ANALYTICAL CHEMISTRY
1876 hydrocarbons in which the 1,2,3,&wbstituents are parts of other aromatic rings.
a reference lo. The wave-length scale was calibrated with known absorption maxima of liquid toluene and of atmospheric water vaDor and rarbon dioxide. Wave lengths are accurate to L
EXPERIMENTAL
Preparation of 1,2,3,4-Tetramethylbenzene. 1,2,3,4-Tetramethylbenzene was prepared from pentamethylbenzene (Eastman Kodak Co.) by the Jacobsen migration reaction, according to the method of Smith and Lux (4). The product was fractionated on a 30-plate column and a center fraction (boiling point 205" C.; ng 1.5200) was taken for study. Infrared Spectrum. -4Beckman IR2 spectrometer equipped with a Brown recorder wa8 used. .\ rock salt plate was used as
*tb.O2p. LITERATURE CITED
(1) Barnes, R. B., Gore, R. C., Stafford, K. W., and Williams, V. Z., ANAL.CHEM.,20, 402 (1948). (2) Colthup, N. B., J . Optical SOC.Am., 40, 397 (1950). (3) Orr, S.F. D., and Thompson, H. FV., J . C h a . Soc., 1950, 218. (4) Smith, L. I., and Lux, A. R., J . 4 m . Chem. Soc., 51, 2994 (1929). (5) Thompson, H. W., J . Chem. Soc.. 1948, 328. RECEIVED February 26, 1951
Dithizone as an Indicator in Titrimetric Determination of Zinc with Ferrocyanide .I.
1'. \IEHLIG AND A . 1'. GUILL', Oregon S t u t r College, Corrallis, Ore.
IPHENYLTHIOCARBAZONE, commonly called dithizone, has been uesd, because of the pink complex it forms nith zinc, as a reagent for the colorimetric and spectrophotometric determination of zinc (9,3, IO), and because of its extwrt ive powers it is the basis for certain titrimetric methods (9). 'Ylie puipose of the present work was t o establish the conditions for the use of the dithizone as an indicator in the titrimetric d
