Order phenomena in aqueous AlCl3 solutions

Abstract

X-ray diffraction data of two aqueous solutions of AlCl3 are interpreted using a model in which the Cl− ions have a coordination number of six and the Al(H2O)3+6 ions interact with twelve water molecules through short and linear H bonds, the water molecules nearest neighbor to the Al3+ ions having a trigonal orientation. Moreover, evidence is given that such a hydration structure tends to persist even when the total amount of water present in the system is rather small.