Page:Popular Science Monthly Volume 63.djvu/65

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61
A NEW SOURCE OF HEAT: RADIUM.
A NEW SOURCE OF HEAT: RADIUM.
By HENRY CARRINGTON BOLTON, Ph.D.

AT a meeting of the French Academy of Sciences held in March MM. Curie and Laborde announced a newly discovered property, of that extraordinary substance radium—its salts emit heat continuously 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 difficulty of obtaining it unmixed with the mineral substances by which it is always accompanied in nature. Tons of minerals have been submitted 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 journals, 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 cultures of Micrococcus prodigiosus to the influence of its rays and ascertained that they were fatal to the bacteria.

The character of the rays given out by radium has been the subject of special research; MM. Curie and Danne observed that solid