Mask, oxygen

A mask that covers the mouth and nose, and is hooked up to an oxygen tank. It delivers oxygen directly to the patient. Oxygen can also be delivered directly through a nasal catheter, a tube that divides into two smaller tubes that go into the nostrils. Oxygen is a colorless, odorless and tasteless gas that makes up about 20 percent of the air we breathe (and at least half the weight of the entire solid crust of the earth) and which combines with most of the other elements to form oxides. Oxygen is essential to human, animal and plant life. The chemical symbol for the element oxygen is O. As a medicinal gas, oxygen contains not less than 99.0% by volume of O2. Oxygen was discovered in 1774 by the British scientist Joseph Priestly but he did not name it "oxygen." He called it dephlogisticated air. (Priestly discovered three other chemical compounds, one of which, nitrous oxide - "laughing gas" - is still used today as a mild anesthetic agent, as during dental procedures.) The word "oxygen" came from the French "oxygene." It was so named by the French scientist Antoine Lavoisier (1743-94) who thought it was a necessary ingredient in all acids. This is not so. Hydrochloric acid (HCl), for example, contains no oxygen.