126 ON THE NEW GASES — ARGON AND HELIUM. 



of a Topler's pump. They also examined the gases obtained 

 from many other minerals by means of the spectroscope, and 

 their spectra are identical with the spectrum of helium from 

 cleveite. From a careful examination of these minerals it seems 

 that the helium is retained by those consisting of salts of 

 uranium, yttrium, and thorium. The three principal minerals 

 which are available as sources of helium are cleveite, uraninite, 

 and broggerite. 



Properties. — -In many cases sufficient helium could not be 

 obtained in order to ascertain its density. Sufficient gas, however, 

 has been obtained from cleveite and broggerite to enable the 

 density to be determined. The maximum density of the original 

 gas from cleveite was 3 "89. This sample contained a little nitrogen. 

 In these determinations of the density of helium the utmost care was 

 taken to get the gas pure from nitrogen, carbon dioxide, sulphur 

 dioxide, sulphuretted hydrogen, and hydrogen. The density of the 

 gas got from broggerite by fusion with potassium bisulphate was 

 taken, and also of the gas from cleveite. The following figures 

 were obtained : — 

 Gas from broggerite by heating ... ... 2-152 



„ ,, „ ,, potassium bisulphate 2'i87 oxygen = 16 



„ „ cleveite ... ... ... 2*205 



Mean. 2t8i 

 The wave length of sound in helium was measured, and from this 

 the ratio of the sp. heats was calculated. This was found to be i "65 2, 

 which comes near the theoretical number i-66. This gas had 

 a density of 2'i33. Hence helium is monatomic. It is not attacked 

 by oxygen under the electric discharge, nor is it oxidised by red- 

 hot copper oxide. Red-hot magnesium does not affect it. It is 

 sparingly soluble in water. At 18'^C i vol. water dissolves '0073 

 vol. helium. It is altogether insoluble in alcohol and benzene. 

 In the spectrum of helium there are two lines in the red which 

 are coincident with two of the argon lines. A close analogy exists 

 between argon and helium. Both are monatomic, if we draw 

 the usual inference from the ratio between their sp. heats. If 

 we assume that this inference is correct, then it follows that their 

 atomic weights are identical with their molecular weights. The 



