RMvalues of a number of phenols (cresols, xylenols, chlorophenols, hydroxynaphthalenes) have been determined for numerous solvent systems of the type, weakly polar solvent/formamide. To determine a quantitative scale of extraction strengths,RM-solvent spectra have been plotted using a modified method of Rohrschneider and Littlewood. 2-Methylquinoline, used in previous investigations as a reference solute for nitrogen bases, has been found unsuitable for phenols, and much more regular spectra have been obtained with 1-naphthol as the reference compound. The experimental results indicate that the extraction strengths of solvents cannot be characterized by a single series. Much more satisfactory results are obtained when two series are determined, based on the partition chromatographic parameters of two solutes of opposite H-bonding properties, e.g., 2-methylquinoline and 1-naphthol. For many of the phenols, linearRM-solvent spectra are obtained when the solvents on the abscissa are arranged to give a linear spectrum for 1-naphthol, so that the spectra can be used to predict chromatographic parameters of related solutes.