The results of this investigation check the earlier work done by Czapek (1) in which he isolated an aldehyde which he termed “Hadromal”, and indicated as possibly being coniferyl aldehyde. The work was extended considerably, however, to positively identify “Hadromal” as being coniferyl aldehyde and to show that it was the substance responsible for the color reactions of wood. A new method as found to isolate “Hadromal”, namely, forming a bisulfite addition product and decomposing this product in the presence of iso-propyl ether. The crystals of “Hadromal” could then be recovered from the iso-propyl ether and purified. By this method, it was possible to identify “Hadromal” as coniferyl aldehyde, and show it to be responsible for the color reactions of wood. If ligroin was used as the solvent in place of isopropyl ether, a yellow oil separated, which evidently had a prohibiting effect upon the formation of crystals of coniferyl aldehyde and which was difficult to separate from the crystals. This oil was present when iso-propyl ether was used, but in a much lesser quantity. This oil was found to contain guaiacol. Pinene and a small amount of resin. As some of the investigation, Risi and Labri (1), who disagreed with Czapek (2) and Hoffmeister (3) used ligroin as the solvent, it is possible that their conclusions that “Hadromal” was composed of guaiacol, furfural, and catechol might have been influenced by the presence of oil. Results of this investigation also show what most earlier investigators had predicted, with the exception of Hoffmeister (3), that “Hadromal” is present in woody tissue in extremely small amounts. / M.S.