Various Gases In/ the a. Particles of Radium, 343 



time when R is measured ; and these data are easily obtained. 

 In the latter, any moderate voltage will do, since the range 

 does not depend on potential ; but it is desirable to have as 

 much gas as possible, and no leakage of air during the expe- 

 riment, so that when the bulb containing a sample of the 

 gas is taken away and weighed in order to find the pro- 

 portion of the mixture, it may truly represent the condition 

 of things during the earlier part of the experiment. It is 

 best to work at a high temperature, if such is required to 

 fill the chamber with gas which is nearly at atmospheric 

 pressure. 



Carbon bisulphide vapour is well superheated at a tem- 

 perature of 30° and a pressure of 25 cm. The apparatus is, 

 therefore, heated to that temperature ; and RI for air is first 

 measured i 



Fig. 4 shows the readings obtained, and the curve which 

 is drawn to find R and I. These are determined to be 4*95 



Fig. 4. 



6 cm / 











#/ 

 ScrnJ 





OLir 



75/ iw TO 

 30°C 



R = 495- 

 1 = 42*8 

 Rl = 212 





^ 



S 



6 



7 "~~~~~ 



8 



and 42*8 respectively, so that RT = 212, the temperature 

 being 30° C, and the pressure being 75*1 cm. The apparatus 

 is then exhausted and filled with CS 2 vapour to a pressure 

 of about 24 cms. It is known from a separate experiment 

 that 1000 volts per cm. is a saturating potential gradient, 

 and a battery of 300 volts is therefore put on to the 3 mm. 

 chamber. 



The readings then taken, and the curve drawn are shown 

 in fig. 5. It appears from these that R = 7*74, 1 = 37*3, so- 



