ON THE MEASUREMENT OF TE^MPERATUEE. 
175 
the temperature of the coil could be determined. By means of the exhaust pump the 
temperature of the liquid hydrogen was rediiced to 110 millims. of mercury, corre¬ 
sponding to a temperature of 15°’3 airs. 
Helium was then allowed to fill the coil at 
normal pressure, and hy ojoening the stop-cock 
the gas was slowly admitted into the ther¬ 
mometers, whicli had previously lieen ex¬ 
hausted,''^ 
AimEXDix IV .—Note on the Vapour 
Pressures of Solid Neon. 
The following experiments are of interest 
both rvith regard to their ajjplication to the 
preparation of pure helium and to the light 
they throw on the homogeneity of neon. 
In the first experiment the neon was con¬ 
densed in a fractionating hulh (Bamsay and 
Travers, ‘Phil. Trans.,’ 1901, vol. 197, A, 
p. 51) which was connected with a manometer 
reading pressures below 100 millims. of mercury 
and, through a stop-cock, with a mercury 
pump. About 20 cub. centims. of neon were 
Introduced into the hulh and condensed hy 
cooling it hy means of liquid hydrogen, boiling 
under the normal pressure (20°'4 on the helium 
scale). The vapour observed hy 
means of the manometer was 12’8 millims. of 
mercury. On ojjening the sto 2 )-cock, and 
allowing some of the neon to evaporate into 
the 2 )umj), the joressure fell momentarily, Imt 
on closing it the pressure again rose to 12'8 
millims. The operation was repeated several 
times with the same result, jjroving that neon 
is a homogeneous sul)stance. On removing the vacuum vessel containing the liquid 
hydrogen, a small quantity of solid neon Avas seen in the fractionating Indh. 
Eig. 
* Note, Jahj 19//?, 1902. — After filling the thermometer, the greater portion of the gas contained in the 
coil, which was maintained at lo^'S ahs., was allowed to escape into the mercury pump, Iw opening the 
stop-cock communicating AAuth it for a few seconds. When this gas had been pumjred off, the stop-cock 
Acas again opened, and the remaining gas rvas collected separateljn The last fraction, which consisted of 
about 10 cul). centims., Avas examined spectroscopically, but it appeared to contain no trace of neon. 
