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A general expression applying to the steady state has been derived which permits calculation of the increase in thermal conductivity due to chemical reaction in mixtures of gases in chemical equilibrium. In addition to the gas composition, heats of reaction and binary diffusion coefficients among the component gases are required. In the case of a simple dissociation, the thermal conductivity may be related to the equilibrium heat capacity. This suggests a possible method for estimating heat transfer in various practical systems with dissociating gases. Approximate calculations for dissociation of diatomic molecules at equilibrium show that the thermal conductivity may be an order of magnitude greater than in nonreacting mixtures. Calculations for the systems 2NO2⇆N2O4 and 6HF⇆(HF)6 are in satisfactory agreement with experiment.

Experimental data on the mean activity coefficient of CaCl(2) in NaCl-CaCl(2) mixtures at ionic strengths below 1 m have been used to prepare a table of activity coefficients for Ca(++) in solutions of physiological interest. The establishment of an empirical calcium ion activity scale is discussed, and a number of possible assumptions are examined. The assumption gamma++ = (gamma+/-)(2) is suggested as being the simplest with a theoretical basis.

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