604 Dfs. Geiger and Kovarik on Relative Number oj Ions 



per year, calculated by Rutherford and Geiger from the 

 results of their experiments on the number of a particles 

 emitted by radium is in excellent agreement with the rate of 

 production which has been found. 



The amount of helium by the disintegration of a known 

 quantity of radium emanation has also been measured and 

 has been found to correspond with the amount to be expected 

 from theory. 



The production of helium by polonium and from a prepa- 

 ration containing radio-lead has also been observed. 



Physical Laboratory, 

 Manchester University. 



LVI. On the Relative Number of Ions produced by the /? 

 Particles from the Various Radioactive Substances. By 

 H. Geiger, Ph.D., and Alois F. Kovarik, Ph.D., John 

 Harling Fellow of the Victoria University of Manchester * . 



Introduction. 



IN recent years many investigations have been carried out 

 in order to settle definitely the number of a-ray products 

 present in the different radioactive series, and to determine 

 the number of a particles emitted in each transformation. 

 The results indicate that probably in all transformations con- 

 nected with the emission of a rays, an u particle of charac- 

 teristic velocity is expelled from the disintegrating atom. In 

 addition a comparison of the a-ray activities of successive 

 products has led to a definite knowledge of the number of 

 these products. There is little chance that a direct a-ray 

 product has remained undiscovered in the radioactive series 

 known at the present time. 



Our knowledge of those transformations which take place 

 with the emission of /3 rnys is by far less definite. It has been 

 suggested that in such transformations ft particles of charac- 

 teristic velocity are emitted, but recent experiments have 

 made this conclusion very doubtful. It appears more probable 

 at present that the (3 particles emitted from the same substance 

 — in some cases at least — vary appreciably in speed. 



At present seven transformations are known which take 

 place with the emission of (B particles of high penetrating 

 power. In about as many cases the disintegration appears 

 to be connected with the emission of soft f3 rays whose 



* Communicated by Prof. E. Rutherford 



