Trans., 18 53, p. 357, 18 54, p. 321, and 1862, p. 579) showed that the statement that no internal work is done when a gas expands or contracts is not quite true, but the amount is very small in the cases of those gases which, like oxygen, hydrogen and nitrogen, can only be liquefied by intense cold and pressure.
It is easily liquefied, the liquid boiling at - 8° C., and it becomes crystalline at - 72.7° C. (Walden, Zeit.
Nitrogen has been liquefied, the critical temperature being -149° C. and the critical pressure 27.54 atmospheres.
The liquefied gas boils at -195.5° C., and its specific gravity at its boiling point is 0 8103 (E.
It is an orange-coloured gas which may be readily liquefied and by further cooling may be solidified.