Dissociation Constants of Hexosephosphoric Acids.

Hexosediphosphoric acid from yeast and hexosemonophosphoric acid from muscle (lactacidogen) were kindly made available from preparations by Professor Embden. Electrometric titration showed both stronger than pure phosphoric acid in the region of the first and, more conspicuously, in that of the second dissociation constant. In each case hexosemonophosphoric acid was the stronger.

From titration data with pure phosphoric acid a second constant at 18 degrees of pK₂ equals 6.82 was calculated, agreeing with the usual values given.

For hexosemonophosphoric acid the value similarly determined gave pK₂ = 6.12.

For hexosediphosphoric acid only an apparent value of the constant corresponding to the actual third and fourth together was determined at pK₂ = 6.25, corresponding with the value of Meyenhof and Suranyi of pK₂, 6.2.