Mass-Spectra of Chemical Elements. 633 



appeared on a chlorine plate 4 , and also on one taken with BF 3 . 

 This is naturally put down to doubly-charged 13. If the 

 source of the mass 13 is put down to OH, it is very surprising 

 that the line should not appear more frequently, also that it 

 should not be accompanied when it did appear by a line at 

 7-50 due to CH 3 . 



The third line of doubtful origin is a very faint one at 

 13*50 which appeared when chlorine compounds were 

 present. The most likely explanation of this seems to be 

 doubly- charged aluminium derived from small quantities of 

 aluminium chloride formed by the action of the gas on the 

 electrodes. 



General Remarks. 



All the seven elements whose analyses form the subject of 

 this paper obey the " whole number " rule within the accuracy 

 of experiment. They may be said to conclude the list of 

 those which can be easily introduced into the apparatus in 

 the form of gases or gaseous compounds. The following- 

 table gives a complete list of all the elements so far analysed. 

 Some very clear results recently obtained with the mercury 

 group of lines, e. g. Spectrum VIII., show that its isotopes 

 202 and 204 need no longer be regarded as doubtful. 



Table of Elements and Isotopes. 



,, . ., . Minimum -».- c T , 



,„, Atomic Atomic u ,. Masses or Isotopes in 



Element. « . Aur • 1 * number or , „ . , r ., 



IN umber. Weight. Isotopes order ot intensity. 



H 1 1008 1 1-008 



He 2 3-99 1 4 



B 5 109 2 11, 10 



C 6 1200 1 12 



X 7 1401 1 14 



O 8 1600 1 16 



F 9 1900 1 19 



Ne 10 2020 2 20, 22, (21) 



Si 14 28-3 2 28, 29, (30) 



P 15 ' 3104 1 31 



S 16 32-06 1 32 



CI 17 35-46 2 35, 37, (39) 



A 18 39-88 (2) 40, (36) 



As 3:! 74-96 1 75 



Br 35 79-92 2 79, 81 



Kr 36 82-92 6 84,86,82,83,80.78 



X 54 1302 5 (128, 131, 130. 133, 135) 



Hg 80 200-6 (6) (197-200), 202, 204 



In conclusion, the author wishes to express his indebtedness 

 to the Government Grant Committee of the Hoyal Society 

 for defraying the cost of some of the apparatus employed. 



Phil. Mag. S. 6. Vol. 40. No. 239. Nov. 1920. 2 T 



