Removal of Less Volatile Impurities from Crude Indium by Vacuum Distillation

The less volatile impurities has been eliminated by high temperature vacuum distillation of crude indium. The experiment was carried out in a self-designed vacuum distillation furnace. The temperature of distillation experiment was carried out at 1273 similar to 1373K and samples of condensate were collected at time intervals of 2, 3, 4 and 5 hour. The content of Ni, Cu, Fe in the crude indium have a little changed with the distillation time extension or the distillation temperature ascension. Both distillation temperature and holding time are principal factors that affected the removal of Sn from In by vacuum distillation. Compared with distillation time, temperature on the removal of less volatile impurities effects is more significant, So the distillation temperature was more important than distillation time. The best conditions of removal of less volatile impurities from crude indium under dynamic vacuum of 1 similar to 5Pa were as follows: 1348K and 2h. Under this condition, the content of impurities could be reduce to the standard of 5N such as Sn, Cu, Fe, Ni in the crude indium that have boiling point. The ELEMENT-GD have been used in testing the element contents of the samples.