By rapid evaporation and cooling under reduced pressure, liquid nitrogen is converted into an ice-like solid, which melts at -210.5° C. under a pressure of 86 mm.
The density at -252.5° C. is 1.0265, and the calculated density at -273° C. is 1.1370.
Nitrogen exists in two solid forms, and the transition temperature is 35.5° abs., with a molecular heat of transformation of 53.8 cals.
The atomic heat increases steadily from 1.60 at T=15.27° abs. to 5.16 at T=55.26° abs.
The variation in the atomic heat with temperature leads to the conclusion that crystallised nitrogen is diatomic.
The dielectric constants of the liquid, and also the solid form, have been determined. |
| The crystals which separate from the liquid at -210° C. were considered to belong to the cubic system. This opinion was not, however, confirmed by an X-ray analysis of the solid at -253° C. The matter was further tested by an observation of the solid in a cell with plane-parallel glass sides, by means of a polarisation microscope. The crystals were weakly doubly refracting, and therefore anistropic at the melting-point and down to -253° C. Nitrogen does not appear to crystallise on the regular system. |