On the crystal structure of the chlorides of certain bivalent elements

Abstract

In 1925 Bruni and Ferrari (1) reported that the lines on a powder photograph of the hexagonal crystal MgCl2 could be accounted for on the basis of a rhombohedral (pseudocubic) unit of structure with a = 5.08 Å and α = 90° containing 2 MgCl2. Later they announced (2) that ZnCl2, CdCl2, and MnCl2 have the same structure, with values of α a few degrees larger than 90°. Ferrari (3) then added CoCl2 and NiCl2 to the group; certain weak lines occurring on the powder photographs of these substances require the value of a to be doubled, giving a rhombohedral unit with α = 90° and a = 10.02 Å and 10.00 Å, respectively, containing 16 M++Cl2. Goldschmidt (4) has also reported that unpublished powder photographic data obtained by Oftedal in his laboratory show that RuCl2, RhCl2, PdCl2, IrCl2, and PtCl2 are to be assigned the same structure as NiCl2.