The water molecules in CuSO4.5H2O

Single crystals of fully hydrated copper sulphate have been studied by neutron diffraction and the measurements have been used to construct projections of the neutron-scattering density, due to the atomic nuclei, on the three crystallographic axial planes. These provide full details of the shape and environment of the water molecules and of the hydrogen bonds which link together the atoms in the structure, which was originally proposed by Beevers & Lipson as a result of X -ray diffraction work. It is found that the H—O—H angles for all the water molecules are within a degree or two of the tetrahedral value and the hydrogen bonds have to be bent by up to 26° in order to accommodate them. Corresponding measurements have been made at a series of five different temperatures between 20 and 90°C in order to test a suggestion that molecular rotations of the water molecules occurred before the onset of dehydration: the neutron data refute this suggestion.