January 15, 1943
ANALYTICAL EDITION
73
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(8)
Slotta, K. H., and Neisser, Klaus, Ber., 71B, 1611-16, 1984-6
40 (1934). (5) Lustgarten, S., hfonatsh., 3, 717 (1882). (6) Paggi, Raoul, Gazz. chim. ital., 70, 328-42 (1940). (7) Pangborn, M. C., and Anderson, R. J., J . Am. Chem. SOC.,58, 10 (1936).
(9)
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(3) (4)
(1938). (1936). (10) Suknevich, I. F., and Chilingaryan, A. A., Be?., 68B, 1210-16 (1935); 69B,1537-42 (1936). ( l i ) Ware, A. H., Chemist and Druggist, 123, 282 (1935).
Detection of Zirconium with 5-Chlorobromamine
Acid JOHN H. YOE AND LYLE G . OVERHOLSER, University of Virginia, Charlottesville, Va.
B
R O M A M I K E acid is the name used b y dye chemists for the sodium salt of l-amino-4-bromo-2-anthraquinonesulfonic acid. A number of substituted bromamine acids react with the tri- and tetravalent cations in aqueous medium, giving red precipitates. In acid solution, the reactivity is limited to only a few ions, of which the reaction with zirconium is the most sensitive. The chloro derivativesnamely, 5-chloro-, 6-chloro-, and 7-chlorobromamine acidwere found to be the most selective of the substituted bromamine acids studied. Although these three compounds behave similarly, the 5-chloro derivative is recommended because of its slightly more selective reactions. The chlorobromamine acids give heavy bright red precipitates with cadmium, copper, cobalt, nickel, palladium, and zinc in ammoniacal medium. Although the attempted application of 5-chlorobromamine acid as a quantitative precipitant for zirconium was unsuccessful, the reagent may be used for the detection of zirconium. Reagents ~ - C H L O R O B R O XACID. ~ ~ N E The compound was obtained from E. I. du Pont de Nemours & Co., Inc. A 50 per cent acetone-water solution containing 2 mg. per ml. of the reagent was used. ZIRCOSIUM.A stock solution containing 1 mg. of zirconium per ml. and 0.2 ilf with respect to nitric acid was prepared from zirconium nitrate and n-as diluted with water to the desired concentration. NITRICACID. A 2 31 solution was employed.
Procedure Transfer 0.05 ml. of the test solution to a depression in a white tile spot plate, and add 0.05 ml. of nitric acid and finally 0.03 ml. of the 5-chlorobromamine acid solution. Shake the spot plate continuously for several minutes before making the observations. A blank prepared in the same manner, except that distilled water is added in place of the test, solution, should be used for comparison. Occasionally, the blank may have a small amount of a pale red colored precipitate, which floats on the surface of the liquid and has the appearance of a slight scum. This should not be confused with the precipitate formed in the presence of zirconium, which is more granular and darker colored and settles to the bottom of the solution. Characteristics of Reaction The reaction rate is dependent upon agitation of the solution, the concentration of zirconium and of the reagent, and the type and concentration of acid present. Continuous shaking hastens the formation of the precipitate. A t the higher Concentrations of zirconium the reaction rate is faster than a t the lower. T h e use of a higher concentration of the reagent hastens the precipitation but may cause interference. The reaction rate is about the same in nitric or hydrochloric acid but the latter tends to cause increased interference by the
reagent. The reaction rate is greatest a t low concentrations of nitric acid and decreases markedly with increasing acid concentration-for instance, using a zirconium concentration of 10 p. p. m. and 0.05 ml. of 0.3 M nitric acid, the precipitate forms within a minute; with 2 M acid, 2 to 3 minutes are required. The 2 M acid is recommended, despite the slower reaction rate, to avoid interference by a number of ions.
T.4BLE
I. LIMITIKG CONCENTRATION Ion
Limiting Concentration Mg./ml.
Na Ba++ Ca++ Sr++ K + Cd++: CO++’C u + v , M g + + , M n + t , N & + Ni++ pbt+’Zn++ Rarekarths*’,Fe+++,G a + + + , H g + +I. n + ’ + , S c + + + , Y + + + +
--
20 10
5 5
1
ce+-++
0.03
Be++ A ] + + + C y + + + ,T h + + + + T , ifit+
0.1
Po,--*-, sod-* Tsivalent ions.
0.26 1
Interference I n testing for the interference of the various ions, the procedure previously given was followed using a zirconium solution containing 10 p. p. m. Solutions of the ions alone, and mixtures of zirconium and the respective ions were used. Suitable blanks were used in all cases. Interference was noted if the ions gave a precipitate in the absence of zirconium and if precipitation was prevented or the character of the precipitate altered in the mixtures of the ions and zirconium. The limiting concentrations given in Table I are for a zirconium concentration of 10 p. p. m . A t higher zirconium concentrations they are somewhat greater. Phosphate and sulfate prevent the formation of the precipitate. Fluoride must be absent. I n the case of aluminum, beryllium, chromium, ferric, thorium, and titanium ions, mixtures consisting of zirconium and the respective ions were precipitated as the hydroxides, the precipitates were Utered off and dissolved in nitric acid, and the interference was determined under conditions comparable t o the preceding interference studies. The results were comparable to those listed in Table I. Sensitivity I n the absence of interfering ions, the minimum concentration of zirconium that may be detected is 2 p. p. m. About 5 minutes of continuous shaking are required and a blank must be used. The reaction rate is slow at 5 p. p. m . A zirconium concentration of not less than 10 p. p. m . (0.5 microgram in 0.05 ml.) is recommended.
