Ammonium Hydroxide → Tricalcium Phosphate

Participants

Reaction Steps

Tricalcium phosphate (β-whitlockite crystalline form) was prepared by the following technique. A solution of 141.7 grams of calcium nitrate tetrahydrate in 400 ml of water was prepared and the pH adjusted to about pH 11 with concentrated ammonium hydroxide. This solution was then diluted to about 900 ml with water and placed in a three liter flask fitted with a dropping funnel and mechanical stirring apparatus. Separately, 66.1 grams of ammonium phosphate dibasic was added to 750 ml of water. The pH of the resulting solution was adjusted to about pH 11 with concentrated ammonium hydroxide resulting in the formation of a precipitate which was subsequently dissolved by the addition of water (about 2000 ml total volume of the solution). The ammonium phosphate dibasic solution was then slowly added to the reaction flask containing the calcium nitrate tetrahydrate solution and the resulting mixture was stirred overnight. A precipitate formed which was collected by centrifugation, washed with water and again collected by centrifugation. The precipitate was then suspended in a 2 percent aqueous ammonium sulfate solution and filtered leaving a residue which was subsequently dried in vacuo at 90° C. leaving 63.7 g of tricalcium phosphate. The tricalcium phosphate was then sintered at 1150° C. for one hour, and then ground to a fine powder.

Provenance & Evidence