The reactions between aluminum dissolved in melts and , , and mixtures have been studied by bubbling known amounts of gas through the melts followed by gas analysis. The results clearly show that is reduced not only to , as commonly assumed, but a part of the is further reduced to carbon. The extent of both reactions is strongly dependent on the ratio and decreases with increasing content over the whole range investigated . Published data indicate that the solubility of aluminum in these melts increases with increasing content when (cryolite); hence, it is suggested that part of the dissolved metal in these melts is present in a state which is nonreactive to . The rate of reduction of to increases markedly with temperature, while the rate of the subsequent reduction to carbon decreases slightly. When the inlet gas is instead of , the fraction of gas reduced to carbon is 7.7% as compared to 0.8% with (at cryolite composition, ).