liquid air
liquid air
liquid air
| Noun | 1. | liquid air - air in a liquid state |
| 单词 | liquid air | |||
| 释义 | liquid airliquid airliquid air
liquid airliquid air,ordinary air that has been liquefied by compression and cooling to extremely low temperatures (see liquefactionliquefaction,change of a substance from the solid or the gaseous state to the liquid state. Since the different states of matter correspond to different amounts of energy of the molecules making up the substance, energy in the form of heat must either be supplied to a substance ..... Click the link for more information. ). Its commercial preparation involves purification by washing to remove soluble impurities and by passage over calcium oxide (lime) to remove the carbon dioxide; compression, under a pressure of 200 atmospheres, or about 3,000 lb per sq in.; cooling, by passage through pipes immersed in cold water; treatment with sodium hydroxide to remove excess water; and rapid expansion, the expanding air passing back over the pipe from which it has just escaped absorbing so much heat that the air remaining in the pipe becomes liquid. Freshly liquefied air consists of 78.1% nitrogen, 21.0% oxygen, 0.9% argon, and very small amounts of rare gases and hydrogen in solution. Its boiling point is approximately −195°C;. Because of fractional evaporation, its oxygen concentration and its boiling point increase with time. It must be kept in a specially designed container, the Dewar flaskDewar flask [for Sir James Dewar], container after which the common thermos bottle is patterned. It consists of two flasks, one placed inside the other, with a vacuum between. The vacuum prevents the conduction of heat from one flask to the other. ..... Click the link for more information. , because at ordinary temperatures it absorbs heat rapidly and reverts to the gaseous state. Liquid air is used commercially for freezing other substances and especially as an intermediate step in the production of nitrogen, oxygen, and argon and the other inert gases. As the temperature of liquid air rises, the nitrogen evaporates first at −195.8°C;, the argon next at −185.7°C;, and the oxygen last at −183°C;. See low-temperature physicslow-temperature physics, science concerned with the production and maintenance of temperatures much below normal, down to almost absolute zero, and with various phenomena that occur only at such temperatures. ..... Click the link for more information. . liquid air[′lik·wəd ′er]liquid airliquid airliq·uid airliquid airliquid air
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