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It was collected for the first time by James Dewar in 1899 and published with the title "Sur la solidification de l'hydrogène" (English: On the freezing of hydrogen) in the Annales de Chimie et de Physique, 7th series, vol. 18, Oct. 1899. [1] [2] Solid hydrogen has a density of 0.086 g/cm 3 making it one of the lowest-density solids.
Liquid hydrogen also has a much higher specific energy than gasoline, natural gas, or diesel. [12] The density of liquid hydrogen is only 70.85 kg/m 3 (at 20 K), a relative density of just 0.07. Although the specific energy is more than twice that of other fuels, this gives it a remarkably low volumetric energy density, many fold lower.
The solid hydrogen is agitated in the liquid and the process is repeated. The resulting hydrogen slush has an increased density of 16–20% when compared to liquid hydrogen. [2] It is proposed as a rocket fuel in place of liquid hydrogen in order to use smaller fuel tanks and thus reduce the dry weight of the vehicle. [3]
The energy needed to overcome the Coulomb barrier corresponds to the energy of the average particle in a gas heated to 100 million K. The specific heat of hydrogen is about 14 Joule per gram-K, so considering a 1 milligram fuel pellet, the energy needed to raise the mass as a whole to this temperature is 1.4 megajoules (MJ). [9]
Hydrogen in an electrical discharge tube. Hydrogen is a colourless, odourless, and comparatively unreactive diatomic gas with a density of 8.988 × 10 −5 g/cm 3 and is about 14 times lighter than air. It condenses to a colourless liquid −252.879 °C and freezes into an ice- or snow-like solid at −259.16 °C.
For many years hydrogen has been stored as compressed gas or cryogenic liquid, and transported as such in cylinders, tubes, and cryogenic tanks for use in industry or as propellant in space programs. The overarching challenge is the very low boiling point of H 2 : it boils around 20.268 K (−252.882 °C or −423.188 °F).
ρ new is the unknown density of the new (green) liquid. RD new/ref is the relative density of the new liquid with respect to the reference. V is the volume of reference liquid displaced, i.e. the red volume in the diagram. m is the mass of the entire hydrometer. g is the local gravitational constant. Δx is the change in displacement.
The effect of pressure and temperature on the densities of liquids and solids is small. The compressibility for a typical liquid or solid is 10 −6 bar −1 (1 bar = 0.1 MPa) and a typical thermal expansivity is 10 −5 K −1. This roughly translates into needing around ten thousand times atmospheric pressure to reduce the volume of a ...