Studies of the Rate of the Formation of Talc under Hydrothermal Conditions at 400–460 °C

Abstract

The rate of the formation of talc from brucite powders with soluble silica under hydrothermal conditions was investigated in the temperature range of 400–460 °C, a range including the equilibrium temperature for the reaction: brucite+serpentine\ightleftarrows2 forsterite+3H2O. Serpentine appeared as an intermediate phase below 415 °C, while above 430 °C forsterite appeared in addition to serpentine. The apparent reaction can be represented as:(Remark: Graphics omitted.)The reaction was apparently expressed as a pseudo-first-order reaction. The overall rate of the reaction did not increase with the increase in the temperature. Arrhenius plots of the rate constants for the overall reaction showed a curve with a maximum at about 415 °C and a minimum at about 445 °C which was caused by the alteration of the reaction by the appearance of forsterite at 430 °C.