Abstract: The present invention relates to a chloral derivative having the general formula ##STR1## in which Y' is a polysaccharide consisting of a chain of anhydroglucose, modified anhydroglucose or uronic acid units as substituent group and in which R is selected from --H, --COCH.sub.2 OH, --[(CH.sub.2).sub.n 0].sub..chi. --H in which n is 2 to 5 and .chi. is 1 to 7; --CH.sub.2 OSO.sub.2 X' or --CH.sub.2 COOX' in which X' is NH.sub.4 or a single equivalent of a non-toxic metallic cation, --(CH.sub.2).sub.n H where n is 1 to 7, --(CH.sub.2).sub.n (OH).sub..chi. Y where Y is --H or --CH.sub.3 n is 1 to 7, .chi. is 1 to 12 and the --OH groups are attached to any or all of the carbon atoms by substitution and wherein when Y.sup.1 is a chain of unmodified anhydroglucose units, these units have the following configurations:.alpha.-D-glucopyranosyl units having a predominantly 1-4 linkage.beta.-D-glucopyranosyl units having a predominantly 1-4 linkage and/or.beta.