One type of gas mixture used in anesthesiology is a 50%/50% mixture (by volume) of nitrous oxide (N2O) and oxygen (O2), which can be premixed and kept in a cylinder for later use. Because these two ga

One type of gas mixture used in anesthesiology is a 50%/50% mixture (by volume) of nitrous oxide (N2O) and oxygen (O2), which can be premixed and kept in a cylinder for later use. Because these two gases don't react chemically at or below 2000 psi, at typical room temperatures they form a homogeneous single gas phase, which can be considered an ideal gas. If the temperature drops below -6∘C, however, N2O may begin to condense out of the gas phase. Then any gas removed from the cylinder will initially be nearly pure O2; as the cylinder empties, the proportion of O2 will decrease until the gas coming from the cylinder is nearly pure N2O. In a hospital, pure oxygen may be delivered at 50 psi (gauge pressure) and then mixed with N2O