The sodium, potassium, rubidium, caesium, and ammonium phosphates are all water-soluble. Most other phosphates are only slightly soluble or are insoluble in water. As a rule, the hydrogen and dihydrogen phosphates are slightly more soluble than the corresponding phosphates.

Which phosphate is most soluble in water?

Primary phosphate compounds in neutral and basic sediment are calcium phosphates. The most soluble calcium phosphate compound is monocalcium phosphate, Ca(H₂PO₄)₂.

Are phosphates soluble or insoluble?

h) All phosphates are insoluble except those of sodium, potassium and ammonium. Some hydrogen phosphates, such as Ca(H2PO4)2, are soluble.