Liquefaction of Neon

Neon can be liquefied under the ordinary atmospheric pressure at the temperature of liquid hydrogen boiling under ordinary conditions.

Its boiling-point has not been exactly determined, but it certainly lies above that of hydrogen (20.4° abs. on the helium scale), and is probably in the neighbourhood of 25° abs. Its vapour pressure is 12.8 mm. At 20.4° abs., and 2.4 mm. At 15.65° abs.

Its triple-point pressure is 35 cm. of mercury, and its critical pressure is 29 atmospheres; but the critical temperature has not been determined. There is, however, a connection between the critical temperatures and the viscosities of the inert gases. The variation of η with T is expressed by Sutherland's equation: -



where η and η₀ are the viscosities at temperatures T° and T₀° abs., and C is a constant for each gas.

When the values of η at the critical temperature are calculated for the other inert gases, it is found that the relationship η_k² = 3.93×10^-10 at. wt., holds good. By interpolation the value of η_k and hence, by Sutherland's equation, of T_k for neon may be found to be 61.1° absolute. This value agrees with that suggested by Travers, Senter, and Jaquerod (loc. cit.), viz. 60° abs. According to Onnes and Crommelin, the critical temperature of neon is a few degrees below 55° absolute.

The surface tension, density, and refractive index of liquid neon have not yet been measured; but Rudorf calculates that its refractive index should be about 1.24.