The solid product is in the form of white granules or flakes, presenting as a white, lustrous crystal. It is stable in the air. It is highly soluble in water and almost insoluble in ethanol, with its solution being acidic. After prolonged boiling, insoluble basic salts precipitate. Iron - free aluminum sulfate is a widely used industrial reagent and is often confused with alum (i.e., potassium aluminum sulfate dodecahydrate). Aluminum sulfate is commonly used as a flocculant in the purification of drinking water and sewage treatment equipment. It is also used for sizing high - grade white paper and post - treatment of high - grade titanium dioxide.