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Studies in the system MgO-SiO2-CO2-H2O(I): The activity-product constant of chrysotile

P. B. Hostetler·C. L. Christ
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Abstract

Chrysotile dissolves congruently in water according to the reaction: Mg 3 Si 2 O 6 ( OH ) 4 c + 5 H 2 O l = 3 Mg aq 2+ + 6 OH aq − + 2 H 4 SiO 4 aq . Experimental determination of the activity-product constant of chrysotile, K chr = [ Mg 2+ ] 3 [ OH − ] 6 [ H 4 SiO 4 aq ] 2 , at 90°C, yields the value of K chr = 10 −49.2 ± 10 0.5 . A synthetic sample and a natural sample from New Idria, California, were used in the determination. Values of K chr were calculated for temperatures ranging from 0°C to 200°C, using the thermochemical data of King et al . (1967) for chrysotile and antigorite, various solubility data for silica, and ionic partial molal heat capacities estimated by the method of criss and Cobble (1964a). K chr is 10 −54.1 at 0°C, rises to a maximum value of 10 −48.5 at approximately 135°C, and is 10 −49.1 at 200°C (all values for the three-phase system, chrysotile plus solution plus vapor). The calculated 90°C value is 10 −49.1 , in excellent agreement with the experimental value; for 25°C, the calculated value is 10 −50.8 .

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P. B. Hostetler, C. L. Christ. 1968. Studies in the system MgO-SiO2-CO2-H2O(I): The activity-product constant of chrysotile. https://doi.org/10.1016/0016-7037(68)90041-0

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