Anode Rays to the Investigation of Isotopes. 867 



serious difficulties in the separation of elements of atomic 

 weights of 100 or more. 



An attempt was made to work the anode rays at pressures 

 as low as those used for ordinary positive rays. A large 

 bulb was used and a powerful coil, and the pressure was 

 kept down by charcoal and liquid air. Under these con- 

 ditions, however, no beam of rays could be obtained. The 

 photographs taken showed the usual lines (non-metallic) 

 due to the ordinary positive rays, and in addition a line due 

 to sodium. The anode consisted of admixture of sodium and 

 beryllium, and no trace could be seen of the latter, while 

 the sodium was only of moderate strength. The lines, 

 however, were very fine. The alkali metals apparently can 

 be obtained easily by all these methods, so that unless it 

 can be made to work for other motals, this particular 

 modification is not of much value. 



Summary. 



(1) Photographs have been obtained for anode rays 

 showing parabolas corresponding to singly charged atoms 

 of the following metals : — Lithium, beryllium, sodium, potas- 

 sium, calcium, strontium. 



(2) Lithium is a mixture of isotopes of atomic weights 

 6 and 7. The proportions in which these appear in the rays 

 are not constant, there being a tendency for the line at 6 to 

 be sometimes considerably stronger than would be expected 

 from the atomic weight. 



(3) Beryllium is apparently single, atomic weight 9. 

 If there is an isotope at 10 or 11, it is present in extremely 

 small proportion. 



(4) The remaining elements could not be resolved with 

 the apparatus used, but calcium must consist of atoms of 

 weight equal to those of either potassium or argon : i. e., a 

 so-called " isobar." 



(5) No trace was found of doubly charged metallic atoms, 

 or of atoms with a negative charge. 



(6) It seems probable that the mechanism of the anode 

 rays is more analogous to spluttering than to electrolysis. 



In conclusion I wish to express my very sincere thanks 

 to my father, Sir J. J. Thomson, for his advice on many 

 occasions during the progress of these researches. 



August 1921. 



