THE TRANSFORMATION OF ELEMENTS 87 



the surface remained constant throughout the experiment, it 

 did not affect the time of half change, but it prevents the 

 determination of the actual volume of gas decomposed in the 

 water phase in the first two experiments. In both, the water 

 phase was much less in volume than the gas phase, the action 

 on water appears to be much greater, volume for volume, than 

 on the mixture of gases. 



The two final experiments show considerable differences 

 from the theoretical values. In the case of ammonia these were 

 due to traces of air, admixed with ammonia, with resulting 

 production of water, which immediately saturated itself with 

 the gas. In the final experiment both volume and pressure 

 were read, and the volume was not kept constant ; the error 

 in reading was therefore much greater than usual. 



The mechanism of the reactions is probably the same that 

 produces the ions which discharge an electroscope (Part I.). 

 Collision between the a particles shot off from the emanation 

 and the gas-molecules produces charged ions of the gases, and 

 these combine. With hydrogen and oxygen, for instance, water 

 is formed, and the resulting diminution in volume, and conse- 

 quently in pressure, is measurable. With water the actual 

 collisions produce atoms of hydrogen and oxygen, some of 

 which give molecules — as in ordinary electrolysis. 



The final part of this paper will contain accounts of the 

 chemical and spectroscopic evidence of the transformation of 

 elements, together with the recent attempts which have been 

 made to cause transmutation. 



The chief authorities which have been consulted in preparing 

 Parts I. and II. of this paper are : 



Rutherford, Radioactivity, 2nd Edition. 



Chemical Society's Annual Reports : Radioactivity (Soddy). 



and the following original papers : 



Boltwood, A New Radioactive Element, Amer. J. Science, 1907, iv. 24, 370-2. 

 Hahn, Parent Substance of Radium, Berichte, 1907, 40, 4415. 



Rays from Thorium Products, ibid. 3304. 



Rutherford, Velocity and Energy of the a Particles from Radioactive Substances, 

 Phil. Mag. 1907, vi. 13, no. 



Production and Origin of Radium, ibid. 14, 7ZZ- 



Marckwald and Keetman, Ionium, Berichte, 1908, 41, 49. 



