Equilibration studies with human bone powder.

In the previous paper (I), we demonstrated that when human bone powder was allowed to come into physicochemical equilibrium with bicarbonate-free buffers, it reproduced a constant ion product [Ca++13 [PO?12 over the pH range from 6.6 to 7.6. The free calcium and trivalent phosphate concentrations varied with pH and were reciprocally related to one another, but the concentration of total inorganic phosphate, measured as phosphorus, appeared to be constant irrespective of pH. Subsequently, in a preliminary communication (2)) we showed that the equilibrium phosphate concentration was quite different in a bicarbonate buffer system and that there appeared to be a direct relationship between it and the concentration of bicarbonate ion in the buffer. The present paper confirms and amplifies these observations.