Page:Popular Science Monthly Volume 66.djvu/271

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HE discovery of radioactivity has opened to physical and probably also to chemical research a field of extraordinary and peculiar promise. We seem to have a source of energy which flows spontaneously for unlimited time without tangible indication of its source; effects of energy are exhibited which neither in essence nor in phenomena resemble those previously known; substances are presented which seem to be of an entirely new kind, though they resemble our oldest and best-known elements so closely as to make their distinction difficult. The most prominent of these substances is radium, which, in the opinion of its discoverers, may be considered a new chemical element and which has been recognized as such by the International Atomic Weight Committee by giving it a place in their table of atomic weights for 1904.

Much more indefinite are the relations of the other radioactive substances thus far made known. The existence of polonium, discovered by P. and S. Curie, was for a time considered dubious, but seems to awake to new life in the radiotellurium of W. Marckwald. On radiolead voluminous researches have appeared which are especially noteworthy in chemical respects, still they do not yet authorize us to recognize a new element with certainty, even if we disregard the objections raised by F. Giesel against these researches. The same may be said of the actinium of A. Debierne and other radioactive substances, such as are supposed to have been detected in the earths of the cerium and yttrium group.

This uncertainty may be understood if we consider that for the researches thus far made only very small amounts of pure or merely enriched materials have been available, which has made the chemical investigation very difficult. The great fascination of tracing the observed phenomena of radioactivity by means of the sensitive photographic plate, the electroscope and the phosphorescent screen had quite naturally made the investigation of the chemical behavior of the substances in question a secondary matter which, while it has not been entirely overlooked, yet has not received that degree of attention that formerly was bestowed on the determination of the characteristic properties of newly discovered elements.