Change of crystal structure of some salts when crystallised from silicic acid gel—the structure of silicic acid gel

In a paper, "Liquid Diffusion Applied to Analysis.' read before the Royal Society in 1861, Graham describes the diffusion of salts through membranes and gels. Crystallisation from gels has, however, only been developed within recent years. The growth of "Rhythmic Bands,' so extensively studied by Liesegang, has been suggested as an explanation of many natural formations in the earth's crust, whilst Hatschek and others applied the results of Liesegang to explain gel structure. Hatschek and Simons showed that gold could be obtained in crystal form, when gold chloride is reduced in the presence of silicic acid gel, the gold being deposited either in the gel, at the surface of the gel, or in both positions, according to the osmotic relationship of the solution and the gel.