Reports

Observations of Hydrogen at Room Temperature (25°C) and High Pressure (to 500 Kilobars)

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Science  09 Mar 1979:
Vol. 203, Issue 4384, pp. 1004-1006
DOI: 10.1126/science.203.4384.1004

Abstract

Hydrogen becomes a solid at 25°C when subjected to a pressure of 57 kilobars. The high-pressure phase appears as a transparent crystalline mass. The refractive index of the high-pressure phase increases sharply with pressure, indicating a density increase of similar magnitude. At 360 kilobars the calculated density of the high-pressure phase is 0.6 to 0.7 grams per cubic centimeter.