addition of dibenzoylmethane in pyridine to the organic phase after extraction shows promise for the spectrophotometric determination of microgram quantities of uranium. ACKNOWLEDGMENT
The authors wish to express their appreciation to J. A. Merrill and F. H. Tingey for calculations and aid in the statistical design and analysis of experiments. They also thank G. V. Wheeler, G. \Ir. Boyes, and K. A. Arnold for spectrographic analyses and W. H. Burgus, R. B. Regier, and E. H. Turk for advice concerning preparation of active isotopes. LITERATURE CITED
--
Commission, Rept. IC-706 (1951). (4) Blake, C. A., Brown, K. B., Coleman, C. F., Ibid., ORNL-1964 (1955). ’
(5) Booman, G. L., Holbrook, W. B., Division of Analytical Chemistry, 133rd Meeting, ACP, San Francisco, Calif., -4pril 1958. (6) Boyd, G. E., ANAL. CHEM.21, 335 (1949). (7) Bruce, F. R., Fletcher, J. M., H man, H. H., Katz, J. J., “Progress in d c l e a r Energy, Ser. 111, Process Chemistry,” hIcGram-Hill, New York, 1956. (8) Burger, L. L., U. S. Atomic Energy Commission, Rept. HW-44888 (1957). (9) Davies, 0. L., ed., “Design and Analysis of Industrial Experiments,” Hatner, Sew York, 1956, p. 495. (10) Dykes, F. W., Fletcher, R. D., Turk, E. H., Rein, J. E., Shank, R. C., ANAL. CHEM.28, 1084 (1956). (11) Eberle, -4.R., Lerner, 11.W.,Ibid., 29, 1134 (1957). (12) Grimaldi, F. S.,Levine,. H., U. S. rltomic Energy Commission, Rept. AECD-2824 (1950). (13) Guest, R. J., Zimmerman, J. B., -4NAL. CHEM. 27.931 (1955). (14) Kaplan, L., ‘ Hildebrandt, R. A., Ader, AI., U. S. Atomic Energy Commission, Rept. AECD-3015 (1950). (15) Katzin, L. I., Simon, D. hl., Ferraro, J. R., J . S m . Chem. SOC.74,1191 (1952). (16) Moore, R . L., U. S. Atomic Energy Commission, Rept. HW-25230 (1949). (17) Morrison, G. H., Freiser, H., “Sol-
vent Extraction in Analytical Chemistry,” Wiley, New York, 1957. ANAL. (18) Nietzel, 0. A., DeSesa, RI. -4., CHEM.29,756 (1957). (19) Paige, B. E., Elliott, M. C., Rein, J. E., Ibid., 29, 1029 (1957). (20) Rulfs, C. L., De, A. K., Elving, P. J., Ibid., 28, 1139 (1956). (21) Rulfs, C. L., De, A. K., Lakritz, J., Elving, P. J., Ibid., 27, 1802 (1955). (22) Scott, T. R., Analysr 74, 486 (1949). (23) Warf, J. C., J . Am. Chem. SOC.71, 3257 (1949). (24) White. J. C.. U. S. Atomic Enerev ’ Commission, Rept. ORNL-2161 (19571. (25) Ibid., CF-56-9-18 (1956). (26) Ibid., CF-57-1-5 (1957). (27) Ibid., CF-57-2-37 (1957). (28) Wright, W.B., Ibid., Y-838 (1952). (29) Yoe, J. H., Will, F., Black, R. A., AXAL.CHEM.25. 1200 11953). (30) Zvyagintsev, ’ 0. E:, Proc. Intern. Conf. Peacejul Uses Atomic Energy 7, Paper 670 (1956). RECEIVEDfor review January 17, 1957. Accepted July 7, 1957. Pittsburgh Conference on Analytical Chemistry and Applied Spectroscopy, Pittsburgh, Pa., March, 1958. The Idaho Chemical Processing Plant is operated by Phillips Petroleum Co. for the U. S. Atomic Energy Commission under Contract No. AT( 101)-205.
Hypophosphorous Acid as a Gravimetric Reagent for Scandium DONALD R. BOMBERGER‘ University of California Radiation laboratory, livermore, Calif.
b During a search for a more specific gravimetric determination of scandium, it was found that hypophosphorous acid produced a weighable precipitate of scandium hypophosphite. A low gravimetric factor, combined with some improvement in selectivity over existing methods, indicated a useful reagent. The granular precipitate was easily transferred, washed, and dried. Quantitative recovery was obtained in the range from 0.1 to 1.0 mmole of scandium.
A
for the gravimetric determination of scandium suffer from incomplete precipitation, poor physical properties of the solid, a high gravimetric factor, and/or lack of specificity. A comprehensive study recently published by T’ickery (4) shows that precipitation of scandium is incomplete using hydroxide, oxalate, carbonate, fluoride, phosphate, and phytin. The basic tartrate is satisfactory only at VdILABLE METHODS
Present address, Research and Development Division, Consolidation Coal Co., Library, Pa.
concentrations of greater than 50 mg. of scandium per ml. This is weighed as the oxide and consequently has a high gravimetric factor. Pokras and Bernays ( 2 ) have reported using 8quinolinol as a precipitating reagent. This method is not as selective as hypophosphorous acid and requires somewhat more care in the control of precipitating and drying conditions. I t s advantages over the hypophosphite method are lower gravimetric factor and greater ease of scandium recovery from the precipitate, REAGENTS
Scandium Oxide, 99.8y0 (Research Chemicals, Inc.), was used in t h e preparation of t h e standard solution. Spectrographic examination indicated less t h a n 0.2% impurities. T h e standa r d solutions were prepared b y dissolving t h e oxide in concentrated hydrochloric acid n5th heat a n d stirring, and diluting t o give final concentrations of scandium desired in 1M acid. This solution was standardized by the basic tartrate method ( 3 ) . Hypophosphorous Acid, 30 t o 32y0, National Formulary grade (Baker and Adarnson) was used. Other rea-
gents and chemicals were of reagent grade. PROCEDURE
A sample containing 5 to 50 mg. of scandium is dissolved in 2 ml. of concentrated hydrochloric acid by warming, and diluted t o 25ml. with distilled water. The solution is heated nearly to boiling, and 2 ml. of 30 t o 32% hypophosphorous acid is added dropwise with stirring. The solution is digested for 1 hour on a steam bath and allowed to cool. The supernatant solution is decanted through a fine sintered glass crucible; the precipitate is transferred and washed with 2% hypophosphorous acid and finally with a few milliliters of distilled water. The precipitate is dried a t 110’ C. for 1 hour, cooled in a desiccator, and weighed. The gravimetric factor for scandium is 0.1878. EXPERIMENTAL
The addition of hypophosphorus acid to a solution of scandium in IN hydrochloric acid results in an immediate flocculant precipitate. This is not quantitative with respect t o scandium (approximately 95% recovery) and is not a weighable form. On digesting VOL. 30, NO. 12, DECEMBER 1958
1907
Table 1.
Analyses of Standard Scandium Solutions
Acid MeScandium, Mg. dium Taken Found HC1 22.20 22.18,22 22,22.18,22.16 21.16 44.60 4.46 22.20 HnSOa 22.20 HClOi 22.20
21.17,21.18,21.17,21.18 44.53,44.53,44.57,44.57 4.41, 4.49, 4.47, 4 . 4 5 22,22,22.27,22.17a 22 23,22.22,22.23,22.14 22.25,22.25,22.22,22.18
0
100 ml. of 1A- acid and 4 ml. of H8PO2 were used.
E
0
o x o
;F
om
2.0
z
8 d
I .o
o x
0
1908
ANALYTICAL CHEMISTRY
0
o 0.5QM
0
x 0.75M 0 1.00 M 0 1.25 M
L 2 L x -
0.0 000
0.05
0.10
SCANDIUW
over steam for 1 hour, the precipitate changes character and sinks to the bottom of the solution as a fine granular solid. Analysis of this solid showed a phosphorus to scandium ratio of 3 to 1. The phosphorus content was determined by cerate oxidimetry of the hypophosphite (1). When a perchloric acid solution of scandium was used, the precipitate formed hard agglomerates. These were crushed with a stirring rod while on the steam bath and found to break down into the fine precipitate, as occurred when scandium mas precipitated from hydrochloric acid. The initial concentrations of hydrochloric and hypophosphorous acids interact in their effect on the precipitation of scandium hypophosphite (Figure 1). To establish the optimum conditions, a series of experiments was undertaken using radioactive scandium-46 as a tracer. Samples were prepared containing 2.115 mg. of scandium and lo6 c.p.m. of scandium-46 in hydrochloric acid ranging from 0.0 t o 4.0S. Sufficient hypophosphorous acid was added to render final concentrations of 0.5 to 1.25M. After digestion, the precipitate was centrifuged, and the supernatant \\-as counted in a well-type scintillation counter. The per cent scandium remaining in solution was calculated. Khile the most advantageous conditions are in the area of 1N hydrochloric acid and 0 . 5 S hypophosphorous acid, considerable latitude is possible with small loss in efficiency. The composition of the precipitate remained constant over the area considered. The precipitate of scandium hypophosphite did not show any change in weight when heated from 110Oto 2 O O O C . A final washing with alcohol in order to speed drying proved satisfactory.
0
0.15
020
0.25
REMAINING IN SOLUTION (%)
Figure 1. Effect of hydrochloric acid and hypophosphorous acid concentrations on precipitation of scandium hypophosphite
Table I illustrates typical results obtained using the recommended procedure. The precipitation was made b y the addition of 2 ml. of hypophosphorous acid in the sample dissolved in 25 ml. of 1N acid, except as noted.
Samples \yere treated by the recommended procedure using 25 ml. of 1N hydrochloric acid (perchloric acid was used where chlorides were insoluble) and 2 ml. of hypophosphorous acid. ACKNOWLEDGMENT
INTERFERENCES
The presence of other acids of phosphorus, even in small amounts, interferes through the formation of mixed precipitates. It follows that any substance which would oxidize hypophosphorous acid under hot, acid conditions also interferes. Higher oxidation states of most elements fall into this category. Kitrate ion must be carefully eliminated by several fumings Tvith perchloric or sulfuric acid. Elements that nrecinitate as salts of hypophosphorousL acid under the described conditions are: Sc(III), Zr(IV), HfUV). Th(IV). and Tallr). Elements that are reduied to a n ‘insoluble form (usually the elemental state) are: Cu(II), Ag(I), Au(III), Hg(I), Bi(III), Sb(III), As(III), Se(III), Te(IV), and Pd(1V). Ions that do not form a precipitate when alone, but coprecipitate or otherwise interfere with scandium determination, are: AI(III), Ga(III), In(III), Y(III), Sn(II), V(IV), Cr(III), AIo(VI), L’(TrI), F(I), Fe(II), Co(II), and Pt(1V). Ions that did not interfere with the determination of 22.2 mg. of scandium, when present in 100-mg. amounts, were: Li(I), Na(I), K(I), Rb(I), &(I), Be(II), -Vg(II), Ca(II), Sr(II), Ba(II), Zn(II), Cd(II), B(III), Tl(I), La(III), Ce(III), Pb(II), S(ISH1+), S(S04--). C1-, Br-, I-, RIn(II), Ki(II), Ru(IV), and Ir(1V).
The author wishes to express his appreciation to Killiam H. Hutchin, whose helpful suggestions were material in the development of this method. LITERATURE CITED
(1) Bernhart, D. N., ASAL. CHEII. 1T98-9 (1954). (2) Pokras, L., Bernaye, P. AI., It 23, 757-9 (1951). (3) Schoeller, IT. R., Pon-ell, A .
(‘Analysis of llinerals and Ores the Rarer Elements,” 3rd ed., p. Hafner. Nem- Tork. 1955. (4) Vick&y, R . C., ’ J . Chem. SOC.1956, 3113-20.
RECEIVED for revier December 2, 1957. Accepted June 2, 1958. Work done under the auspices of the U. S. Atomic Energy Commission.
Determination of Cadmium in Zinc Concentrates and Other Zinc-Rich Materials-Correction I n the article on “Determination of Cadmium in Zinc Concentrates and Other Zinc-Rich RIaterials” [ANAL. CHIXI. 30, 1846 (1958)], the name of the third author should hare been giren as Robert Liu.
