Ionic Mobilities in Hydrogen. 347 



positive are composed of aggregates whose simplest elements 

 contain 1, 3, 6, and 9 molecules of hydrogen, respectively, 

 per electronic charge. These integers are marked out as a 

 scale in fig. 4. along the ordinate at one atmosphere, com- 

 paring theoretical values of u with actual. 



These experiments explain clearly the results recorded by 

 other workers on the subject, using methods which failed 

 to distinguish between the different kinds of negative ions. 

 Lattey and Tizard *, working at low pressures, remark on 

 the need to use freshly prepared gas to obtain the high 

 mobilities they record. They state that inconsistent results 

 were obtained from hydrogen after it had stood for some 

 time in the apparatus, which was, no doubt, due to the 

 variable proportions in which ions A and B appeared. Also 

 the large rise in mobilitv as the voltage increased was no 

 doubt due — at least in part — to the failure to distinguish 

 between ions of various mobilities. Chattock and Tyndall |, 

 working at atmospheric pressure, found an exceptionally high 

 mobility in pure hydrogen, and record quantitative measure- 

 ments of the effect of the addition of small proportions of 



Summary. 



Measurements are recorded of the mobilities of the 

 positive ion and three different negative ions in hydrogen 

 over a range of pressures between 8 cm. and 76 cm. 



The results for two of the negative ions are expressed 

 by the equations Pz/. = 604'7 and Pw = 1206 respectively. 

 The work for the third and lightest ion is not yet so 

 complete. 



Theoretical considerations indicate that the three negative 

 ions are built up from elements containing one, three, and 

 six molecules of hydrogen per electronic charge respectively, 

 and the element in the positive ion has nine molecules per 

 electronic charge. 



Imperial College of Science and Technology 



* Lattey and Tizard, Prcc. Ko>\ Soc. 1912, p. 349. 



t Chattock and Tyndall, Phil. Mag. 1910, sei\ t>, vol. xix. p. 449. 



