1285
V O L U M E 28, N O . 8, A U G U S T 1 9 5 6 Table V. X-Ray and Emission Spectrographic Determination of Zinc in Pacific Ocean Pelagic Clays Zinc Oxide, 3' 2 Sample
X-ray
Emission
30 BG 24 31 BG 32 49 BP 52 49 R P 140 50 B P 1 6 50 B P 760
0.014 0.017 0 018
0.011
0 027 0.018
0.036
0.013 0.022 0,024 0.017 0.031
Results of zinc determinations on six red clays were assayed both by x-ray fluore-cenee and by the emission spectrographic method of Wedepohl (4,5 ) in Gottingen. The results are given in Table T'. The reproducibility of an analysis on a given sample n-as governed by the random errors resulting from the counting techniques. For the lanthanum and barium determination, the absolute counting error varied from 10 to 47,, where the elements varied in concentration from 0.1 to 2 . 0 5 . In the case of zinc, the counting error varied from 15 to 4 5 , n-here the zinc concentration ranged from 0.004 to 0.67,. ACICSOW LEDGM ENT
This work was sponsored by the Office of Ir'aval Research and the American Petroleum Institute, Project 51, under contracts with the University of California.
001
I
0005
I
001
005
01
O!
C.P.S. Zn/C.P.S. As 11% AIPOI
Figure 5.
Calibration curve for zinc in clay sediments
(2) Davis, E. N., Van Nordstrand, R. A, ANAL.CHEM.26, 973-7
(1954).
(3) Sandell, E. B., "Colorimetric Determination of Traces of Metals," p. 575, Interscience, New York, 1950. (4) Wedepohl, K. H., Geochim. et Cosmochim. Acta 3, 93-142 (1953). ( 5 ) Wedepohl, K. H., personal communication.
LITERATURE CITED
(1) Adler, I., Axelrod, J. AI., Spectrochim. Acta 7, 91-9 (1955).
RECEIVED for review December 5, 1955. Accepted M a r 9, 1956. Contribution from Scripps Institution of Oceanography, No. 860.
Rapid Polarographic Determination of Uranium in Nonaqueous Solvents D. J. FISHER
and P. F. THOMASON
Analytical Chemistry Division, O a k Ridge National Laboratory, O a k Ridge, Tenn.
Rapid but precise polarographic methods have been developed for the determination of uranium in dissolved ores or inventory solutions, after its separation by solvent extraction from ions that interfere or from hazardous radioactivity. Optimum conditions are discussed for the separation and the subsequent polarographic analysis. Uranium is extracted with tributyl phosphate-isopropyl ether, the organic extract is diluted with a solvent, such as glacial acetic acid, and supporting electrolyte is added. By use of standard polarographic apparatus well formed uranium waves are obtained in several nonaqueous media. The simplicity of the manipulations required is advantageous in work with radioactive samples.
T
HE determination of the uranium content of dissolved ores or of various inventory solutions is frequently complicated by the presence of ions that interfere with the analytical method and/or by the hazardous presence of very radioactive fission products. For such analyses, the first step is usually the separation of uranium from the solution. A well-known and very effective means of separation is solvent extraction with tributyl phos-
phate, either alone or diluted with various solvents which tend t o improve the separation of the phases. Such samples presented for analysis often contain nitric acid and may contain large amounts of aluminum nitrate. Rapid polarographic methods for the determination of uranium in which uranium is first separated from copper and/or fission products by extraction have been developed ( I , 8, IO). The extraction serves two purposes: decontamination of uranium from radioactivity, if present, and elimination of polarographic interferences caused by overlapping waves of cations, such as those of copper, having half-wave potentials very close to that of uranium. This method ( I , I O ) assumes prior dissolution of sample. The procedure ( 1 , I O ) consists of the extraction of uranium into either tributyl phosphate-Varsol ( a kerosine-type hydrocarbon) or tributyl phosphate-isopropyl ether, followed by the polarographic determination of the uranium in a nonaqueous solution of the extract or, alternatively, in a water strip (aqueous extract) of the organic extract. The isopropyl ether extraction is preferred because very satisfactory diluents were found which permit the uranium to be determined directly in the organic solution by polarographic analysis. Two procedures have been used to obtain polarograms of the uranium in the preferred extract. The tributyl phosphate-isopropyl ether extract may be diluted t o
ANALYTICAL CHEMISTRY
1286 bring the uranium concentration within the polarographic range (approximately 50 -/ of uranium per ml.) with a suitable solvent (glacial acetic acid or ethyl alcohol), to which a supporting electrolyte (0.25M lithium perchlorate) is added. Alternatively, the extract may be stripped with water and an aliquot of the heated strip, to which supporting electrolyte (nitric acid) has been added, analyzed polarographically for uranium. ~
Table I. Effect of Nitric Acid Concentration of Aqueous Phase on Extraction of Uranium(V1) into Tributyl Phosphate-Varsol (30:70 Vol. YO) 1.3M Al(N0a)r 1.0 mg. of U per ml. 0.07 mg. of Cu per ml. "01, as indicated Volume of aqueous and of organic phases. 50 ml. Uranium Recovered, Mg. HKOl in Aqueous Phase, N Run1 Run2 50.2 50.1
