The solubility of stearic acid in each of the solvents CCI2FCCIF2, CCI3CF3, CH3CCI3, CCI2FCCI2F, CF2BrCF2Br, CCI4, CH2CI2, CH3CH2OH, and the azeotropes of CCI2FCCIF2 with CH3CH2OH, CH2CI2, CHCI3, (CH3)2CO, and (CH3)2CHOH was determined as a function of temperature in the range from 20-50°C by the phase disappearance method.Stearic acid is a monocarboxylic acid of great interest in both industry and science. Careful solubility studies of this compound in a variety of organic solvents were carried out by Ralston and Hoerr (6, 7), Ralston et al. ( 8), Preckshot and Nouri (5), and by Brown and co-workers (2, 3). In this work we have extended the range of solvents to include an important class of halofluorocarbons wellknown for their nonflammability and low toxicity.These data are particularly pertinent to cleaning operations inasmuch as stearic acid is a common contaminant on many metal and plastic surfaces owing to its use as a metal-working lubricant and its occurrence in human sebum. Since gross contamination-i.e., more than a monomolecular layer-is commonly removed by immersing the contaminated object in a bath of solvent, it is of interest to study the solubility of a typical long-chain fatty acid, such as stearic acid, in a variety of chlorofluorocarbon solvents and in their associated azeotropes with other industrially important solvents such as acetone, ethanol, methylene dichloride, and chloroform.The method used to determine the solubility of stearic acid in these solvents was the phase disappearance method, also known as the plethostatic or synthetic method (1,11). This method involves determining the temperature at which the last trace of a known quantity of the solid solute disappears when the temperature of the solute/ solvent system is raised very slowly.Comparison with the data of Ralston and Hoerr (7) for stearic acid in carbon tetrachloride showed agreement within 10% up to 38°C. It is not known how much of the difference can be ascribed to purity differences and how much to technique and bias. We believe the purity