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But this radioactivity hardly attains the ten-thousandth part of that presented by uranium, or the ten-millionth of that appertaining to radium. Two other bodies, polonium and actinium, the one characterised by the special nature of the radiations it emits and the other by a particular spectrum, seem likewise to exist in pitchblende.
These chemical properties have not yet been perfectly defined; thus M. Debierne, who discovered actinium, has been able to note the active property which seems to belong to it, sometimes in lanthanum, sometimes in neodynium.
Radium and thorium possess in somewhat large proportions the three kinds of rays, and it is the same with actinium. Polonium contains especially alpha rays and a few gamma rays. In the case of uranium, the alpha rays have extremely slight penetrating power, and cannot even impress photographic plates. But the widest difference between the substances proceeds from the emanation.
Radium, uranium, thorium, actinium all the radioactive elements are, as everybody knows, continually disintegrating, discharging the enormous energy that is imprisoned in their molecules. It may take generations, epochs, centuries, for them to get rid of it and transform themselves into other substances, but they will inevitably do so eventually.
The same is the case with actinium, which is said to come in the long run from uranium, but not so directly as does radium.
In the same way, Professors Rutherford and Soddy have discovered a so-called thorium X to be the stage through which ordinary thorium has to pass in order to produce its emanation. Since the above was written, another product has been found to intervene between the X substance and the emanation in the case of actinium and thorium. They have been named radio-actinium and radio-thorium respectively.
Bodies which contain actinium are particularly rich in emanations. Uranium, on the contrary, has none.
To that which accompanied barium taken from the same ore they called Radium and to the substance which was found among the rare earths of the pitchblende Debierne gave the name Actinium. None of these elements have been isolated, that is to say, separated in a pure state from the accompanying ore.
The genuine diamond phosphoresces strongly when brought into juxtaposition, but the paste or imitation one glows not at all. It is seen that the study of the properties of radium is of great interest. This is true also of the two other elements found in the ores of uranium and thorium, viz., polonium and actinium. Polonium, so-called, in honor of the native land of Mme.
Curie, is just as active as radium when first extracted from the pitchblende but its energy soon lessens and finally it becomes inert, hence there has been little experimenting or investigation. The same may be said of actinium. The process of obtaining radium from pitchblende is most tedious and laborious and requires much patience.
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