdc #a ,t#a #jcjaj - #fe #abjj #a f :i* ,t#a #abcg abs4 ,example ,,ii4--,! int5sity ( ! radiations f a black body at #bjjj abs4 are f\nd to be equal to ^? f a giv5 /&>d1 tak5 z unity4 ,to f9d ! int5sity at #cjjj abs41 comp>$ ) ! same /&>d4 #fe #aj-f cms4 ,apply+ 9 7#c7 z be=e1 ,j#a #adejjjj #jdcdce #a #a log - #a #fe #bjjj #cjjj f :i* log ,j#a #afae1 & ,j#a #ade4 ,9 apply+ ,wi5's law to ! calibration ( an in/rum5t 9 :i* ! int5sity ( a s\rce may be measur$ photometrically aga9/ t ( a /&>d1 an electric furnace 7fig4 #bi7 may be us$1 ) a piece ( iron 9 ! c5tre1 coat$ ) oxide1 :i* gives black-body radiations4 ,a !rmo-electric pyromet] 9 contact ) ! oxide may be us$ to measure ! /&>d temp]atures1 & brightnesses may !n be comp>$ ) t ( an amyl-acetate or o!r lamp giv+ a flame ( con/ant lum9osity4 ,temp]atures correspond+ to o!r int5sities may !n be d$uc$ by calculation1 z previ\sly %[n4 ,practical ,=ms ( ,optical ,pyromet]s4--,! in/rum5ts us$ 9 practice fall "u ! foll[+ heads3-- #a4 ,! /&>d light is con/ant1 & ! int5sity ( ! light f ! s\rce v>i$ 9 ! in/rum5t until equal to ! /&>d4 7,fry1 ,le ,*ateli]1 ,wann]1 & ,cambridge47 #b4 ,! /&>d is v>i$ until equal to t ( ! s\rce1 :i* may be r$uc$ 9 int5sity if ?is exce$ t ( ! /&>d4 7,holborn-,kurlbaum1 made 9 comm]cial =m by ,siem5s47 #c4 ,! col\r ( ! s\rce is mat*$ aga9/ a /&>d col\r1 made to agree ) t obta9$ 9 a giv5 op]ation 7,lovibond72 or ! s\rce may be made to produce a /&>d col\r by a pol>is+ device 7,mesur & ,n\el72 or ! col\r ( ! s\rce is ext+ui%$ by suitable absorb5ts 7v>i\s =ms74 ,examples ( ea* type w n[ be describ$4 ,illu/ration3 ,,fig4 #ee4--;,f,,ry',s ,,optical ,,pyromet]4 ,,section4 ,illu/ration3 ,,fig4 #ef4--;,f,,ry',s ,,optical ,,pyromet]4 ,,ext]nal ,,view4 ,fry's ,optical ,pyromet]4--,?is in/rum5t 7%[n 9 figs4 #ee & #ef7 consi/s ( a telescope furni%$ ) a side-bran*1 9 :i* a /&>d lamp ,e is plac$4 ,light f ,e is focus$ ^u a piece ( transp>5t glass ,f1 incl9$ at an angle ( #de to ! axis ( ! telescope1 f :5ce x is reflect$ into ! eye-piece4 ,to r5d] ! light receiv$ f ! lamp mono*romatic1 a piece ( r$ glass is int]pos$ betwe5 ,e & ! mirror4 ,! telescope is sight$ on ! hot sub/ance1 rays f :i* pass ?r\gh a piece ( r$ glass ,d1 & !nce ?r\gh two w$ges ( d>k5$ glass1 :i* dim9i% ! int5sity to a great] or less degree accord+ to ! ?ickness ( absorb5t glass int]pos$1 :i* is r$uc$ by slid+ ! w$ges ap>t1 & increas$ by ! contr>y movem5t4 ,aft] pass+ ?r\gh ! w$ges1 ! light proce$s ?r\gh ! incl9$ mirror to ! eye-piece2 consequ5tly1 ! appe>ance pres5t$ to ! eye is t ( a field illum9at$ "o-half by ! /&>d lamp1 & ! o!r by ! hot s\rce4 ,! adju/m5t consi/s 9 slid+ ! w$ges1 by a screw movem5t1 until bo? portions ( ! field are equally illum9at$4 ,a temp]ature scale is provid$ on ! mov+ piece :i* actuates ! w$ges1 & is d]iv$ by ,wi5's equation f ! ?ickness ( ! w$ges int]pos$ :5 equality is obta9$4 ,calibration is effect$ by not+ ! ?ickness ( ! w$ges correspond+ to two kn[n temp]atures1 f :i* a /raight l9e connect+ ?ickness ) ! reciprocal ( ! absolute temp]atures may be drawn1 & a table =m$ giv+ values ( ,t 9 t]ms ( ! ?ickness ( ! w$ges4 ,! calibration may be ext5d$ indef9itely1 ! accuracy ( ! read+s dep5d+ ^u ! tru? ( ,wi5's law4 ,fry's optical pyromet] is a conv5i5t in/rum5t = occasional read+s ( high temp]atures1 comb9+ simplicity ) portability4 ,le ,*ateli]'s ,optical ,pyromet]4--,?is pyromet] 0 ! orig9al =m ( in/rum5t 9 :i* ! temp]ature ( a lum9\s s\rce 0 d$uc$ by photometric comp>ison ) a /&>d light2 & ,fry's app>atus1 describ$ above1 is m]ely a conv5i5t modification ( ! orig9al4 ,in/ead ( ! absorb5t glass w$ges1 ,le ,*ateli] employ$ an iris diaphragm to r$uce ! quantity ( light ent]+ ! telescope2 ! adju/m5t be+ c>ri$ out by alt]+ ! size ( ! op5+ 9 ! diaphragm until ! brightness ( ! s\rce agre$ ) t ( ! /&>d4 ,! int5sity ( ! light receiv$ 9 ! telescope w v>y z ! squ>e ( ! diamet] ( ! op5+2 & calibration at two kn[n temp]atures ) a giv5 mono*romatic glass enables a temp]ature scale correspond+ to diamet] ( op5+ to be comput$ by ,wi5's law4 ,le ,*ateli]'s pyromet] is a valuable implem5t = rese>* "w 9 ! laboratory1 b is n s conv5i5t = work%op purposes z ,fry's modification4 ,illu/ration3 ,,fig4 #eg4--,,wann]',s ,,pyromet]4 ,,section4 ,wann]'s ,pyromet]4--,! pr9ciple ( ?is pyromet] is ! comp>ison ( ! brightness ( a r$ ray f ! /&>d ) t ( ! ray ( "s wave-l5g? obta9$ f ! s\rce1 bo? rays be+ produc$ spectroscopically & !re=e be+ truly mono*romatic4 ,! brightness is comp>$ by ! aid ( a pol>is+ device1 result+ 9 a some:at complicat$ optical arrangem5t1 :i* is %[n 9 fig4 #eg4 ,light f a /&>d electric lamp passes ?r\gh ! slit ,s#a1 & f ! hot s\rce ?r\gh ,s#b4 ,bo? beams are r5d]$ p>allel by means ( an a*romatic l5s ,o#a1 :i* is plac$ at a di/ance equal to its focal l5g? f ! slits4 ,! p>allel beams are disp]s$ by ! direct-vision spectroscope ,p2 & !n pass ?r\gh ! pol>is+ prism ,r1 :i* sep>ates ea* beam into two beams1 pol>is$ 9 planes at "r angles4 ,a biprism1 ,b1 plac$ 9 contact ) a second a*romatic l5s1 ,o#b1 is made ( su* an angle t two fields ( r$ light1 pol>is$ 9 planes at "r angles1 "o f ! s\rce & ! o!r f ! /&>d1 are focus$ on ! slit ,d4 ,^! fields are view$ ?r\gh an analys] ,a1 & are br\ght to equal brightness by rotat+ ! analys]1 to :i* a graduat$ scale is atta*$1 ! temp]ature be+ d$uc$ f ! angle ?r\gh :i* ! analys] is turn$4 ,! calibration is effect$ by ,wi5's law 7equation 7#c7 page #agb71 ! int5sities ( /&>d & s\rce be+ relat$ to ! angle ( rotation z indicat$ by ! equation4 ,j#b_/;,j#a tan#b :]e ,j#b & ,j#a repres5t ! int5sities ( s\rce & /&>d respectively1 & angle ( rotation4 ,introduc+ ?is value into ,wi5's equation 7page #agb71 ! relation betwe5 & ,t may be %[n to take ! =m log tan a b_/,t1 :]e a & b are con/ants4 ,h5ce1 if log tan be plott$ aga9/ #a_/,t a /raight l9e is obta9$1 & h5ce by a few obs]vations at kn[n temp]atures a calibration curve may be drawn f :i* int]m$iate & extrane\s read+s may be obta9$4 ,messrs ,hadfield h introduc$ a special *>t1 divid$ s t actual read+s 9 degrees ,c4 may be tak5 directly by obs]v+ ! angle 4 ,z s5t out = use1 ! temp]ature scale is prep>$ be=eh&1 s t direct read+s may be tak54 ,z ! /&>d electric lamp w v>y 9 brightness ) repeat$ use1 means mu/ be provid$ to re/ore x to its prop] value4 ,?is c be done by plac+ a rheo/at 9 ! circuit ( ! lamp1 & adju/+ ! curr5t until ! brightness1 z view$ ?r\gh ! pyromet]1 exactly agrees ) t ( a gr\nd-glass surface illum9at$ by a /&>d amyl-acetate lamp4 ,! flame ( ?is lamp really con/itutes ! /&>d2 b z x w\ld be bl[n ab\t by air-curr5ts :5 us$ 9 a work%op1 ! electric lamp1 light$ by a portable batt]y1 is br\ght to equality & us$ = g5]al measurem5ts4 ,cambridge ,optical ,pyromet]4--,dur+ ! rec5t w> ! manufacture ( pyromet]s ( ?is type 0 tak5 up by ! ,cambridge & ,paul ,in/rum5t ,company4 ,! ext]nal =m ( ! ,cambridge optical pyromet] is %[n 9 fig4 #eh1 9 :i* an obs]v] is %[n us+ ! in/rum5t1 ! accessories consi/+ ( a #d-volt accumulator1 an ammet]1 & an adju/able resi/ance = regulat+ ! curr5t ?r\gh ! electric lamp us$ = comp>ison2 & a /&>d amyl-acetate lamp = adju/+ ! electric lamp to ! correct brightness4 ,! scale is m>k$ on a circul> disc1 & direct read+s are obta9$ f ! position ( a po9t] :i* rotates ) ! analys]4 ,by int]pos+ a mono*romatic glass to dim ! s\rce1 ! range ( ! pyromet] c be modifi$2 & in/rum5ts are provid$ 9 f\r ranges3 #gjj-adjj ,c42 #ijj-bjjj ,c42 #abjj-bejj ,c41 & #adjj-djjj ,c4 ,! ,cambridge optical pyromet] has prov$ a useful in/rum5t 9 skill$ h&s1 & has be5 f\nd ( great s]vice 9 ! /eel1 glass1 & pott]y indu/ries4 ,tra9$ obs]v]s h f\nd x possible to detect a diff]5ce ( #aj ,c4 at ! region ( #aijj ,c4 ,! adju/m5t ( ! two fields to equality1 h[ev]1 involves a judgm5t :i* v>ies ) diff]5t obs]v]s1 & 9 practice x is advisable = "o individual to be entru/$ to take all read+s4 ,illu/ration3 ,,fig4 #eh4--;,,cambridge ,,optical ,,pyromet]4 ,holborn-,kurlbaum ,pyromet]4--,9 ! optical pyromet]s previ\sly describ$ a con/ant /&>d is us$1 & ! brightness ( ! light f ! s\rce v>i$ until equality is obta9$4 ,! idea ( v>y+ ! brightness ( ! filam5t ( an electric lamp until its col\r mat*$ t ( ! s\rce1 & d$uc+ ! temp]ature f ! curr5t tak5 by ! lamp1 0 due to ,morse1 :o us$ a filam5t 9 ! =m ( a flat spiral1 heat$ by a batt]y ( ,e4,m4,f4 #dj volts4 ,?is spiral 0 plac$ 9 a metal tube & int]pos$ betwe5 ! eye & ! heat$ object4 ,! ,holborn-,kurlbaum pyromet]1 z made by ,siem5s1 is a ref9em5t ( t ( ,morse1 & capable ( read+ ov] a m ext5d$ range4 ,9 fig4 #ei1 ,l is a small electric lamp ) a hairp9 filam5t1 z %[n at ,a4 ,?is lamp is plac$ 9 a telescope1 s t ! filam5t is 9 ! focus ( ! eye-piece & is light$ by a #d-volt accumulator1 9 s]ies ) :i* is a rheo/at1 ,r1 & a milliammet]1 ,m4 ,! heat$ s\rce is focus$ by mov+ ! object-glass ( ! telescope1 & bo? lamp & s\rce are view$ ?r\gh r$ glass plac$ 9 front ( ! eye-piece1 ,d4 ,! rheo/at1 ,r1 is !n adju/$ until ! tip ( ! filam5t is indi/+ui%able f ! backgr\nd1 :i* is illum9at$ by ! s\rce4 ,if ! lamp be too bright1 ! filam5t w appe> z a bright l9e2 if dull] ?an ! s\rce1 z a d>k l9e2 & :5 equal to ! s\rce x w m]ge into ! backgr\nd4 ,:5 equality is obta9$1 ! milliammet] is read1 & ! temp]ature d$uc$ f ! curr5t tak5 by ! lamp4 ,illu/ration3 ,,fig4 #ei4--;,,holborn-,,kurlbaum ,,pyromet]4 ,,section4 ,! relation betwe5 curr5t & ! temp]ature ( ! filam5t v>ies ) ea* lamp1 b is 9 all cases repres5t$ by a =mula ( ! type ,c a bt ct#b :]e ,c curr5t1 t temp]ature 9 degrees ,c41 & a1 b1 & c are con/ants dep5d+ ^u ! lamp us$1 & :i* c be det]m9$ by mak+ a numb] ( obs]vations at kn[n temp]atures4 ,! in/rum5t is calibrat$ 9 ?is mann] by ! mak]s1 & a scale affix$ f :i* temp]atures may be read correspond+ to obs]v$ curr5ts4 ,:5 ! temp]ature ( ! s\rce exce$s t ( ! /&>d at maximum curr5t1 an absorb+ device1 ,e1 consi/+ ( two prisms ( d>k5$ glass1 ) _! reflect+ faces p>allel1 is plac$ ov] ! end ( ! telescope1 s z to r$uce ! int5sity ( ! s\rce bel[ t ( ! lamp4 ,a sep>ate calibration is p]=m$ ) ! absorb] 9 position1 & a second temp]ature scale provid$1 f :i* read+s are tak5 :5 ! absorb+ device is us$4 ,fig4 #fj repres5ts ! in/rum5t z made by ,messrs ,siem5s1 = use 9 a fix$ position1 ! telescope1 milliammet]1 & rheo/at be+ m\nt$ on an upright support$ by a tripod1 & ! curr5t obta9$ f a portable accumulator4 ,a second =m 7fig4 #fa7 is design$ = use 9 cases :5 obs]vations at a numb] ( diff]5t places are requir$1 ! rheo/at be+ m\nt$ on ! telescope1 & ! milliammet] conta9$ 9 a lea!r case provid$ ) %\ld]-/raps4 ,illu/ration3 ,,fig4 #fj4--,,siem5s' ,,optical ,,pyromet]1 ,,on ,,/&4 ,illu/ration3 ,,fig4 #fa4--,,siem5s' ,,optical ,,pyromet]1 ,,portable ,,=m4 ,! adju/m5t 9 ?is pyromet] is simple1 & ! condition ( equality %>ply def9$4 ,:]eas1 9 mat*+ ! col\rs ( two contigu\s fields1 sep>ate obs]v]s may disagree to an ext5t repres5t+ #dj ,c4 or m1 a div]g5ce ( #aj ,c4 is seldom exce$$ :5 diff]5t op]ators adju/ ! tip ( ! filam5t to ext9ction4 ,9 a special te/ to decide ?is po9t1 ! au?or comp>$ ! obs]vations ( five p]sons1 "s tra9$ & o!rs untra9$1 ) ! result t all agre$ to )9 #aj at a /eady temp]ature 9 ! vic9ity ( #abjj ,c42 & 9 ?is respect ! ,holborn-,kurlbaum pyromet] is sup]ior to o!r =ms ( optical pyromet]4 ,! cont9u\s accuracy ( ! read+s dep5ds ^u ! p]man5ce ( ! /&>d lamp1 :i* is ensur$ by ov]-burn+ = #bj h\rs1 aft] :i* ! lamp may be us$ at its prop] voltage = a long p]iod )\t fur!r *ange4 ,z us$ = occasional read+s 9 ! work%op1 su* a lamp w la/ = a ye> or m )\t v>y+ 9 brightness by an am\nt repres5t+ #aj ,c4 at a temp]ature ( #ahjj ,c4 ,:5 a new lamp is us$1 a fre% calibration is necess>y2 ! mak]s1 h[ev]1 9 su* case s5d out a new temp]ature scale ) ! lamp4 ,lovibond's ,pyromet]4--,x is possible1 by ! use ( col\r$ glasses sup]pos$1 to mat* closely any giv5 col\r2 & ,lovibond1 ^: t9tomet] = ?is purpose is well kn[n1 has appli$ ?is me?od to temp]ature measurem5t4 ,tak+ ! case ( a block ( /eel 9 a furnace1 x is possible to arrange comb9ations ( glasses :i*1 :5 illum9at$ by a /&>d light1 w give ! same t9t z ! /eel at any specifi$ temp]ature4 ,if x be desir$ to "w ! /eel at #hej ,c41 = example1 glasses are provid$ :i*1 :5 view$ by ! light transmitt$ f a #d-volt gl[-lamp1 us+ a con/ant curr5t1 repres5t ! t9t ( /eel at #hdj1 #hej1 & #hfj respectively4 ,! image ( ! /eel is reflect$ by a mirror ?r\gh "o hole 9 a brass plate1 :i* =ms ! end ( a wood5 box1 at ! opposite end ( :i* an eye-piece is plac$4 ,a second hole 9 ! brass plate receives light f ! /&>d lamp1 aft] pass+ ?r\gh ! glasses2 & ! appe>ances ( ! two lights are !n comp>$4 ,a skill$ eye c readily detect a disagreem5t 9 ! two fields correspond+ to #aj ,c42 & by introduc+ ! glasses 9 turn x c be obs]v$ :e!r ! /eel is )9 #aj ,c4 ( ! temp]ature requir$4 ,?is in/rum5t is *eap & simple1 b is obvi\sly only useful 9 decid+ a pre-arrang$ temp]ature1 z to take a measurem5t at an undef9$ temp]ature w\ld involve an unwieldy numb] ( glasses1 & absorb a consid]able "t4 ,! correct glasses to use = a giv5 op]ation are decid$ "u work+ conditions at temp]atures measur$ by a /&>d pyromet]2 aft] :i* any numb] ( in/rum5ts may be made f glasses ( ! same col\r & absorptive p[] z ^? us$ 9 ! calibration4 ,correct mat*+ is difficult bel[ #gjj ,c4 ,mesur & ,n\el's ,pyromet]4--,?is in/rum5t1 %[n 9 fig4 #fb1 consi/s ( two ,nicol prisms1 betwe5 :i* is plac$ a piece ( qu>tz cut p]p5dicul>ly to its axis4 ,light f ! s\rce1 9 pass+ ?r\gh ! fir/ ,nicol prism1 is all pol>is$ 9 ! same plane2 b on pass+ ?r\gh ! qu>tz is pol>is$ 9 v>i\s planes1 accord+ to ! wave-l5g?4 ,! col\r se5 aft] pass+ ?r\gh ! second prism1 us$ z analys]1 w dep5d ^u ! angle betwe5 ?is & ! fir/ or pol>is+ prism4 ,! analys] is connect$ to a rotat+ disc1 divid$ into angul> degrees2 & on view+ ! heat$ s\rce ! col\r w appe> r$ if ! analys] be turn$ 9 "o direction1 & gre5 if rotat$ 9 ! opposite4 ,! int]m$iate col\r is a lemon-yell[2 & ! adju/m5t consi/s 9 rotat+ ! analys] until ?is t9t is obta9$4 ,! angul> read+ is !n tak51 & ! temp]ature read (f f a table prep>$ by mak+ obs]vations at kn[n temp]atures4 ,obs]v]s may disagree by z mu* z #ajj ,c4 9 us+ ?is pyromet]1 ow+ to diff]5ces 9 eyesight & judgm5t ( ! lemon-yell[ t9t2 b a giv5 op]ator1 :o has tra9$ himself to ! use ( ! in/rum5t1 may obta9 mu* clos] results ) practice4 ,! *ief use ( ?is device is to enable a judgm5t to be =m$ z to :e!r a furnace is above or bel[ an assign$ temp]ature1 )9 limits ( #be ,c4 on ei!r side at ! be/2 & h5ce x is conv5i5t = a =eman or metallurgi/ to c>ry ab\t = ?is purpose :5 o!r pyromet]s are n 9 use4 ,a great advantage is t ! in/rum5t is always ready = use1 & has no accessories4 ,illu/ration3 ,,fig4 #fb4--,,mesur ,,& ,,n\el',s ,,pyromet]4 ,col\r-ext9ction ,pyromet]s4--,v>i\s attempts h be5 made to produce sup]pos$ glasses1 or cells ( col\r$ fluids1 :i* w h ! effect ( ext+ui%+ ! col\r ( a heat$ s\rce4 ,z an example1 ?ree cells conta9+ v>i\s dyes 9 solution may be prep>$ :i*1 :5 look$ ?r\gh1 w ext+ui% ! col\r at #hdj1 #hej1 & #hfj ,c4 respectively4 ,if x be desir$ to "w at #hej1 a diff]5ce ( #aj on ei!r side may be detect$ by a tra9$ eye2 b to foll[ a *ang+ temp]ature a l>ge numb] ( cells w\ld evid5tly be necess>y4 ,hea?cote's ext9ction pyromet]1 9 its e>ly =m1 consi/$ ( an eye-%ade 9 front ( :i* two pairs ( cells conta9+ col\r$ fluid 7 m\nt$4 ,9 br++ a furnace to an assign$ temp]ature1 obs]vation 0 made f "t to "t until a fa9t r$ image 0 p]ceiv$ ?r\gh "o pair ( cells1 :5 ! heat supply 0 regulat$ s z to ma9ta9 ! exi/+ temp]ature4 ,:5 view$ ?r\gh ! second pair ( cells1 :i* conta9$ a slightly d>k] fluid1 no r$ image 0 to be se5 at ! correct temp]ature4 ,) tra9+1 a workman c\ld control a furnace to a fair degree ( accuracy by ?is means1 b ! op]ation 0 t$i\s1 & useful only = ! atta9m5t ( a s+le temp]ature4 ,9 a lat] in/rum5t1 kn[n z ! 8,pyromike0 7fig4 #fc71 ,hea?cote employs a s+le cell ) flexible walls1 s t by turn+ ! screw-end1 ! l5g? ( ! column ( fluid int]pos$ betwe5 ! eye & ! furnace c be alt]$4 ,9 tak+ a read+1 ! furnace is sight$ & ! screw turn$ s z to increase ! l5g? ( ! column ( col\r$ fluid1 until ! image is no long] visible4 ,a direct read+ ( ! temp]ature is !n obta9$ on a spiral scale m>k$ on ! cyl9drical body ( ! in/rum5t1 ov] :i* ! screw$ portion rotates4 ,?is =ms a simple & conv5i5t temp]ature gauge = work%op use4 ,illu/ration3 ,,fig4 #fc4--;,,hea?cote',s ,,ext9ction ,,pyromet] ,,or 8,,pyromike40 ,illu/ration3 ,,fig4 #fd4--8,,w$ge0 ,,pyromet]4 ,! 8,w$ge0 ,pyromet]1 design$ by ,ald] & ,co*rane 7fig4 #fd71 consi/s ( a small telescope ?r\gh :i* a prism ( d>k5$ glass may be mov$1 & :i* is focus$ on ! heat$ object4 ,by turn+ a head ! w$ge may be mov$ s z to int]pose a ?ick] lay] ( d>k glass betwe5 ! eye & ! furnace1 & ! same op]ation causes a temp]ature scale to pass 9 front ( a fix$ po9t]4 ,:5 ! image ( ! hot s\rce is j ext+ui%$1 ! temp]ature is read f ! m>k opposite ! fix$ po9t4 ,tra9+ is ne$$ to enable an obs]v] to judge ! exact po9t ( ext9ction1 :5 x becomes possible to obta9 results ( #bj ,c4 9 ! region ( #acjj ,c4 ,on ! o!r h&1 :5 us$ by "o unaccu/om$ to ! in/rum5t1 ! read+ may be wrong by #ej ,c4 or m4 ,z an aid to ! judgm5t ne> ! ext9ction po9t1 ! h& may be int]pos$ betwe5 ! telescope & furnace1 :51 if ext9ction be complete1 no alt]ation %\ld be obs]v$ 9 ! field ( view4 ,! simple con/ruction ( ?is pyromet] is an advantage1 no accessories be+ ne$$2 & :5 us$ ) ! precautions /at$ above1 read+s suffici5tly close = _m processes c easily be obta9$4 ,managem5t ( ,optical ,pyromet]s4--,c>eful usage is ess5tial ) optical pyromet]s1 :i* are liable to get out ( adju/m5t ) r\gh h&l+2 & = ?is reason a tra9$ obs]v] %\ld be 9 *>ge ( su* in/rum5ts4 ,skill$ att5tion is equally requisite 9 tak+ read+s1 z ! mat*+ ( t9ts correctly is an op]ation :i* dem&s a high degree ( judgm5t4 ,c>eful att5tion mu/ be paid to ! /&>d lights2 if flames1 regulation to ! /&>d height is ess5tial2 if electric lamps1 c>e mu/ be tak5 n to use !m = a long] p]iod ?an necess>y1 9 ord] to increase ! useful life4 ,accumulators %\ld be re*>g$ regul>ly--say once 9 two weeks--to keep 9 good ord]4 ,sep>ate p>ts1 su* z absorption glasses1 %\ld be kept 9 a place ( safety1 z _! de/ruction may involve a new calibration4 ,x %\ld be kept 9 m9d t ! temp]atures indicat$ by optical pyromet]s are 8black0 temp]atures2 t is1 !y correspond to ! read+s t w\ld be giv5 by a black-body ( ! same degree ( brightness4 ,9 consequ5ce1 read+s %\ld always be tak5 "u black-body conditions1 ! precautions 9 ?is respect be+ id5tical ) ^? necess>y = total-radiation pyromet]s1 giv5 on page #afc4 ,9 "s special cases ! connection betwe5 ! app>5t & true temp]atures has be5 work$ out = a giv5 type ( pyromet]1 b1 ow+ to ! diff]5t emissive p[]s ( diff]5t sub/ances1 no g5]al relation c be giv54 ,special ,uses ( ,optical ,pyromet]s4--,! advantage\s use ( optical pyromet]s is re/rict$ to obs]vations at temp]atures beyond ! scope ( in/rum5ts :i* h ! work+ "p 9 ! furnace2 or to cases 9 :i* occasional read+s ( temp]ature suffice4 ,to foll[ a *ang+ temp]ature cont9u\s adju/m5t is necess>y1 involv+ lab\r1 & !re=e co/ly4 ,among/ work%op uses may be m5tion$3 7#a7 asc]ta9+ ! temp]ature ( pott]y kilns & glass & /eel furnaces2 7#b7 9 ! treatm5t ( /eels at v high temp]atures1 to :i* end ! pyromet] may be set to a giv5 read+1 & ! process c>ri$ out :5 ! /eel is obs]v$ to atta9 su* assign$ temp]ature2 7#c7 to take casual read+s :5 a numb] ( furnaces are 9 use1 or :5 a numb] ( sight+-holes are provid$1 z 9 l>ge brickmak+ furnaces2 & 7#d7 = occasional obs]vations ( ! fir+ end ( rot>y cem5t kilns4 ,z an in/rum5t ( rese>* 9 ! laboratory1 a good =m ( optical pyromet] is v useful1 z1 = example1 9 inve/igat+ ! work+ temp]atures ( electric lamps1 & tak+ obs]vations 9 electric furnaces4 ,x is a great drawback t records _c be tak5 by optical pyromet]s1 z mu* valuable in=mation c be ga!r$ f an accurate k ( temp]ature fluctuations 9 mo/ op]ations4 ,?is disadvantage mu/ always militate aga9/ ! g5]al use ( ^! in/rum5ts4 ,,*apt] ,,vii ,,calorimetric ,,pyromet]s ,g5]al ,pr9ciples4--,if a piece ( hot metal1 ( kn[n weight & specific heat1 be dropp$ into a kn[n weight ( wat] at a temp]ature t#a1 :i* rises to t#b 9 consequ5ce1 ! temp]ature ( ! hot metal1 t#j1 c be obta9$ by calculation1 z %[n by ! foll[+ example3-- ,example4--,a piece ( metal weigh+ #ajj grams1 & ( specific heat #ja1 is heat$ 9 a furnace & dropp$ into #dge grams ( wat]1 conta9$ 9 a vessel :i* has a capacity = heat equal to #be grams ( wat]4 ,! temp]ature ( ! wat] rises f #e to #be ,c4 ,to f9d ! temp]ature ( ! furnace4 ,! heat lo/ by ! metal is equal to t ga9$ by ! wat] & vessel4 ,equat+ ^!1 #ajj #ja 7t#j - #be7 7#dge #be7 7#be - #e7 f :i* t#j #ajbe ,c4 ,! above calculation1 :i* applies g5]ally to ?is me?od1 dep5ds = its accuracy ^u a correct k ( ! specific heat ( ! metal us$4 ,?is value is f> f con/ant1 increas+ z ! temp]ature rises1 & ! result w only be correct :5 ! av]age value ov] a giv5 range is kn[n4 ,! metal us$ 9 ! exp]im5t %\ld n oxidise readily1 & %\ld possess a high melt+ po9t4 ,plat9um is mo/ suitable1 b ! co/ ( a piece suffici5tly l>ge w\ld consid]ably exce$ t ( a !rmo-electric or o!r outfit4 ,nickel is next be/ 9 ^! respects1 & is n[ g5]ally us$ = ! calorimetric me?od1 up to #ajjj ,c4 ,! specific heat v>ies to "s ext5t 9 diff]5t specim5s1 b c be det]m9$ = ! ranges involv$ 9 practical use4 ,?is may be done by heat+ a giv5 weight to kn[n temp]atures & plung+ into wat]1 ! result be+ obta9$ z 9 ! =ego+ example1 t#j 9 ?is case be+ kn[n & ! specific heat calculat$4 ,f a s]ies ( su* det]m9ations1 a curve may be plott$ connect+ specific heat & temp]ature range1 f :i* int]m$iate values may be read (f4 ,illu/ration3 ,,fig4 #fe4--,,specific ,,heat ,,( ,,nickel ,,ov] ,,ranges ,,f #j ,c4 ,regnault1 :o fir/ sugge/$ ! calorimetric me?od = high temp]ature measurem5t1 attempt$ to measure ! specific heat ( iron ov] diff]5t ranges1 ) a view to us+ ?is metal 9 ! process4 ,ow+ to ! abs5ce ( reliable means ( det]m9+ ! exp]im5tal temp]atures1 h[ev]1 ,regnault's values 7 consid]ably 9 error4 ,= ! range #j to #ajjj ,c4 he gave ! av]age specific heat ( iron z #jabf1 a figure mu* bel[ ! tru?4 ,?us1 if a piece ( iron be heat$ to #igj ,c41 z measur$ by ! !rmo-electric me?od1 & dropp$ into wat]1 ! temp]ature calculat$ f an assum$ specific heat ( #jabf w be f\nd to be #abaj1 or #bdj too high4 ,! values n[ employ$ are obta9$ by exp]im5ts ) a !rmo-electric pyromet]1 s t temp]atures d$uc$ by ! calorimetric me?od agree1 )9 ! limits ( manipulative error1 ) ^? ( ! /&>d scale4 ,! accompany+ curve1 fig4 #fe1 %[s ! av]age specific heat ( nickel ov] all ranges betwe5 #j & #ajjj ,c41 & f ?is curve ! correct figure to use 9 ! calculation = any range may be det]m9$4 ,?us = a furnace betwe5 #hjj & #ijj ,c4 ! specific heat w\ld be tak5 z #jacf2 & al?\gh ! *oice ( ! value to be tak5 involves a k ( ! temp]ature )9 #ajj1 no difficulty arises 9 practice1 z x is easy to judge ?is limit by exp]i5ce at temp]atures bel[ #ajjj ,c ,9 ! mo/ approv$ =ms ( calorimetric pyromet]s = indu/rial purposes ! temp]ature ( ! hot metal may be read directly f a scale1 prep>$ 9 accordance ) ! value apply+ to ! specific heat at v>i\s ranges4 ,copp] & iron are /ill us$ to a limit$ ext5t 9 ^! pyromet]s1 b lose cont9u\sly 9 weight by oxidation1 ! scales ( oxide fall+ (f :5 qu5*$1 necessitat+ weigh+ be=e ea* te/ to ensure accuracy4 ,nickel oxidises v little bel[ #ajjj ,c41 & z ! ?9 film ( oxide :i* =ms does n readily peel (f1 ! weight may increase slightly4 ,qu>tz w\ld probably be m suitable ?an metals1 n be+ alt]$ by heat+ & qu5*+1 b does n appe> to h be5 tri$ = ?is purpose4 ,ano!r possible mat]ial is ni*rom1 :i* resi/s oxidation bel[ #ajjj ,c4 ,! weight ( ! solid %\ld be at lea/ #a_/bj ( t ( ! wat]1 9 ord] to ensure a tangible rise 9 temp]ature1 & ! !rmomet] %\ld be capable ( detect+ #a_/bj ( a degree ,c4 ,! rise 9 temp]ature %\ld n be s great z to cause ! wat] to exce$ ! atmosph]e 9 temp]ature by m ?an #d or #e ,c41 z o!rwise radiation losses w\ld h a m>k$ effect4 ,! limits ( accuracy ( ! me?od w be %[n by ref]5ce to examples4 ,example ,i4--,a piece ( nickel1 weigh+ #ajj grams1 is plac$ 9 a furnace1 & aft] heat+ dropp$ into #bjjj grams ( wat] at #aj ,c41 conta9$ 9 a vessel ( wat] equival5t #ej grams4 ,! temp]ature rises to #afbe ,c4 ,! specific heat ( nickel = ! range is #jacg4 ,to f9d ! temp]ature ( ! furnace & ! limits ( accuracy1 ! !rmomet] be+ readable to #a_/bj ,c4 ,equat+ heat lo/ by ! nickel to t ga9$ by ! wat] & vessel3-- #ajj #jacg 7x - #afbe7 #bjej 7#afbe - #ajj7 f :i* x #ieb ,c4 ,if ! error 9 ea* !rmomet] read+ am\nt$ to #a_/dj ! maximum diff]5ce 9 ! above calculation is obta9$ by introduc+ ! alt]$ values z "u3-- #ajj #jacg 7x - #afbbe7 #bjej 7#afbbe - #ajjbe7 :5 x #idd ,c4 ,! maximum error due to a possible incorrect read+ ( #a_/dj is !re=e less ?an #a p] c5t4 ,example ,,ii4--,! loss ( heat by radiation 9 transf]r+ #ajj grams ( nickel at #ibg ,c41 possess+ a surface ( #cj squ>e c5timetres1 & ) radiat+ p[] #jg ( a black body1 may be %[n by ! f\r?-p[] law to be #ej calories p] second 7see page #aci74 ,if two seconds 7 occupi$ 9 ! transf]1 ! error f ?is cause w\ld be #a 9 #acj2 & add+ ?is to ! !rmometric error1 ! total is less ?an #b p] c5t4 ,practical ,=ms ( ,calorimetric ,pyromet]s4--,:5 requir$ to e/imate ! temp]ature ( a muffle furnace or o!r laboratory appliance1 a %eet-copp] vessel ( ab\t #aejj c4c4 capacity may be us$4 ,?is %\ld re/ on wood5 supports 9 a second simil> vessel1 ab\t #b in*es wid]1 :i* acts z a %ield aga9/ radiation4 ,a cyl9d] ( nickel ab\t #a in*es long1 & #a in*es 9 diamet]1 ) a hole ( -in* diamet] 9 ! c5tre1 is suitable = te/ purposes4 ,?is may conv5i5tly be heat$ 9 a nickel crucible2 & :5 transf]r+ to ! wat] ! crucible may be grasp$ ) a pair ( tongs1 & tilt$ s z to all[ ! cyl9d] to drop into ! wat]4 ,:5 us$ 9 a tube furnace1 a l5g? ( ?9 nickel wire may be atta*$ to ! cyl9d] to enable )drawal to be accompli%$ rapidly1 all[ance be+ made = ! weight ( ! heat$ wire4 ,! transf] %\ld be accompli%$ z spe$ily z possible1 to avoid radiation errors4 ,! figure to be us$ to repres5t ! specific heat ( nickel may be obta9$ f ! curve 7fig4 #fe71 :5 ! range to be measur$ is approximately kn[n4 ,! wat] equival5t ( ! vessel & !rmomet] %\ld be det]m9$ z foll[s3--,place 9 ! vessel "o-half ! quantity ( cold wat] us$ 9 ! exp]im5t--say #gej c4c4--& note ! temp]ature 7t#a7 aft] /irr+ ) ! !rmomet]4 ,!n add an equal quantity ( wat] at a temp]ature 7t#b7 ab\t #aj high] ?an t#a ,mix ?or\ghly ) ! !rmomet]1 & note ! temp]ature ( ! mixture 7t#c74 ,*eck results may be obta9$ by v>y+ ! proportions ( cold & w>m wat]1 ! total quantity always be+ equal to t us$ = qu5*+ ! hot nickel4 ,if ,w#a ! weight ( cold wat]1 & ,w#b t ( ! w>m1 ! wat] equival5t 7x7 is obta9$ f ! equation ,w#b 7t#b - t#c7 - ,w#a7t#c - t#a7 x t#c - t#a4 ,?is figure repres5ts ! weight ( wat] equal 9 !rmal capacity to ! vessel1 & 9 a pyrometric measurem5t is add$ to ! weight ( wat] tak54 ,9 indu/rial practice1 x is desirable to disp5se1 if possible1 ) ! necessity = calculations1 s t a read+ may be tak5 by an unskill$ obs]v]4 ,! e>lie/ =m ( calorimetric pyromet]1 pat5t$ by ,by/rm 9 #ahfb1 consi/$ ( a lagg$ z9c vessel into :i* a piece ( plat9um 0 dropp$1 & a table 0 provid$ f :i* ! temp]ature ( ! furnace c\ld be read by not+ ! rise 9 temp]ature ( ! wat]4 ,! mod]n indu/rial =m1 made by ,messrs ,siem5s1 w n[ be describ$4 ,illu/ration3 ,,fig4 #ff4--,,siem5s' ,,calorimetric ,,or 8,,wat]0 ,,pyromet]4 ,siem5s' ,calorimetric or 8,wat]0 ,pyromet]4--,fig4 #ff %[s ?is in/rum5t 9 longitud9al & transv]se section4 ,x consi/s ( a d\ble copp] vessel1 ! inn] conta9+ wat]1 & ! out] provid$ ) a h&le4 ,! space betwe5 is lagg$ ) felt1 to prev5t escape ( heat f ! wat]4 ,! !rmomet]1 b1 is protect$ by a p]=at$ brass tube f damage t might be caus$ on dropp+ 9 ! holl[ nickel cyl9d]1 d4 ,opposite ! /em ( ! !rmomet] is plac$ a slid+-piece c1 on :i* a temp]ature scale is m>k$4 ,9 us+ ! in/rum5t1 ! specifi$ quantity ( wat] is plac$ 9 ! inn] vessel1 & ! po9t] on c br\ght opposite to ! top ( ! m]cury column 9 ! !rmomet]4 ,! nickel cyl9d]1 :i* has be5 heat$ 9 a crucible or muffle 9 ! furnace1 is !n dropp$ 91 & ! vessel %ak5 to secure an equal temp]ature ?r\gh\t ! wat]4 ,:5 ! !rmomet] is /ation>y1 ! m>k on c opposite ! top ( ! m]cury gives ! temp]ature ( ! furnace1 ! scale on c hav+ previ\sly be5 m>k$ f calculations made = ea* #ej degrees4 ,! correctness ( ! read+ evid5tly dep5ds ^u ! accuracy ) :i* c has be5 calibrat$1 an op]ation :i* involves tak+ into acc\nt ! wat] equival5t ( ! vessel & ! v>iation ( ! specific heat ( nickel at diff]5t temp]atures4 ,all[+ = ! s\rces ( error atta*+ to ! me?od1 results by ?is pyromet] _c be gu>ante$ to bett] ?an #b or #c p] c5t1 at #ijj or #ajjj ,c41 b 9 cases :]e ?is degree ( inaccuracy is n ( importance1 ! in/rum5t may be us$ ) advantage4 ,z no calculation is necess>y1 ! det]m9ation may be made 9 ! work%op by any workman :o ex]cises c>e 9 conduct+ ! op]ation4 ,copp] & iron cyl9d]s are sometimes suppli$ in/ead ( nickel1 b are n to be recomm5d$1 z !y decrease 9 weight ) ea* te/1 & necessitate ! use ( a multiply+ factor to conv]t ! read+ on c into ! true temp]ature4 ,special ,uses ( ,calorimetric ,pyromet]s4--,! great drawback to ! calorimetric me?od is t ea* obs]vation necessitates a sep>ate exp]im5t1 involv+ "t & lab\r4 ,! accuracy1 moreov]1 is n comp>able ) t obta9able by ! use ( a !rmo-electric or resi/ance pyromet]2 & practically ! only recomm5dation is ! l[ initial co/ ( ! outfit4 ,:5 an occasional read+ ( temp]ature1 true to #c p] c5t41 suffices1 ! calorimetric pyromet] may be us$2 & 9 special laboratory det]m9ations ! me?od w frequ5tly be f\nd ( value4 ,consid]+ ! l[ co/ ( !rmo-electric pyromet]s at ! pres5t "t1 x is probable t ! calorimetric me?od w be entirely sup]s$$ 9 indu/rial practice1 z ! =m] me?od gives a cont9u\s1 automatic read+1 & is capable ( furni%+ records4 ,_m firms h already replac$ _! 8wat]0 pyromet]s by ! m accurate & useful appliances n[ available4 ,,*apt] ,,viii ,,fusion ,,pyromet]s ,g5]al ,pr9ciples4--,if a numb] ( solids1 possess+ progressive melt+ po9ts1 be plac$ 9 a furnace & aft]w>ds )drawn1 "s may be obs]v$ to h und]gone fusion :il/ o!rs w\ld be unaffect$4 ,! temp]ature ( ! furnace w\ld !n be kn[n to be high] ?an t ( ! melt+ po9t ( ! la/ solid melt$1 & l[] ?an t ( ! fir/ :i* rema9$ intact4 ,tak+1 = example1 a s]ies ( salts1 ! foll[+ might be us$3- ,melt+ ,po9t4 ,salt4 ,deg4 ,c5t4,deg4 ,fahr4 #a molecule common salt #fej #abjb #a molecule potassium *loride ,common salt #hjj #adgb ,anhydr\s sodium c>bonate #hej #aefb 0 0 sulphate #ijj #afeb ,sodium plumbate #ajjj #ahcb ,anhydr\s potassium sulphate #ajgj #aieh 0 magnesium sulphate #aaej #bajb ,if1 on inspection1 x 7 f\nd t ! sodium sulphate _h melt$1 :il/ ! sodium plumbate _h surviv$1 ! temp]ature ( ! furnace w\ld be kn[n to lie betwe5 #ijj ,c4 & #ajjj ,c4 ,if a numb] ( salts or o!r solids c\ld be f\nd ) melt+ po9ts rang+ betwe5 #ijj & #ajjj1 x w\ld be possible to obta9 a read+ )9 n>r[] limits4 ,! accuracy ( ! me?od 9 all cases is decid$ by ! int]val betwe5 ! melt+ po9ts ( successive te/ mat]ials4 ,w$gwood1 ! fam\s pott]1 appe>s to h be5 ! fir/ to apply ?is me?od ( det]m9+ ! condition ( a furnace1 8 te/-pieces consi/+ ( special clay compositions4 ,! effect ( ! furnace on ^! 0 not$1 & ! suitability ( ! temp]ature = ! "w 9 h& d$uc$ f ! obs]vations4 ,w$gwood 9 ?is mann] inve/igat$ ! v>iations 9 temp]ature at diff]5t levels 9 8 fir+-kilns1 & 0 ?us enabl$ to place ! v>i\s w>es at ! positions be/ suit$ = _! successful fir+4 ,mod]n pott]s /ill use su* te/-pieces1 z ! in=mation ga9$ is n m]ely ! degree ( heat1 b ! effect ( su* heat on ! articles und]go+ fir+4 ,! fusion me?od1 h[ev]1 is n[ us$ to det]m9e ! temp]ature ( all k9ds ( furnaces1 & ! *ief modifications w n[ be describ$4 ,illu/ration3 ,,fig4 #fg4--,,seg] ,,pyramids ,,or 8,,cones40 ,seg] ,pyramids or 8,cones40--,seg]1 ( ,b]l91 publi%$ 9 #ahhf an inve/igation deal+ ) ! production ( silicates ( progressive melt+ po9ts4 ,by v>y+ ! composition1 he 0 able to produce a s]ies ( mat]ials ) melt+ po9ts rang+ f #ahij ,c4 to #eij ,c41 ! int]val betwe5 successive compositions be+ #bj betwe5 #ahij & #iej1 & #cj f ! latt] temp]ature to #eij4 ,! highe/ memb] ( ! s]ies has ! composition ,al#b,o#c1 ,si,o#b2 & ! l[e/ memb] #b,si,o#b1 ,b#b,o#c4 ,= conv5i5ce 9 use ! mat]ials are made 9 ! =m ( triangul> pyramids1 #e cms4 9 height1 & ea* side ( ! base #ae cms4 long4 ,ea* pyramid is /amp$ ) a di/+ui%+ numb]1 & altoge!r #fj are made to cov] ! range #ahij to #eij4 ,:5 conduct+ a te/1 sev]al pyramids are select$ ) melt+ po9ts kn[n to be ne> ! temp]ature ( ! furnace1 z discov]$ by previ\s trials4 ,^! are ins]t$ 9 ! furnace /&+ on a slab ( refractory mat]ial1 z 9 fig4 #fg1 & may be wat*$ ?r\gh a sight-hole or )drawn f ! furnace = exam9ation aft] atta9+ ! exi/+ temp]ature4 ,if ! "r pyramids h be5 *os51 ! appe>ance pres5t$ w be z 9 fig4 #fg1 9 :i* ,d is se5 to h collaps$ completely1 ,c has b5t ov]1 ,b has be5 r\nd$ at ! top1 :il/ ,a is intact4 ,! temp]ature ( ! furnace is !n tak5 to correspond to ! melt+ po9t ( ,c1 :i* is f\nd by ref]5ce to a table 9 :i* ! melt+ po9ts correspond+ to ! diff]5t di/+ui%+ numb]s are giv54 ,! pyramids are extremely *eap1 & only ^? ) melt+ po9ts ne> to ! work+ temp]ature ne$ be pur*as$4 ,9 cases :]e x is desir$ to increase ! heat to a specifi$ po9t1 & !n to all[ ! furnace to cool1 ^! pyramids fulfil all requirem5ts2 an exam9ation ?r\gh a sight-hole clos$ ) d>k5$ glass enabl+ ! furnace att5dant to discov] :5 ! requisite temp]ature has be5 atta9$4 ,! proc$ure is m difficult :5 x is desir$ to ma9ta9 a /eady temp]ature1 z ?is involves frequ5t r5ewal ( pyramids already melt$4 ,^! appliances are sold "u ! "n ( ,seg] 8cones10 ! latt] ^w be+ evid5tly a misnom]4 ,watk9's ,heat ,record]4--,?is arrangem5t consi/s ( a small block ( fireclay1 hav+ a numb] ( cyl9drical holes 9 its upp] face4 ,pellets ( mat]ials ( progressive melt+ po9ts are plac$ 9 ! holes1 9 :i* !y fit loosely4 ,! block is plac$ 9 ! furnace1 & aft]w>ds )drawn & exam9$1 :5 ^? :i* h completely melt$ w be se5 to h sunk1 & to possess a concave surface2 o!rs :i* h be5 sup]ficially fus$1 w %[ r\nd$ edges1 :il/ o!rs w be intact4 ,! melt+ po9t ( ! highe/ memb] ( ! s]ies :i* is obs]v$ to h r\nd$ edges is tak5 z ! temp]ature ( ! furnace4 ,! mat]ials us$ 9 ! manufacture ( ! pellets are approximately ! same z ^? employ$ by ,seg]1 be+ ! same 9 numb] 7#fj71 & diff]+ progressively by simil> int]vals4 ,x is n evid5t t ! me?od ( obs]vation is sup]ior to ! use ( pyramids1 al?\gh "s work]s may pref] x1 & ! arrangem5t is m]ely an alt]native plan ( us+ ! ,seg] compositions4 ,watk9 has also introduc$ a modification 9 :i* /raight b>s ( clay compositions are support$ at ! edges1 ! temp]ature be+ d$uc$ by obs]v+ :i* numb]s melt1 droop1 or rema9 intact4 8,s5t9el0 ,pyromet]s4--,"u ?is "n1 ,bre>ley1 ( ,%effield1 has introduc$ a numb] ( compositions1 *iefly ( salts1 :i* possess def9ite melt+ po9ts4 ,^! are made 9 ! %ape ( cyl9d]s1 ab\t #a in* long & in* 9 diamet]1 :i* collapse completely :5 ! melt+ po9t is atta9$4 ,compositions h be5 f\nd :i* melt at c]ta9 temp]atures kn[n to give ! be/ results 9 ! treatm5t ( diff]5t k9ds ( /eel1 & a cyl9d] ( correct melt+ po9t1 plac$ 9 ! furnace on a small di% ne> to ! /eel1 furni%es a simple & correct clue to ! atta9m5t ( ! desir$ temp]ature4 ,! exi/+ condition ( a furnace may be discov]$ by tak+ a numb] ( cyl9d]s1 hav+ progressive melt+ po9ts1 & mak+ obs]vations aft] ! mann] describ$ "u ! head+ ( ,seg] pyramids4 ,a few 8,s5t9el0 cyl9d]s are frequ5tly ( use 9 ! work%op or laboratory = o!r purposes1 su* z a rapid *eck ( a giv5 temp]ature 9 confirmation ( ! read+ ( an indicat+ pyromet]1 or 9 discov]+ :e!r a c]ta9 temp]ature has be5 exce$$ 9 a giv5 case4 8,s5t9el0 cyl9d]s h be5 us$ 9 su* a mann] z to give audible w>n+ ( ! atta9m5t ( a giv5 temp]ature by means ( a metal rod1 :i* is made to re/ on ! cyl9d]1 & :i*1 :5 ! cyl9d] melts1 falls & completes ! circuit ( an electric bell4 ,! upp] range atta9able by ! use ( ord9>y metallic salts is n s great z 9 ! case ( silicates1 b up to #aajj ,c4 metallic sulphates1 *lorides1 etc41 or mixtures ( ^!1 give results q z good z ^? obta9$ ) ,seg] pyramids4 ,/one's ,pyromet]4--,?is in/rum5t is int5d$ to indicate ! correct temp]ature at :i* a metal or alloy %\ld be p\r$1 & consi/s ( a silica tube at ! bottom ( :i* is plac$ an alloy melt+ at ! temp]ature at :i* ! mat]ial op]at$ on %\ld be p\r$4 ,a silica rod re/s on ?is alloy1 & is connect$ at its upp] end to an iron ext5sion1 ! extremity ( :i* engages a po9t] mov+ ov] a scale4 ,:5 ! alloy 9 ! silica tube melts1 ! rod falls ?r\gh ! molt5 mass & moves ! po9t] ov] ! scale1 ?us giv+ a c]ta9 indication t ! desir$ temp]ature has be5 atta9$4 ,arrangem5ts exi/ = adju/+ ! po9t] to z]o at ! comm5cem5t ( a te/4 ,fusible ,metals4--,in/ead ( clays or salts1 a numb] ( metals & alloys are sometimes us$4 ,^! are plac$ 9 ! =m ( %ort rods 9 numb]$ holes 9 a piece ( firebrick & ins]t$ 9 ! furnace1 & on )drawal ^? :i* h und]gone fusion w be se5 to h tak5 ! =m ( ! holes 9 :i* !y 7 plac$4 ,! temp]ature ( ! furnace is consid]$ to lie betwe5 ! melt+ po9ts ( ! la/ ( ! s]ies to und]go fusion & ! fir/ :i* rema9s un*ang$4 ,a s]ies ( metals ( ?is description is m co/ly ?an clays or salts1 b is m rapid 9 action1 ow+ to ! sup]ior conductivity ( metals4 ,fusible ,pa/es4--,^! consi/ ( salts incorporat$ ) vasel9e or o!r suitable fat1 & are us$ to detect ! atta9m5t ( a specifi$ temp]ature by a piece ( metal4 ,if1 = example1 x 7 desir$ to heat a piece ( /eel to #hjj ,c4 = a giv5 purpose1 a pa/e conta9+ common salt might be sme>$ on its surface be=e plac+ 9 ! furnace4 ,on heat+1 ! vasel9e burns away1 leav+ a :ite m>k due to ! salt1 & ?is :ite m>k w be visible till ! salt fuses4 ,! disappe>ance ( ! :ite m>k !re=e indicates t ! requir$ temp]ature has be5 rea*$2 & ! me?od is simple & useful 9 cases :]e a numb] ( articles are to be work$ at a uni=m temp]ature4 ,,*apt] ,,ix ,,miscellane\s ,,appliances ,expansion & ,contraction ,pyromet]s4--,mo/ sub/ances1 on heat+1 exhibit an increase 9 size1 & on cool+ return to ! orig9al dim5sions4 ,if1 h[ev]1 a *emical alt]ation occur dur+ ! heat+1 ! resultant mat]ial may be p]man5tly alt]$ 9 size1 s t on cool+ ! sub/ance may be ( less or great] dim5sions ?an be=e4 ,bo? ^! ph5om5a h be5 appli$ to ! measurem5t ( high temp]atures2 ! p]man5t %r9kage und]gone by clay be+ utilis$ by ,w$gwood 9 ! in/rum5t :i* 0 ! fir/ practical pyromet]2 ! expansion ( a solid by ,daniell1 & ( liquid by ,nor?rup4 ,bo? =ms are /ill 9 use to a limit$ ext5t1 & w n[ be describ$4 ,illu/ration3 ,,fig4 #fh4--,,w$gwood',s ,,pyromet]4 ,w$gwood's ,pyromet]4--,9 #aghb ,w$gwood introduc$ a me?od ( det]m9+ ! condition ( a furnace by obs]v+ ! contraction %[n by cyl9d]s prep>$ f a special clay4 ,! measur+ device took ! =m ( a tap]$ groove 7fig4 #fh7 made 9 two p>ts1 ea* #f in*es long1 & "o a cont9uation ( ! o!r4 ,ea* in* ( ! groove 0 divid$ into #bj equal p>ts1 mak+ #bdj divisions 9 all1 & ea* division 0 call$ #a degree4 ,! wid? ( ! groove opposite ! z]o m>k 0 #je in*1 & opposite #bdj1 #jc in*4 ,be=e fir+1 ! cyl9d]s ent]$ ! groove until ! l[] end 0 opposite or ne> ! z]o m>k2 & aft] be+ ins]t$ 9 ! furnace & all[$ to cool on removal1 ! cyl9d]s 7 pu%$ z f> z possible d[n ! groove1 :5 ! m>k opposite ! l[] end indicat$ ! condition ( ! furnace 9 t]ms ( ,w$gwood's scale4 ,! degrees 71 ( c\rse1 arbitr>y2 b ) cyl9d]s ( uni=m make a giv5 position 9 ! groove aft] heat+ always repres5t$ ! same furnace temp]ature1 & ?us furni%$ an indication m reliable ?an ! judgm5t ( a workman's eye4 ,w$gwood attempt$ to express ! divisions on 8 scale 9 t]ms ( ,fahr5heit degrees1 & by extrapolation ( results obta9$ at ! highe/ limits ( ! m]cury !rmomet]1 :]e #a degree ( contraction 0 caus$ by a rise ( #acj ,f41 arriv$ at figures :i* n[ appe> ludicr\s1 b :i* 7 accept$ = =ty ye>s4 ,z examples1 ! melt+ po9t ( silv] 0 giv5 z #dgag ,f42 ( ca/ iron1 #agigg ,f42 & ( wr\ght iron1 #bafcg ,f4--! la/ figure be+ ne>ly #aijjj high] ?an ! pres5t accept$ value ( #bggj ,f4 ,! error arose f ! assumption ( uni=m contraction ) increase ( temp]ature1 & furni%es a /rik+ example ( ! dang] ( indef9ite extrapolation f meagre data4 ,b al?\gh ! expression ( ! result 9 ,fahr5heit degrees 0 s errone\s1 ! obs]v$ contraction always correspond$ to a giv5 condition ( ! furnace1 & ! fir+ 0 cont9u$ until t kn[n to be ! be/ = ! "w 9 h& 0 atta9$4 ,! p]man5t %r9kage ref]r$ to is caus$ by dehydration ( ! clay1 & x !re=e foll[s t ?is me?od c only give uni=m results :5 exactly ! same k9d ( clay is us$ = ! te/-pieces4 ,a giv5 manufactur] might secure consi/5t indications by mak+ a quantity ( clay1 to be kept specially = ?is purpose2 b ! same contraction at a giv5 temp]ature w\ld n be obta9$ by a second obs]v] :o also _h prep>$ a quantity ( clay1 z slight diff]5ces 9 composition cause l>ge v>iations 9 ! obs]v$ contraction4 ,9 practice1 !re=e1 pyromet]s ( ?is type are n int]*angeable1 & ea* us] mu/ /&>dize = 8 own special conditions4 ,w$gwood's pyromet] is /ill us$ to a small ext5t2 its replacem5t1 h[ev]1 by ! m conv5i5t & accurate in/rum5ts n[ available is only a "q ( "t4 ,daniell's ,pyromet]4--,9 #ahbb ,daniell publi%$ an acc\nt ( a pyromet] bas$ on ! expansion ( a plat9um rod enclos$ 9 a plumbago tube4 ,"o end ( ! rod press$ aga9/ ! end ( ! tube1 :il/ ! o!r end 0 free to move1 & 0 connect$ to a multiply+ device :i* magnifi$ ! expansion1 ! increas$ movem5t be+ indicat$ by a po9t]1 mov+ ov] a dial4 ,! scale on ! dial 0 divid$ ev5ly into a suitable numb] ( p>ts1 x be+ assum$ t ! diff]5ce betwe5 ! expansions ( graphite & plat9um 0 uni=m at all temp]atures4 ,! scale 0 calibrat$ z f> z possible by comp>ison ) a m]cury !rmomet]1 ! rema9d] be+ extrapolat$4 ,) ?is pyromet] ,daniell obta9$ a value ( #bbcc ,f4 = ! melt+ po9t ( silv]1 & #cdgi ,f4 = t ( ca/ iron--results consid]ably high] ?an ^? n[ accept$1 b mu* ne>] ?an ^? obta9$ by ,w$gwood4 ,daniell's pyromet] 0 widely us$1 & its mod]n repres5tatives are fairly common4 ,plat9um1 ow+ to its co/1 is no long] us$ 9 ^! in/rum5ts1 :i* are n[ g5]ally made ) a graphite rod encas$ 9 an iron tube1 on ! end ( :i* ! graduat$ dial is plac$1 z %[n 9 fig4 #fi4 ,ano!r =m1 commonly us$ 9 bak]'s ov5s1 is con/ruct$ ) an iron rod surr\nd$ by a porcela9 or fireclay tube4 ,illu/ration3 ,,fig4 #fi4--;,,expansion ,,pyromet]4 ,! defect ( pyromet]s ( ?is type is t ! coeffici5t ( expansion ( ! mat]ials alt]s ) prolong$ heat+1 caus+ ! read+s to become errone\s4 ,re-adju/m5t 9 boil+ wat] or o!r sub/ance does n comp5sate prop]ly = ?is alt]ation1 z bo? mat]ials are n equally affect$4 ,aga91 ! read+s w be too l[ unless ! :ole ( ! exp&+ p>ts are 9 ! int]ior ( ! furnace1 9 :i* respect ?is pyromet] is inf]ior to a !rmo-electric in/rum5t1 :i* may be ins]t$ at any conv5i5t dep?1 & may !re=e be us$ = a great] v>iety ( purposes4 ,! *ief recomm5dation is *eapness2 b an expansion pyromet] %\ld nev] be us$ = "w ( precision4 ,a graphite rod 9 an iron enclosure gives m consi/5t results ?an o!r mat]ials4 ,nor?rup's ,molt5 ,t9 ,pyromet]4--,t9 melts at #bcb ,c41 & boils at #bbgj ,c4 ,x does n give (f vap\r s5sibly up to #agjj ,c41 & exp&s ) great uni=mity4 ,x is !re=e suitable = measur+ high temp]atures on ! same pr9ciple z an ord9>y !rmomet]1 & ,duf\r1 9 #aijj1 attempt$ to make a high-read+ !rmomet] by enclos+ t9 9 a silica bulb4 ,nor?rup has con/ruct$ an in/rum5t 9 :i* ! bulb & /em are ( graphite1 & ! height ( ! molt5 t9 is det]m9$ by l[]+ a nickel wire ?r\gh a gl& until x t\*es ! t91 !reby complet+ an electric circuit & caus+ a bell to r+ or produc+ a deflection on a galvanomet]4 ,! upp] end ( ! nickel wire moves ov] a scale1 :i* may be m>k$ at two suitable fix$ po9ts1 & ! scale divid$ up z 9 ! case ( an ord9>y !rmomet]4 ,! durability ( ! graphite cov] w det]m9e ! utility ( ?is pyromet]1 & protection by "s good refractory w be ess5tial to prev5t oxidation4 ,su* a pyromet] w n respond quickly to *anges 9 temp]ature1 b may prove useful 9 read+ temp]atures at ranges beyond ! scope ( pres5t !rmo-electric pyromet]s4 ,nor?rup anticipates t ?is in/rum5t may be us$ up to #ahjj ,c4 ,vap\r-,pressure ,pyromet]s4--,9 ^! in/rum5ts m]cury is plac$ 9 a /\t /eel tube1 to :i* a pressure-gauge is atta*$1 :i* regi/]s ! vap\r-pressure ( ! m]cury4 ,read+s ( pressure may be translat$ into temp]atures by calibration ) a /&>d pyromet]4 ,! range ( ^! in/rum5ts is limit$--#fjj or #gjj ,c4--& !y are seldom us$ at pres5t1 hav+ be5 sup]s$$ by m mod]n types4 ,wat]-,jet ,pyromet]s4--,9 ^! in/rum5ts wat] is pass$ ?r\gh a pipe plac$ 9 ! furnace or hot space at a def9ite rate1 & f ! rise 9 temp]ature produc$ 9 ! wat] t ( ! furnace may be obta9$4 ,an outfit ( ?is k9d entails ! provision ( a /eady s\rce ( wat]-pressure1 & ! indications c only rema9 accurate s long z ! bore ( ! pipe rema9s uni=m4 ,! calibration is made by comp>ison ) a /&>d pyromet]4 ,! drawbacks to ! me?od are its inconv5i5ce1 & ! necessity = cont9u\s skill$ sup]vision2 & 9 consequ5ce ( ^! ! arrangem5t is seldom us$4 ,pneumatic ,pyromet]s4--,attempts h be5 made to d$uce furnace temp]atures by bl[+ air at uni=m pressure ?r\gh a pipe locat$ 9 ! hot space1 & notic+ ! increase 9 ! temp]ature ( ! air4 ,9 ! ,uehl+ pyromet]1 air f ! hot space is drawn ?r\gh an op5+ ( fix$ size by means ( a /eam-jet1 :i* acts z an aspirator4 ,! op5+ is plac$ at "o end ( a *amb]1 & ! /eam-jet aspirator at ! o!r end2 & a diaphragm ) a c5tral hole divides ! *amb] into two p>ts4 ,! pressures exi/+ 9 ! two portions ( ! *amb] v>y accord+ to ! temp]ature ( ! air drawn 91 & are measur$ by wat]-gauges1 ! read+s ( :i* may be translat$ into temp]atures by calibration aga9/ a !rmo-electric or o!r pyromet]4 ,! me?od is +5i\s1 b is elaborate & co/ly2 & is !re=e little us$4 ,conduction ,pyromet]s4--,if "o end ( a rod ( metal be ins]t$ 9 a furnace1 heat w be conduct$ along x to ! portion ext]nal to ! furnace1 & a /eady condition w be obta9$ :5 ! heat escap+ f ! ext]nal "p ( ! rod1 by convection & radiation1 is equal to ! quantity conduct$ along ! rod4 ,! hott] ! portion 9 ! furnace1 ! high] w be ! temp]ature ( all p>ts ( ! ext]nal l5g?4 ,a s]ies ( !rmomet]s plac$ at int]vals 9 ! ext]ior portion w\ld %[ a progressive fall 9 temp]ature along ! rod2 & ! hott] ! furnace ! high] w\ld be ! read+ on ea* !rmomet]4 ,9 apply+ ?is pr9ciple to ! measurem5t ( high temp]atures1 a b> ( copp] or iron is pass$ ?r\gh ! wall ( ! furnace1 s t a l5g? ( #b feet or m protrudes on ! outside4 ,ne> ! end ( ! ext]nal portion a hole is drill$ to a suffici5t dep? to cov] ! bulb ( a !rmomet]1 :i* is ins]t$ 9 ! hole1 into :i* a quantity ( m]cury is p\r$ to make a metallic contact betwe5 ! bulb & ! b>4 ,! read+ ( ! !rmomet] furni%es an approximate clue to ! temp]ature ( ! furnace1 ris+ or fall+ ) correspond+ *anges 9 ! hot space4 ,a calibration might be effect$ by comp>ison ) a /&>d2 b ! me?od is only appli$ to ! production ( a prescrib$ condition1 kn[n by exp]i5ce to be atta9$ :5 ! !rmomet] read+ has a c]ta9 value--say #abj ,c4 ,*anges 9 atmosph]ic temp]ature1 or curr5ts ( air1 s]i\sly affect ! read+s1 & ! me?od at be/ is only approximate4 ,gas ,pyromet]s4--,wiborgh1 ,bri/ol1 & o!rs h con/ruct$ pyromet]s 9 :i* ! pressure ( an enclos$ gas is record$ by a ,b\rdon pressure-gauge1 ! scale ( :i* is calibrat$ s z to read temp]atures4 ,a porcela9 bulb1 t]m9at+ 9 a capill>y tube :i* is connect$ to ! gauge1 is us$ to conta9 ! air or o!r gas2 b at temp]atures above a r$ heat ! read+s become unc]ta91 ow+ ei!r to leakages or ! di/ortion ( ! bulb4 ,! mo/ suitable mat]ial = ! bulb 7alloy ( plat9um1 #hj p] c5t41 & rhodium1 #bj p] c5t47 is too co/ly to use indu/rially1 & w\ld det]iorate "u ! influ5ce ( furnace gases4 ,9 ! ,bri/ol record+ in/rum5t ! mov+ index ( ! pressure-gauge t]m9ates 9 a p51 :i* t\*es a *>t-pap] revolv+ by clockwork4 ,good results are obta9$ up to #djj ,c41 b beyond ?is ! indications are unc]ta91 & ! in/rum5t is m correctly describ$ z a record+ !rmomet]4 ,wiborgh's ,!rmophones4--,^! consi/ ( infusible clay cyl9d]s1 #be cms4 long & #b cms4 9 diamet]1 :i* conta9 an explosive4 ,:5 plac$ 9 a hot space1 ! explosion occurs aft] a def9ite "t1 ! int]val be+ less at high temp]atures ?an at l[]1 z ! rate at :i* heat is conduct$ ?r\gh a solid v>ies directly z ! diff]5ce betwe5 ! ext]nal & int]nal temp]atures4 ,! int]val elaps+ betwe5 plac+ 9 ! furnace & ! subsequ5t explosion is not$ on a /op-wat* to ! ne>e/ #a_/e second1 & f ! obs]v$ "t ! temp]ature is obta9$ f a table1 drawn up f ! results ( exp]im5ts "u kn[n conditions4 ,if ! cyl9d]s be kept dry1 an obs]v] exp]i5c$ 9 ! use ( !rmophones may secure a read+ to )9 #dj ,c4 ,joly's ,meldomet]4--,?is device1 due to ,dr ,joly1 is int5d$ = laboratory det]m9ations ( melt+ po9ts4 ,x consi/s ( a /rip ( plat9um1 heat$ by electricity1 ^u :i* a t9y fragm5t ( ! mat]ial is plac$1 :i* is view$ ?r\gh a microscope4 ,! temp]ature ( ! plat9um is regulat$ by means ( a rheo/at 9 ! circuit1 & 9 mak+ a te/ ! temp]ature is gradually rais$ until ! mat]ial is obs]v$ to become globul>1 or to fl[ ov] ! plat9um /rip4 ,! temp]ature at :i* ?is occurs is d$uc$ f ! l9e> expansion ( ! plat9um /rip1 :i* is measur$ by a micromet] atta*$ to ! in/rum5t4 ,:5 c>efully us$1 v accurate det]m9ations may be made by ! meldomet]1 ! results1 moreov]1 be+ obta9$ rapidly1 & ) ! use ( ! m9imum ( mat]ial4 ,bre>ley's ,curve ,trac]4--,?is app>atus made by ! ,cambridge & ,paul ,in/rum5t ,company1 is design$ to take a l>ge-scale record ( an op]ation :i* only occupies a %ort p]iod ( "t4 ,x consi/s ( a drum1 r\nd :i* ! record pap] is w\nd1 & capable ( rotat+ on its axis once 9 t5 or ?irty m9utes by ! aid ( clockwork4 ,atta*$ to ! arm ( ! p5 is a po9t]1 :i* moves along ! scale ( a s5sitive mirror galvanomet] to :i* a !rmoc\ple is connect$4 ,! op]ator1 by turn+ a h&le1 moves ! drum longitud9ally s z to keep ! po9t] opposite ! c5tre ( ! spot ( light1 & ?is movem5t is trac$ on ! *>t1 comb9$ ) ! rot>y movem5t1 by ! p54 ,9 ?is mann] ! l>ge *ange 9 deflection1 due to a few degrees increase or decrease 9 temp]ature1 c be record$ 9 ink4 ,?is in/rum5t is ( special s]vice 9 record+ ! critical po9ts ( /eel1 or any op]ation :i* involves delicate read+s ov] a limit$ range ( temp]ature4 ,index ,air pyromet]s1 #bai4 ,anti-vibration /& = galvanomet]s1 #dg4 ,atmosph]ic temp]atures1 measurem5t (1 #if1 #acb4 ,automatic comp5sators1 #ff4 ,b>rett1 ,sir ,w41 discov]y ( recalesc5ce1 #d4 ,becqu]el1 ,ed41 optical pyromet]1 #e4 ,black-body radiations1 #acf4 ,bre>ley1 s5t9el pyromet]s1 #bjh4 -- curve-trac]1 #bba4 ,bri/ol1 air-record+ pyromet]1 #bai4 -- comp5sator1 #ff4 ,by/rm1 calorimetric pyromet]1 #bja4 ,calorimetric or 8wat]0 pyromet]s1 #aie4 -- -- -- special uses (1 #bjc4 ,c5tigrade scale ( temp]atures1 #f4 ,clay-contraction pyromet]s1 #baa4 ,col\r-ext9ction pyromet]s1 #ahi4 ,col\r1 9 relation to temp]ature1 #afg4 ,comp>ison ( gas & plat9um scales1 #aaa4 ,comp5sators = cold junctions1 #ff4 ,conduction pyromet]s1 #bah4 ,con/ant temp]ature cold junction1 #ga4 ,contact-p5 record]s1 #hh4 8,critical0 po9ts ( /eel1 #id4 ,daniell1 expansion pyromet]s1 #b1 #bad4 ,d>l+1 automatic comp5sator1 #fh4 -- & ,grace1 liquid elem5t !rmoc\ples1 #dc4 ,day1 ext5sion ( gas scale1 #ae4 ,electromotive =ce 7,e4,m4,f47 develop$ by junctions1 #ca4 -- -- measurem5t (1 #fb4 ,expansion pyromet]s1 #bad4 ,fahr5heit1 temp]ature scale1 #g4 ,fry1 l5s pyromet]1 #adb4 -- mirror pyromet]1 #adc4 -- optical pyromet]1 #agd4 -- spiral pyromet]1 #aej4 ,fix$ po9ts = calibration ( pyromet]s1 #af1 #ag4 ,fo/]1 base-metal pyromet]1 #ci4 -- fix$-focus pyromet]1 #aeb4 -- record]1 #hb4 ,furnace1 electric tube1 #ie4 -- temp]atures1 control (1 by pyromet]s1 #hg4 ,fusible metals1 #bji4 -- pa/es1 #baj4 ,fusion pyromet]s1 #bjd4 ,gas pyromet]s1 #bai4 -- scale ( temp]atures1 #aa4 -- !rmomet]1 con/ant volume1 #aa4 ,hadfield1 effect ( temp]ature on h>dness ( /eel1 #d4 ,h>ris1 indicator1 #aba4 ,holborn-,kurlbaum1 optical pyromet]1 #aha4 ,hold5-d',arsonval1 galvanomet]1 #de4 ,holman1 =mula = !rmal junctions1 #fb4 ,h[e1 col\r-temp]ature table1 #afg4 ,indicators1 = radiation pyromet]s1 #aef4 -- = resi/ance pyromet]s1 #aah-abd4 -- special range1 #ga4 -- /&>diz+ (1 #ed1 #ajh1 #aeg4 -- = !rmo-electric pyromet]s1 #de-ec4 ,in/allations ( resi/ance pyromet]s1 #acj4 -- ( !rmo-electric pyromet]s1 #hi4 ,joly1 meldomet]1 #bbj4 ,kelv91 !rmodynamic scale ( temp]ature1 #i4 ,k[alke1 base-metal c\ples1 #cj4 ,lamb]t1 anti-vibration /& = galvanomet]s1 #dg4 ,le ,*ateli]1 optical pyromet]1 #agg4 -- !rmo-electric pyromet]1 #e1 #bb4 ,le$s-,nor?rup1 indicator1 #abb4 -- record]s1 #he1 #abg4 -- resi/ance pyromet]s1 #aae4 ,liquid elem5t !rmoc\ples1 #dc4 ,lovibond1 optical pyromet]1 #ahf4 ,l[ temp]atures1 measurem5t (1 #ig1 #acb4 ,meldomet]1 #bbj4 ,m]cury !rmomet]1 limits (1 #a4 ,mesur & ,n\el1 optical pyromet]1 #ahg4 ,morse1 optical pyromet]1 #ahb4 ,national ,physical ,laboratory1 scale ( temp]atures1 #ag4 ,newton1 rese>*es on high temp]atures1 #b4 ,nor?rup1 molt5 t9 pyromet]1 #baf4 -- pyrovolt]1 #gd4 ,optical pyromet]s1 #afg4 -- -- managem5t (1 #aib4 -- -- special uses (1 #aic4 ,paul1 base-metal pyromet]1 #ci4 -- comp5sator1 #gj4 -- radiation pyromet]1 #aee4 -- record]1 #hc4 -- uni-pivot indicator1 #di4 ,peake1 comp5sat$ leads1 #fg4 ,pivot$ galvanomet]s1 #di4 ,planck1 modifications ( ,wi5's =mula1 #aga4 ,plat9um scale ( temp]atures1 #ajf4 ,pneumatic pyromet]s1 #bag4 ,pot5tiomet] indicators1 #gc4 -- me?od = measurem5t ( ,e4,m4,f41 #fc4 ,pr9sep1 gas pyromet]1 #c4 ,protect+ %ea?s = pyromet]s1 #cd4 ,pyromet]1 def9ition (1 #a4 ,pyromike1 #ahi4 ,radiation pyromet]s1 #acd4 -- -- calibration (1 #aeg4 -- -- indicators =1 #aef4 -- -- managem5t (1 #afa4 -- -- record]s =1 #afa4 -- -- special uses (1 #afd4 ,ras*1 lum9osity =mula1 #afh4 ,recalesc5ce ( /eel1 #d1 #id4 ,record]s = radiation pyromet]s1 #afa4 -- -- resi/ance pyromet]s1 #abd4 -- -- !rmo-electric pyromet]s1 #ge4 ,resi/ance1 measurem5t (1 #ajb4 -- ( plat9um1 #aje4 ,resi/ance pyromet]s1 #aja4 -- -- indicators =1 #aah4 -- -- managem5t (1 #acj4 -- -- record]s =1 #abd4 -- -- special uses (1 #acb4 -- pyrometry1 t]ms us$ 91 #aaa4 ,rob]ts-,au/51 record]1 #gf4 ,salts1 melt+ po9ts (1 #bjd4 ,seebeck1 discov]y ( !rmo-electricity1 #c1 #bj4 ,seg]1 pyramids or 8cones10 #bje4 ,siem5s1 calorimetric or 8wat]0 pyromet]1 #bja4 -- indicator = resi/ance pyromet]1 #aah4 -- -- -- !rmo-electric pyromet]1 #dh4 -- optical pyromet]1 #ahb4 -- record]1 #ha4 -- resi/ance pyromet]1 #aad4 ,specific heat ( nickel1 #aig4 ,/&>diz+ ( indicators1 #ed1 #ajh1 #aeg4 ,/&>ds ( temp]ature1 #i4 ,/eam1 measurem5t ( temp]ature (1 #ih4 ,/efan-,boltzmann1 f\r?-p[] law1 #aci4 ,/one1 pyromet]1 #bji4 ,surface temp]atures1 measurem5t (1 #ig4 ,susp5d$-coil galvanomet]s1 #de-dh4 ,temp]ature diff]5ces1 measurem5t (1 #ii4 -- scales1 #g-i4 -- fix$ po9ts (1 #af-ag4 ,!rmal junctions1 *anges 91 #bi4 -- -- *oice ( metals =1 #ba4 -- -- ,e4,m4,f41 develop$ by1 #ca4 -- -- me?ods ( jo9+1 #bf4 -- -- us$ 9 pyromet]s1 #bg4 ,!rmo-electric circuits1 #bb4 -- pyromet]s1 #bj4 -- -- calibration curves =1 #ei4 -- -- = surface temp]atures1 #ig4 ,!rmo-electric circuits1 indicators =1 #de-ec4 -- -- managem5t (1 #ia4 -- -- practical =ms (1 #cb4 -- -- record]s =1 #ge-hg4 -- -- /&>dization (1 #ed4 ,!rmodynamic scale ( temp]atures1 #i4 ,!rmomet]1 con/ant volume gas1 #aa4 -- m]cury1 #a4 ,!rmophones1 #bbj4 ,?read record]1 #gh4 ,uehl+1 pyromet]1 #bah4 ,uni-pivot galvanomet]1 #di4 ,vap\r-pressure pyromet]s1 #bag4 ,wann]1 optical pyromet]1 #agh4 ,wat]-cool$ cold junction1 #cc4 ,wat] equival5t ( calorimet]1 #bjj4 8,wat]0 pyromet]1 #bja4 ,wat]-jet pyromet]1 #bag4 ,watk91 heat record]1 #bjg4 ,w$ge pyromet]1 #aij4 ,w$gwood1 pyromet]1 #baa4 -- te/-pieces1 #bje4 ,:eat/one bridge = measur+ resi/ance1 #ajd-aad4 ,:ipple1 indicator1 #abj4 ,:ipple-,fry1 pyromet]1 #aed4 ,wiborgh1 gas pyromet]1 #bai4 -- !rmophones1 #bbj4 ,wi51 lum9osity law1 #aga4 ,,pr9t$ ,,9 ,,great ,,brita9 ,,by ,,neill ,,& ,,co41 ,,ltd41 ,,ed9burgh4