Abstract: There is herein disclosed a process for preparing a carboxypolysaccharide by oxidizing a polysaccharide with a combination of a transition metal compound and an oxidizing agent, said process comprising the step of separating the transition metal from a reaction mixture with a chelating agent. According to the present invention, the transition metal can be removed to a low concentration of less than 100 ppm from an aqueous solution including the transition metal and the tricarboxypolysaccharide. The process of the present invention is important to reduce the loss of a transition metal catalyst such as the ruthenium catalyst and to industrially manufacture a purified tricarboxypolysaccharide.

Abstract: In a process of producing a carboxypolysaccharide by oxidizing a polysaccharide in the presence of a ruthenium compound and an oxidizing agent, the expensive ruthenium is easily and efficiently recovered. Ruthenium dissolved in a reaction mixture after the oxidation of the polysaccharide is converted, after or without being subjected to a heat. treatment, to high oxidation sate, which is then recovered by the extraction with a water-insoluble organic solvent. The recovered ruthenium is reduced to low oxidation state and reused in a subsequent production of the carboxypolysaccharide.

Abstract: Hydrazine sulfate having a relatively large particle diameter and a high purity is produced by hydrolysis of benzophenoneazines by sulfuric acid having a concentration of 75% by weight or less in an amount of 1.1 times by mole or more the stoichiometric amount in a very high conversion and a high yield with less operational loss.