PRACTICAL PHYSIOLOGY. 



[LXVI. 



Suppose the gas to be collected in A ; measure its amount when B is so 

 placed that the level of the acidulated water is equal in both. 



Remove the Mohr's clip from a, raise B, and force all the air into p. Then 

 lower B, and withdraw unabsorbed air from p. Measure the volume of air. 



Connect A now with the phosphorus pipette and force the air into it by 

 again raising B. Lower B, and estimate the remaining volume of air. In 

 each case the difference of the volume of air corresponds to the quantity of 

 gas absorbed. 



FIG. 



238. Hempel's Burette connected with 

 i Potash Pipette to absorb the C0 2 . 



Fio. 239. Pipette with Phosphorus 

 to absorb the Oxygen. 



The temperature of A can be kept constant by placing it in a wide tube 

 through which water is kept circulating as in a Liebig's condenser. 



7. Waller's modification of Znntz's apparatus is very convenient (Waller's 

 Human Physiology, 2nd Ed., p. 126). In this apparatus, the measuring tube 

 is filled by means of a bulb, and not a long tube, and the measuring tube has 

 on it above a bulb whicli communicates by means of three tubes guarded by 

 simple taps ; two of these horizontal go to the two absorption (0 and C0 2 ) 

 pipettes, while the vertical one is an outlet tube. (The apparatus is made by 

 Baird & Tatlock.) 



