CORRELATION OF SOLUBILITY DATA .3. ISOPLETH REFERENCE METHOD FOR PREDICTING SOLUBILITY DATA FOR LONG CHAIN HOMOLOGOUS AND ANALOGOUS COMPOUNDS

A new graphical method for correlating and predicting solubility data for homologous and analogous compounds is described. It complements the isotherm and isopleth methods which are applicable only to long chain homologous compounds. This method is based upon the linear relationship, {Mathematical expression} derived from the approximate freezing point depression equation in which T and T′ are the primary freezing points of two analogous compounds at the same molar concentration in a given solvent. The basic assumption that ΔH′f/ΔHf remains essentially constant for homologous and analogous compounds in the same solvent over wide ranges of temperature was validated by construction of isopleth reference plots using both published and new experimental solubility data for a number of long chain fatty acids and fatty acid derivatives in a variety of solvents. Complete solubility data are reported for behenic, stearic, palmitic, heptadecanoic, brassidic, erucic, petroselaidic and petroselinic acid in acetone, methanol, toluene and isopropyl ether. Complete solubility data are also included for elaidic acid in acetone, toluene and isopropyl ether and oleic acid in isopropyl ether. © 1969 AOCS Press.