Equilibrium in the System Calcium Oxide–Phosphorus Pentoxide–Water

Abstract

INCONNECTION with the experimental preparation of phosphate fertilizers from rock phosphate or limestone and phosphoric acid, it became evident that more complete data were needed on the equilibrium between phosphoric acid and its calcium salts. The published phase-equilibrium data (1, 2, 4, 5) concerning the calcium phosphates in phosphoric acid solutions extend only up to the concentrations of 51, 62, 86, and 66 per cent phosphoric acid at 25°, 40°, 50.7°, and 80°C ., respectively. This investigation was undertaken primarily to extend these data into the region of more concentrated phosphoric acid solutions and higher temperatures. The study completed is a phase-equilibrium investigation of the calcium phosphates in 2 to 98 per cent phosphoric acid solutions at 40°, 75°, and 100°C ., and in 27.5 to 98 per cent phosphoric acid solutions at 25°C.

Electrochemical preparation of chitosan/hydroxyapatite composite coatings on titanium substrates

“…Stock solutions of aqueous calcium phosphates typically were prepared by adding 20 g of Ca(H 2 PO 4 ) 2 to 100 grams of distilled/deionized water. The solutions were stirred vigorously for 2 h and then filtered to remove excess brushite, which is the solid that ultimately equilibrates with this particular solution 29. Stock solutions of dissolved chitosan were prepared by combining solid chitosan with an equal number of moles of acetic acid in water.…”

Monetite (CaHPO4) Synthesis in Ethanol at Room Temperature

“…M onetite (CaHPO 4 , DCPA, dicalcium phosphate anhydrous) is one of the mildly acidic and soluble (at the physiological pH) calcium phosphate (CaP) phases 1,2 and currently finding a significant place to itself in the powder components of self‐hardening CaP pastes used for skeletal repair 3–6 . Moreover, it must hereby be noted that even the world's very first patented CaP putty‐like paste development study, by Driskell et al 7 back in 1974, involved CaHPO 4 mixed with those of self‐hardening α–Ca 3 (PO 4 ) 2 powders.…”

Disproportionation of Zn(H2PO4)2·2H2O Crystals (Topochemical Particularities)

“…It is assumed that this process is associated with the hydrolysis of initial phosphates (Elmore and Farr, 1940;Corbridge, 1980). However, in actuality, as follows from the stoichiometric equations water is the only medium in which reaction proceeds, but it does not take place there directly.…”