The kinetics of the reaction 2H(2)S(aq) + S2O32- + 2H(+) --> 1/2S(8)(s) + 3
H(2)O has been investigated at 0-40 degrees C in the pH interval from 5 to
7. The rate law was found to be r = -d[S2O32-]/dt = k[H2S][S2O32-], where k
= 8 x 10(11) exp(-74 300/RT) M-1 s(-1). Thermodynamic calculation shows th
at the reaction is unfavorable at pH greater than or equal to 8, which is c
onfirmed by the experimental observation. The ionic strength effect on the
reaction also has been studied. The mechanism postulated to account for the
observed rate law involves the formation and subsequent reactions of an in
termediate H2S3O32-.