452 



Some Experiments on Helium, 

 FIG. 2. 



To facilitate the absorption of the gases during the experiment, 

 the vacuum- tube was kept cool by a water-jacket, G, closed at the 

 bottom by a cork fitting tightly round the tube. When it was 

 necessary to heat the vacuum-tube, the jacket could be loosened from 

 the cork, and slipped up the side- tube B, which was bent round, and 

 extended vertically for about 10 inches in a straight line with the 

 vacuum-tube. 



The gas was made to circulate for about six hours, and at the end 

 of that time the tap F was closed, the tap E was opened, and the 

 apparatus thoroughly exhausted. The jacket Gr was then raised, and 

 the gas expelled from the platinum by heat was pumped off. From 

 mixtures containing very little helium, a small quantity of that gas 

 was separated, mixed with a trace of argon. 



