A NEW SOURCE OF HEAT: RADIUM. 6i 



A NEW SOUKCE OF HEAT: EADIUM. 



By henry CARRINGTON BOLTON, Ph.D. 



A T a meeting of the French Academy of Sciences held in March 

 -^-*- MM. Curie and Laborde announced a newly discovered prop- 

 erty, of that extraordinary substance radium — its salts emit heat con- 

 tinuously and to a measurable extent. Headers of the Popular 

 Science Monthly may remember that in the number for July, 1900, 

 we sketched the history of the discovery of this new body by M. and 

 Mme. Curie in 1898, and we gave some account of its marvellous 

 physical and chemical properties so far as known at that date; its 

 power of giving out light perpetually without any exciting cause, its 

 emission of rays that penetrate solids like the X-ray, its faculty of 

 acting on sensitized plates, and of causing air to conduct electricity. 

 Now a fifth property must be added, that of the emission of heat. 



During the few months that have elapsed since the publication of 

 the above summary, physicists and chemists on both sides of the 

 Atlantic have been actively experimenting with the interesting body, 

 in no wise discouraged by its excessive rarity and by the great diffi- 

 culty of obtaining it unmixed with the mineral substances by which 

 it is always accompanied in nature. Tons of minerals have been sub- 

 mitted to laborious processes in the chemical laboratory to obtain a 

 few grammes of the precious material; and at the end of the task 

 the conscientious scientist can only claim that the product is such 

 and such a salt containing a small, unknown percentage of radium. 



To enumerate the peculiar activities of radium with any degree 

 of completeness would occupy more pages of the magazine than could 

 well be spared; for details we must refer to the purely technical jour- 

 nals, but some points arrest the attention of every one. 



Becquerel, the French physicist whose name is attached to the rays 

 emitted by uranium, observed the powerful physiological action of 

 radium when in a comparatively pure state; a few grammes enclosed 

 in a bottle carried in his waistcoat pocket burned holes into the flesh 

 in six hours, producing superficial sores that took several weeks to 

 heal. Some experimenters have remarked that their fingers are made 

 sore by handling its salts. Aschkinass and Caspari have exposed cul- 

 tures of Micrococcus prodigiosus to the influence of its rays and ascer- 

 tained that they were fatal to the bacteria. 



The character of the rays given out by radium has been the sub- 

 ject of special research; MM. Curie and Danne observed that solid 



