Superphosphates

Definition

Substance obtained by treating phosphate rock with sulfuric acid or a mixture of sulfuric and phosphoric acids. Composed primarily of calcium phosphates and calcium sulfate.

Flammability and Explosibility

Non flammable

Agricultural Uses

Enriched superphosphate is essentially a mixture of single superphosphate and triple superphosphate made by acidulation of phosphate rock with a mixture of sulphuric and phosphoric acids.

Agricultural Uses

Monocalcium phosphate is one of the components (the other being calcium sulphate) of single superphosphate. Single superphosphate is a principal phosphate fertilizer. It also supplies two secondary elements, namely sulphur and calcium as it contains 21 % calcium.
Monocalcium phosphate of single superphosphate dissolves in soil moisture and in that form the roots absorb phosphoric acid. The rest of the solution of monocalcium phosphate precipitates in soil pores and forms different phosphate compounds which are not water-soluble and do not leach out.

Agricultural Uses

Normal superphosphate is made by treating ground rock phosphate with sulphuric acid.
The above reaction yields monocalcium phosphate and gypsum.
For the manufacture of normal superphosphates, a continuous process rather than a batch process is in vogue. Some of these processes are named after their inventors, for example, the Tennessee Valley Authority process, the Maxitz-Standard Den process, the Broadfield Den process and the Kuhlman Den process.
The treated mass is sent to a curing shed and stored for 3 to 4 weeks for curing and final drying. The dried product is excavated, milled, screened, and either bagged for marketing or sent for granulation.
Granulation is done in a granulator in the presence of steam and the finished product is then bagged. It contains 16 to 21% phosphorus pentoxide (P₂O₅) in a watersoluble form. In addition, it contains 11 to 12% sulphur as calcium sulphate.