August 1, 1774 (Sino-Japanese June 24), Priestley, British chemist in the laboratory of the heating mercuric oxide oxygen. In August 1774,


Priestley, British chemist, discovered in the laboratory of the heating mercuric oxide oxygen.
the gas chemistry research, Priestley's most important discovery of oxygen. In 1774, he received a large convex lens (fire mirror), began to study certain substances released by the high temperature of the convex lens concentrating production main gas. Red precipitate (mercuric oxide) and mercury gray cinder quicksilver, he studies the material is (mercuric oxide). Mercury surface, Priestley mercuric oxide is placed in a glass bell jar with a diameter of 30 cm, the fire mirrors with a focal length of 50 cm, the sunlight collecting on the mercuric oxide. Soon discovered mercury oxide is decomposed to release a gas, glass mercury squeezed out. He called this gas "off phlogiston air. Drainage gas gathering, this gas is collected, and then study its nature. Found candles will be burning in this air, very bright flame, and mice living a normal life in this gas, and about four times longer than the time to live in an equal volume of ordinary air; He also personally tried, feeling this kinds of light air makes breathing comfortable. A detailed description of the whole process of his experiments.

comment: do laboratory to be good at discovering, or experiment done more futile!