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Replies to Frederic R. Siegel's comments on the authors' paper on the hydrogen-ion concentration necessary for the formation of primary dolomite. Direct precipitation; Diagenetic metasomatism of lime; Thermodynamics and environmental factors.

Three methods for the determination of the free energy δ F1 of the reaction, (CaCO[sub3])[subsolid] + (MgCO3])[subsolid] = [Ca(CO3])[subsolid]d are discussed the method of two triple points, that of combining solubility products and that of combining dissociation pressure curves. The first method, although thermodynamically well founded, fails by irreversibility, and by the third method data of sufficient accuracy are unlikely. The solubility products (L) necessary for the second method may be derived either from solubility or from pH measurements, the results being in good agreement. For dolomite, L[sub25, supD) = (1.26 &plusmin; 0.24). 10[sup-17] is the average of values from the experiments described in this paper and these of KRAMER (1959). The mean value obtained from the solubility and the pH data is δ F[sub1]° = 1720 &plusmin; 280 cal; for L[sub25, supM] the two values 3.43 . 10[sup-S] and 1.3 . l0[sup-7] have been found in both ways. [ABSTRACT FROM AUTHOR]

Comments on G. V. Chilingar and H. J. Bissell's paper on the hydrogen-ion concentration necessary for the formation of primary dolomite. Seasonal precipitation of dolomite-calcite sediments; Effect of photosynthesis of plants in water on precipitation.