ANALYTICAL CHEMISTRY
1510 As the standardization curve is linear, iodide concentration is easily and conveniently calculated. With the increased quantity of arsenious acid used, the reaction rate is elevated and the method is more sensitive and practical for small quantities of iodide. The method is reliable, measuring iodides in a range of 0 to 0.r2 microgram with a standard error for duplicates of 0.0012 microgram. LITERATURE CITED
Barker, S. B., J . B i d . Chem., 173,715 (1948). Chaney, A. L., ANAL.CHEM., 22,939 (1950). Chaney, A. L., IND.ENG.CHEM.,ANAL.ED.,12, 179 (1940). Connor, A. C., Swenson, R. E., Park, C. W., Gangloff, E. C.. Liberman, R., and Curtis, G. M., Surgery, 25, 510 (1949). ( 5 ) Freedman, A. J., and Hume, D. E., ANAL.CHEM., 22, 932 (1950). (1) (2) (3) (4)
(6) Jones, E. G., and Soper, F. G., J . C h a . SOC.,1935, pt. I, 802. (7) Lein, A., EndocrinoE., 29, 905 (1941). ( 8 ) Salter, W. T., W e s t . J. Surg., Obstet., Gynecol., 55, 15 (1947). (9) Salter, W. T., and Johnston, M. W., J. Clin. E n d o c r i n d . , 8 , 911 (1948). (10) Salter, W. T., and McKay, E. A , Endocrinol., 35, 380 (1944). (11) Sandell, E. B., and Kolthoff, I. M., J . Am. Chem. Soc., 56, 1426 (1934). (12) Sandell, E. B., and Kolthoff, I . M., Mikrochim. A c t a , 1, 9 (1937). (13) Sappington, T. S., Halpern, N., and Salter, W. T., J . P h a r m . E z p t l . Thm., 81,331 (1944). (14) Taurog, A., and Chaikoff, I. L., J . Biol. Chem., 163, 313 (1946). (15) Weybrew, J. A., Matrone, G., and Boxley, H. M., ANAL,CHEM., 20,759 (1948). RECEIVED August 10, 1950.
Infrared Spectroscopic Analysis of Mixtures of Bromochlorobenzenes LLOYD N. FERGUSON AND ALMA J. LEVANT' Howard University, Wushington, D . C .
S A tool for studying orientation in aromatic bromination, a
A procedure has been worked out for analyzing mixtures of
chlorobenzene, and o-, m-, and p-bromochlorobenzene. This method waa chosen because it was desired to have a single analytical technique for examining the reaction products from the bromination of various monosubstituted benzenes. The mean relative error for ten synthetic four-component mixtures was =k0.3%, Considering the inertness of the type compounds studied here, these results would undoubtedly be difficult to obtain on a small male by other methods.
A Perkin-Elmer spectrophotometer, Model 12B, was used. As a solvent that would not appreciably react with bromine nor interfere with the carbon-halogen light absorption carbon disulfide was selected. The spectra, in carbon disulfide, of the substances studied are pictured in Figure 1. For analyses, optical densities were measured a t 13.46, 13.3, 12.89, and 1 2 . 2 5 ~with slit widths of 0.3 to 0.5 mm. Concentrations were always adjusted, by dilution, so that optical densities were read between 0.15 and 0.35. At these concentrations (
