Becker — Apparatus for Observing Reaction between Gases, etc. 335 



is in contact with the gas in F^. When the tap is closed, any absorption of 

 gas by the liquid from V2 results in a decrease in pressure, which is indicated 

 on the manometer,and from the manometer reading the volume of gas absorbed 

 can be calculated. With such an arrangement it is possible to vary the sensi- 

 tivity of the manometer considerably. The smaller the volume Vi becomes in 

 comparison with Fi, the greater the movement of the manometer (within 

 limits) for a given absorption of gas by the liquid. Further, when the tap 

 connecting Vz and Fi is opened, the manometer returns to zero, and the 

 difference in pressure previously existing in F2 is distributed between the 

 combined volume, thus making it a much smaller fi-action of the whole. 

 With such an arrangement it becomes possible to reset the manometer to 

 zero several times during the course of an experiment, without allowing the 

 pressure in Fj to fall to such a value as would seriously affect the solubility 

 of the gas. The tap also affords an easy method of replenishing the supply 

 of one of the constituent gases of a mixture contained in F,. Thus, if Fa 

 contains atmospheric air in contact with a liquid absorbing oxygen, and F, 

 contains pure oxygen, then, after a given absorption, the opening of tap 

 resets the manometer, and also replaces the oxygen absorbed to an extent 



which will depend on the ratio -^. 



The conditions at the start of an experiment are such that the pressures 

 in Fi and V^ are equal to each other and to the atmospheric pressure P mm. 



Now, suppose an absorption of Q c.c. takes place in Fs, and that the 

 resulting manometer reading is p mm., then (Fa - Q) c.c. at P are 

 occupying ( F2 - ■y,) at P^., where v^ = the volume of liquid which has risen 

 above the zero point in the manometer, and Fi c.c. at P are occupying 

 ( Vi + Vi) c.c. at Py. 



Now, since Py = P^ + p, 



PV, P{V,-Q) 



F + V, Fa 



+ p, 



which gives Q = v^ ,-/,, - ^ ^{V^i- v,). 



If the two vessels are now connected by opening the tap, Py becomes 

 equal to P^-, and p = 0. 



There is then Fi + ( Fa - §) c.c. at P occupying a volume F, + Fa at Pz. 



Hence P. - ^^ W ^) 



F, + Fa 



P(l- ^ 



F, + V,) 



SCIENT. PBGC. B.D.S., VOL. XVI, HO. XXVII. 2 S 



