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.
