Liquid air is air that has been liquified by compression and cooled to very low temperatures. It must be kept in a Dewar flask, as at room temperature, liquid air can absorb heat rapidly and revert to its gaseous state. It is often used for freezing other substances, and as a source of nitrogen, oxygen, argon, and other inert gases.
The most common process for distillation of liquid air is the two column Linde cycle. Air is fed at high pressure (>60 psig) into the lower column, in which it is separated into pure nitrogen and oxygen-rich liquid. The rich liquid and some of the nitrogen are fed as reflux into the upper column, which operates at low pressure (<10 psig), where the final separation into pure nitrogen and oxygen occurs. A raw argon product can be removed from the middle of the upper column for further purification.
The air in the troposphere consists of the following proportions of gases: 78 percent nitrogen, 21 percent oxygen, 0.9 percent argon, 0.03 percent carbon dioxide, and the remaining 0.07 percent is a mixture of hydrogen, water, ozone, neon, helium, krypton, xenon, and other trace components.
After being compressed, the air passes through beds of adsorption beads that remove carbon dioxide, the remaining water vapor, and molecules of heavy hydrocarbons, such as acetylene, butane, and propylene.
After filtering the air, a portion of the air stream is decompressed in a device called a centrifugal expander (which is basically a compressor that runs in reverse).
The incorporation of air in the form of bubbles as a dispersed phase in the bulk liquid.
Air may be entrained in a liquid through mechanical means and/or by release of dissolved air due to a sudden change in environment.
An analytical technique whereby a complex substance is adsorbed on a solid or liquid substrate and progressively eluted by a flow of a substance (the eluant) in which the components of the substance under investigation are differentially soluble.
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