Lavoisier collected the red powder (proved to be mercury oxide) generated on the surface of mercury and put it in another smaller container. After intense heating, mercury and oxygen are obtained, and the volume of oxygen is exactly equal to the reduced air volume in the original closed container. He added the obtained oxygen to about four-fifths of the remaining gas in the previous container, and the gas obtained was exactly the same as air in physical and chemical properties. Through these experiments, lavoisier came to the conclusion that air is composed of oxygen and nitrogen.