be dissolved in concentrations as high as 50 60 weight and the adduct cabr 2 forms a hexahydrate thus the combination of albr 3 and ca oh 2 in accordance with the invention should form a solid product the solid aluminum hydroxide compositions of the invention exhibit superior solubility in acidic solutions such as alum solution even after periods of aging substantially longer than those tolerable for amorphous aluminum hydroxide as a result these solid products are highly suitable for transport in bags thus facilitating on site preparation of basic aluminum complexes for water treatment basic aluminum sulfate complexes can be prepared by adding water to the granular aluminum hydroxide product of the invention to form a slurry for example a slurry consisting essentially of aluminum hydroxide and sodium sulfate this slurry is then filtered to remove the solution having an aluminum hydroxide sludge which is added to a solution of an aluminum salt such as aluminum sulfate or aluminum chloride after extended aging however such as 6 months in open containers it has been found that the material is no longer soluble moreover aqueous slurries of the compositions exhibit excellent filterability which makes it possible to readily remove the adduct of the anion of the aluminum salt and the cation of the base before use the invention will now be further described by way of the following examples these examples are not intended to limit the scope of the invention which is set out in the accompanying claims 300 g of an alum solution 8 3 al 2 o.