
1) Alternative fuel
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https://www.crosswordclues.com/clue/liquid-air

Liquid Air was the brand name of an unusual automobile produced by a joint American/English concern between 1899 and 1902. The first factory opened in Boston, Massachusetts in 1899, and its owners claimed that they could construct a car that would run a hundred miles on liquid air. By 1901 the company had gone into receivership. In 1902 the produc...
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http://en.wikipedia.org/wiki/Liquid_Air

Liquid air is air that has been cooled to very low temperatures (cryogenic temperatures), so that it has condensed into a pale blue mobile liquid. To protect it from room temperature, it must be kept in a vacuum insulated flask. Liquid air can absorb heat rapidly and revert to its gaseous state. It is often used for condensing other substances int...
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http://en.wikipedia.org/wiki/Liquid_air

• A transparent limpid liquid, slightly blue in color, consisting of a mixture of liquefied oxygen and nitrogen. It is prepared by subjecting air to great pressure and then cooling it by its own expansion to a temperature below the boiling point of its constituents (N -194
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http://thinkexist.com/dictionary/meaning/liquid_air/

Air that, by means of intense cold and pressure, has been liquefied. ... (05 Mar 2000) ...
Found on
http://www.encyclo.co.uk/local/20973
Liq'uid air (Physics) A transparent limpid liquid, slightly blue in color, consisting of a mixture of liquefied oxygen and nitrogen. It is prepared by subjecting air to great pressure and then cooling it by its own expansion to a temperature below the boiling point of its constituents (N -194° C; O - 183° C.).
Found on
http://www.encyclo.co.uk/webster/L/47

Type: Term Definitions: 1. air that, by means of intense cold and pressure, has been liquefied.
Found on
http://www.medilexicon.com/medicaldictionary.php?t=1868

[
n] - air in a liquid state
Found on
http://www.webdictionary.co.uk/definition.php?query=liquid%20air
noun air in a liquid state
Found on
https://www.encyclo.co.uk/local/20974

Air that has been cooled so much that it has liquefied. This happens at temperatures below about -196°C/-321°F. The various constituent gases, including nitrogen, oxygen, argon, and neon, can be separated from liquid air by the technique of fractional distillation. Air is liquefied by the Linde process, in which air is alterna...
Found on
https://www.encyclo.co.uk/local/21221
No exact match found.