NOTES 637 



was dissolved in water. They showed by the spectroscope that helium 

 was present in the first and not in the second. Four days later, however, 

 the second showed also the spectrum of helium. These experiments proved 

 that not only was helium present in old preparations of radium, but that 

 helium was produced directly by the transformation of radium and its pro- 

 ducts. This discovery was of great importance, because it was the first 

 definite evidence of the production of a known element from another. 



After settling in Glasgow in 1904 as Lecturer in Physical Chemistry at 

 the University, Mr. Soddy commenced a long and difficult research on the 

 parent body of radium. Radium was thought to be connected in some 

 way with the radio-element uranium, but the relationship was obscure. It 

 was possible that between the two there stood one or more elements of 

 relatively long life-periods. Mr. Soddy carefully purified several large quan- 

 tities of uranium, and measured from time to time, over a period of years, 

 the rate at which radium was being formed in them. The rate was ex- 

 ceedingly slow, and the mesaurements difficult to make, but by working 

 out a very delicate way of measuring radium in excessively minute amount, 

 and exercising the most scrupulous care, Mr. Soddy was able to solve his 

 problem successfully. He found eventually that between uranium and 

 radium there lay one element with a life-period of about a hundred thousand 

 years. Years later, when knowledge of radio-activity was very much 

 greater, it was found from other evidence that only one body did lie between, 

 and that its period actually was about a hundred thousand years ! 



One of the most illuminating subjects on the border-line of physics and 

 chemistry at the present day is that of " isotopes." In 1910 knowledge 

 concerning the chemical properties of most radio-elements and their rela- 

 tionship to the common elements was in a state of chaos. By 19 13 every- 

 thing was straightened out and the major difficulties solved. Much of the 

 credit for this important simplification goes to IVIr. Soddy. He found that 

 it was possible for two distinct chemical elements (" isotopes ") to be so 

 similar in all their chemical properties that, although recognisable as indi- 

 viduals when separated, they were indistinguishable and inseparable when 

 mixed. This fact has led to some very important developments in our 

 knowledge of the structure of an atom. And it has had this practical use, 

 that the properties of several elements have been predicted with certainty 

 from knowledge of but one particular property of them. More particularly 

 it has led to the discovery of a few radio-elements. And the most important 

 of these, the parent of actinium, was discovered in 191 7 by Prof. Hahn and 

 independently by Mr. Soddy himself, a practical piece of work directly 

 suggested by his own theory. 



Mr. Soddy has done important work on several subjects besides those 

 mentioned in this brief survey, notably that on high vacua with his calcium 

 furnace, on the separation of radium and mesothorium, on the " end-pro- 

 ducts " found in radio-active minerals, and on the gamma-rays — the exceed- 

 ingly penetrating X-rays — spontaneously emitted by certain radio-elements. 

 Much of this is pioneer work and of great importance. 



Les Prix Nobel. 



The annual publications of the Nobel Committee called Les Prix Nobel 

 and issued by P. A. Norstedt & Soner, Stockholm, are always extremely 

 interesting reading because they give in detail the work of the Nobel prize- 

 men of the year, described by themselves, together with an account of the 

 ceremony of distribution in the year concerned, written in French. The 

 publication is beautifully printed, and illustrated with admirable portraits of 

 the laureates, and the whole series, which is probably possessed by few, 

 contains an almost unique history of science since 1901, and in fact from 

 before that date. Most of the contributions are in English, French, and 



