IONS PRODUCED BY RONTGEN RAYS IN GASES AND VAPOURS. 



259 



The actual potentials of B and B' during the experiment will, of course, depend, as 

 above explained (section 2), on the particular nick in the curve whose position is sought ; 

 these potentials are controlled by means of the key k, and also by adjustable connections 

 (s and s') at the battery. 



+15 







!-= 

 I 



s 



5-10 



I 



15 



10 



S! 



-5 



006 -012 -018 



TIME w SECONDS 



-024 



050 



3 O O 



006 -0^ -018 -04 



TIME. IN SECONDS. 



030 



Fig. 6. Fig. 7. 



In fig. 6 and fig. 7 are given typical curves which were obtained by the null method 

 from observations made to determine the position of the nicks corresponding to the 

 negative and positive velocities respectively in sulphur dioxide at a pressure of 

 269 mm. of mercury, the electric field being 387 volts per centimetre. 



6. Manipulation of Gases and Vapours. 



The atmospheric air employed was dried by passing through phosphorus pentoxide. 



The nitrous oxide and carbon dioxide were obtained from cylinders of compressed 

 gas and were dried by passing through phosphorus pentoxide. 



The ammonia was obtained from a cylinder of the compressed gas and was dried by 

 passing through solid potassium hydroxide. 



The carbon monoxide was liberated by the action of sulphuric acid on sodium 

 formate and was dried by passing through phosphorus pentoxide. 



The sulphur dioxide was liberated by the action of dilute sulphuric acid on sodium 

 sulphite and was dried by passing through calcium chloride. 



The vapours employed were, in most cases, dried according to the method followed 

 by W. H. PERKIN* in his investigation of the " Magnetic Rotary Polarisation 01 

 Compounds in relation to their Chemical Constitution." In all cases Kahlbaum's 

 preparations were used. 



The ethyl alcohol, methyl acetate, ethyl formate, and ethyl acetate were from samples 

 kindly lent me by Mr. T. H. LABY, who had previously obtained them by fractionating 

 and drying Kahlbaum's preparations till each sample had a constant boiling-point. 



* ' Journ. Chem. Soc. Trans.,' vol. 45, p. 421, 1884. 

 2 L 2 



