A polarographic study of acid-insoluble fractions from iodo-proteins.

1. A considerable advance has been made in the study of the fulvic extract of soil organic matter. A new method has been introduced whereby the fulvic extract is separated by a selective adsorption technique into four distinct fractions. 2. These fractions have been obtained from the fulvic extracts from four widely diverse types of soil. 3. A preliminary examination of the chemical properties of the fractions has been made. 4. A pure polysaccharide containing uronic acid groups has been isolated from the four soils. The presence of a glycosidic fraction in the four soils has also been shown. 5. The fulvic nitrogen has been shown to be in part contained in nitrogenous acidic complexes and in part as simple degradation products.