VOLUME
2 4,
NO.
7,
JULY
1952
reactions of the excess bromine with the organic compound. In the inorganic field, the accuracy and convenience of the spectrophotometric end point are considerably better than the usual visual method employing methyl orange. For example, when 2- to 30-mg. samples of either arsenic or antimony were titrated, the analyses were accurate to within 2 parts per thousand. The actual results of these inorganic applications are shown in Table III. Analyses of mixtures of arsenic and antimony which were determined by a single photometric titration are shown in Table IV. Although the accuracy from these simultaneous determinations is only about 1%, this method offers a very fast and convenient technique for the analyses of arsenic and antimony mixtures. SUMMARY
AND CONCLUSIONS
The use of spectrophotometric titrations with bromate-bromide solutions for the determination of olefins by addition of phenols and amines by substitution, and of inorganic ions by oxidation, was investigated. The spectrophotometric end point in these bromometric methods is equally useful in the determination of large and small amounts of substances that can be determined by addition, substitution, or oxidation with bromine. These methods should find application in the plastic, natural oil, pharmaceutical, and various inorganic fields. A method for the simultaneous determination of arsenic and antimony has been developed. With favorable conditions (separation of oxidation potentials, stability of complexes, etc.), the accuracy of the determination of each component in a mixture should be as good as for a single
1111
determination. Further use of the ultraviolet region of the spectrum for determining successive end points is being investigated at the present time. LITERATURE (1) (2) (3) (4) (5) (6) (7) (8) (9) (10) (11) (12)
(13) (14) (15) (16) (17) (18) (19) (20) (21) (22) (23)
CITED
Awtrey, A. D., and Connick, R. E., J. Am. Chem. Soc., 73, 1842 (1951). Braae, B., Anal. Chem.. 21, 1461 (1949). Bricker, C. E., and Sweetser. P. B., Ibid., 24, 409 (1952). Custer, J. J., and Natelson, S., Ibid., 21, 1005 (1949). Day, A. R., and Taggart, W. T., Ind, Eng. Chem., 20, 545 (1928). DuBois, H. D., and Skoog, D. A., Anal. Chem., 20, 624 (1948). Duyckaerts, G., Bull. soc. voy. sci. Liége, 18, 152 (1948). Francis, A. W., Ind. Eng. Chem., 18, 821 (1926). Francis, A. W., and Hill, A. J., Anal. Chem., 13, 357 (1941). Gyory, S., Z. anal, Chem., 32, 415 (1893). Johnson, H. L., and Clark, R. A., Anal. Chem., 19, 869 (1947). Keefer, R. M., and Andrews, L. J., J. Am. Chem. Soc., 72, 4677 (1950). Kolthoff, I. M., and Bovey, F. A., Anal. Chem., 19, 499 (1947). Koppeschaar, W. F., Z. anal. Chem., 15, 233 (1876). Lewis, J. B., and Bradstreet, R. B., Anal. Chem., 12, 387 (1940). Lucas, H. J., and Pressman, D., Ibid., 10, 140 (1938). Petrova, L. N., Zhur. Priklad. Khim., 22, 122 (1949). Ruderman, I. W., Anal. Chem., 18, 753 (1946). Sprung, . M., Ibid., 13, 35 (1941). Uhrig, K., and Levin, H., Ibid,, 13, 90 (1941). Volmar, . M., and Wagner, Bull. soc. chim., (5) 2, 826 (1935). Wilson, G. E., J. Inst. Petroleum., 36, 25 (1950). Witter, R. F., Newcomb, E. H., and Stotz, E., J. Biol. Chem., 185, 537 (1950).
Received for review December 17, 1951,
Accepted May 15, 1952.
Reaction of Sodium Nitrite and Sulfamic Acid Indirect Gravimetric Determination of Nitrites ROBERT C. BRASTED School of Chemistry, University of Minnesota, Minneapolis, Minn.
The research was carried out to determine the nature of the gaseous products when an excess of sulfamic acid reacts with a soluble nitrite, and to develop an indirect of nitrites. gravimetric determination Nitrogen oxides, represented by nitrogen trioxide, to the extent of nearly 10% are formed with nitrogen when sulfamic acid reacts with nitrite. The percentage of nitrogen trioxide decreases with decrease in nitrite concentration. An apparatus suitable for the analysis of nitrogen(II) oxide and nitrogen(IV) oxide mixtures is described. Nitrites over a concentration range of
