PHOSPHATE OF LIME.

Sun (Christchurch), Volume II, Issue 334, 4 March 1915, Page 3

PHOSPHATE OF LIME.

There are three different; distinct forms of phosphate of lime, viz., triealeic phosphate, bicalcic phosphate, and monocaleie phosphate. These all have phosphoric acid as a base. The former contains three parts of lime to one of phosphoric acid, and is generally termed insoluble phosphate, that is, it requires the acids of the soil to render it available for plant food, hence it is slow in action. The phosphate of lime in bonedust is in this form. The bicalcic phosphate has one part of phosphoric acid, one part of water, and two of and is more readily soluble than the former. Monocaleie phosphate has only one part of lime, two of water, and one of phosphoric acid, and is soluble in water. The phosphate of lime in superphosphate is in this latter form and is immediately available for plant food. The crushed bones are treated with sulphuric acid in the manufacture of superphosphate, and this does in a short time what the rain and acid 3 in the soil take years to do. In addition to bones, various rocks containing tricaleic phosphate of lime have been discovered from time to time, and these are treated with sulphuric acid to change the phosphate to monoealcic phosphate of lime, and this produces the fertilisers known as mineral superphosphates.—''' Rural World.''