1896.] More about Argon. 9 



proportion of argon was only one-half of that contained in the 

 residue, after similar treatment from the atmosj^here. After the 

 discovery of helium by Professor Kamsay, the question presented 

 itself as to whether this conclusion might not be disturbed by the 

 presence in the Bath gas of helium, whose lightness would tend to 

 compensate the extra density of argon. 



An examination of the gas which had stood in my laboratory more 

 than a y^ar having shown that it still contained no oxygen, it was 

 thought worth while to remove the nitrogen so as to determine the 

 proportion that would refuse oxidation. For this purpose 200 c.c. 

 were worked up with the oxygen until the volume, free from nitrogen, 

 was reduced to 8 c.c. On treatment with pjrogallol and alkali the 

 residue measured 3 • 3 c.c. representing argon, and helium, if j^resent. 

 On sparking the residue at atmospheric pressure and examining the 

 spectrum, it was seen to be mainly that of argon, but with an un- 

 mistakable exhibition of D3. At atmospheric pressure this line 

 appears very diffuse in a spectroscope of rather high power, but the 

 place was correct. 



From another sample of residue from the Bath gas, vacuum tubes 

 were charged by my son, Mr. R. J. Strutt, and some of them showed 

 D3 sharply defined and precisely coincident with the line of helium 

 in a vacuum tube prepared by Professor Earn say. 



Although the presence of helium in the Bath gas is not doubtful, 

 the quantity seems insufficient to explain the low density found in 

 October 1894. In order to reconcile that density with the proportion 

 of residue (8-3/200 = 0*016) found in the experiment just described, 

 it would be necessary to suppose that the helium amounted to 25 per 

 cent, of the whole residue of argon and helium. Experiment, how- 

 ever, proved that a mixture of argon and helium containing 10 per 

 cent, of the latter gas showed D3 more plainly than did the Bath 

 residue. It is just possible that some of the helium was lost by 

 diffusion during the long interval between the experiments whose 

 results are combined in the above estimate. 



Gas from the Buxton springs, kindly collected for me by 

 Mr. A. McDougall, was found to contain no appreciable oxygen. 

 The argon amounted to about 2 per cent, of the volume. When its 

 spectrum was examined, the presence of D3 was suspected, but the 

 appearance was too feeble to allow of a definite statement being made. 

 The proportion of helium is in any case very much lower than in the 

 Bath gas. 



Is helium contained in the atmosphere? Apart from its 

 independent interest, this question is important in connection with 

 the density of atmospheric argon. Since the spectrum of this gas 

 does not show the line D3, we may probably conclude that the pro- 

 portion of heliuin is less than 3 per cent. ; so that there would be less 

 than 3 x 10"^ of helium in the atmosphere. The experiment about 

 to be described was an attempt to carry the matter further, and is 

 founded upon the observation by Professor Ramsay, that the solu- 



