Phosphoric Acid
. Phosphoric Acid, common acid of phosphorus that is the source of industrially important compounds called phosphates. At room temperature, phosphoric acid is a crystalline material with a specific gravity of 1.83. The solid melts at 42.35° C (108.23° F). Phosphoric acid is usually stored and sold as a solution. Phosphoric acid is made by treating calcium phosphate rock with sulfuric acid, followed by filtration of the resultant liquid to remove calcium sulfate. It can be prepared also by burning phosphorus vapor and treating the resulting oxide with steam. The acid is useful in the laboratory because of its resistance to oxidation, to reduction, and to evaporation. Among the many uses of phosphoric acid are as an ingredient in soft drinks and dental cements, as a catalyst, in rustproofing metals, and in making phosphates, which are used in water softeners, fertilizers, and detergents. PHOSPHATES Phosphates are products formed by the replacement of some or all of the hydrogen of a pho