1760
ANALYTICAL
drops of concentrated sulfuric acid and 10 ml. of hydrofluoric acid (48%). This is heated until dry, ignited, cooled, and weighed. The difference in weight represents silica. Any residue left in the platinum crucible is fused with potassium acid sulfate, the mass dissolved in hydrochloric or sulfuric acid (1 to 9), and the contents are added to the combined original filtrates which should have a total acidity of 10 to 20% and a total volume of not more than 250 ml. The required amount of halomandelic acid is now added and the zirconium content of the sample determined as described above.
Results obtained by this procedure
are
given in Table III.
SUMMARY
Zirconium in aluminum alloys can rapidly and conveniently be 'determined gravimetricaliy by the mandelate method. The use of p-chloro- or p-bromomandelic acid is preferred to mandelic acid (4). No significant difference exists between the chloro and bromo derivative. These reagents are now available com-
CHEMISTRY
mercially from the H. and S. Chemical Co., 528 Howard St., Buffalo 6, N. Y. and Dajac Laboratories, 511 Lancaster St., Leominster, Mass. LITERATURE
CITED
(1) Aluminum Co. of America, “Chemical Analysis of Aluminum”
(Methods Standardized and Developed by the Chemists of the Aluminum Co. of America under the Direction of . V. Churchill and R. W. Bridges), 2nd ed., New Kensington, Pa., Aluminum Research Laboratories, 1941. (2) Association of Light Oil Refiners, “Modern Methods for the Analysis of Aluminum Alloys” (by a Committee of Chemists Convened by the Association of Light Alloy Refiners), London, Chapman and Hall, Ltd., 1949. (3) Gavioli, G., and Traldi, E., Metallurgia ital., 42, 179 (1950). (4) Klingenberg, J. J., and Papucci, R. A., Anal. Chem., 24, 1861 (1952). (5) Mayer, A., and Bradshaw, G., Analyst, 77,476 (1952). (6) Wengert, G. B., Anal. Chem., 24, 1449 (1952). Received fcr review June 24, 1953.
Accepted July 24, 1953.
Separation of Hydrogen Peroxide from Organic Hydroperoxides Application to Polarographic Analysis of Mixtures WILLIAM M. MACNEVIN AND PAUL F. URONE McPherson Chemical Laboratory, The Ohio State University, Columbus, Ohio hydrogen peroxide and certain organic hydroIt has been observed in this laboratory that the polarographic wave for hydrogen peroxide can be eliminated entirely, as shown in Figure 1, by complexing the hydrogen peroxide with titanium(IV) ion and precipitating the complex in alkaline solution. The organic hydroperoxides reported here seem to be unaffected by the complexing ion and by its precipitation. The yellow color formed by reaction of titanium(IV) and hydrogen peroxide is the basis for the colorimetric determination of hydrogen peroxide. According to Schwarz {2, 3), the yellow complex formed in sulfuric acid solution has the formula Ti02(SO
