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Till'* > ■.»".■'.' ■^:-:v.>-::h- ' ' -'"">.« i^' -jr.,. ■I fc.■%i^l,; >■ ■ V, •-•. 5 r< "vtvi- ;'CV'-^^ -.1 ■■ J --«;..• -.-4 -'. - •i. ■''^■p ...;^:'* ^^■'-' V ;\*-M^^. - '"• >, V-'.. -_J'' ■,v •■', ■f; ■-. .'-V' '■ - iiiJ^A««MMattirftiafa UHi •ifM«n*l The Application of Polarimctry to the Estimation of Tartaric Acid in Commercial Products. m^ W S^ .;>!-■ MS^ r*" ^l ■'■\ * i^fJi By Edgor B. Kenrick and Frank B. Kenrick. rmM^^- 7i^m* ,■>■', ' . - ' H-' i^i'S;. >',-.mi.§rt|ii^5 .:^ 'W^'^ ;«.«« ;>• :i0< <■ -f IKrpriiited from the Journal o( the Amrricftn Chemical aodcty. Vol. XXIV. No. lo. rtclohrr. 1901 THE APPLICATION OF POLARinETRY TO THE ESTIflA- TION OP TARTARIC ACID IN COnriBRCIAL PRODUCTS.' Bv Bdoar B. Kenkick and Fkahk B. Kbnrick. Received June 19, ifoi. In comparing the optical rotation of the sugars with that of active substances generally, we meet witn one great point of diflFer- ence. While concentration and t' 'ircscnce of foreign substa.ices play only a subordinate part in thi' station of the former, sc 'hat their influence may usually be ignored, in the case of other i -tive substances the effects of these disturbing factors may he extremely complex. The object of the present research has been to investi- gate the influence of various commonly occurring substances on the rotation of tartaric acid, and, by taking these eflfects into account, to devise methods for the polarimetric estimation of tar- taric acid in its chief commercial compounds. Tartaric acid, in aqueous solution, rotates the plane of polari- zation to the right. Strc g acids slightly decrease this rotation. The rotation of the salts is, in general, a little greater than that of the free acid, and, in case of dilute solutions, is independent of the nature of the base. The facts, so far, are in accordance with the hypothesis of elec- trolytic dissociation. There are, however, a number of substances which exert a Tiuch greater effect on the rotation, and whose action is best explained on the assumption of the forma- tion of complex molecules. As early as 1837 Biot observed that borax increased the rotation of tartaric acid, and subsequently Gcrnez= and others pointed out that the acids of arsenic, antimony, molybdenum and tungsten, also the salts of beryllium and uranium, exercised a similar influence. The present writers, besides confirming the observations of the earlier experimenters, have studied the influence of a number of other elements on the rotation of tartaric acid. The following is a summary of the conclusions arrived at, the results given being the effects noted, except where otherwise stated, in the presence of ex- ' A preliminary note on this subjef t was published in the Appendix to Bulletin No, 65 (P- 157> of the Bureau of Chemistry t' ft Icpartment of Agriculture. In the present paper fuller details are given, and some sli^.^i changes have been mode in the methoda of analysis. • Compi rend , IDS, 8oj (1887). POLARIMKTKV IN COMMKRCIAI. PKl)I)tl.TS. 9Jy cess of ammonia. Where the clTects arc ilescrib.'l as small, the slight changes observed in the rotation were otleii within the limits of experimental error. VVii- Alkalt Metals.— IMhium. sodiniii. i)otassiiitn ami caesium were found to have a sinal! effect only on the rotation. Coffer and i"i7:vr.— These metals, the former in the presence of l«itassium cvanide, had practically no effect on the rotation. /■/,.■ .llkaliiu- Earth Metals. .MthouKh the tartrates in this -roup are nearh insoluhle, small (|uantities of the salts of calcium, strontium and barium tnay lie added to an amnuiniacd solution of tartaric acid and the solution (Kjlarized before the tartrates have time to crystallize out. It was found that, while calcium exercise ' an insiKnificaiit effect only, strontium and barium lowered the ro- tation. M.i:^iicsiiim. Zinc and ( ulmium.— The first two had a small effect oidv; cadmium increaj..'d the rotation. Boron and .(/iim/dM/ii.— Boraeic acid (in alkaline soliuion) lowered the rotation; compounds of aluminum had the opposite effect Tin and /..-(k/.— Both stannous and staiuiic salts increased the rotation ; lead diminished it. Arsenic. Antimony and Bismnt',\.—'\'\K<><.- all Iowereimonia. It has lon^r been known that a solution of tartar emetic has a much higher rotation than a solutioi. containinj; the cpiivaleiu quantity of tartaric .-cid. The authors found that when ammonia is added in excess to an a(iueous solution ct tartar emetic part only of the antimony is pre- cipitated. The filtrate then has a lo7i'er rotation than an er.iiva- Icnt solution of ammonium tartrate. Similarly, if an .immoniacal solution of crenin of tartar is shaken up with excess of antimony oxide, a certain quantity nf antimony passes into solution. The solution so obtained has a lowe rotation than the original cream of tartar solution, its rotation corresixindin^'. in fact, to i;..it of the fil'r-jte referred to above— provided, of course, the solutions of cream of tartar and tartar emetic arc made of equiv.ilent strength. .U(i)j.?i7»«c.-Manganese sulphate, added to an amnioniacal solution of tartaric acid and made up to volume with freshly boilc.l water, gives a colorless solution, and the rotation of the tartaric ')io Knr.AK B. KKN'RICK AND FRANK R. KENKICK. <•;> - aciil is practically iiiuiflfictfd. lint if this niixturt is ex|«)scil to llu" air it very (|iiickl. itirns to a dvv\>, reddish brown, and a cnn- si(U'ral)lc decrease in the rotation tall many of the effervescing prep-rations of the pharmacoi)oeias. (,>o,. '/.— Mixture it:. ,iiii« both tartaric acid and sugar. Some of the officinal vescinj; comp -unds an.l most of the similar patent ■)r^'!iarati . fall into this ms, or traces of op'ically active substances. This :■ -ip ...mipn- . -.aicrials of which alum is an in(;redienl, mix- . , containing 'races of iron or aluminum, ard those of which starch is a coi.siitiunt. Conse<|uintly all tartar bakinK-powders and mixtures of cream of tartar with cream of tartar substitutes are included in this ^roup. Kor apart from the fact that the latter are liable to contain iron and alumina, the authors found that the starch mixed with hakinKpowdcrs' and Mtperphosphates almost invariably contained traces of active substances soluble in cold water (.\ppendix 87-101). MF.TIIODS OF ANALYSIS. In the followiiiK section, workiiiR „„/. /.—The methwl employed in the analysis of materials of this group is based on the fact that in the presence of excess of ammonia the rotation of the solution is proportional to the con- centration of the tartaric acid, and i. in.lependcnt of the other bases and acids present. (I) The Tartrates Present ,i»v Comfletely Soluble in Dilute Ammoiiin.—\ weighed quantity of the substance containing not more than 2 gr.ims tartaric acid is placed in a 50 cc. measuring flask, moistened with 3 or 4 cc. of water, and concentrated am- monia (sp. gr o..)24) added in ciuantity sufficient to neutralize all acid that may be present and leave alMDUt 2 cc. in excess. The ■ Thtre are, howtvtr, a few tartar baking-powders on the market which .re entirely free from starch These may be cla»Md in Gronp 1 w^^ »..■-•• r^M r ■■■::. ^ » ■'■*,. '"(■s- .:^/ ■ V t-'i '■'■ y V;\; - ■>:'" J T*. ■ ■ ■ ( _ i:' •. /r '■ '■ .UV r r^'Ji^r' h' ' ')t\' 3*^ - ^ 1'-.' >■ \ >-■' - ' *' ■ f ^ ■:.*'>, ' 4V>v': 'V y :.-.>.> .-'"■'• ' 93a EDGAR B. KKXKICK AND FRANK B. KENRICK. actual amount of the excess is not of importance, but a greater (|nantity than 2 cc. of free .ciimonia should be avoided. The solu- tion is then made up to 50 cc. with water, filtered, if necessary, through a dry filter, and the rotation read in a 200 mm. tube. The amount of tartaric acid (CjHuOj) in grams (v) in the material taken is given by the formula y =: 0.005 ig^r, where .r is the rotation in minutes. (2) The Mixture Contains Insoluble Calcium Tartrate. — In this case proceed as follows : Treat 2 grams of the sample (or an amount containing not more than 2 grams of tartaric acid) in a small beaker with 30 cc. w-ater and 20 drops concentrated hydro- chloric acid. Heat gently till both the potassium and calcium tartrates have passed into solution, and then, while still hot, add 4 cc. concentrated ammonia (or enough to produce an arinoniacal smelling liquid) and about 0.2 gram sodium | hosphate dissolved in a little water. Transfer to a 50 cc. measuring tlask, cool, make up to the mark with water, filter through a dry filter, and polarize the filtrate in a 200 mm. tube. The tartaric acid is calculated by the forinula given imder ( i ) . The precipitation of the calcium l)y sodium phosphate is not absolutely necessary, but. when this is not done, in cases where the proportion of calcium tartrate in the sample is high, there is a great tendency for the calcium tartrate to crystallize out from the ammoniacal solution before the reading is made. The tartaric acid present as bitartrate of potash may be de- termined by proceeding as in ( i ), the cilcinni tartrate being prac- tically insoluble in cold ammonia solution. The tartaric acid in the calcium tartrate may be olitaincd with sufficient accuracy for most purposes from the difference between the results in ( i ) and (2). If more exact results are required, the residue insoluble in ammonia in ( i I may be dissolved in a little hydrochloric acid, and treated as above with sodium phosphate and ammonia. It may be noted that the method given below under Group III, is applicable to this group also, but in most cases the course described above will be found more simple. Group II. — Tlie method of analysis for substances of this group ^kSvi POLARIMETRY IN COMMERCIAL PRODVCTS. 933 is essentially the same as the one just described, but takes into ac- count the presence of sugar in the mixtures. In amnioniacal solu- tions containing both tartaric acid and sugar, the rotation of each is unaffected by the presence of the other (Appendix 45-46). and consequently the rotation of the tartaric acid may be obtained by subtracting from the total rotation the part due to the sugar. The cane-sugar may be determined by Clerget's method, but in carry- ing out the process the additional precautions described below must be observed. .Mthough magnesium sulphate, even in comparatively large pro- portions, has but little effect on the rotation of solutions of sugar and of tartaric acid alone, it is a curious fact that the rotation of these two substances when present together is considerably de- creased by the addition of magnesium sulphate ( Appendix 22 and 67). In "effervescing magnesium sulphate", and in other mix- tures where magnesia is present, it is therefore necessary to pre- cipitate the magnesium by means of sodium phosphate and am- monia before making the i)olarimetric readings. In carrying out the inversion of cano-sugar, moreover, it must be remembered that in order to effect complete inversion in ten minutes, without further decomposing the products of hydrolysis, a fairly definite concentration of free hydrochloric acid is required, and that when salts of weak acids (such as citric and tartaric ) are ])rosent, it is only the hydrochloric acid added over and abtive the amount necessary to compleu ly set free all these weak acids that is to be considered capable of effecting the inversion in the pre- .scribed time. The difficulty of finding the point where hydro- chloric acid is free in the solution was overcome by the use of methyl \ioIet as indicator. This indicator was found to be (luite unaffected by citric and tartaric acids, yet sufficiently sensitive to hydrochloric acid for the purpose in hand. It is also to be noted that in some commercial samples the sugar is alreadv partly in the inverted condition. In such cases the reducing sugar must be determined by Fehling's process, and due allowance made for it. ( n Magnesium Absent.— An amount of the sample containing not more than 8 grams of tartaric acid .>r 5 grams of sugar is dis- solved in cold water and made up to mi cc. (Solution A). 934 EDGAR B. KENKICK AND FRANK B. KENRICK. I Twenty-five cc. of this solution are pipetted into a 50 cc. measuring tlask u ill a few drops of methyl orange solution and, if alkaline, approximately neutralized with concentrated hydrochloric acid. One cc. concentrated aminonia ( sp. s^r. 0.924) is then put in, the flask filled to the mark, and the solution polarized in a 200 mm. tiihc (reading a). To another 25 cc. of Solution . / a little methyl violet solution is added, and concentrated hydrochloric acid run in from a burette till the indicator turns pale green, the amount of acid required being noted. A third 23 cc. portion of Solution . ) is ])laced in a 50 cc. measur- ing flask (without methyl violet, the color of which would inter- fere with the polarimetric readings ) and a quantity of hydrochloric acid run in etpial to the amount required in the l»st experiment, fills 2.5 cc. The flask and contents are next heated to 70° C. for ten minutes, as in the ordinary C'lerget process, and immediately cooled to (• linary temperature. -\ little methyl orange is then added and < ough ammonia to turn the inilicator yellow and leave about I cc. Ill excess. Finally, after making up the volume to 50 cc. and cooling to the temperature of the room, the solution is polarized in a 200 mm. tube (reading b\. The weight of sugar (r) in the amoiuit of the sample taken is given by the formula 2 (a — ^t 1.254 142 — 0.5/ where t is the lemjierature and d and b are the readings expressed in minutes. The rotation of s grams nninverteil sugar is yi)':. and the rota- tion ( .r I of the tartaric acid is eon.se(|ueiitly .V — 2(1 — 7'>v-- from whicli the tartaric acid (v 1 is founf this solution are placed in a beaker and ...wmt j; cr. of water aiul 4 cc. of eoneeii- I rated ammonia addeik I f a i)recipitate fi .rius, enough ammonium chloride is added to keep it in solution. The magnesium is then precipitated bv .sodium phosphate. Since it is desirable to keen I'OI.AKlMIiTKY IN fOMMEKCIAL PKODVCTS. 935 ti:c liulk of tlic solution as small as i)ossil)lc. ami to avoid iiniitcis- sarv I'xci'ss of salts in solution, tlio roi|uiroil (|naiuity of ])ho-phati' (alxmt Scrams XaJll'l ),i<)H,( ) to oven 3 };rai. .Mi;S( >,7ll,<'l should be dissolved in a small volunu' of hot water ( 10 vc. In S ijrams |)hos])liatc 1 and the solution added j;radnally while hot. .After tile preeipitate lias eoiiipletely formed it is filtered off on the filter-pump and washed with small ipiantities of water, lare beiiif; taken not to hriiif; the total volume to more than lU) cc. l-"veii a fairly l)ulky precii)itate ean be siifticicntly washed in this way. The filtrate is now made up to kxi cc. ( Solution H). anrl part of this .solution read at once in the polariiiK'er ( readiii}.j <■. ) Twentv-five ce. of Solution B are now titrated w itli hydroehlorie acid and methyl violet, and another J5 cc. inverted as described under ( r ). made up to 50 cc. and jiolarizcd (readins,' 1/ ). The wei);ht of suijar {:) in the substance taken is io(r ~ 2J) 1.254 142 — 0.3/ The rotation of the tartaric acid is. therefore. .V = IOC — -!).~c and the weifjht of tartaric acid, \ -= 4 X O.C)05!(;.V. The directions given for this inctho• » "» 1 ^ •f 1^^ r.~ ■ iCLults calcvilated from the formulas in the pharmacopoeias. This is owing to the fact that a considerable amount of decomposition takes place in the process of manufacture. Hence tartaric acid, and all other constituents with the exception of carbon dioxide, come out higher in the analysis than in the result calculated from the formula. This consideration does not apply to the test analyses gi en. as in these the whole of the mi.xturc made up was taken for a' dysis, and no attempt was made to imitate exactly the "f ranu- lated" commercial article. Group ///.—Direct readings of rotation in ainmoniacal solution are inadmissible in analyses of the substances of this group on account of the influence of iron and aluminum on the rotation ot tartaric acid, and owing to the small, but unknown, rotation of tl.J trace of inverted starch (.\ppendix 2". 40, 87-101 ). .\ccurate determinations may. however, be made in the picsencc of excess of ammonium molybdate in neutral solution. The latter salt not only annuls the effect of iron and aluiuinum, but also has the property of greatly increasing the rotation of tartaric acid, so that by its use the small rot.ition of the inverted .st.i.ch is rendered insignificant. It is to be noted, however, that this in- creased rotation is very sensitive to the presence of acid and alkali, and is. moreover, modified by the presence of p'.iosphatcs. It therefore becomes necessary to first remove the phosphoric arid, anil then to bring the solution to a definite state of neutrality. These results are attained by the following procedure, the details of which must be strictly adhered to. Solutions Required.— The following solutio- must be prepared, but neetances ii takon into account in this paper. APPKNDIX. In this section some of the experimental ilata are recorded. T readings wore ni.ide mostly with a Schmidt & Ilaensch ha shadow instrument, graduated in degrees and minutes. A 200 m tube was used for the readings. The iij.'ht was supplied by flame in which sodium chlorate was heated on platinum. It w found that the readings for tartaric acihate in loo cc. amnioninm oxalate in lotj cc. litliium chloriiie •• in io> cc. so'Uuni chloride .. in loo cc. sodium phosphate- in loo cc. sodium acetate •-.. in loo cc. potassium chloride in loo cc. potassium bromide in lou cc. potassium iodide. . . in loo cc. :k. icciir in prac- liowcvcr. be 11(1 Rreat can- iiiftlioils de- iili>taiiccs IK It fcordcd The laonscli bait- s. A 200 mm. uppliod by a mm. It was ictically indc- herwise indi- erature. The expressed in acid; KHT. \ (Irate ; XH,. itratcd li vdio- I alum. used ill these and found by «■ 01- Tart.xric Roln- lion. n UK) cc. 1 93 -5 n i(X) cc. 194 11 I no CC. 19.1 II 100 cc. 196 11 KX) CC. 194 11 i(X) cc. 196 Ill lotj cc. 192 n 10.1 cc. 187 Ill 100 cc. 194 n 100 cc. 188 in 100 cc. 186 11 no cc. 197 n 100 cc. 194 in 100 cc. 194 POLARIMETRY I.N COMMERCIAI. PRODUCTS. y.W Rota- ttnll. ( 15) 4 ?■ TH. 8 cc. NH, 4 g. potassium cyanide, in icx> cc. 194 ( 16) 4 g- T:I, 8 cc. XH, 4 K. potassium chlorate- inicxjcc. 191 ( 17) 4 K- TH., 8 -c. NHj 4 K- potassium nitrate • in 100 cc. 196 ( 18) 4 K- TH, 8 cc. NH, 1 ({. potas-sium sulphate in 100 cc. 197 ( 19) 4 g. TH, 8 cc. NH, I g. caesium sulphate.- in 100 cc. 197 { 20) \ g. TH-j 8 cc. >:il, 4 K- copper sulphate • potassium cyanide in 100 cc. 196 (21) 4 g. TH.J 8 cc. XH, 4 g- silver nitrate in luo cc. 19" ( 22) 4 g TH-i 8 cc. XH, 4 g. magnesium sulphate in 100 cc .94 ( 23) 4 g. TH, 8 cc. XH, 4 g. zinc sulphate iniix.cc. 194 ( 24) 4 g. TH, 8 cc. NH;, ! g. zinc '■ceia'e in luo cc. 19.1 ( 25) 4 g. TH, 8 -c. NH, 4 g. cadmium sulphate, in uw cc. 220 ( 26) 4 g. TH, 8 cc. XH, 4 g- boracic acid in loo cc. 150 (2/) 4 g. TH, 8 cc. XH, 2 s'. alum in K« cc. 24h ( 281 4 g. TH.j 8 cc. XH, 4 g. stannic chloride . •- in Tfw cc. 305 ( 29; 4 g. TH, 8 cc. XH, 4 g- stannous chloride (precipitate filtered off) mi 100 cc. 2;.; ( 30) 4 g. TH, 16 cc. XH, 2 g. lead acetate in 100 cc. .S3 (31) 4 g. TH, 8 cc. NH, 4 g. sodium arsenite .-- in kk) cc. 179 ( 32) 4 g. TH., 8 cc. NHj 4 g. sodir.m arsenate .- - inioocc. 1S5 ( 3J) 4 K- H, 14 cc. XH, 4 g. bismuth suhnitrate 4 6 I . Hydrochloric acid i 1 ino cc. 25 ( 34) 4 g. TH, 28 cc. NH, 4 g. bismuth suhnitrate • 6 cc. hydrochloric acid n loo cc. 114 (35) 4 g. TH, 8 cc. NH, excess of antimony oxide n 100 cc. 177 { - 3.86 g. tartar emetic, ammoni.i in excess ( filtrate I - in ion cc. 17S ( V, 4 g. TH, 8 cc. XH, ,t g. mangr.iicse sulphate in 100 cc. 193 ( 38) The same exposed to the air for a few minutes 167 ( 39) 4 g. TH, 8 cc. XH, o I g. manganese sulphate after exposure *" '^* *^'-'- *' 3 ( 40) 4 g. TH, 8 cc. XH, 0.02 g. ferric chloride ••.- inioocc. 2in (41) 4 g. TH, 8 cc. XH, 0.3 g. nickel sulphate...- inioocc. 202 ( 42) 4 g. TH, 8 cc. XH, 0.1 g. colialt nitrate in 100 cc. 1S9 (.(3) 4 g. Th", 8 cc. :;H, 4 g. citric acid inioocc. 192 ( 44) 4 g. TH, 16 cc. NH, 4 g. citiic acid inioocc. 194 (43) 4 g. TH, 8 cc. Xll, 4 g. cane-sugar inioocc. 508 ( 46) 8 cc. XH, 4 g. caiR-sugar in 100 cc. 314 Difference hctweeii 1 45) and (46 1 due to 4 g. TH, 194 Thk Rkl.\tio.n bktwkkn thk Rot.\t'o?: and Cosckntration of Tar- taric .\CII> IN .\MMON'.\CAI. SOI.ITIDN. (471 I g. TH, 8 cc. XH, inioocc. 48 (48) 2 g. Th", 8 cc. XH, inioocc. 95.S (49) 3 g. TH, 8 cc. XH inioocc. 145.5 (50) 4 g. THJ 8 cc. NH inioocc. 193.5 940 EDGAR B. KENRICK AND PRANK B. KENRICK. ■^■^'it'} ■■■'■ s* --»N ■ Ekfkctof Ammonia and Ammoniim Chloridk on thk Rotatidn i Cank-Sioar. (51) 8.17 g. cane-sugar in 100 cc. 64; ( jj) S. i7({ cane-sugar 8cc. NH, inioocc. 641 Thk Samk in More Dimth Sou'tion. ( 55) 2 g. cane-sugar inioocc. 15; ( 56) 2 g. cane-sugar 4 cc. NH, in i(« cc. ly { 57) a g. cane-sugar Sec. N;I, inioocc. 15* (58) J g. cane-sugar 16 cc. NH, inioocc. 16 Consequently more than 4 cc. free ammonia in 100 cc. should Iw avoiili I 59) 2 g. cane sugar 4 cc. NH, S g. aninioniuni chloriile in 100 cc. 15: Note : 8 g. ammonium chloride are t uivalent to about 16 cc. animoni hence, the ammonium chloride has much less influence than the equivalt of ammonia. Kffect of .Ammonia and .Xmmonitm Chloridk on thk Rotation Invertkd Src.AR. .\ solution of 16.34 g. cane-sugar in 100 cc. was invcrteil according to CI get's metho cc. 161 Lilil f>e avoided. II 100 cc. 155 i cc. ammonia ; 1 the equivalent Rotation of cordiiiK 'o Cler. ilrocliloric acid iimonia, the so- change of color to 25 cc. 145.5 to 25 cc. 147. s to 25 cc. 138 •e : 18M . conceit - 40 . concen- . . > 40 . concen- .17 . concen- 39 cc. ammonia so :. in 100 cc. or t OF SlGAP ANI> lowing : acid, and 4.2 )(. POLARIMETKY IN COM.MERCIAI. PKODfCTS. 94' ■drochlo- 347 25 cc. of this solution, 2 cc. ammonia, I cc. hydrochloric acid, 5 g. magnesium sulphate made up to 50 cc 315 The same amount of magnesium sulphate, with anmionium chloride to prevent precipitation, has practically no effect on sii on thh Rotation of Tahtakic .\tii) in THK I'RKSKNCK OF .\MMONHM Mol.VBDATE. (68) 3 g. Til, 3.33 CC. Ml iniooce. 145 ( <>9) 3 K- Til, 45 cc. NII^, iniooce. 147 ( V^t 3 K- TH, 3.33 cc. NHj, alxmt 4 g. ammonium mo- lyl«late iniooce. 1501 ' 711 3 g- TH, 45 cc. Nil,, about 4g. ammonium mo- lyhdatf in Kio cc. 152 ( 72) .'. g- TII_, 3.33 cc. NH;,, about 4 g. anmionium nio- iybdatf, alMuit 4 cc. concentrated ii'tric acid in ux) cc. 1147 (7.1) 3 K- TH 3-33 ce. NH,. alxiut 4 g. ammnninm mo- lybdate. about 12 ec. concentrated nitric acid ■•. in 100 cc. 445 ( 74) 0.64 g. KIIT (impure), 0.65 cc. Nil,, 4 g. ammo- nium molybdate. 4 cc. normal acetii- acid in loo cc. 297 ( 75) 0.64 g. Kill" impure), 0.65 cc. NH,, 4 g. amiiio- iiium mol' ", 20 cc. normal acetic aeillo:iiiii; exfierimenls the mixtures ivere treated according to the directions giz'eri under Croup III. (77) o.ig.KHT 65.S ( 78) o.ig.KIIT 66.5 '. 79) 0.1 g. KHT, 0.2 g. alum 65.5 ( !onate 66.5 ( S2) Similar results were obtained uMng 0.2, 0.05, and 0.025 g. of KHT. ( 83) o.2g.KHT 130 ( 84) 0.2 g. KHT, 0.02 g. ferrous sulphate, o.oi g. ferric chloride •• 130 The last two are earlier experiments and were mail' with solutions differ- ent from those described in the paper. I'or this reai. jii the numliers are lower than t'.iose given l)elow for 0.2 g. KHT, but the two readings show that iron has no influence. K.xrKRiMKNT TO Tf:stthk Soi.rBii.iTv of CAtcirM Tartratk and thk Effect of Starch. The following acre treated according to the method III. ( 85) o.2g.KHT 134 ( 86) 0.1 g. KHT, 0.138 g. CaT ( — O.I g. KHT), 0.2 g.alum, 0.3 g. phosphate cream of tartar substitute containing starch 133 ■fe ',-■•-.'*■* •>■■■■' [.<'■•-:'- tn L^:^^:--^ 94a KDGAR B. KENKICK AND FRANK B. KENRICK. Thk Rotation Due to Invhhthd Starch is Commkbciai, Crkam Tartar Sibstititks ani> BAKisr.-PownKRS. /« t/ie /ol/ouing erf>frimeHts Sg. 0/ Ike sainf/r and .<> of concenira ammonia ;vere made up to km lii>ii nraiid. Percent KuUt ( 87) Sujierpliospliate sui)StiHite 16 **• ( W) SuiMTplKwplialc substitute I J '°' ( 89) IMiospliate bakinKP""'''''' ^- '7 ^■ ( y>) Alum bakinKpnwiler I. l-"- 5" '5- ( 91) Alum bakin>tp<»wwilcr It R. 48 J. ( 93) Alum-phnspliate baking-powder W. S. 49 "■ ( -•) Alum-pliosphale bakiiiK-powder W. S. 19 "■ ( 95) Aluni-pliuspliale bakinK-j)OW(lcr W. S. , ) "I. ( 96) Alum-pbospbate bikinn-powler C. 4" °- (97) Aluni-pliiispbate bakin^;-i)OW(ler C. S. 5^ 5- ( 981 Alum-pluispbatc liakinKiMiwiler (f. S. 5' 5- ( 991 Aluni-pliospbate baking lH)wdcr W . V,. S" '4 (lOu) Alum-pliospbatf bakinK-powder S. C. 5" '" (101) Alumpliospliatc bakiuK jiowdcr V . SO 3 Kxi'KRiMKNTs Ti) Show that thk Rotation of Invi;rtki> Starci Not Incrkaskd by MoLYBDatk. 1 102 1 4 K. i>lio5phate substilule, S ic. Nil, to ioo cc ( 1031 0.5 K- phosphate substitute, treated by molybdate method lioj) A solution of inverted starch was prepared by treating starch \ sulphuric acionil- inj; to the so{rams citric acid 7. VI )*• v/^ jvwrxv^3iif.ftr /. \A?3i