Identifying Oxygen Elements

While oxygen is one of the most common elements in minerals, its presence is ordinary determined indirectly by testing for the different oxygen acids. In the case of a few oxides in which their is an excess of oxygen, a direct test may be made.

1. Closed Tube Test. The powdered oxide is placed in a closed tube with a small splinter of charcoal resting just above it. The tube is heated and if free oxygen is evolved the charcoal will at first glow and then burn with a bright light. It is to be noted that only a few oxides which contain an excess of oxygen will give this test.
2. Evolution of Chlorine. Oxides that contain an excess of oxygen when dissolved in hydrochloric acid will produce chlorine gas.