DEGREE OF POLYMERIZATION OF SODIUM POLYGALACTURONATE BY MEMBRANE OSMOMETRY

Customarily membrane osmometry is the method of choice for measuring number-average degree of polymerization between 100 and 1000. Polygalacturonic acid (PG) was dissolved in distilled H//2O and centrifuged for 1/2 h at 8000g. PG was dissolved in 60 mL of 0. 05M Na phosphate buffer, pH 7. 0, titrated with 0. 1M NaOH to pH 7. 0, and dialyzed against four changes of distilled H//2O over 48 h. Osmotic pressures for NaPG thus obtained were measured in a membrane osmometer equipped with a thermostatted cell. It has been demonstrated that NaPG is ideally suited as a reference compound for aqueous membrane osmometry. 8 refs.