It was found that aluminum sulfate reacts with potassium chloride to produce $K_2SO_4$, $Al_2O_3$, and $Cl_2$ in the solid phase at $700^o$C. This reaction was investigated with thermal analysis under air and nitrogen atmosphere. By changing temperature and time parameters, the actual yield of conversion in question was examined analytically and the optimum temperature and time were found for the reaction. The rate expression of the solid phase reaction was also investigated and the rate equation was obtained.