Graft copolymerization of acrylonitrile onto coal humic acids was studied in aqueous medium at low pH. Several redox initiating systems were tested

among them

K2S3O3-FeSO4 and K2S2O3-ascorbic acid pairs are promising. Degree of grafting of humic acids of different types differs not widely

and usually comes up to more than 75%. A portion of grafted humic acid

20% in average

splited down under strong alkaline condition. It is supposed the grafting at the carboxylic group of humic acid is through ester linkage. This fact may be noteworthy for the purpose of preparing driling mud additives through saponification of such copolymers.