Dissociation of Hydrogen and Nitrogen. 



779 



which would give out as little heat as possible in order to 

 conserve liquid air. The experimental tube E was a glass 

 tube 2 cm. in diameter internally. The source o£ electrons 

 was a platinum strip (F) 1 cm. long and 1 mm. wide, coated 



Fig. 1. 



*-| To McLeod cjauge 



Accel, 

 potential 



with a mixture of BaO and SrO. The anode was a nickel 

 gauze (40 mesh to the inch) which fitted snugly inside the 

 glass tube. The advantage of this type of anode was that 

 there were no large areas of glass surface to become charged 

 up and give erratic results, as so often occurs when electrons 

 and ions have an opportunity to lodge on such areas. The 

 number of electrons available was controlled by a rheostat, 

 while the energy of the electrons was determined by the 

 accelerating potential applied between the gauze and the 

 filament. The experimental tube was connected to a mer- 

 cury trap and a diffusion pump through a U-tube. The 



