294 TAYLOR-RAPID 1\IETHOD FOR DETERMINAT'ION OF ZINC IN PRESENCE OF IRON

Keywords: 

\VOW prncticnlly unchniigetl.

~i i d c r tho conditions of the procdss a siiinll qunntity of sulpliiirous ncitl is omploycd for n short tirnc only nnd wry little sulpliuric ncid is fornied. It. would stwii tlint the ncitl nets licrc ns n cntalyscr iriduciiig n rnpid ligdrolgsis of tho ligiioiiu complex niid of n ~iro~iortioii of easily ~ttnclicd celldosc. The osy-cclliilow for tlic iiiost p r t niid the true celliilosc present nrc not srl.iously nltcretl cliciiiicnlly. I t \vo~ild sceii~ pussiblo tlint, niitlioritiw to the coiitrnry ~iot\ritlistiriidiirg, tho lignoiir coiiiplcs is cnp~ible of yirldiiig n ccrtniii ninoiiiit. of fcrtiieiitnl)lo sugar. Slioiilcl this. oii fiirtlicr study, lirovc to be tlic cnsc, it might bo Iiossil)lc to trcnt pulp wood Iiy this procrss ns n ~ircliiiiiiinry to its coiivoiuioii iiito pulp, and thtm 1)y n sc-co~~tl trcntiutmt to 1irodiico pulp fibro from the unnttnclicd msidue. Tho publislied roluiiiutric ~nutliods for tho dutcriiiiii?tioi of ziiia iii tliu 1ircsuiico of i i o ~i rctpiro u ~ircli~iiiiiur~ troatiiioiit to obtain it pure zinc solutioii. This usunll! iiicniis tho sopnrntioii of coppr, Iuatl, tin4 bisrnutlr 1): 
Iiydrogoii sulpliidu.

the Ue~inrtii~ciit of Agriculture nt ij'nsliiiigtoii Iins Iirouowiccd it to lie, i t will ntltl iiiucli to tho w n l t l i of iintioiis. I t will iiot oiily open UI) iiew fields for tlic use of iiitlitstrinl nlcoliol, but will liberate for uso nR'fOd tliu iiiillioii of Iiusliuls of ginin 11ow usctl iili in the ~iiniiiifnctiirc of etligl ~ilcoliol, !)O p r cciit. of \vliicli is useti ns II Iusury iii life niid rt~giirtlvtl hy iiiiiiiy ns n clistiiict evil iii tlio coniiiiiiiiity.

  Tlierc id little doubt tlint i n tliu origiiinl Clnsueii process tlicro wns, oiriiig to the Inrgcr ~iroportion of ncitl niid tlic prolonged nction, n iiiorc profoulitl nctioii on tlic cellulose itiid tliu ligiioiic COIII~IFS, ns well 11s Iirobnbly n sccoiidnry nctioii on the cnrl~oliydrntes ~iroducctl. 111 n luiiibor protluciiig couiitry lilic Ciirintln, nny industry t.lint cnii iitiliro wnstc wood niid give it coiiiiiicrcinl \ d u e s1ioiild receive eticoiirngciiieiit. If this l o tliu " rcvolutioiiary cliscovcry," \vliicli 



The c s c e ~s of

  Iiydroguii .qulpliiclo i Loilutl oli, uiid iron osidisctl. l'rccipittrtioii by niiiriioiiii or niuiioiiiuiii ncctntc, in tho prusciicu of niiiiiioiiiuii olilorido, tliro\vs dowii ferric Iiytlrosiclo with vnryiii; niiioutits of zinc; this is disvolretl iir ucid, untl ruprcei )i 



tntctd uuiinoiiin, t 
~i e process bciiig repented ti11

  1'11 tiltrntu is free froiii zinc. hi iiiost methods i t is irls . iicucuuary to reriiovu ~nuiigniiosu buforo cstiinntioii of ziiic Tliu prccipitirtion of ziiio suljiliide in tliu prcsciicc 



u cl1lorucotic ncid is not coiitplutu if eliloridus itre prcsoii( T ~~U H U twpurntioiis ruyuiro too inucli tiiiic, niltl ~netliotl iiivolviiig tl~cni \voro not iiscfd oii ~I I I ~~~I L C C ~I I I I ~.A ~i i o t l ~o of titrntiiig ziiic iii tho ~ircsui~cu of iroii scc~iictl, tliorc~forc u iiecosuit .Xiiu s\i'p\iido is pruL.1 '1 iitntctl whcii Iigdroguii sulphid is ~i i t s ~c diiito IL tlilutc ~ioutrul solutioii of n zinc H d t , wit tho liburittioii of ILII cquivuloiit of uoid, 
Forroue stilt idcr siniilnr conditions, nro unnffcctcd. An endeavour as made to utilisa those fncts, by

  titrnting tho frco acid icmtod with cnustic sotln, using niotliyl ornngo ns dicntor.Hydrogoti ~ulpliidu wns ndde;l to n nlixturo of zinc and DII sulplintcs, niitl normal cniistic sodn run in from a irottu ; townrds the end of the titrntiori " clots " of rrous Iiytlrosido tvcro formed wliuru tho cnustic sodn .oppcdiiito tliu liquor, wliicli did not rcndily dissolve.lie white zinc sdphide liivt obtniiicd dnrkoncd when tliu iutrnl point ~r n s renclicd.Tliu frirtlicr ndditio~~ of nliout 2-0.3 C.C. of cnustic yodn gnvo nil ulriiost blnck conting ' ferrous sulpliitle.Tho rudts i v c r ~ not sntivfnctoq-.Sotliuiii cnrboiintc \vns trird invtcntl of cn~istio sodn, itli somu success, niitl pointctl to tho possililu ntltlitioiinl Ivniitngo of tisiiig bicnrboiintc. The latter wns adopted itli inimedinte success, uiid coiicortlunt results were Iitniiird. Tlicb IISC of nictliyl orniigo ns indicntor \vus abnndoiied, lid tlic p i n t \vlit!ii nll zinc \vns lirccipitntctl nntl ferro!ls ilpliido coiiiiiiciiccd 



to bu tIiro\v~i dowi, giving n rcyisli tiocolutu colour to tile prccipitntc, wns tnlicn ns t i c uric1 oiiit

  . 


	The follo\viiig is tliu inetliod oniployed for 1110 dctcr-
	iitintion of zinc i i i solutions contniiiing ferrous nnlts,
	ulqiosiiig

tliciii to be free froni lend niid coppur-5 or 0 C.C. of the liquor aro riicnsured into

  II (Joo c.e. flnsk 0 C.C. of n sntiirntotl solution of itn~moniuni cliloritle, iicl a drop of iiietliyl orniigc solution nro ndtled, nntl the diitioii iiuutrnlised with A'/2 sotliuni bicnrboiinto. Bboiit 00 U.C. of wntur snturnted with 11 drogcii 



sulpliitlc nru t ~o d , nrid t~icii AT/? sodiuiii

  b i c n r i h t t u is run 



from It liircttc, nt first nt the rntc of nbout 2 or 3 drops per second. 'Iio COntuiits of tho flnsk lllust bo \ v d shllicll t h ' 0 U g ~l O l l ~ lie titmtion

  . Each dro of sodium bictrrboliiita ns it. ouc~ics tliu liquor gives u E ~n c ~i lirecipitatu w~iio~i instautly lissolrcu. Sliould tho blnck prccipitntu of ferrous ulpliidu iiot form, i t is it sign tlint iiisuficiciit liydrogcri ulpliidc is presoiit. Who11 tlic zinc sulpliido C 



~I I I I I I U ~O ~B o turii grey, tho

  sodium bicnrboiirrte is trddcd 111oru lowly, slinkiiig for four or five sccorids nftcr tlic ntldition if every 0.1 o x . Fiilnlly, o 



m drop will cliange the colour o it dccidcd cliocolnto, wlicn tho

  titrnt ion is finislictl. 



i C.C. of Ar/2 sodiuiii bicnrboiinto solutioii is uquivnleiit 
to b016 grin. of ziiic. The sodium bicnrboiintc solution Y nindc by dissolviiig 42 p i i s . of bicnrboiinto in wirtur tint1 tliliitiiig to oiiu litrc

  . 1110 solution is stnbh, but i t is idvisablu to titrntu n liiiowii nniouiit of zinc ulongsidtj . 



he snniplo till the oporntor bcconies nccustomd to tho !iid point, t.trkiiig the suniple to tlic sniiiu tluptli of colour. L'lic bicarboiinto solutioii is stniitlnrdised us follows :- ).15-0.28 grin

  . of ziiic is ~~~e n s u r e d iiito D 



600 C.C. flnsk, iiid 80 c.c. of snturntctl iininioiiiuiii chloritlc soliitioii iiiitl I ~O U L 0.1 grw. of furrow sulpliatu w e added. Tl~u joliitioii is ~ieutriilisccl, treirtctl with Iiydrogoii sulpiiiclo. wid titrntctl 11s tluscribctl nborc for

  tliu nctunl detoriiiinntioii of zinc. The end point is iiiorc distinot if tho ferrous aulplratu is aclded 



nbout 0.5 c.0. beforo tho finish. oiic, or

  nt tho iiiost two d r o p of sodium bicurboiinte r;olutioii cniisu n clistiiict tlrirltciiirig tlint is not innturinllg iiicrensed Iiy t l i o ntltlitioii of n fiirtliur cubic cciitimetrt*. 



111 
cnrryiiig out tho dotoriiiiiintio~i of zinc Lg this nict ~i o t ~, tiio foIIowiiig ptiiiits iiiiist ~i u noted :- (A) co~qlor, lentl, lilld bisnlutll, lllllCSS ],rcsont o d y iii trncus, Iiiust l)u rumo~ed Iiy iiiuaiis oi iron guuet or Iiytlrogoii sulpliidu

  iii ncitl soliitioii. 


	(u) lroii diould be p~csciit in tho' forrous stnte
	otlicrwisu the iioutrril poiiit, is obsoured. Hcnt irih with iron wire or HIII~IIII~OIIS ncitl sli(!udily ncconililislii~:
	this.

(a) Tho voluiiio of ~olutioii slioultl be nboiit 1. 50 0.u irftur nddiiig hydroguii sulpliidu wiitur, wliuii tho zinc in 0.1-0*3 griii. lf tho ziiie is ~irusciiL iii siiiiill cluniitit.y HILY 0.1 griii., it slinrpor o ~i t l runotion is givciii if 
t1ii \~ollllllll clous llot oscood 70 01' 80

  

e.c.(I))As iii the eiisu of iiiolit zinc titnttions, tlii coiitlitioiis slioulcl I)u 
us iit!ni* nliktt ns Iinwililtt iii sniiipli Illltl olluok tost. I London Section.

  Although dcsignad priinnrily for tlic rapid dotorminntion of zinc in ferrous liquors, tho nictliod is crrpnblo of , widor npplicntion if tlic ~)ruscribcd conditions nru ndliorcd to. Unliko niost \vcll-kiio\vn inctliods, iron rind niringnnoso A ~O not tIctriiiicntnI ; in fnct, t ~i e forinor is neeesanry. 1 i JlCCfiJlg held crt ~Irr~ilrrJloiL f!ousc, OIL ~foilduy, A'otwiibcr Id. c1lcc.t uf vnrioiis nrotnls on thu zinc nssny : 



ITIIO fo~~o\siiig uspbriiiicnts 
\vcre inride to s ~i i n v tIiv ! 1 w0n.

  
	.__ Wcirht of zinc tiLkCll. -_ . . . .	. . . -lroii. 1 51:111. .......... gn11esc.	........	I	-..........	I	-.
	ynaa. 0.05						
	0.25						
	0.45						
	n.ifr						
	U.15						
	0.16						
	(I. 1 I ,						
	0.15						
	0.15						
	W1U						
	0.10						
	0.10						
	0.10						
	0.01						
	.....
294 TAYLOR-RAPID 1\IETHOD FOR DETERMINAT'ION OF ZINC IN PRESENCE OF IRON