Radioactivity Science Circa 1914

Today’s installment concludes Early Science of Radioactivity,
the name of our combined selection from Mme. Marie Curie, Sir William Ramsay, and Sir Oliver Lodge. The concluding installment, by Sir Oliver Lodge from a special aticle to The Great Event Evemts by Famous Historians, Volume 20, was published in 1914.

If you have journeyed through all of the installments of this series, just one more to go and you will have completed selections from the great works of seven thousand words. Congratulations! For works benefiting from the latest research see the “More information” section at the bottom of these pages.

Previously in Early Science of Radioactivity.

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Time: 1903
Place: Paris

But it is a very curious one. For it is unstable. Now, stability was believed to be the essential characteristic of an element. Radium, however, disintegrates — that is, changes into other bodies, and at a constant rate. If one gram of radium is kept for 1,760 years, only half a gram will be left at the end of that time; half of it will have given other products. What are they? We can answer that question. Rutherford and Soddy found that it gives a condensable gas, which they named “radium emanation”; and Soddy and I, in 1903, discovered that, in addition, it evolves helium, one of the inactive series of gases, like argon. Helium is an undoubted element, with a well- defined spectrum; it belongs to a well-defined series. And radium emanation, which was shown by Rutherford and Soddy to be incapable of chemical union, has been liquefied and solidified in the laboratory of University College, London; its spectrum has been measured, and its density determined. From the density the atomic weight can be calculated, and it corresponds with that of a congener of argon, the whole series being: helium, 4; neon, 20; argon, 40; krypton, 83; xenon, 130; unknown, about .178; and niton (the name proposed for the emanation to recall its connection with its congeners and its phosphorescent properties) , about 222.4. The formation of niton from radium would therefore be represented by the equation: radium (226.4) = helium (4) + niton (222.4).

Niton, in its turn, disintegrates, or decomposes, and at a rate much more rapid than the rate of radium; half of it has changed in about four days. Its investigation, therefore, had to be carried out very rapidly, in order that its decomposition might not be appreciable while its properties were being determined. Its product of change was named by Rutherford “radium A,” and it is undoubtedly deposited from niton as a metal, with simultaneous evolution of helium: the equation would therefore be :

niton (222.4) = helium (4) + radium A (218.4).But it is impossible to investigate radium A chemically, for in three minutes it has half changed into another solid substance, radium B, again giving off helium. This change would be represented by the equation:

radium A (218.4) = helium (4) + radium B (214.4).Radium B, again, can hardly be examined chemically, for in twenty-seven minutes it has half changed into radium C¹. In this case, however, no helium is evolved; only atoms of negative electricity, to which the name “electrons” has been given by Dr. Stoney, and these have minute weight which, although approximately ascertainable, at present has defied direct measurement. Radium C¹ has a half-life of 19.5 minutes, too short, again, for chemical investigation; but it changes into radium C², and in doing so each atom parts with a helium atom, hence the equation:

radium C¹ (214.4) = helium (4) + radium ² (210.4).In 2.5 minutes radium C² is half gone, parting with electrons, forming radium D. Radium D gives the chemist a chance, for its half-life is no less than sixteen and a half years. Without parting with anything detectable, radium D passes into radium E, of which the half-life period is five days; and, lastly, radium E changes spontaneously into radium F, the substance to which Madame Curie gave the name “polonium,” in allusion to her native country, Poland. Polonium, in its turn, is half changed in 140 days, with loss of an atom of helium, into an unknown metal, supposed to be possibly lead. If that be the case, the equation would run:

polonium (2104) = helium (4) + lead (206.4).But the atomic weight of lead is 207.1, and not 206.4; however, it is possible that the atomic weight of radium is 227.1, and not 226.4.

Attention has repeatedly been drawn to the enormous amount of energy stored up in radium and its descendants. That, in its emanation, niton is such that if what it parts with as heat during its disintegration were available, it would be equal to three and a half million times the energy available by the explosion of an equal volume of detonating gas — a mixture of one volume of oxygen with two volumes of hydrogen. The major part of this energy comes, apparently, from the expulsion of particles (that is, of atoms of helium) with enormous velocity. It is easy to convey an idea of this magnitude in a form more realizable by giving it a somewhat mechanical turn. Suppose that the energy in a ton of radium could be utilized in thirty years, instead of being evolved at its variable slow rate of 1,760 years for half-disintegration, it would suffice to propel a ship of 15,000 tons, with engines of 15,000 horse-power, at the rate of 15 knots an hour for thirty years — practically the lifetime of the ship. To do this actually requires a million and a half tons of coal.

It is easily seen that the virtue of the energy of the radium consists in the small weight in which it is contained; in other words, the radium-energy is in an enormously concentrated form. I have attempted to apply the energy contained in niton to various purposes; it decomposes water, ammonia, hydrogen, chloride, and carbon dioxide each into its constituents; further experiments on its action on salts of copper appeared to show that the metal copper was converted partially into lithium, a metal of the sodium column; and similar experiments of which there is not time to speak indicate that thorium, zirconium, titanium, and silicon are degraded into carbon; for solutions of compounds of these, mixed with niton, invariably generated carbon dioxide, while cerium, silver, mercury, and some other metals gave none. One can imagine the very atoms themselves, exposed to bombardment by enormously quickly moving helium atoms, failing to withstand the impacts. Indeed, the argument a priori is a strong one; if we know for certain that radium and its descendants decompose spontaneously, evolving energy, why should not other more stable elements decompose when subjected to enormous strains?

This leads to the speculation whether, if elements are capable of disintegration, the world may not have at its disposal a hitherto unsuspected source of energy. If radium were to evolve its stored-up energy at the same rate that gun-cotton does, we should have an undreamed-of explosive; could we control the rate we should have a useful and potent source of energy, provided always that a sufficient supply of radium were forthcoming. If, however, the elements which we have been used to consider as permanent are capable of changing with evolution of energy, if some form of catalyzer could be discovered which would usefully increase their almost inconceivably slow rate of change, then it is not too much to say that the whole future of our race would be altered.

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Master List

This ends our selections on Early Science of Radioactivity by three of the most important authorities on this topic:

• Lecture by Mme. Marie Curie published in NA.
• Presidential Address to the British Association for the Advancement of Science by Sir William Ramsay published in either 1911 or 1912.
• a special aticle to The Great Event Evemts by Famous Historians, Volume 20 by Sir Oliver Lodge published in 1914.

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