Equilibria involving calcium,hydrogen,carbonate,bicarbonate,primary,secondary and tertiary phosphate ions

Abstract

The complete equilibrium involving CO₃ = and PO₄ = takes place when the solution is made more alkaline. This relationship may be derived from the equation.

The above equation for the complete equilibria is not applicable until better values for the third dissociation constant are available. Therefore, the values may be better derived from the simpler relationship for K₇.

This gives a value for the equilibrium in terms of Ca⁺⁺, HCO₃ ^-, HPO₄=, and H⁺. This value calculated theoretically from known values of the intermediate constants was found to agree well with the experimentally determined value reported elsewhere.¹ The concentration of the ions could be determined from analysis of all the salts in the system and the calculated degree of ionization. In systems in which this is not possible, due to the presence of unknown compounds as in blood serum, the CO₂ from bicarbonates and H₂CO₃ the P from inorganic phosphates and the H⁺ must be determined. The only unknown is the Ca⁺⁺ which may then be calculated from the equation.