The chemical reactions are as follows:

P → CaHPO4 (Monocalcium phosphate)
This reaction involves the reaction between phosphorus (P) and calcium hydroxide (Ca(OH)2) to form monocalcium phosphate (CaHPO4).

CaHPO4 → Ca(H2PO4)2 (Dicalcium phosphate)
This reaction involves the reaction between monocalcium phosphate (CaHPO4) and phosphoric acid (H3PO4) to form dicalcium phosphate (Ca(H2PO4)2).

Ca(H2PO4)2 → Ca3(PO4)2 (Tricalcium phosphate)
This reaction involves the dehydration reaction of dicalcium phosphate (Ca(H2PO4)2) to form tricalcium phosphate (Ca3(PO4)2).

Ca3(PO4)2 → P + PH3
This reaction involves the breakdown of tricalcium phosphate (Ca3(PO4)2) into calcium oxide (CaO) and phosphorus (P), which further reacts with water to form phosphine gas (PH3).