Method for determining the solubilities of hydrophobic organics in subcritical water.

A rapid and simple method has been developed to determine the solubility of organic compounds in water at temperatures from 25 to 250 degrees C and with enough pressure to maintain the liquid state ("subcritical" water). Water is heated and then passed through a cell containing excess test solute. The water, now saturated with solute, is blended with chloroform, cooled, and collected, and the chloroform fraction is analyzed by gas chromatography. Replicate determinations have typical reproducibilities, indicated by the relative standard deviation, of < 5%. Solubilities at 25 degrees C determined by this method are in good agreement with published data. Increasing the temperature of water from 25 degrees C to near the normal melting point of the organic solute results in solubility enhancements ranging from 6-fold for naphthalene (at 65 vs 25 degrees C) to 130,000-fold for chlorothalonil (at 200 vs 25 degrees C).