Dehydration of NiCl2·6H2O

Powdered samples of nickel chloride hexahydrate prepared by grinding small crystallites grown by slow evaporation of an aqueous solution have been studied by dynamic and isothermal TG measurements. It is observed from dynamic TG that hexahydrated nickel chloride dehydrates in two steps releasing 5 moles H2O and 1 mole H2O at mean temperatures of 224 and 291°C, respectively. Isothermal TG measurements, dependent upon temperature show different dehydration pattern with respect to time. In the temperature range 240–300°C dehydration pattern similar to dynamic TG has been observed. From dynamic and isothermal measurements the kinetic parameters E and Z are calculated. It is observed that the general mechanism of dehydration in these samples for both steps is random nucleation and subsequent growth. The same mechanism is described by different functions in isothermal and dynamic studies.