A further study has been made of the isolatio~~, by acidolysis, of lignin from aspen wood meal (Popztlzts tre~~zz~loides Michx.) using a dioxane-water (9:l) solvent medium containing hydrogen chloride and a low extraction temperature of 8 7 f 2" for a short extraction time of 0.5 hour. Lignins so isolated included those: ( a ) under different initial acid concentrations of 0.0, 0.05, 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.8, and 1.7 equivalents of HCl/liter of solvent medium; ( b ) from successive extractions under increasing initial acid concentrations of 0.2, 0.4, 0.8, and 1.6 equivalents/liter; and ( c ) from successive extractions under constant initial acid concentrations of 0.2 equivalent/liter.All the lignin fractions so isolated were studied with respect t o their yield, methoxyl content, infrared absorption spectra, and the yields of vanillin and syringaldehyde obtained from them by oxidation using allraline nitrobenzene.Evidence is presented in s~~p p o r t of the non-homogeneity of the whole protolignin. This may be the result of the presence of possibly two basic types. One fraction, comprising around 70-8570, is most readily extracted, has a consistently high methoxyl content (ca. 210jo), and is capable of being oxidized to give high yields of syringaldehyde and vanilli~l in a ratio close to 2.5:l. T h e second fraction is characterized by a greater difficulty of extraction, lower methoxyl content, and significantly lower yields of the aldehydes in a ratio closer to 1:l.In a previous communication, Pepper, Baylis, and Adler (1) reported a study of the effect of extraction time on the isolation and properties of the lignin fraction obtained by the acidolysis of spruce and aspen wood meals. The extractions were carried out under reflux for periods ranging from 0.5 to 48 hours using a constant initial hydrochloric acid concentration, namely 0.2 N with respect t o the dioxane-water (9:l) solvent medium. As the time of extraction was increased, the yields of the isolated lignin fractions also increased, but the yields of phenolic aldehydes (vanillin from spruce or a mixture of vanillin and syringaldehyde from aspen) obtained from them by alkaline nitrobenzene oxidation gradually decreased. I t was also shown t h a t with increasing time of acidolysis of the aspen wood, a rise in the carbon-methyl t o methoxyl ratio was observed for the isolated lignins. A similar finding had been made earlier for spruce lignin isolated under the same conditions (2). As a result of these studies, it was suggested t h a t such a lignin fraction isolated under conditions of l-hour extraction with the 0.2 N acid solvent may be only mildly modified during extraction and hence suitable for subsequent chemical investigation.This report deals with a study of the effect of the initial acid concentration on the yield and nature of the lignin isolated by a similar acidolysis of aspen wood.An extraction time of 0.5 hour was chosen and all extractions were effected a t 87&2', which represented a simmering state for all media. The l...

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X brief review is presented of the che~nical nature and the methods of separation of those lignin derivatives obtained by the oxidation and/or alkaline hydrolysis of woody plants and isolated lignin or lignosulphonates. Nine such closely related derivatives, vanillin, syringaldehyde, p-hydroxybenzaldehyde, acetovanillone, acetosyringone, p-hydrosyacetopheno~~e, vanillic acid, syringic acid, and p-hydroxybenzoic acid, were selected for a detailed study of their separation by cellulose column chromatography. Methods are presented whereby, by either a one-or two-stage process, a mixture of from any two to all nine of these compounds may be separated and the components recovered, using solvent systems which are suitable for subsequent quantitative spectrophotolnetric analysis. The applicatioll to a study of lignin chemistry is discussed. INTRODUCTIONIn recent years considerable attention has been given to tlie chro~~~atographic separation of the products of oxidation and/or alltalilie li~~clrolysis of the lignin component of woody plants ancl cereal straws. Froill the earlier \\rorl; the characterization of these various lignin clerivatives has colitributed substantially to the present I