Phosphoric Acid from Bone Ash: Digested with Sulphuric Acid, the Lime Thrown Down

Phosphoric acid the commercial way of Thorpe's Dictionary (1913): bone ash digested for two or three days with sulphuric acid and water gives a solution of superphosphate of lime. Pressed free of the calcium sulphate, concentrated, and treated with strong sulphuric acid to throw down the rest of the lime, it is filtered, evaporated and heated to drive off the sulphuric acid. It still holds magnesia and other impurities. Strong sulphuric acid burns: goggles, gloves, fume hood. The picture: our diagram.