216 Mr. E. Jacot on a Relation between Ionization by 



The writer examined the effect of a direct beam of cathode 

 rays on white phosphorus. Rapid transformation of the 

 phosphorus (apparently to the red modification) occurred, 

 and this was attended by rapid exhaustion of the gas in the 

 tube. Now direct chemical effects of cathode rays are, in 

 the particular case of phosphorus, not necessarily to be 

 expected. The better known effects of the rays are reducing 

 effects as they appear in the cases of various salts. Any- 

 observed chemical effects of the rays on phosphorus could 

 therefore reasonably be accepted as secondary effects following 

 on the direct thermal effects of the rays ; and the observed 

 modification of the phosphorus to the red variety, when 

 viewed in this light, would seem to be a very natural effect. 

 Bat quantitative experiments showed that, even on making 

 the extreme assumption that all the kinetic energy of the 

 rays could be converted into available heat energy, and 

 calculating the mass of phosphorus so modifiable, the mass 

 actually modified was yet in excess of the calculated value. 



A definite mass of white phosphorus was subjected to a 

 direct stream of cathode rays for a definite interval of time, 

 a part being so transformed apparently to the red modification. 

 The remaining white modification was separated by solution 

 in carbon bisulphide, and an estimate obtained of the mass 

 modified by the rays. From a knowledge of the order of the 

 kinetic energy of the rays used, and on the hypothesis that 

 all the energy of the rays was reducible to heat, a comparison 

 could be made between a maximum value of the heat supplied 

 by the rays and the heat actually required for the observed 

 transformation. In every case the mass of phosphorus 

 actually modified proved excessive. 



The rays, then, had two distinct effects at least on white 

 phosphorus. There was a purely thermal effect; and there 

 was a more directly chemical effect. The latter might be 

 due either, (1) to a direct effect of the corpuscles on the 

 phosphorus ; or (2), to an effect of the corpuscles on the gas 

 in the tube (ionizing or otherwise) followed by a reaction 

 between the modified gas and the phosphorus. 



Experiments were made with various modified forms of 

 discharge-tubes in which the phosphorus was carefully kept 

 out of the direct path of the rays, screened from any ultra- 

 violet light from the discharge, &c. These experiments 

 made it evident that a large part of the original effect must 

 be due to a reaction between the phosphorus and the gas in 

 the tube, modified in some way by the passage of the rays 

 through it. The passage of the discharge continued to be 

 attended by a certain exhaustion of the gas in the tube and 

 a similar simultaneous slow modification of the phosphorus. 



