Studies on the Determination of 10(-10) - 10(-8) g Cu, Bi, Cd, Sb in Zinc and Cadmium Sulfide
Abstract Generated abstract
This paper develops amalgam polarographic procedures with accumulation for determining trace impurities in semiconductor-grade zinc sulfide and cadmium sulfide. Using a 1 N hydrochloric acid background, the authors study the dependence of anodic peak currents on electrolysis potential, accumulation time, and analyte concentration, showing that copper, lead, cadmium, and bismuth can be recorded simultaneously in zinc sulfide, while copper, bismuth, and antimony are determined in cadmium sulfide. The proposed methods dissolve 0.1 g samples in hydrochloric acid, remove sulfur as hydrogen sulfide during evaporation, and quantify impurities by standard additions, reaching sensitivities in the range of about 10^-5 to 10^-7 percent for zinc sulfide.
Full Text
STUDIES ON THE DETERMINATION OF \(10^{-10}\)—\(10^{-8}\) g OF Cu, Bi, Pb, Cd, Sb IN ZINC AND CADMIUM SULFIDES
A. A. Kaplin, Z. S. Mikhailova, V. M. Pichugina
(Presented by the scientific seminar of the Department of Physical Chemistry)
Zinc sulfide, as a material for the semiconductor industry, is finding ever wider application. In recent years, for determining the content of microimpurities in semiconductor and especially pure substances, the method of amalgam and film polarography with accumulation has found wide use [1]. The advantages of the method include high sensitivity, the possibility of simultaneous determination of several elements, simplicity of the apparatus design, the use of small sample weights, and a small number and volume of reagents.
We have carried out studies on the development of an amalgam-polarographic procedure for determining Cu, Bi, Pb, and Cd in ZnS sample weights (0.1 g) and Cu, Bi, Sb in CdS. On the basis of the studies performed, a procedure is proposed for the simultaneous determination of \(10^{-5}\)—\(10^{-6}\%\) Cu, Pb, Cd, Bi in ZnS and Cu, Bi, Sb in CdS.
In the work we used an ON-101 polarograph, an electrolyzer with insert cups, and a circulating electrolyzer [2].
We studied a background of 1 N HCl in order to determine the possibility of simultaneous recording of the anodic peaks of Cu, Pb, Cd, and Bi. For this purpose, dependences were recorded for the above-mentioned elements on the potential of electrolysis, on the accumulation time, and on the concentration of the elements being determined. The data obtained show that, against a background of 1 N HCl, simultaneous determination of Cu, Pb, Cd, and Bi is possible.
Procedure for the Determination of Copper, Lead, Cadmium, and Bismuth in Zinc Sulfide
The procedure is based on dissolving ZnS in HCl, distilling off sulfur in the form of H₂S at \(t = 100\)—\(110^\circ\)C, and subsequent polarography against a background of 1 N HCl. The sensitivity of the procedure is \(10^{-5}\)—\(10^{-7}\%\) for a sample weight of 0.1 g ZnS.
Course of the Analysis
A sample weight of 0.1 g ZnS is dissolved in 2 ml HCl; the solution is evaporated to dryness in a quartz cup at \(t = 100\)—\(110^\circ\). The residue is dissolved in 5 ml of 1 N HCl and polarographed. Electrolysis is carried out at a potential of \(-1.0\) V (relative to the saturated calomel electrode). The solution is stirred with nitrogen purified from oxygen. After completion of the accumulation process, [[unclear: text continues on next page]]
anodic peaks of the impurities being determined at the following potentials: Cd—0.68 V; Pb—0.5 V; Cu—0.3 V; Bi—0.08 V. The concentration of the elements being determined in the sample is estimated by the method of additions.
Procedure for the determination of copper, bismuth, and antimony in cadmium sulfide
The essence of the procedure is that CdS is dissolved in HCl; in this process sulfur is driven off in the form of H₂S at \(t = 100\text{–}110^\circ\), followed by polarography in 1 N HCl.
Course of analysis
A weighed portion of 0.1 g of CdS is dissolved in HCl and evaporated at \(100\text{–}110^\circ\) to a dry residue. The residue is dissolved in 1 N HCl and polarographed. The concentration of the elements is estimated by the method of additions.
Conclusions
- The dependences of the anodic current of the elements being determined on concentration, potential, and electrolysis time have been studied.
- A procedure has been developed for the determination of copper, lead, cadmium, and bismuth in zinc sulfide.
- A procedure has been developed for the determination of copper, bismuth, and antimony in cadmium sulfide.
REFERENCES
- A. G. Stromberg, E. A. Zakharova. Zav. lab. 30, 261, (1964).
- V. I. Kuleshov, V. M. Pichugina. Zav. lab. 34, 1557, (1968).