Abstract: The characteristics of a staged bubble column can be described by a multistage backmixing model, provided: (1)Each stage can be considered as a perfect mixing reactor, and(2)The backmixing coefficients do not vary with time and reagent concentration. Experimental results indicate that the first condition is approached under certain conditions, while the second assumption is correct. Studies were made using steady state chemical tracer method to determine the backmixing coefficients of each plate between stages. The fluid flow through the holes of perforated plates is a stochastic process. From the statistical point, the experimental data could be correlated by a semiempiri-cal equation developed. This equation can also be used to correlate the data reported by Nishiwaki et al. for bubble column with plates having high percentage of opening area and large sized holes between stages. Continuous oxidation of unsaturated sulfur compounds (mainly in the form of S2O3= and also some in S3O6=, S4O6=etc. polythionates form) in nickel ammonium carbonate solution were carried out in bubble column with height of 3400mm and diameters of 36mm and 100mm respectively. The oxidation has to be taken in a multi-stage bubble column for high degree of oxidation. The concentration of unsaturated sulfur compounds along a multi-stage bubble column can be calculated from the backmixing model and the kinetic equation of oxidation. The results of calculation agree with the data taken along the column. Equation was also developed to calculate the optimum temperature of oxidation which agrees favorably with the experimental results.