To prepare 8,000 gallons of a 48% alum sulfate solution, first determine the density of the 48% solution. The weight of a gallon of water is multiplied by the specific gravity of the 48% alum sulfate to find the weight of one gallon of the solution. This weight is then multiplied by 0.48 and subsequently by 8,000 to calculate the required amount of anhydrous aluminum sulfate. If purchasing octadecahydrate, the calculated amount should be multiplied by the ratio of 666/342, and for hexadecahydrate, by the ratio of 648/342 to obtain the correct quantity needed.