Calcium Dihydrophosphite, Ca(H₂PO₃)₂

Calcium Dihydrophosphite, Ca(H₂PO₃)₂, or Acid Calcium Phosphite. - By dissolving calcium carbonate in phosphorous acid, in the proportion of 1 molecule of the former to 2 of the latter, and evaporating in vacuo, a crystalline compound of the composition Ca(H₂PO₃)₂.H₂O is obtained. It loses its water of crystallisation above 150° C. It is very readily soluble in water and from the solution alcohol precipitates the neutral salt.

By dehydrating the acid phosphite between 145° and 170° C., calcium pyrophosphite, CaH₂P₂O₅, may be prepared.