The reduction rate of cobalt chloride (CoCl2) vapor by hydrogen in the gas phase was determined between 800 ℃ and 950 ℃ in a furnace aerosol reactor. Reaction temperature and concentration of CoCl2 were chosen as process variables for the determination of reaction rate constant, and chemical titration method was used to measure the degree of reaction. When H2 was exceeded compared to CoCl2, the reaction rate was found to be first order with respect to CoCl2 and to follow the Arrhenius form. The activation energy for the reaction was 98.94 kJ/mol.