Abstract: A dextran derivative gel in particle form for use in the separation of substances according to their molecular size and/or electrical charge by means of gel-chromatographic and/or ion exchange techniques is disclosed which gel comprises a copolymerizate obtained by the free-radical copolymerization of a dextran derivative containing vinyl and/or substituted vinyl groups with (a) a divinyl compound of the formula ##STR1## wherein R' and R" are equal or different and each represent hydrogen or methyl and X is ##STR2## --SO.sub.2 -- or the group ##STR3## wherein n is an integer from 1 to 6, inclusive, and optionally (b) a low-molecular weight monovinyl compound.