Isothermal section of the Ni-Co-S phase diagram at 1273 K
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An even more sensitive polarographic method than that described above was adapted which removed Cu by electrolysis, thus avoiding the N a O H and then H2SO 4 additions (these limit the method sensitivity by increasing the volume of the sample). The polarographic methods finally used to determine the Se in copper refining electrolyte can be characterized as follows: A) 1) Oxidation with aqua regia; 2) Cu precipitation with NaOH; 3) DPP in 0.1 M H2SO 4 or a phosphate buffer at pH = 2. B) 1) Cu removal by electrolysis at E = 0.040 v; 2) oxidation with aqua regia; 3) DPP in 0.1 M H2SO 4 or a phosphate buffer at pH = 2. In each case, the final DPP signal is quantified by comparison with results for Cu2Se-spiked synthetic electrolyte put through the entire analytical procedure, along with the samples. The order of the steps in these methods is important as 1) selenide particles are removed from the system with the CuO precipitate and must be dissolved (by oxidation) prior to the Cu precipitation, and 2) copper electrolysis removes Se (IV) and must be performed before the insoluble selenides are oxidized to Se(IV). It is interesting that this last observation, in an analytical context, verifies the chemistry of Eq. [2]. The second goal of this work, i.e., verification of the co-precipitation/X-ray method for total selenium, was realized when determinations by this method were found to agree, within the precision of the methods, with those performed by the polarographic methods (cf. Table I).
Table I. Comparison of Coprecipitation/X-ray and Polarographic Determinations o! Se in Various Electrolyte Samples Se by Polarographic Sample Electrolyte a Electrolyte b Electrolyte c Electrolyte d Electrolyte e
Method in/Lg/ml 5.2, 6.4 7.2, 9.2, 10.2, 11.8, 13.2 3.8, 4.4, 6.0 7.0 7.0, 8.6
Se by Coprecipitation/ X-ray Method in ~tg/ml 6.2 12.0 5.2 8.4 6.6
1. C. W. Eichrodt and J. H. Schloen: Copper, The Science and Technology of Metal, Its Alloys and Compounds, A. Butts, ed., pp. 169-71, Hafner Publishing Co., Inc., New York, NY, 1970. 2. J. S. Smart, Jr.: ibid, pp. 410--16. 3. K. E. Burke and M. M. Yanak: Anal. Chem., 1969, vol. 41, pp. 963~5. 4. C. L. Luke: Anal. Chim. Acta, 1968, vol. 41, pp. 237-50. 5. G. Maassen: Z. Erzbergbau Metallhuttenwes., 1965, vol. 18, pp.
116-21. 640--VOLUME 11B, DECEMBER 1980
6. C. C. Bertrand and T. A. Linn, Jr.: Proceedings of the Third Corporate Analytical Conference, pp. 22-37, Kennecott Copper Corporation, June 24-26, 1971. 7. J. J. Lingane and L. W. Niedrach: J. Am. Chem. Soc., 1948, vol. 70, pp. 4115-20. 8. J.J. Lingane and L. W. Niedrach: J. Am. Chem. Soc., 1949, vol. 71, pp. 196-204. 9. G. D. Christian, E. C. Knoblock, and W. C. Purdy: Anal. Chem., 1963, vol. 35, pp. 1128-32.
Isothermal Section of the Ni-Co-S Phase Diagram at 1273 K K. T. JACOB Recent interest in the recovery of cobalt in nonferrous extractive metallurgy and the design of high temperature alloys resistant to sulfidation has motivated a study of phase relations in the Ni-Co-S system at 1273 K using the conventional evacuat
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