Kinetic analysis of the dehydration and linkage isomerization of potassium hexanitronickelate(II) hydrate

Abstract The dehydration of K 4 [Ni(NO 2 ) 6 ] · x H 2 O has been studied by TG and DSC in a highly replicated study. Mass loss data indicate that the material used in this work contained 2.685% water, and this is consistent with the compound being formulated as K 4 [Ni(NO 2 ) 6 ] · 0.75H 2 O. Out of 128 combinations of the α, T data sets from TG experiments, the Reich and Stivala procedure gave the best fit with the A2 rate law 55 times and with the A1.5 rate law 41 times. Out of 48 combinations of α, T data sets obtained from DSC experiments, the A2 rate law fitted best in 29 cases and the A1.5 in 8 cases. In contrast to previous studies, there is no evidence that the reaction follows a first-order process but rather the dehydration appears to be best considered as following an Avrami rate law with an index of 1.5–2.