ACKNOWLEDGMENT
Table I.
25 125
500 500 500 500
Separation of Uranium from Bismuth
0.100 0.100 0.100 1.000
1.000 1.000
0,099 0.097 0.097 0.980 0.976 0.987
shaken for 10 minutes. The acetylacetone phase was separated, filtered, and made up to a volume of 10 ml., of which 2 ml. was withdrawn by a pipet into a 10-ml. borosilicate glass volumetric flask. The flask was very gently warmed until the liquid was reduced in volume to about 0.5 ml. Then the supporting electrolyte was added and the resulting solution deaerated for 5 minutes in a 10-ml. Lingane-Laitinen H-type polarographic electrolysis cell. The polarogram was then recorded and the concentration of uranium found from suitable calibration curves. The results are shown in Table I. The separation of uranium from a 5000-fold excess of bismuth did not present much difficulty. The amount of bismuth was limited only by the low
0.101
0.099 0,099 0.995 0.991 1.002
The authors gratefully acknowledge the financial assistance of the U. S. Atomic Energy Commission in this work.
+o. 001 -0.001
-0.001
-0.005 -0,009 $0,002
solubility of disodium ethylene(dinitrilo)tetraacetate, which must be present in a thirtyfold excess. The amount of uranium found is consistently low, as might be expected from the extraction curves (Figure 2 ) . Complete extraction is not reached in the case of uranium, but it is a simple matter to allow a correction factor, as the percentage extraction for uranium acetylacetonate is 98.48% a t pH values higher than 6.5. When this correction is applied (Table I), the results fall within the experimental error of =t1%. Experimental data not presented here indicate that this method for separation of uranium would be equally applicable in the presence of copper, zinc, and lead.
LITERATURE CITED
Irving, H., Williams, J. P., J. Chem, SOC.1949, 1841. Kolthoff, I. M.;, Lingane, J. J., “Polarography, p. 494, Interscience, New York, 1952. Kolthoff, I. hl., Sandell, E. B., J.A m . Chem. SOC.63, 1906 (1941). Lingane, J. J., IND.ENG.CHEnr., ANAL. ED. 15,583 (1943). Pribil, R., Jelinek, M., Chem. Listy 47, 1326 (1953). Rydberg, J., Arkiv Kemi 8, 115 (1955). Ibid.,9, 95 (1955). Sharma, R. N. S., hfalik, A . K., 2. anal. Chem. 148, 179 (1958). Souchay, P., Faucherre, J., -4naL Chim. Acta 3, 252 (1949). Steinbach, J. F., Freiser, H., ASAL, CHEY.25, 881 (1953). Ibid., 26,375 (1954). Taylor, R. P., Ph.D. thesis, Princeton University, 1954. RECEIVEDfor review June 25, 1956. Accepted October 31, 1956. Presented in part, Pittsburgh Conference on Analytical Chemistry and Applied Spectroscopy, Pittsburgh, Pa., March 1956. Contribution from Chemistry Department, University of Pittsburgh, Pittsburgh 13, Pa.
Analytical Solvent Extraction of Molybdenum Using Ace tylace t one JAMES P. McKAVENEY I and HENRY FREISER University of Pittsburgh, Piftsburgh 73, Pa.
FAcetylacetone has been found to be a selective extraction reagent for molybdenum in ferrous materials. Molybdenum(V1) is extracted from a 6N sulfuric acid solution while copper, tungsten, and chromium, which normally interfere in the colorimetric procedure for molybdenum, are not extracted at this acidity. The molybdenum is determined as the thiocyanate after extraction.
A
IS UNIQUE in the field of solvent extraction because it can be used as both a solvent and as a reagent. It functions as a reagent by first forming a metal chelate with the metal ion. The neutral metal CETYL-4CETOXE
1 Present address, Crucible Steel Co. of America, Research Laboratory, 234 Btwood St., Pittsburgh 13, Pa.
290
ANALYTICAL CHEMISTRY
chelate which is thus formed, being more of an organic nature than inorganic, is then extracted by the excess acetylacetone in the organic layer. The percentage of metal ion extracted into the organic layer is principally a function of the pH of the aqueous layer and the oxidation state of the metal ion. As early as 1900, Urbain (8) discovered that the acetylacetonate of thorium could be extracted by chloroform from an aqueous solution acidified with sulfuric acid. I n 1949 Abrahamczik (1) used a 1 to 4 mixture of acetylacetone and carbon tetrachloride to separate small amounts of iron, aluminum, and manganese from a weakly ammoniacal solution prior to the determination of magnesium with Titan yellow. Steinbach and Freiser (5-7), using acetylacetone as both solvent and reagent,
have made a detailed study on the extraction charatteristics of aluminum(II1) , beryllium(II), copper(II), cobalt(III), chromium(III), iron(III), nickel(II), vanadium(IV), zinc (11), and zirconium(1V). I n the present work the study has been extended to include iron(II), molybdenum(V-I), manganese(I1) , titaniumIIV), and tungsten (VI). I n particular, this work deals with the extraction of molybdenuni from ferrous materials. REAGENTS AND APPARATUS
Chloroform, reagent grade. Acetylacetone (2,4 - pentanedione) , Carbide and Carbon Co. reagent is ordinarily of sufficient purity as received. If any appreciable discoloration is present, the solvent is distilled.
100
I
I
I
h
I
&
h
0
5
6
I
\96%
80-
c
