Studies on the kinetics of chlorination of tantalum pentoxide powder by carbon tetrachloride vapor in dilution with nitrogen have been carried out by weight-loss measurements in two temperature ranges, i.e., 698 to 773 K and 793 to 853 K. The effect of time, temperature, and partial pressure of CCl 4 (P CCl 4 ) on the kinetics of chlorination of the powder Ta 2 O 5 , (Ϫ105 ϩ 74 m) has been investigated. In both the temperature ranges, the chlorination results have been found to fit the following relationship during the "initial periods:"where ␣ is the fraction of the oxide reacted in time t and k 1 is the rate constant. In the low-and hightemperature ranges, the activation-energy (E ) values have been calculated and were found to be 145 and 71 kJ/mole, respectively. The k 1 value was found to be proportional to P 1.5CCl4 in the lowertemperature range, while in the higher-temperature range, it was found to be proportional to P 0.9CCl4 . In the "latter periods" of the chlorination of Ta 2 O 5 , the following relationship was found to be applicable in both the temperature ranges:where k 2 is the rate constant and c is another constant. However, in the latter periods of the chlorination, the activation energy in the lower-temperature range was calculated to be 31 kJ/mole, while that in the higher-temperature range was found to be 142 kJ/mole. Further, in the lower-temperature range, k 2 was found to be nearly independent of P CCl 4 , while in the higher-temperature range, it was found to be proportional to P 0.9 CCl4 , as observed in the initial periods. Based on these kinetics results, two different mechanisms for the chlorination of Ta 2 O 5 by CCl 4 vapor have been suggested for the two temperature ranges studied.It was possible to chlorinate Ͼ92 pct of Ta 2 O 5 (Ϫ105 ϩ 74 m) at 833 K in 210 minutes, by using CCl 4 at a partial pressure of 0.6 atm.