USES OF PHOSPHATE ROCK
Phosphate rock is chiefly used, after treatment with sulphuric acid, as an ingredient of artificial fertilizers. A small quantity is finely ground and used directly as fertilizer. Lesser quantities are used for making phosphoric acid and phosphorus. Phosphorus plays an important part in military operations, being used for incendiary bullets and smoke screens. Phosphorus also is a common ingredient of matches and the striking surface on boxes of safety matches, and it enters in small proportion into phosphor-bronze, phosphor-copper and phosphor-tin.
Substitutes.
—Substitutes for phosphate rock may be classed as natural and artificial. Natural substitutes are phosphatic limestone; other phosphate-bearing minerals, such as apatite, nelsonite, and wavellite; guano; marl; animal excrement and bones. Artificial substitutes include basic slag and manufactured compounds, like ammonium phosphate.