A colloidal or soluble stannic acid is obtained by dialysing a mixture of tin tetrachloride and alkali, or of sodium stannate and hydrochloric acid.
Trans., 1861, p. 163); the first named decomposing aluminium acetate (from lead acetate and aluminium sulphate) with boiling water, the latter dialysing a solution of the basic chloride (obtained by dissolving the hydroxide in a solution of the normal chloride).
Graham obtained a colloidal tungstic acid by dialysing a dilute solution of sodium tungstate and its equivalent of hydrochloric acid; on concentrating in a vacuum a gummy product is obtained, which still remains soluble after heating to 200°, but it is converted into the trioxide on heating to redness.
Thomas Graham obtained a soluble hydrate by dissolving the freshly prepared hydrate in ferric chloride and dialysing the solution, the soluble hydrate being left in the dialyser.
The mucilage must be acidulated with hydrochloric acid before dialysing, to set free the gummic acid.