Apatite is acidulated with HCl for the stoichiometric degree needed for creating dicalcium phosphate. The reaction product when mixed with ammonium sulphate enough to doubledecompose calcium chloride and dicalcium phosphate yields a nonhygroscopic product made up of almost all phosphorus from the water-soluble form. Rates are determined by earlier info. https://chemicaltspsrilanka68013.blogdigy.com/the-single-best-strategy-to-use-for-tsp-for-nutrient-enrichment-sri-lanka-53912873