Abstract In one of our previous works we have shown that vulcanization structures contain mono-, di- and polysulfide bonds between the molecular chains of the rubber. The concentration, proportion, and distribution of these various bonds depend on the type of rubber and the conditions of vulcanization, but mainly on the nature of the curatives. Inasmuch as the vulcanization structures determine in large degree the physical, chemical, and mechanical properties of the vulcanizate, the different methods which enable us to determine the types of sulfide bonds in the vulcanizate are very important. Among the chemical methods applied for this purpose are the reactions of sodium sulfite and of methyl iodide with the vulcanizate. Of great interest in research on the nature of sulfur bonds in vulcanizates is the method of exchange reactions with radioactive sulfur; since sulfur, as numerous experiments have shown, diffuses easily in rubber, thus insuring the possibility of carrying out exchange reactions without having to get the vulcanizate into solution.