Cathode Rays and certain Chemical Effects. 221 



served as a volumenometer, and by its means V 1? V 2 , and V 3 

 were determined. With the apparatus used Y 2 was 90*12 c.c. 

 and V 8 , 343-78 c.c. 



At the beginning of any one experiment, nitrogen, under 

 any required pressure;?, occupied Vi-\-Y 2 + V 3} the orifice 

 and the tap T x being open. 



T x was then closed and V 3 very thoroughly exhausted by 

 means of the charcoal tube C 2 to a small residual pressure p'. 

 (In all the experiments this was of the order of '0001 mm. 

 of mercury.) 



Cathode rays, of known velocity v 9 were then passed 

 through I and the galvanometer deflexion 6 noted ; this 

 deflexion being proportional to the number of corpuscles 

 passing through the chamber per second. (By suitably 

 regulating the current through B it was found possible to 

 ensure very constant and steady galvanometer deflexions, 

 even when working with rays of a velocity approaching 

 10 10 cm. per sec.) 



After 90 seconds S was dropped, closed and the rays 

 cut off. Tj was immediately opened and the nitrogen in I 

 allowed to distribute itself between the volumes V 2 and V 3 , 

 a certain proportion " reacting " with the phosphorus in P 

 — which was of course always present in excess. This 

 "action" was rapid. The resultant pressure in V 2 + V 3 was 

 observed after an interval of one minute; this pressure II 

 being the pressure under which that proportion of the 

 nitrogen from V which was "inactive " occupied the volume 



v 2 +v 3; 



If (j> is the pressure under which the " active " proportion 

 of nitrogen would have occupied the volume V 2 + Y 3 , 



we have pV 2 + p'Y, = (II + <£) (V 2 + V 3 ), 



and can deduce <j> = ±-^ — *L 3 — II from the experiment; 



and hence, if necessary, the actual mass of nitrogen rendered 

 "active." 



For all purposes of discussion, we need only concern 

 ourselves with the quantity </>. <f> is the pressure under 

 which a mass m of " active " gas occupies the volume 

 ^2 + ^3- The volume V 2 + Y 3 is a constant quantity ; and 

 provided the gas undergoes no important changes of tempe- 

 rature in the course of the experiments, </> is proportional 

 to m. 



