The various compounds obtained by the reaction P 4 0 10 + 4ROH (where R represents hydrocarbon radicals of various length and structure) were identified by infrared spectrophotometry of the fractions separated by column chromatography. The identification was made possible by a comparison between the relative values of the integrated absorption for the P = 0, p-o-P, P-O-C and O-H bands with those of known standards. For the reaction of phosphorus pentoxide with ethanol, the compounds formed were found to be; mono-, di-and triethyl phosphate, mono-, (1,2) di-and triethylpyrophosphate; (1,3) di-and (1,2,3) triethyl triphosphate; mono-and diethyl trimetaphosphate, With other alcohols, only homologs of these compounds were found, but always fewer compounds. Uncertainty between possible isomers was resolved by identification of their acid hydrolysis products.In the preceding parts [1,2] of this series, it has been shown that the reaction P 4 0 10 + 4ROH yields a mixture of phosphorus compounds. While theoretically this mixture could contain up to 34 different compounds [l], chromatographic separation methods showed that the number ranged from a maximum of 10, obtained with ethanol, down to 3 when heptadecanol was used [2]. The identity of these compounds, however, had to be determined, and infrared spectrophotometry appeared as the only promising method.The investigated compounds could be expected to show absorption in the following ranges of the infrared spectrum.