86 Prof. W. Ramsay. Helium, a Gaseous [May 2, 



although some were well marked, were not symmetrically arranged. 

 Every attempt was made by altering the length of the india-rubber 

 tubing which connected the wave-length tube with the supply of gas, 

 to induce appropriate echoes. This plan works well with denser 

 gases. But I found it of no avail. The half -wave-lengths were 

 always between 67 and 71 mm., and there appears no reason which 

 would justify choosing the lower figure, which would give the ratio 

 of specific heats 1 : 1'74. 



One conclusion, however, may be drawn : that the gas has a high 

 ratio of specific heats, and that it is probably monatomic, if this 

 inference is legitimate for argon.* 



6. Is the Gas evolved from Cleveite a Hydride or an Element ? 

 It was soon discovered that the eras evolved from cleveite by treat- 



/ 



ment with dilute sulphuric acid contained a not inconsiderable amount 

 of hydrogen. Now if the element helium is in combination in cleveite 

 with the uranium, or the lead, or the yttrium, it is to be expected 

 that it will be evolved as a hydride. It is true that a hydride might 

 be unstable, in which case free hydrogen should be mixed with the 

 helium. 



An attempt was made to decide which alternative is correct by 

 absorbing the free hydrogen by palladium. A measured quantity of 

 the gas was treated with palladium sponge, hammered on an anvil, 

 so as to avoid the introduction of air into the gas as much as possible, 

 and it was passed up into the tube containing the gas. The numbers 

 obtained are these : 



Original volume of crude gas 12'20 c.c. 



Residue after absorption of hydrogen. . 2'40 ,, 

 Hydrogen absorbed 9'80 



The gas therefore consisted or 19'7 per cent, of a substance mi- 

 attacked by palladium, after standing for a night in contact with it, 

 and 80'3 per cent, of hydrogen. The residue was transferred to a 

 sparking-tube, and sparked with oxygen over caustic potash. The 

 volume then decreased to 2'20 c.c., and the residue is 18'0 per cent, of 

 the total. The contraction is too small to allow of the hypothesis 

 that a hydride of helium has been decomposed on sparking, although 

 if the formula of the hydride were HHe, decomposition and removal 

 of hydrogen might take place without change of volume. 



7. The Spectrum of the Gas from Cleveite. 



A careful comparison was made between the spectra of various 

 samples of gas from cleveite and the spectrum of argon. As my 

 spectroscope does not admit of accurate measurements being taken, I 

 * 25th June, 1895. This conclusion has been amply confirmed. 



