Abstract:The aim of the current study is to identify the dimerization and decomposition kinetics of the F-DM type.The regeneration of F-VS from FiFj-DM or the reversibility of the dimerizations were investigated. The order of real rate constants of the dimerization(′ D ij ) would seem to be similar to that of rate constants of a dimerization( D ij ) for VS dyes at a given pH because of the constancy of the equilibrium constants( a j -value). The reverse reactions of the DM types are appeared to occur in two steps, the deprotonation of α-carbon of the DM types and disproportionation. The ratio of the decomposition of the DM type to F-Hy and F-VS appears to be related with the ratio of i/ j. Similarities were also found among various other reactions, including homo-and mixed dimerization. VS dyes undergoing fast hydrolysis have difficulty in forming a dimer. The higher the reactivity with cellulose or hydroxide ion, the smaller the dimerization. The easiness of the dimerization was thus found to be inversely proportional to the rate of hydrolysis.