.De war's Method of producing High Vacua. 501 



Then we have a volume V at pressure p' and temperature T, 

 and a volume v at pressure p' and temperature t. 



So that 



or 



^i+4h Y+v '> 



( v+ v)f =y+v - 



0-) 



"When the bulb contains charcoal the final pressure reached 

 will be less than when it contains air, in consequence of the 

 absorption of air by charcoal. Denote this pressure by p. 

 Then the volume of air not absorbed by the charcoal (measured 

 at pressure P and temperature T) is 



P +V Ft 

 = (V + !>)£, from (i.) 



Therefore the volume of air absorbed by the charcoal 



=(v+.)(i-| 7 ) (ii.) 



§ 9. The following table gives the results of experiments 

 carried out in this way : — ■ 



Table T. 





Total Volume. 







Volume of Air 





Y + v. 



P'- 



X>- 



absorbed by Charcoal. 



1.... 



335 c.c. 



393 mm. 



180 mm. 



181 c.c. 



II. ... 



70-8 c.c. 



520 mm. 



386 mm. 



18-2 c.c. 



III. ... 



934 c.c. 



558 mm. 



42S mm. 



217 c.c. 



IV... 



1250 c.c. 



598 mm. 



495 mm. 



21-5 c.c. 



v.... 



6740 c.c. 



726 mm. 



702 mm. 



22-3 c.c. 



The figures in the last column show that the volume of air 

 absorbed by the charcoal is, to a first approximation, independ- 

 ent of the quantity of air present in the apparatus at the 

 commencement of the experiment. 



The small differences observed in the figures giving the 



amount of air absorbed may be attributed to the influence of 



pressure *. In accordance with the principle of Least Action 



the effect of raising the pressure is to make the reaction take 



* Mellor, ' Chemical Statics and Dynamics,' p. 435. 



