This section is from the book "A Treatise On Beverages or The Complete Practical Bottler", by Charles Herman Sulz. Also available from Amazon: A Treatise On Beverages.
The pure salt is best prepared by dissolving aluminium hydrate in hydrochloric acid and evaporating carefully, when crystals containing 12H3O are obtained, which are readily soluble in water and alcohol and are decomposed by heat. Chloride of aluminium is employed to add the insoluble component "alumina" to the mineral water, where other chlorides enter as components.
A ready-made solution may be prepared by dissolving 27 parts by weight of pure alumina in 560 parts of hydrochloric (muriatic) acid of 1.048 specific gravity. Digest and agitate, then add 680 parts of distilled water. Filter, and keep in stoppered bottles. The filtrate should have 1.072 to 1.073 specific gravity at 15° C. 100 parts of the liquid contain 10 parts of aluminium chloride in solution. Proportion 10 to 1.
One part by weight of the commercial chloride of aluminium is dissolved in nine parts of distilled water (10 per cent). Filter. Specific gravity 1.073 at 15° C. This commercial salt contains water in various proportions; its solution, therefore, should be regulated by the hydrometer. At 1.073 specific gravity and 15° C. it will contain 10 per cent of aluminium chloride, anhydrous.