Products of the Alkaline Nitrobenzene Oxidation of Soil Organic Matter

Summary Further studies have been made of the alkaline nitrobenzene oxidation of soil organic matter and certain fractions thereof, as well as of some plant materials, on the lines of a previous investigation. By using dichloromethane in place of diethyl ether as an extractant the recovery of aromatic aldehydes, especially syringaldehyde, has been greatly improved. Methods have been developed for the identification and determination of the related acids: syringic, vanillic, p ‐hydroxybenzoic, ferulic, and p ‐coumaric acids. Some minor aromatic products of the oxidation have also been identified. Application of the improved methods to samples of soils and peats has, in many instances, resulted in an increased proportion of the total carbon accounted for as aromatic products. The results are, however, only about 20 per cent higher than those previously obtained, and the outcome of the investigation has been to confirm and extend the results previously obtained. Whereas the proportion of carbon in the organic matter of peats which can be recovered as aromatic products is commonly about 5 per cent, in aerobic soils it remains low, generally less than 1 per cent, and it seems likely that this represents only a small fraction of the total aromatic material present in such soils.