By 1 : S. HARRISON ood W. FISHER I'liosphoriia mny Lo clctcnninrd iii iroii tine1 strrl by menus of tliu Spkkcr plioto.olcctric nlisorptinmctcr. The nictliocl cluncrilxd gives rclinblo, ro-]iroiliiciblo meiilts, nnd in quicker t l i i i i i nny of tho u a i i d chclnicnl processes. Importnnt fiirtcira wliicli coiitriliutc to its eiicccsn nru tliu rcmovnl of nny nrscnic prcmnt, ciad tho cmllloymeiit of tho ntnblu ~~Iio~~~liornnircloiiiol~li. dntc complcx for nbnorptiomctric! incwnimniunt.
The nccurntc determiiiiition of phosphorus in iron niitl steel 8nnq)lcs by niiy one of the usunl chemicul Inetllods is n tediousnnd time-coiisuniing operntion. Fiirt,hcrniore, if nrsenic is present i t niust be removed, or speciul nteps niust be tnkeii to prevent the co-precipitation of nn nrseiioinolybdntc. Most ' of the iimilnble cheiiiicnl methods nre open to severnl crrors, niid ii quicker, iiiore ncciirnte procedure is tlesirnlh This is proritled by tlie ubsorptioiiictric nietliotl herein tlcscribed. Its eniployineiit lins ulwtrys given nccurntc, reproducible results, wlicreiix uiirelinble figures hnre frequently beeii ol)tninrd by the volulnetric process. Coiifidence in this u1)sorptionietric inctliod lins ciinbletl us to use it solely in plncc of the usuiil nietliotls in the niirdysis of cust irons cult1 steels.
Of the i~l~~orptioinct~ric iintl colorimetric niethods for determining phosphorus 'iiuglicinl prefers the use of tho " niolyl)deuuiu-blue " coq)lex, whilst Bliirrny nni1 Anliley2 hnpc worked on the yellow pliosplio~~uiiacloiiioly),tlnte. Xisson3 hiis giveti the forniuln (h'H~)~~'O,,h.l~,'O,,lC;\loO, to this coinpiex, wiiicli proved t o be very stnble, sliowitig rilniost iio colour clinligc after 14 tlnys. As such stnhility is very clesirnblc for niiy nbsorptiomctric tleterminntion, n study of t,lic pliosplio.niintloiiiol3.)rlntc coinplex yns undertaken, the preliminnry cxperiiiients liciiig bnscd on illisson's work.3 The genernl principles iiiitl tecliniquc irit,rotlucetl I)y Vnuglianl for Spekkcr nbsorptiomctric determiiintioris were followed, with pnrticulnr refereiice to his use of " direct " mid " difference " mctliods iind grnpha.
As n tuiigsteii-filniiieiit Innip was usetl us source of illuniinntioli, di&rence nictliods w r e fouiitl esscntinl for ciccurncy in certnin cnses. Furtlicrniorc, owing to the spectrnl baud-width of the light trnnsniit.ted by the filter, the direct nnd difference grnplls obtitiiiecl were not, linenr, niid i t \vns tlierefore esseiitinl to tlrnw scpnrnte grnphs for erich size of cell eiiiployed. PrcZiitthiry c~~criiireir~s.-illisso~i's procedure3 was ripplied to * Inetitutu of Cliomistry loctuma, lU41 nnd IN?. * hid. E I I ~. C h ~m .