ammophos

Agricultural Uses

Ammophos is the trade name of one of the most popular brands of ammonium phosphate fertilizers. It contains 16% nitrogenand 20% phosphorus (as P₂O₅). Ammophos is made by ammoniating a mixture of sulphuric and phosphoric acids. After ammoniation, the slurry formed is granulated in a pugmill or a drum unit, dried, and screened to give a product that is two-thirds by weight of ammonium sulphate and one-third that of ammonium phosphate. This water-soluble product has good storage properties.
Two grades of ammonium phosphate are known. One contains 11 % nitrogen and 48 % phosphorus (as P₂O₅), the other contains 16.5% nitrogen and 20% phosphorus (as P₂O₅). The first grade is made by neutralizing phosphoric acid with ammonia, and the other is made by neutralizing a mixture of phosphoric and sulphuric acids with ammonia. The first grade of ammophos has a theoretical lime requirement of 5 kg of calcium carbonate per kg of fertilizer, which indicates the acid forming nature of the fertilizer.
Ammonium dihydrogen phosphate sulphate is also called ammoniated sulphate. It is a double salt of ammonium dihydrogen phosphate, NH₄(H₂PO₄) and ammonium sulphate, (NH₄)₂SO₄, and is formed by neutralizing a mixture of sulphuric acid and phosphoric acid by gaseous ammonia.