The yields of vanillin and syringaldehyde obtained by the allcaline nitrobenzene oxidation of aspen wood meal have been determined a t various temperatures for various times. The maximum yield of each of these aldehydes, ca. 15 and 36y0 respectively, was obtained under the same conditions. Similar maximum yields result at 130&5°C. as at 170&5"C. if the reaction time is markedly increased. Treatment of the wood meal with sodium hydroxide a t 160°C. for two and one half hours prior to the addition of nitrobenzene and subsequent heating under the same conditions decreases, by over 30y0, the yields of aldehydes. Samples of 3,4,5-trimethoxybenzaldehyde, @ -~-g l~c o~a n i l l i~~, and 8-D-glucosyringaldehyde were oxidized by alkaline nitrobenzene a t 160°C. for two and one half hours and yields of the corresponding phenolic aldehydes of 10.7, 69.6, and 71.9% respectively were obtained. These results are discussed with respect to the chemistry of aspen lignin.Little has been reported regarding the establishment of the optimum conditions for obtaining the maximum yields for each of vanillin and syringaldehyde by the alkaline nitrobenzene oxidation of hardwood lignins. Brauns (2) has summarized the value of this tcchnique in lignin chemistry. The major part of this work was concerned with softwood lignins and various reaction temperatures, ranging from that of boiling alkaline sulphite spent liquor to 200°C., and various reaction times from 10 min. t o three hours. Since this book was published Leopold (9) has determined the vanillin yields obtainable from synthetic model lignin substances as a function of temperature and time and found that a t 180°C. for two hours the best yields were obtained. Subsequently Leopold and co-mo1-1~ers(10, 11, 12) used these conditions to study the oxidation products of a wide variety of both hardwoods and softwoods. I t is significant that almost all the conifers studied gave small amountsof p-hydroxybenzalclehyde while several (Pi~zaceue family) gave small amounts of syl-ingaldehyde, this latter observation representing the first isolation of syringaldehyde from softwoods. Stone and Blundell (14) used a temperature of 160°C. for two and one half hours in their analytical niicromethod for the alkaline nitrobenzene oxidation of plant materials.A detailed study of these conditions of oxidation as applied to hal-dwoocls was ~~nclertaken, therefore, with the belief tliat some useful information would be obtained wit11 respect,to tlie following problenl. If vanillin and syringaldehyde ai-ise by the hydrolysis and/or oxidative cleavage of different type linkages in tlie protolignin, then maximum yields of each might be obtained under different conditions. In this way a greater combined yield of aldehydes could rcsult than tliat now obtai~led under conditions whereby both yields are deter-

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