Dissociation constants of phosphoric acid at 25°C and the ion pairing of sodium with orthophosphate ligands at 25°C
The first and second acidity constants of phosphoric acid were determined in a 0.70 ionic strength solution of both a sodium and a potassium ion background salt at 25°C. These experimentally determined constants were compared to literature values as well as values calculated from a theoretical model. Assuming negligible ion pairing of the phosphate ligand with the potassium ions, the stability constants of the NaHPO4- and NaH2PO40 complexes were determined to be 1.3±0.3 and 0.49±0.07 (mol-L−1), respectively. These constants were used to model the speciation of orthophosphate in a background of a sodium salt from pH 3 to 10.
Key wordsSodium phosphate phosphoric acid dissociation constants marine systems
Unable to display preview. Download preview PDF.
- 1.E. Atlas, C. Culberson, and R. M. Pytokowicz,Marine Chem. 4, 243 (1976).Google Scholar
- 2.SAS User's Guide, SAS Institute, Inc., Box 8000, Cary, NC 27511 (1981).Google Scholar
- 3.D. R. Migneault and R. K. Forcé,J. of Automatic Chem. 9, 125 (1987).Google Scholar
- 4.R. K. Forcé, J. Boyd, and E. Harris,Interfaces in Computing 1, 59, (1982).Google Scholar
- 5.R. M. Smith and R. A. Aberty,J. Phys. Chem. 60, 180 (1956).Google Scholar
- 6.P. G. Daniele, C. Rigano, and S. Sammartano,Talanta 30, 81 (1983).Google Scholar
- 7.R. G. Bates,Determination of pH, Theory and Practice (Wiley, New York, 1973).Google Scholar
- 8.R. M. Smith and A. E. Martell,Critical Stability Constants, Volume 4: Inorganic Complexes (Plenum Press, New York, 1981).Google Scholar
- 9.D. P. Shoemaker and C. W. Garland,Experiments in Physical Chemistry (McGraw-Hill, New York, 1967).Google Scholar
- 10.W. Strumm and J. J. Morgan,Aquatic Chemistry (Wiley, New York, 1981).Google Scholar