1. The solubility of mustard (H) in water and in molar sodium chloride was found to be 5.8 x 10–3 molar and 3.2 x 10–3 molar respectively or 0.92 mg. per ml. and 0.5 mg. per ml. Solubility curves have been drawn and the usefulness of this method in examining the homogeneity of H preparations as well as in establishing their solubility, is discussed.
2. Certain detergents increase the solubility of H in water. The solubility was found to increase with the concentration of detergent.
3. Many detergents were found to affect the interfacial tension between H and water so that with slight agitation liquid H breaks up into minute droplets. This in turn greatly accelerates the rate of solution.