Phosphinic Acid → Tricalcium Phosphate

Participants

Reaction Steps

An aqueous solution of 8.51 g 50 wt % hypophosphorous acid, H3PO2 (Alfa/Aesar reagent #14142, CAS #6303-21-5), equivalent to 71.95 wt % [PO4]−3 was combined with 8.00 g distilled water to form a clear, colorless solution contained in a 250 ml Pyrex beaker. To this solution was added 22.85 g calcium nitrate tetrahydrate salt, Ca(NO3)2.4H2O (ACS reagent, Aldrich Chemical Co., Inc. #23,712-4, CAS #13477-34-4), equivalent to 16.97 wt % Ca. The molar ratio of Ca/phosphate in this mixture was 3/2 and the equivalent solids level [as Ca3(PO4)2] was 25.4 wt %. Endothermic dissolution of the calcium nitrate tetrahydrate proceeded under ambient temperature conditions, eventually forming a homogeneous solution. Warming of this solution above 25° C. initiated a reaction in which the solution vigorously bubbled while evolving red-brown acrid fumes characteristic of NOx(g). The sample turned into a white, pasty mass which foamed and pulsed with periodic expulsion of NOx(g). After approximately two minutes, the reaction was essentially complete, leaving a white, pasty mass which was warm to the touch. After cooling to room temperature, the solid (A) was stored in a polyethylene vial.

Provenance & Evidence