The crystal structure of copper sulphate pentahydrate, CuSO 4 .5H 2 O

Abstract

Despite their frequent appearance in the laboratory, few of the structures of hydrated salts have as yet been found. This may be due to the large numbers of parameters usually involved, which, in the absence of any general laws concerning water of crystallization, makes the analysis very difficult. It was thought that clues to such general laws might be obtained from a determination of the structure of copper sulphate pentahydrate which has many interesting properties and which has been studied from many different points of view. For example, the decomposition on heating proceeds in three distinct stages, CuSO 4 .5H 2 O→CuSO 4 . 3H 2 O→CuSO 4 . H 2 O→CuSO 4 , reactions which should be explainable from a knowledge of the structure. Also, four of the waters are replaceable by ammonias, while the other one is retained. This suggests that one of the waters is very different from the others.