Cobalt Metaphosphate, Co(PO₃)₂

Cobalt Metaphosphate, Co(PO₃)₂, is obtained by evaporating a mixture of cobalt sulphate and phosphoric acid in a platinum dish, and subsequently heating to 300° C. It is deposited as a beautiful, rose- coloured, anhydrous compound, insoluble in water and dilute acids, but soluble in concentrated sulphuric acid.

Several Orthophosphates have been described, namely:

2CoHPO₄.5H₂O, 2CoHPO₄.3H₂O, and Co₃(PO₄)₂.