NEW YORK ACADEMY OF SCIENCES 579 



"The experiments of Sir William Ramsay and Seddy on 

 the formation of helium from the radium emanation account 

 very readily for the well-known fact that the minerals which 

 contain helium in appreciable quantity contain as well one or 

 more of the radioactive elements. It might therefore be ex- 

 pected that all radioactive minerals should contain helium. 



"I have recently been testing various specimens of carnotite 

 to determine whether or not helium is present in them. Car- 

 notite promises to become an important source of radium ; 

 certain specimens have been found which have a radioactivity 

 1.6 times that of the metallic uranium, although it appears to 

 be difficult to obtain large quantities of mineral of this high 

 activity. On heating in vacuo several grams of this carnotite, 

 considerable quantities of carbon dioxide and water were 

 driven off, and when these were absorbed by caustic potash 

 and phosphorus pentoxide, respectively, only the nitrogen 

 spectrum could be observed in a vacuum tube connected to 

 the pump. No trace of helium could be detected, although 

 no difficulty was found in obtaining the helium spectrum when 

 only a tenth as much pitchblende, monazite sand, or thorianite 1 

 was used. 



"The quantit)^ of gas which was obtained from this amount 

 of carnotite was so small that it was thought worth while to 

 work with a larger quantity of the mineral. For this purpose 

 300 grams of carnotite, of activity 0.8 times metallic uranium, 

 was heated at a red heat in vacuo for three hours, and after 

 absorbing the carbon dioxide by caustic potash, about 10 c.c. 

 of a gas remained. On sparking this, after adding oxygen, 

 in order to absorb the nitrogen present, a rapid decrease 

 in volume took place, and when finally the excess of oxygen 

 was absorbed by means of phosphorus, only about 0.1 c.c. of a 

 gas remained. This, when introduced into a spectrum tube, 

 showed the characteristic red spectrum of argon. It was 

 observed that the greater part of the gas, aside from the carbon 

 dioxide, was given off on the first gentle heating; and it is 



1 The recently discovered mineral from Ceylon, containing about 75% 

 of thorium, was kindly supplied by Dr. George F. Kunz for this purpose. 



