THE EFFECT OF THE WATER-VAPOR PRESSURE ON THE KINETICS OF THERMAL DEHYDRATION OF MANGANESE(II) FORMATE DIHYDRATE

The effect of the water vapor pressure on the thermal dehydration of manganese(II) formate dihydrate was studied by means of isothermal gravimetry under various water vapor pressures, ranging from 4.6 to 24.4 torr. The kinetics of dehydration was described by a two-dimensional phase-boundary model, R(2). The rate of dehydration decreased with increasing atmospheric water vapor pressure, but the Smith-Topley phenomenon was not observed for the present dehydration. The activation energy and the frequency factor for the dehydration were 110-170 kJ . mol(-1) and 10(10)-10(16) cm . s(-1), respectively. These values increased with increasing water vapor pressure, and were much larger than those reported for the dehydration in vacuum.