Pfeiffer (1) and others have investigated the colored molecular compounds resulting from quiñones with aromatic hydrocarbons, ethers, or amines. Pfeiffer has classified these compounds with the quinhydrones and has shown that a series extends from the intensely colored quinhydrones existing as crystalline compounds, through colored complexes difficult to crystallize, to complexes impossible to crystallize and identified largely by a slight color change on mixing the liquid components. These latter "molecular compounds" are tied by forces which are weak in comparison with the intermolecular forces in the crystals of the components, for, on cooling, the components of the mixture crystallize out separately. Foreign solvents tend to dissociate the compounds and as a result Beer's law does not hold.We undertook a spectroscopic study of the more weakly tied compounds of this type in the hope of extending the series of molecular compounds to loosely tied complexes which had escaped detection because the color change occurred in the ultra-violet or was too slight to be seen with the eye. There was also the possibility that the "solvent effect" of absorption spectroscopy could be linked with these color changes. Foremost, however, there was the hope that a correlation between color and oxidation-reduction potentials might be established. RESULTSWe have carried out quantitative light absorption measurements on the five quiñones-chloroquinone, benzoquinone, toluquinone, xyloquinone, and duroquinone-in a melted state and in the absence of any solvent.The resulting curves are compared with the light absorption of equimolecular mixtures of these quiñones with various aromatic ethers, hydrocarbons, and the junior author after the death of Dr. Hunter in 1931.-L. I. Smith.