378 (8) (9) (10) (11) (12) (13) (14) (15) (16) (17)
Ih-DUSTRIAL AND ENGINEERIh-G CHEMISTRY Hall, P. E., Ibid., 9, 373-92 (1930). Korn. N. L., Power, 78, 249 (1934). hlacrae, J. C., and Wandless, A. M., F u e l , 15, 68-74 (1936). Pallot, A. C., J.Inst. F u e l , 8 , 250-69 (1935). Ralston, 0. C., Bur. Ilfines Tech. P a p e r 93 (1915). Rose, H. J., T r a n s . Am. Inst. ~TliningM e t . Engrs., Coal Division, 411-15 (1930). Schuster, F., Brennstof-Chen., 15,309-11 (1934). Seyler, C. h.,CoZKery G u a r d t a n , 155, 9 9 0 4 , 1046-8, 1087-9, 1137-9, 1231-3 (1937). Spooner, C. E., J . Inst. Fuel, 11, 134-40 (1937). Sprunk, G. C., Selrig, W.A,, and Ode, V ,H., “Chemical and Physical Properties of Spores” (in press)
VOL. 10, NO. 7
(18) Sprunk, G. C., and Thiessen, R., IXD. ESG. CHEM.,27, 446-51 (1935). (19) Kandless, A. M., and Macrae, J. Colliery Guardian, 155, 1232 (1937). (20) T\’andless, A. M., and Macrae, J. C , , Fuel, 13, 4-15 (1934). (21) Wright, C. C., and Gauger, A. W., Penn. State College, M i n e r a l I n d . Tech. R e p t . 2 (October, 1936).
c.,
RECEIVED May 3, 1938. Presented before the Division of Gas and Fuel Chemistry a t t h e 95th Meeting of t h e American Chemical Society, Dallas, Texas, dpril 18 t o 22. 1938. Published by permission of the Director, Bureau of Mines. t-.Y. Department of the Interior (not subject t o copyright).
Detection of Cobalt, Copper, and Ferrous Iron With 2-Nitroso-1-Naphthol-4-SulfonicAcid L. A. SARVER L-nitersity of Minnesota, Minneapolis, 31in11.
I
MMEDIATELY after the description by Ilinski ( 2 ) of the reaction which takes place between cobalt and l-nitroso2-naphthol, Hoffmann (1) called attention to the fact that he had observed it in 1883, when he prepared and studied not only this compound, but also 2-nitroso-1-naphthol and 2nitroso-1-naphthol-4-sulfonic acid. The latter substance is a dyestuff, and its preparation was patented in 1884, with the claim that it gave a green with iron and a red with cobalt. The free acid is a brownish yellow crystalline substance, very stable, and easily soluble in water. It is strongly acidic, and capable of forming two series of salts; however, only the hydroxyl group is inrolved in its most characteristic color reactions, the hydrogen being replaced by one equivalent of the metal, which then forms a coordinate bond with either the nitrogen or the oxygen of the neighboring nitroso group to give a five- or six-membered chelate ring:
Since the strains, and therefore the stabilities, of five- and six-membered rings are so nearly equal, it is difficult to say which of the two structures is correct. The reagent may be prepared easily, and with excellent yields, b y the action of nitrous acid upon l-naphthol-4sulfonic acid, according to the method of K i t t and Kaufmann (5). A 1 per cent solution is made up in water, and is stable for several months, at least. Although i t forms sparingly soluble salts with several metals, none is sufficiently insoluble to make it of value as a precipitant. However, i t gives beautiful red, orange, and green color reactions with cobalt, copper, and ferrous iron, respectively. I n concentrated solutions precipitates are formed, but from dilute solutions the dyestuffs do not settle out, and are stable over a period of months.
The reaction with ferrous iron is most intense at a p H of 5 , and the colors are markedly weaker a t higher and lower acidities. With cobalt, on the other hand, a greater latitude is permissible, and the most favorable range is 7 to 8; however, if the solutions are not too dilute, good colorations can be obtained a t any p H greater than 3. Ferric iron gives a much weaker color reaction than do cobalt, copper, and ferrous iron, but nevertheless enough to cause interference; this can be suppressed b y the addition of fluoride. S o means have been found for suppressing the mutual interference of the other ions, but ferrous iron can be oxidized to ferric, which does not interfere in the presence of fluoride. Copper can be removed as sulfide, and cobalt may be removed by classical methods when required. However, they may usually be recognized in the presence of each other by the color. Sickel interferes only when present in high concentration; i t is possible t o detect cobalt in the presence of 1000 times as much nickel, or more. Chromium and other conimon ions, except cyanide, do not interfere; cyanide prevents the reaction from taking place. The sensitivity of the test is very great. When none of the interfering ions is present, i t is comparatively easy to detect cobalt or iron in concentrations of one part in 20 million; the colors given by copper are only slightly less intense. Blanks must be used for the great dilutions, since the reagent itself is yellow. It is also necessary to allow some time for the color to develop in very weak solutions; the reaction may be speeded u p by heating. About 0.01 gamma can be detected by means of a spot test for either of the three metals; when a sufficient sample is available, i t is convenient to work in Nessler cylinders, adjusting the p H with sodium acetate and acetic acid. The study of these reactions is being continued, with the object of adapting them to quantitative colorimetric determinations.
Literature Cited (1) Hoffmann, 0.. Ber., 18, 46 (1886). (2) Ilinski, M.. Ibid., 17, 2581 (1884). (3) Witt, 0. N., and Kaufmann, H., Ibid., 24, 3160 (1891). RECEIVED May 9, 1938.
