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|Section2= |Section7= }} Liquid hydrogen (LH2 or LH2) is the liquid state of the element hydrogen. Hydrogen is found naturally in the molecular H2 form. To exist as a liquid, H2 must be cooled below hydrogen's critical point of 33 K. However, for hydrogen to be in a full liquid state without boiling at atmospheric pressure, it needs to be cooled to 20.28 K〔(IPTS-1968 ), iupac.org, accessed 2009-06-12〕 (−423.17 °F/−252.87°C).〔Chemical elements data references〕〔(Properties Of Gases ). Roymech.co.uk. Retrieved on 2011-08-28.〕 One common method of obtaining liquid hydrogen involves a compressor resembling a jet engine in both appearance and principle. Liquid hydrogen is typically used as a concentrated form of hydrogen storage. As in any gas, storing it as liquid takes less space than storing it as a gas at normal temperature and pressure. However, the liquid density is very low compared to other common fuels. Once liquefied, it can be maintained as a liquid in pressurized and thermally insulated containers. Liquid hydrogen consists of 99.79% parahydrogen, 0.21% orthohydrogen.〔(Liquid Air/LH2 ). Astronautix.com. Retrieved on 2011-08-28.〕 ==History== In 1885 Zygmunt Florenty Wróblewski published hydrogen's critical temperature as 33 K; critical pressure, 13.3 atmospheres; and boiling point, 23 K. Hydrogen was liquefied by James Dewar in 1898 by using regenerative cooling and his invention, the vacuum flask. The first synthesis of the stable isomer form of liquid hydrogen, parahydrogen, was achieved by Paul Harteck and Karl Friedrich Bonhoeffer in 1929. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Liquid hydrogen」の詳細全文を読む スポンサード リンク
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