Isotopic exchange reactions of sulfur-containing compounds (i. e. carbon disulfide, thiophosphoryl chloride, ethyl phosphonothionic dichloride, phenyl phosphonothionic dichloride, diethyl phosphorochloride thionate, triethyl phosphorothionate, diethyl disulfide, ethyl mercaptan) with ³⁵S in the presence of aluminum chloride were studied.