twice recrystnllised from hot ivntcr. Found C28.7, H 4.8, Zn 2G.8yo ; cnlculntnl for zinc lactate, C 29.6, I1 4.1, %II 26.9%.

The iirJlitciice of pfZ ojt /c.r/itre.-Ati ncid, cheesy tnste nnd n clinrncteristit: testurc \vcrc noticen1)le in n scrnnible ~vlien tlie 1'11 of tlic s:irnplc ivns roughly i nntl Iicc:inic incrensingly nppnretit :it lower $1 viiliics. A norniiil tcsturc could l ie obtnincd by iidjustitig the p I i of the reconstituted liquid to iibout 8.6 1)y t.lic ntltlition of caustic s o h Idore scrnnibling. Tliis treatnicnt iilso iinprovcd tlie flavour : for csnniple, tlic iliivour score4 of t h e ncitl snniples ivns incrciisctl froni 3 to 6. The iniprorcincnt wns, Iio\vever, liniitcd to the removal of the acid tiiste n i d the scr;uiililcs still lind nn un- pliwritnt ofi-flnruur. Th:it tcstiire wis n function of pH wis con- firnictl by niGling liyclrocliloiic iicid to a xiontin1 reconstituted snniplc until thc 1'11 wis 6 . 5 ; the scr;iuil)lc prcpnrel froni this niixtiirc hntl tlie siitiie chmncteristic tcst,urc :is tlic ncitl coniniercinj sniiiplcs.

coitiiiiercid scfijiplcs nJ low $1 n d hi!gh F.F.d. coii/c)tt.-ii few coiiinicrciiil R I I I I I ~ I C S of tlrictl egg of low pH were found to coiitnin lnrgc nnioiints nf F.F.:\., e.y., t,he ncitlity of tlic ctlicr cstrnct wns iis high ils 65 nil. .hilyscs of two sucli sninplcs :ire quoted below ; tlicse snniplcs had not I~ccit stored nt high tcnipcrntiircs.

nil. 0.OSs-SnOEt . Lnrtic

Iodino i r r P. Volntile ncitl. rnlue c t G r esirnct neitls % pli 83.3 $2.7 0.40 0. I7 4.71 83.1 54.8 0 * 43 0.16 5.76

Siiniplcs of high F.F.X. content, unlike tliosc of high lnctic acid content,, usunlly contniticd increiiscd niiiouiits of ortliopliosplintc nntl'ncid-soluble phosphorus, probnblg the result of tlie hydrolysis of phosphoric ester litikiigcs. Hydrolytic chniiges of this nature niny Iiiive lielpctl to lower tlie pIi.

DISCUSSION If rnnrloiii nniounts of cnrboti tlioxidc were lost during drying, the

pH of different siiinplcs of freslily-dried egg would wry from nbout 7.8 to 9*nnJ n1)ot-e. During spray-drying, however, iipprosinintc equilibriuin nppenrs to be reached between the b u h systems of the egg nntl t,lic sninll ntiiouiit of cnrboii diositlc present in nir. Consequently, tlie pH of fresh, cnrcfully-preperctl niiiterinl slioas little-virriiition.

During storngc tlie p€I tlecrcnscs, bu t uiilcss tlic nnter content of the dried egg niid tlie tenipcrnt.urc of storage lire high there is only 11 simll clinngc even nftcr long periods. Tlic chniigc in p H runs pnriillcl wit.li cliniigcs in t,lie content of F.F.A. nnil ortliopliosplintc.

Coinnicrcinl snniplcs of 'dried cgg of pIi lcss tlinii i wcrc found to cotitsin reliitively lnrgc irniounts of lnctic iicitl or to Iiiivc sun'crctl extensive hydrolytic breitkdowii. Tliese sniiiplcs w r e of normnl wnter content nntl I~ i i t l not Iieen stored n t high tenipcratiircs. Tlic defects coiiltl not lie rcproducctl by storing nit~terinl prepired froni tiorinn1 pulp.* In t,hcso storiigc ex1)erinieiitu tlic lnctiu iicitl con- cetitrntioii tlitl'not change nlitl nltliongli the F.P.A. content incrcrisetl, it litis previously been pointed out5 tlint the rntes of increciso nre too sninll to iiccount for t.lic ltirgc nniouiits found in sonic coiiitiicrcinl sninples. I t is true tlitit snniplcs of pH lcss thwi 6.5 h i i w been produced espcritnctitnlly (Tiiblc \'I), but tho wiitcr content of tltcse saiiiples wits nbiiortniilly high iititl tlte tcnipernture of stornge w n s 37".

The niost probnblc csplninit~ioii of tlic low pH of sonic coniiiicrcial sntnplcs is Iiiicterinl spoilage. Tlic results obttiinetl t lo not show wlictlicr t h c t postulntetl spoiltigc occurred Idore o r id'tcir drying. 1Tiiiisud cltiiiigcs iniiy occur in tlrictl ninieritil contiiiiiing Iiirge niuii1it:rs of tiiicro-or#ciiiistiis nntl tlicir iicrontpiiiiying cnzyine systeins; Ilot the fortiier iiltcrntrtivc is inore probable. It should be iiiciit.iouet1 tlint the predotnin;int bncterinl strnin fountl in these nt id other sniiiples of clrietl (!gg is cn~inlile of producing i n c h acid.

* (.'t,uiniin~iiii qiriiy-ilriril egg i H olirn prqinrcil frmi II niisturii of fresh n1i11 ~~IJ/.CII 1i i i I I i . Siiniplrn propwed frum niisturca iwiitiiiniiig iip to lUtYj& uf frozun 1ni111 I i i i w Iircri usntniiiotl but only II fuw coiitniiiril iiiinuriniil ~ i ~ ~ ~ u i i ~ i t a of liictiu w i d : tlio iitio of fruron piilp is tl iuii nut rcaliunwiblu fur tlic low pll of somo tillm~lles.

JIcssrs. II. 1'. Hnlc nncl 11. F. Davis cnrried out the nnnlyses mid were rcsponsiblc for t.he npplicntion of tlte incthotls to tlie piirticulnr problctiis cticoutitered in the course of this work.

The work tlcscribecl nl)ovc wiis cnrrictl ont as part of tlie pro- grnninic of the' Food Invcstigntion 13oiird. I t is ~~ul~lisl ietl by per- tiiission of tlic I)cp:irtnient of Scientific and liidustrinl Resenrcli.

Low Teinperntitre Stntion for Rrscnrcli in 13ioclicniistry nntl I~iopliysics,

C;inil)ritlgc

DRIED EGG. VI. THE WATER RELATIONS OF DRIED EGG By R. CANE

Tll'c rrntrr relntioiis of clrictl aliole egg Iinvc IJC~II iletcrn~iiiecl nt t cnqrm- tiirea of 10". :lie, UO", nnil SOo c. over tlie riuigo of Iinmiclity 0 ' 0 3 4 ' 7 0 . From t h o dntn i t is posiblo t o e ~ t i ~ n n t o tho wntcr content of dried egg in eqnilibrioni with Iiuiiiiclitics nt ntiy tcnipcrnturc likcly to I ~ C encountered i n iioniid comincrrinl storngc. Tho ilntii nlso rrlntc wntcr content t o tho tctiqiernturo inid Iiinniility of 1110 iiir in conimerrinl drviiig plntitn. IIcnnturntion of tho proteins, by Iierttilig prior to drying. II:M 6n1y R slight cfFect on tho wnter rclntipna of the dry product. Wiu mcthod of drying (alirny-drying. or drying in tho frozen state) cloos not tierioouly nltor tlio water relntioiis,. Tho bclmviour of clricd ~rliolc egg is dircctly proportionnl to, nntl cnn be cnlrulntecl from, tho rclntiro nnlounts of white nnd yolk pcscnt in thc mixture. Siiice the intc of detcriorntion of dried egg is dctertnined by its

wnter content nnd thc tenipernturc of stornge' i t is importnilt-to know under wlint conditions the wntcr content niny chnngc. WCh cotitniiiers thnt Lire not tiioistureproof there will I)e a. transfer of wnter viipour to or froni the dried egg, depending on the difference in prcssurc of water vnpour inside niid outside the pncknge,. and 'on its pcrnicaliility. It is clenrly R n i n t h of i ~ n p o r t ~ n c c to estnblish tlie relntiotisliip bctwccti water content and rnpour pressure of water (or equilibrium relntivc Iiuiiiidity) in the ninterinl over the rnnge of conditions likcly to be ciicouiitcrerl in storiigc ; by mnlring iiieiisiireiiicnts at the tcnipcrntures used in tlrying plnnts the uscfulticss of tlie dntir is considcrnbly cstended.

Whilc most of the dotn gircti refer to spmy-dried whole egg, sonic observations arc given on white niid yolk dried sepnrntcly (n),ly spray tlrying,%nd (b) by drying in the frozen stnte, and (c) cooked egg white nnd egg yolk nlso dricd in the frozen state.

All tlic dried product.^ used for tlie niensurenients were freshly prepnrctl itt tlie 1iibor;itory. Tlie s p y - d r y e r used wns nn esperi- nicntnl one, siiiiilrir to thnt clescribed by Wnite,? with nn otonliscr Iinving n jet 0.76 inin. in tliiinicter i i i id n pressure of 7 Ib. per sq. in. on I)ot,li t.lic Iiqnitl i i n i l tlic iiir supplies to the ntoniiscr. Tho tctnpcrntures of tlie nir iit the inlet nnd outlet of tlic dryer mere 100" nncl ti0" c. rcspcct,ively.

Drying in tlic frozen stntc \vns ciirried out in ;in appiirntus similar to t.liat c1cscril)cd by C;rcnws nnd i\tlnir,3 in which tho nintcrial was rnpitlly frnzcii i n 1-2 minutes, rind tlrictl nt 11 tclllpernturc of about -40' c. until irbout sOo/, of tlie wnter hiid been .relnoved,, nfter which t,lie tctnperuturc rose quickly to n tiinxiniunl of +30° c. at tlie conipletioti of tlic drying period.

JIcthorl nf ildcriiiiit iiig wdcr re1dinit.e This hns been described in dctnill : r i d consisted of exposing

\wiglieti ~t~ni~iIcs, i n t.Iiiri tiiycrs, to iiir of knowvli hut id i ty Ittitif the wetglit becnnie constiiiit. l"ic sniiiplcs re~niii~ied in tlic Iiuinidity clininlrcrs, n t consttint, tcnipcrciture, while the wighitigs were niade. Otic or other of tho following nicthorls \YLIS itscd : (i) 11 ~ n t n l ~ l a was

* dried otit o \ w pliosphorus pelitoxide a t 90' u., niid then cquilibruted to tlilTerent Iittiiosphcres in n series of stiigcs of incrensing huinitlities 1111 to n iitiisittiitni of 0.80 (SOYo scitnriitiotl) n 1 ~ 1 'tlum II scriw of

llncc'Lliornu, i / id . . 135.

llrccirril Scptembrr 17. 1013

1 lJnte.Sniitli, Ilruiilt~. iind lliiwtl~urni~, J.S.C.I., 11)1:1, 62, 1B7.

9 Cllelll. s: 1lll1.. LUW, (15% 3 .I. Hyyieiw. I!U!B, 39. 413. 4 annc, .I.S.C.I., 11M1, 80.44.

decreasing humidity down to 0.00 (over phosphorus pntoxide) ; the wnter content nt each humidity was cnlculated from the change in weight; or (ii) samples were exposed to known conditions of temperature and humidity until equilibrium (constnnt weight) wns rcnched and the wnter content of ench snniple was determined by drying for 24 hours in on nir oven nt 102".

The first method was used for detailed exominntion, e.g., effects of hystcresis, nnd the second method, n more rnpid and more convenient one, when dntn werc obtained on tlie behnviour of dried whole egg over n wide rnnge of conditions of temperature nnd humidity. The usc of this cmpiricnl method niny give n constnnt difference in tlic vnlucs quoted as wnter contents by comparison with other methods in USC, e.g., G hours at 103", the conditions more geriernlly cniploycd in this lnborntory, or tlie toluene distillation method of Tntc nnd Wnrren.6 The difference is so small. as not seriously to nffect tlic vtrlidity of the dntn.

RESULTS AND, DISCIJSSIOS Spray-dried whole egg.-Tlic series of curves given in Fig. 1 arc

strict,ly npplicnhle only to tlic mnterinl used in the esperinient nnd to nny similar product, e.g., one with nn initial water content of 2.6% (2-7 g. of wnter per 100 g. dry .weight). A different product

I 0'10 0'20 0'30 U-4b U.80. U'LO u.70

R.H. Fia. 1

agninef rclafire hroiridily

niny have a grentcr or less humidity tlinn that of tbc experimental mntcrinl n t n given wuter content but the difference will rnrcly exceed hO.05, nnd the dntn will serve for most prncticnl purposes. These wnter contents were determined by drying in on OVCII.

As tlie tenipernture of storage of egg powder is increnscd tliere is nn incrense in tlie nctivity of wnter, mensured ns tlie equilibrium relntive humidity, wliicli will linvc n innrked influencc on , the renctions tnking place. This effcct of tempernturc is more pronounced nt tlic higher wnter contmits und nt temperatures nbovc 37" 0. thnn in the rnngc 10-37' c., as slioan by the curves in Fig. 2, where the dnt4 lire plotted ugriinst tcnipcrature.

The curves for tlie \niter rclntions a t GOo C. (1.10' F.) and 80" c. (176' F.) niny be of interest to tlic operntors of spmy- nnd other dryers, by shoring the equilibrium, nnd therefore tlie iiiiiiintmn water content of the prod!xct, for oily givcn conditions of tenipeniturc nnd huniidity of the outlet nir ; thus, with the outlet nir u t 176" Y. mid 50% snturirtcd, the water content of tlie powder will be nbout 4.5% (4.7 g. per 100 g. dry weight). From the curves in Pig. 2 the vnlues a t interrnedinte humidities and tempcrnturcs cnn bo cstimnted.

Spray-dried egg while arid egg yolk.-Tlic dutn given in Tnble I show thnt, under the snmc conditione of temperature and humidity, the equilibrium wnter contents of egg yolk ure much lower thnn

1)'atcr relafioiio of apraydried egg at dijjercat fctiiperafiirea. Wafer cosfcnl

' Anulyst, 1930, 61, 307.

those of egg white. This is probnbly due to the presence of " inert " fnt ; if the vnlues for egg yolk are expressed on n " fat-free " basis (nssuming 63% of fat, the wnter content of which can be

I 1

* 10

0 10 20 80 40 5J LO 70 RO TClllll. (" C.)

FIO. 2

ugrcinsl ftmpcrafrtre

neglected), then the r e s i i l t p e nenrly identical with those for egg white, Showing thnt the protein nnd snlts of egg yolk have nlmost the snme wnter relations as those of egg white.

* \ .TADLE I

ll'ufer rrlations of spraydried egg at different lctnpcrufrrrea. i!'ater content

i l 'akr relafioiis at 10" o., of apruydricd egg iuhife ond egg ydP \Vliito . ' Yolk

\\'ntcr contcnt, g. por 100 K. of: Humidity 3Iaterinl Dry at. . Material Dry st. Fnt-free

dry wt. 0.00 0.05 3.0, 3.7, 1 *G, 1.G. 4.3, 0.10 8.0, 6.9, 1.0, 1.7, 4: G, 0.20 0.8, 7.3, ..-.lo o r 2.5, 0.9, 0.30 8.4, 9.1, 3.1, 3.2, 8.8, 0.40 10.6, 11.8. 0.50 0.60 0.70 0.80 0.00 0.40 0.20 0.00

vator colltullt

Initial

11.8; i w , 18.0, 22.4,

1 1 .o, 8.2,

16.7,

0.0.

13.4;

21.0, 28.0, 18.0,

9.0,

17.1,

13-G,

0.J8

4.3, 5.0, 0.9,. 9.1, 0.1, 4.4, 3.1,

2.0,

4.5, 5.9, 7.4,

10.0,

4.7, 0.G.

3.2,

2.0,

12.1, 16.1, 20 27.2, 17.7, 12.7. 8.7,

The effcct of hysteresis can be seen if thc two water contents at ench of tlic humidities 0.20, 0.40, and 0-GO are compnrcd; when equilibrium is nppronched from n lower wnter content the value is less thnn thnt obtnined when equilibrium is nppronched fruni n higher water content. If the two humidities corresponding to n given wntcr content nrc compnrcd it will be seen thnt they do not differ by more thnn 0.09 where the difference is grentcst, is., u t a wntcr content of 12 g. pcr lo0 g. dry wt., and by only 0.01 nt a wtrter content of 5 g. per 100 6. dry weight, so that the datn given in Figs. 1 trnd 2 can be applied to commercial egg powdcre without serious error.

Egg d d e and qg-yolk dried in the frozen stafe.-JVIien fresh egg yolk nnd egg white ore dried in the frozen state there is very little likclihood of tlie proteins being denntured by drying. The water relntions of these dried products nre given in Table I1 ; when the vnlues are compnrcd with thoso in Tnble I it is clenr thnt the method of drying hns u negligible effect on the wntcr relntions of dried egg.

Humidity

0.00 0.05 0.10 0.20 0.30 0.40 0.lX 0.00 0.70 0.80 0.70 0.00 0.50 0.40 0.30 0.20 0.10 0.05 0.00

wnter contcnt

Initinl

Raw Whit0 I Yolk

Water content, g. p r 190 g. Matcrinl Dry wt. I Material Dry wt. ~~~~

I

Cooked \Vhite I YOU(

Wntcr content, g. per 100 g. Mntcrinl Dry art. 1 Mntcrinl Dry wt. Fnt-frw d r y a t . ,

I 4.2, 4.4, 5.0, 5.3, 0.0, 7.1, 8.0. 0.4.

'

10.3; 11.5: 12.3, 14.0, 14.4, 10.8, 17.6,- 21.4, 22.7. 20.5..

3.4, 4.3, 0.4,

0.7, 11.4, 13.3, 10.1,

14 5, 12.7,

wn, 8.1, 0.2, 5.1,

8 . 0 -i

20.5, 1'1.0,

11.3,

18.0; 22.8; 15.5, 184,

10.0, 11.1, 8.1, 8.8, '

6.1, 6.5,

13-5, 15.0, 11.0, 13.2,

5-2, 5.5,

1.3, 1.0, 2.4, 3.4, 4-2, 5-0, f3*21 7*7b 0.0, 7.a1 0.4, G-4 , 4.5, 3.0, 3.1, 2.4, 2.0,

1'3, 1.0, 2.5, 3.8, 4.4, 5.3, 0.0, 8-4,

11 '0, 8.4, 6.8, 5.7, 4.7, 4.0, 3.2, 2.5, 2.1,

3.7, 4.4, 6.7, 0.7.

11.0, 14.4, 17.8, 22.8, 20. 0, "2.0 18.5, lG.JI 12.7, 11.0, 8.8, 0-7, 5-6,

3.5, 4.6, 0.8, 8.4,

10.8, 12.9,

10.3. 25.8, 20.5, 17.0, 14.0, 12.7, 10.0, 8.0,

6.4,

16.4,

6.0,

1.2, 1'5, 2.3, 3.2, 34, 4.8, 5.7, 0.0, 8.0, 7.1,

5.2, 4.4, 3.8, 3.2, 2.4, 1.8,

6.1,

1.2,

2.4, 3.3, 4.1, 6.0, 0.1, 7.5, 0.8, 7 4, 11.5, 5.5, 4.7, 4.0, 3.3, 2.5, I 'H,

1.6, 3 4 , 4.3,

0.0, 11.0" 13.7, 10.6, 20.2, 26.5, 20.7, 17.5, 15.0, 12.7, 10.H, 0.0, 0.8,

8.5,

5.0,

bennturntion of the protein tins only n slight Hcc t on tile wnter relntions ns shown by the values given in Tnble I1 for cooked egg n-hite nnd egg yolk nlso dried in the frozen state ; this is surprising in view of the considerable chnngcs thnt dcnnturution produces in other propertics of the proteins. It is significont thnt, while over- henting during drying niny produce mnrked effects on the quality of the product, i t is unlikely thnt the wnter relntions of the powders will be nffected to nny grent extent, except where conditions of drying nre so severe ns to produce decomposition products by charring.

From the rntio of the solid constittictiti of yolk and white ns found in whole eggs, nnd their sepurntc wnter rehtions, i t should be possible to cnlculntc the wntcr relations of the mixture if there is no disturbing internction when mixed. Dried whole egg consists of 69.6% of solids from tlic yolk nnd 30.4% of solids from the white, and the cnlculnted wntcr relations of such n mixture nre given in Tnble 411, where the experimentnl vnlucs for dricd wliole egg nre giycn for comparison. The agrcerncnt is very good, ant1 is better than would be expected from the nssuniptions ninde.

Tnnm 111 '8 The unfer rclations at 10' c. of whole rgg

Hurniditr .. .. 0.05 0-10 0.20 0.30 0.40 0.50 0.00 0.70 \\'ntcr content, g. per 100 g. dry weight

Cnlculnted (i) .. .. 2.2, 2.7, 3.0, 5.3, 6.5, 7.0, 0.7, 12*4, Obserrcd(ii) .. .. 2.5, 2.9, 4.0, 5.4, O.Uo 7.0, 0.5, 12.0,

(i) Cnlculntcd from vnlues in Tnblo 11. (ii) Obacrved \*nlucs for spy-dried cvholo egg.

The work described nbow ivns carried out ns purt of the progrnnime of the Food Investigntion Uonrd. It is publislied by pcrinission of the Dcpiirtntcnt of Scientific nnd Industrinl Research. Mr. H. J. Shepherd ninde the ntensuremcnts publislied in this pnpcr. Low Temperature Station for Resenrch in Bioclicinistry

and l3iopliysics, Cnnibridge

Ilrc:ived July 0, IO(3

THE RAPID PtIoToMETRlC DETERWNA'IION OF AtuMUguAt lN IyIA(3iEsluM ALLOYS

% F. W. HAYWOOD, F. WRRISON, d A. A. R WOOD A study of tho mnction of aluminium ions with nliturin S hns k n

mode, in pnrticulnr with mforeucc to the detcdnnt ion of duminiua in mngnesium alloys. This magent is spceific. A motl id hns beon de\*elcpd

in whieh the nllr~y is dia~olveti in nrctic nriil. thrs Iiroriuring 1111 nirtomitie. ally bufFerctl aul~tion of pH 4.0. Unml on thew investigations nnd using tho Spkker pIiota.lcctric nbaorptiomotcr, tho mcthotl evolved has proved qmdy. nccumte, gnd ruprodueilile owr thc normirl rnngc of duminiirm contents encountercd in stnndnd engineering mngricairnn nlloyu. The two renctiops most generally eniployetl i n the colorimetric

nnalysis' of nluininium ure the one introduced by Atnck' using iiliznrin S, and thnt by Hiimet and Sotteryz using nluminon (em- moniuni sntt of nurintricnrborylic acid). In our early work using, uluininon, i t wns found that nltliougli the pH of the solution need not be critical, tlic intensity of colour of the aluminium complex varied grcntly with the teinpernture of development and the time nllowed for development. Furthe<more, work was confined to the use of nliznrin S (sodium oliznrinsulplioante) in order to provide a rnpid, nccurntc, arid repetitive method for the dcternlination of iiluniiniunt in ~nngnesiu~it nlloys using the Spekker photoelectric nbsorptiomctcr.

FSPEIIIMESTAL Enrly expcriinentnl work wns I)nsetl on Atiick's method, which

may be surnmnrised ns follows. ~o n iiciitrul or sli&Iy acid soh- tion of an ulununiuni salt is ntltletl IIII ~ X C C S S of nninionin solution, glycerol to suppress the precipitution of the filial complex, nnd a definite volume of n stnndiirtl solution of nlixririn S, followcd by ucidificntion with ncctic acid uiitil no further colour chnnge takes plncc. The colour of t.ltc solution obtained is tnatclied ngninst a stnndnrd siniilnrly prepnretl nntl mntc1le.d n t OIICC owing to fndi~~g. The colour of the nluininiunl complex i n solution is omnge-red and thnt of the nliznrin S rcngent ycllow-bro\rn, so thnt w11c11 excem of rilizarin S is prcscnt the solution is reddish-lirown. The use of glycerol is undcsiniblc since i t nffects the gloss cells of the nbsorptioinetcr. I t wns found that rcIntiveIy high conceiltrntions of the ulurniiiium complex ill solution could he obtuined without glycerol which gnve suitable rciidiiigs 011 the nbsorptioinetcr. With high concentrations of the aluniiiiium complex in solution the coinplex was precipitated 011 keeping, but on slinking tliis pnsscd into rjolutiw nnd rcudirlgn identical with the I'ornlcr solution were obtuincd.

It was found thnt ~ n n g i i e s i u n i - n l u n l i ~ ~ ~ ~ ~ ~ ~ nlloys were soluble in ncetic ncid untl tlurt the solutiolt wus iiutolnuticnlly buffered, fiving n pH in the region of 4.0. On ndding aliznrin S t o eucli solut~une a colour wns produced owing to the formation of uluniiniuni olizurinate* Such n reaction formed the basis of all other work.

1 J.S.C.I., 1Dl5.84, U36. . 1 J. Amor. Chcm. bbc.. 1025, 47. 142.

Ia