INDUSTRIAL AUD ENGIKEERING CHEhIISTRY
96
Discussion I n developing the above inethods the indicators, potassium ferrocyanide and potassium periodate, were fii st tried on aqueous solutions containing kiion n amounts of copper and manganese. Later, sodium diethyldithiocarbainate nab investigated as the indicator for copper and found to be more sensitive. Follon ing the establichineiit of satisfactory indicators the destruction of the organic matter n a s inveqtigated. Obviously, the organic matter niust be completely destroyed without the loss of copper or manganese or the introduction of appreciable amounts of the same or interfering substances. Ignition in porcelain or platinum crucibles had been used and found unsuitable in most cases, owing to the formation of insoluble residues. Aehing in porcelain frequently results in contamination with siliceous matter or losses due t o embedding of part of the copper or manganese. Platinum ware is sometimes attacked and if platinum is dissolved it interferes with the copper determination. Wet digestion with mixed acids is somewhat longer than ashing but gives more accurate results because of the solubilizing action of the acids. An excellent article by Hiltner ( 2 ) emphasizes the benefits of the acid digestion procedure.
Summary Uethods have been described for the determination oi m a l l quantities of copper and manganese in dyes, intet mediates, rubber chemicals, and rubber, which may contain, in addition
T'OL. 12, XO. 2
to copper aiid manganese, iron, lead, zinc, barium, aluminum, and sinal1 amouiit)s of cadmium. Materials containing other metals may require special treatments. Both methods are accurate within * L O per cent of the amount of nietal present. Under best conditions amounts as low as 0.0002 per cent of copper and 0.0001 per cent of manganese may be determined 011 &gram samples.
Acknowledgment ,Ickiio\~letlgriieiitis macle to S.Strafford, of the Imperial Chemical Industries, Dyestuffs Group, Analytical Department, for his technical comments on these methods and to the manageinelit of Imperial Chemical Industries, Dyestuffs Group! for permission to publish information obtained froni their official methods. The authors also wish to express their appreciatioii for the assistance and suggestions contributed by past and present menil,ei~sof the analytical staff of this laboratory.
Literature Cited (1) Callan and Henderson, A n ~ Z y s t 54, , 650 (1929). (2) Hiltner, Vierner, Z . anal. Chem., 110, 241 (1537).
(3) Imperial Chemical Industries, Dyestuffs Group, private ~ 0 1 x 1 munications. (4) Willard and Greathouse, J . Am. Chem. Soc., 39,2306 (1517). C O N T R I B U T ISo. ~ N 44 from t h e Organic Chemicals Department, E. I. i l u Pont de Seiriours & Company, Inc.
Stability of Peroxidized Titanium Solutions GILBERT H. I l H E S ~ N E D D M i Y _\I. \ I E S S E A U Smith College, Northanipton, >lass.
IK
THE colorimetric determination of titanium by the hydrogen peroxide method (4), the color compaiison is usually made by the method of balancing, dilution, or duplication. For the analysis of titanium in bauxite, Gautier ( 1 ) recommended comparison with a series of standards, but indicated that the color was so unstable that renewal of standards was necessary after 8 days. He therefore ( 2 ) proposed the use of helianthin, or methyl orange 111, for the preparation of artificial standards which do not fade. The data presented heren-ith show that the color of titanium by the hydrogen peroxide method is stable over a period of a t least 2 years.
In Sovemher, 1936, standard titanum solution A4was prepared from pure titanium oxide by fusion with potassium pyrosulfate follon-ed by solution in sulfuric acid; the solution v a s standardized gravimetrically. Suitable dilutions were used for the devclopment of the yellow color by hydrogen peroxide. Colorimetric measurements Tvere made with a Toe ( 5 ) photoelectric colorimeter. The second column of Table I gives the per cent of light ahsorption by t,hene solutions. Column three shows the light absorption by the same solutions in November, 1938-that is, after standing for 2 years. During this time the samples were stored in glass-stoppered Pyrex bottles, but no special precautions \yere taken to protect them from light. Column four s h o w the results obtained, also in Sovemher, 1938, on freshly prepared samples made from standard titanium solution B obtained from potassium titanium oxalate by the method of Thornton arid Xoseman (3).
TABLE I. LIGHTABSORPTIONBY PEROXIDIZED TmasIuv SOLCTIOSS
of the instrument-namelv. 0.4 per cent light - absorvtion. At any rate, there is no indication of fading of t'he color. The
I n most cases the readings are within the limit of accuracy
Concenti ation of Ti Mg./l. 4 R
12 16 20 24
2s
32 36 40 48 56 64 72 80
From Standard . 1 Xoveniber, 1936 Xovember, 1938
Froin Standard B, November, 1938
%
70
7c
6.0 8.6 10.8 12.8 14.0 15.2 16.6 17.8 1 8 .. 88 19 21.2 22.8
G.0 9.2 11.6 12.8 14.4 14.8 16.0 17.4 18.G 19.8 20.6 22.6 24.0 25.2 26.2
5.4 8.6 10 G 12.6 14.G 1; 4
23 (i 25.0 20.0
1S:O 21 09 .. 42 22.0 23.6 24.6 25,G ".C
"
I
results indicate that the yellow color of titanium in acid s o h tion of hydrogen peroxide is entirely stable, so t'hat t>heuse of artificial standards for the purpose of obtaining stability is unnecessary.
Literature Cited (1) Gnutier, .I.,Chimiste, 1, 177 (19101. (2) Gautier, :I,, Ibid., 2, 2 (1911); Kec. ycn. chim., 14, 1ti (1911); A m , chim. arial. chim. a p p l . , 12, 135 (1930). (3) Thornton, IV. 31.. and Roseman, R.. A m . J . Sci.. 20, 1-1(I9:N). , Ber., 15, 2593 (1882). ( 5 ) T o e , J. H., and Crumpler. T. B., ISD. ENG.CHEM..Anal Ed.,
7, 28 (19353.
