We used bromine generated and detected on the ring-dise electrode for the titration of aquo-alcoholic solution of dithiaalcanediol. The analysis of the ring currentvsdisc current curve provided a means of determination of the rate constantkof the second order homogeneous and fast reaction of bromine with each of the two sulfide groups of dithiaalcanediol. A value of (3+1)× 10−6M−1s−1was found forkat 25°C.