Dehydration of NiCl2 center dot 6H(2)O

Powdered samples of nickel chloride hexahydrate prepared by grinding small crystallites grown by slow evaporation of an aqueous solution have been stu died by dynamic and isothermal TG measurements. It is observed from dynamic TG that hexahydrated nickel chloride dehydrates in two steps releasing 5 m oles H2O and 1 mole H2O at mean temperatures of 224 and 291 degreesC, respe ctively. Isothermal TG measurements, dependent upon temperature show differ ent dehydration pattern with respect to time. In the temperature range 240- 300 degreesC dehydration pattern similar to dynamic TG has been observed. F rom dynamic and isothermal measurements the kinetic parameters E and Z are calculated. It is observed that the general mechanism of dehydration in the se samples for both steps is random nucleation and subsequent growth. The s ame mechanism is described by different functions in isothermal and dynamic studies. (C) 2001 Elsevier Science B.V. All rights reserved.