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some thiophenic and selenophenic anionic complexes, in which the Ke values for complex formation were larger than 490 M"1. It appears that a complex must have a Kc value larger than about 200 M"1 in order to be isolated.From Table III it is clear that the differences between the ki and k-X values for la" and Id" are attributable to the entropy of activation rather than to the enthalpy of activation. Here, rigorous comparison is impossible, since the data of Fendler et al. were obtained in the absence of added salt, so that ion pairing must be taken into account. The results may indicate that the transition state for the formation of la" is more solvated than that for the formation of Id", which seems reasonable, because the negative charge donated is less delocalized in la" than in Id", and consequently the former should be more solvated. According to the principle of microscopic reversibility, this should also be the case for the transition state for the decomposition of la". The result, however, is the opposite, which may be due to the ion pairing of Id" with sodium ion.

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Isothermal P-x data for the binary system water/methyl acetate at 50 °C are reported. Reduction of data by a modification of Barker's method allows calculation of Ge.We previously have reported experimental and correlated vapor/liquid equilibrium (VLE) data taken on an isothermal static total-pressure device. However, none of these studies dealt with systems which form two liquid phases. Herein are results of our first investigation of a binary system exhibiting vapor/ liquid/liquid equilibrium (VLLE): water (1)/methyl acetate (2) at 50 °C.Data were taken on the total-pressure apparatus described by Gibbs and Van Ness (1), as modified by DKIsi et al. (2). The water was doubly deionized with conductivity less than 1 X 10~® "1. The methyl acetate was chromatoquality reagent supplied by Matheson Coleman and Bell, with a stated purity of 99.7 mol %. Both reagents were thoroughly degassed.

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