Some new sulfur containing chelating agents

Nine new sulfur containing chelating agents have been prepared by the reaction of aldehydes with appropriate compounds containing sulfhydryl groups. These compounds all contain thioether donor groups and several contain carboxylate groups as well. Three of the compounds which are tetracarboxylic acids have carboxyl groups whose ionization is practically independent and give titration curves with but a single inflection point. A method is presented for obtaining all four dissociation constants in such cases.