Duane — Heat Generated by Radio-active Substances. 267 



The y-radiation and the generation of heat increased 

 between the 7th and the 21st of December, but after that no 

 increase was perceptible. This was due to the accumulation 

 of the emanation and the induced activity, which after three 

 weeks attained approximately their saturation values. 



The sixth column contains the ratios between the tubes A 

 and B. It appears that these ratios are the same no matter 

 what the date of the experiment was and no matter whether 

 the y-rays or the heat effect was measured. It follows that 

 the presence of the phosphorescent salt does not appreciably 

 change the rate of generation of heat by the radium. 



The following facts may be noticed in passing : The phos- 

 phorescence of the mixture has become less intense than at 

 first but is still brilliant. The light has also changed its color, 

 becoming more orange. 



In order to investigate the heat effect in the case where the 

 phosphorescence is produced by the /3 and 7 rays in willemite 

 and in platinum-barium cyanide, I arranged the following 

 experiment : A long, fine tube is inserted into tube B of the 

 calorimeter and around the end of this tube is packed the 

 phosphorescent salt. A very small glass capsule hermetically 

 sealed containing radium can be lowered down the fine tube 

 to the center of the salt. The walls of the tube and capsule 

 are so thin that under these conditions the salt phosphoresces 

 brilliantly. 



I compared twice the y-rays from the capsule with those 

 from the standard and found that the quantity of radium in 

 the capsule corresponded with 1-91 and 1*92 mg. of RaCl 2 . 



The heat effects observed on lowering the radium to the 

 center of the phosphorescent salt were the following : 



Table 4. 



Heat 

 calorie 

 Salt used per hour 



•67 gr Platinum-barium cyanide - 170 



1-19 gr. Willemite.. -172 



No phosphorescent salt *171 



No phosphorescent salt *169 



It is evident that the generation of heat is the same whether 

 the phosphorescent salt is present or not. It follows from 

 these two series of experiments that there is no appreciable 

 absorption of energy in producing chemical reactions, and that 

 the rays do not liberate an appreciable amount of chemical 

 subatomic energy. 



These results are interesting from the point of view of 

 the amount of energy necessary to effect the organs of sight. 



