Several of the contaminants of uranium can be removed or controlled by vacuum melting and liquation. The lower limits of carbon content which can be attained by liquation in urania crucibles are 225 to 250 ppm at 1195°C, 190 to 225 ppm at 1150°C, and 170 ppm at 1138°C. In magnesia crucibles the reaction 3 MgO + UC → UO2 + CO + 3 Mg proceeds to the right in a high vacuum resulting in incomplete carbon removal. Oxygen and nitrogen are rapidly removed by liquation and contents of less than 10 ppm are readily obtained. Iron and silicon are not removed by a simple melting and liquation process. Various crucible materials were investigated and the effect of addition agents such as nitrogen, tantalum, titanium, and zirconium was studied. Under optimum vacuum melting conditions a metal is produced that will contain no more than 130 to 200 ppm total impurities.