Patent ID: 7723119

Claim:
A method of determining the solubility of a chemical compound containing one or more acidic or basic groups comprising: (a) preparing a close to saturated solution of said chemical compound with solid of the chemical compound present; (b) measuring and recording the pH of the test solution at regular time intervals until a consistent rate of pH change is obtained, and measuring the slope of said consistent rate of pH change with time; (c) subsequently adding an aliquot of base or acid titrant of known concentration to the test solution to adjust the pH slope; (d) repeating steps (b) and (c) until the measured pH slope changes from a positively-signed pH slope to a negatively-signed pH slope, or vice-versa; (e) determining the concentration of unionised compound in a said test solution when said consistent rates of pH change were obtained, and (f) determining the solubility of the compound as the concentration of unionised compound in solution when the measured pH slope is interpolated to be zero on a graph of concentration of said unionised compound versus pH slope.