Hydrogen and Nitrogen produced by <x Rays. 457 



entrance and exit tubes respectively for moist air, used in 

 the detection of chemical compounds produced. As a rule, 

 the active gases will not react with any element unless the 



Fig-, l. 



=S=fc 



D GAS 



surface of the latter is clean and free from occluded gas. In 

 all experiments a thin film of the substance being tested 

 was deposited over the surface of A by distillation in vacuum. 

 The volume of A was about 50 c.c. 



3. Experiments with Nitrogen. 



The nitrogen used was prepared by warming a solution of 

 sodium nitrite and ammonium chloride. The gas was then 

 passed over sodium-potassium alloy, calcium chloride, and 

 phosphorus pentoxide to the reservoir. ■ The whole of the 

 apparatus was thoroughly washed out with nitrogen. The 

 gas was then pumped out, and the element at the bottom of 

 A heated to produce the pure deposit on the interior of A, 

 care being taken that there was no film formed on G. Again 

 the apparatus was evacuated, and the gases liberated by the 

 melting of the element were removed. The tap H being- 

 closed, the oil manometer C was calibrated by admitting 

 known volumes of gas from D, the pressure before and after 

 the gas was admitted being noted. The a rays then acted 

 on the gas in A, producing active nitrogen which combined 

 chemically with the element present. As a result the gas 

 gradually disappeared, this absorption being shown by a 

 gradual decrease in the pressure indicated by C. From the 

 initial and final readings of C the amount of gas absorbed 

 could be calculated. This was repeated, using different, 

 pressures of gas. The polonium was never more than 6 cm., 

 away from any part of A, and the range of the a rays was 

 always greater than this distance, at the pressures used. The 

 latter were measured by a mercury gauge, not shown 

 in the diagram. 



