High-Temperature isopiestic studies on the liquid solutions Hg-Cd-Sn
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I.
INTRODUCTION
AN entire isoactivity curve of one component in a ternary metallurgical melt is an important quantity relating to the interaction between atoms, molecules, or ions in it. Almost all measured and calculated activity data in the literature for ternary molten alloys, salts, slags, and mattes have been displayed and reported in the form of the entire isoactivity curves. So far, however, the direct measurements of the entire isoactivity curves have hardly been realized in the melts, mainly because of the elaborate and time-consuming technique required. A high-temperature isopiestic technique, introduced by Herasymenko [u and improved by many others, 12q41 has been applied to the activity measurements for binary and ternary molten alloys with one common volatile component. In one case, the pure volatile metal at a low temperature was used as a reference system for the alloys at a high temperature, tl-sJ In another case, one binary alloy whose selected data had been available in the literature was chosen as a reference system for one to three alloy sarr/ples with the same volatile component and at the same temperature, t7 L4[ The object of this series of articles is to show that, after some further improvements have been made in the high-temperature isopiestic technique, each entire isoactivity curve of the volatile component, not only in ternary molten alloys but also in ternary salts, slags, and mattes, may be measured directly by only one experiment, with an accuracy comparable with that achieved in other reliable methods, and then the activities of the involatile components may analytically be calculated from the ternary isopiestic data. This further improved isopiestic technique, in which many more isothermal samples than those used in previous techniques could be brought to equilibrium, has been proposed and applied to both the comparative investigations of the activities of Hg among the binary melts Hg-Bi, Hg-Cd, Hg-Ga, Hg-In, Hg-Sn, Ilsl and Hg-Pb ll61 and the direct measurements of the entire isoactivity curves of Hg in the ternary melts Hg-Bi-Sn. t~71A strict analytical solution of the ternary Gibbs-Duhem equation has ZHI-CHANG WANG, Professor, is with the Northeast University of Technology, Shenyang 110006, Liaoning, China. XIN-HUA ZHANG, Research Associate, and JIAN-KANG ZHOU, Research Assistant, are with the Shanghai Institute of Nuclear Research, Academia Sinica, Shanghai 201800, China. Manuscript submitted December 3, 1991. METALLURGICAL TRANSACTIONS B
also been presented t~Sl and applied to the activity calculation of involatile components Bi and Sn in the ternary amalgam Hg-Bi-Sn. I171 The results for the binary alloys are in good agreement with the literature data, and those for the ternary alloy approximately fit a partial ideal solution model proposed previously, r~9-23j More studies shortly to be reported deal with PbO-containing slags, PbC12-containing salts, and other ternary amalgams. Here we deal with the ternary amalgam Hg-Cd-Sn at 600 K. II.
EXPERIMENTAL PROCEDURE
The high-t
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