Thermodynamic quantities for the dissociation equilibria of biologically important compounds. 2. The acid dissociations of glycerol 2-phosphoric acid

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Abstract
The 1st and 2d thermodynamic dissociation constants of glycerol-2-phosphate on the molal scale were measured at 5[degree] intervals from 5 to 50[degree] using H and Ag-Ag chloride electrodes in cells without liquid junctions. From these measurements were calculated the standard free energy, heat content, entropy and heat capacity for the 2 ionizations over the whole temp, range, together with the respective standard deviations of the values obtained. The magnitude and sources of the errors are discussed. Some assessment is given of the importance of changes in ionization during hydrolysis of phosphate esters and of the proportion of the total free-energy change assignable to this change. The results demonstrate that the methods worked out by Harned and Owen (1950) for inorganic acids are applicable to compounds of interest to biochemists and also that the glycerol phosphoric acids closely resemble the simpler weak acids in their dissociation properties. Sufficient information has been given about the acid dissociations of glycerol 2-phosphate to allow its solns. to be used as standard buffers in the pH range 5-7 and at ionic strengths up to 0.15.