The Hydrolytic Extraction of Carbohydrates From Soil by Sulphuric Acid

Summary The parameters of the extraction and hydrolysis of soil carbohydrates by methods involving 24N H 2 SO 4 and N H 2 SO 4 were studied for a sandy granitic loam. Sugars were measured by alkaline ferricyanide, orcinol, anthrone (hexoses), orcinol‐ferric chloride (pentoses), cysteine‐sulphuric acid (methyl pentoses), glucose oxidase (glucose), and also by analysis of the individual sugars by paper chromatography. After shaking the soil with 24N H 2 SO 4 at 20° C a further period of treatment with N H 2 SO 4 at 100° C was required to obtain maximum hydrolysis of the soil carbohydrates. This period decreased from 17 h to 5 h as the time with 24N H 2 SO 4 increased from 2 to 16 h. NH 2 SO 4 at 100° C alone was less efficient. The extraction of pentoses by 24N H 2 SO 4 reached a maximum within 8 h, and methyl pentoses within 4 h, both declining thereafter. The release of hexoses was continuing after 40 h. The best compromise involved extraction with 24N H 2 SO 4 for 16 h followed by hydrolysis with N H 2 SO 4 for 5 h. By this treatment yields of pentoses and methyl pentoses were respectively 99 and 92 per cent of the maximum obtainable.