METHOD TOR DETERMINING RESPIRATORY EXCHANGE I N MAN 



equal weight of water. The mark /■ on the Btem of the bulb indi- 

 cates the level a1 which the solutions should Btand. Enough pyrogallate 

 Bolution is introduced through tube 15 to fill bulbs 12 and U two-thirds 

 full. Then pyrogallate solution is poured into tube 16 until the differ- 

 ence in level of the llui<ls is sufficient to produt aough pi •• to 



raise the level of the pyrogallate solution in 12 to the level IS on the 



stem. Stopcock 6 must I pen during this procedure. It may be ne 



Bary to add or take awaj a little pyrogallate solution through t5 to 

 tain the above level. 



Care must be taken to allow for complete absorption of oxygen \v<<m 

 the air thai is entrapped between 14 and 16 before an analysis is made; 

 otherwise changes will be produced in the level of the pyrogallate solu- 

 tion. The air in the capillary tubing connecting the burettes with 



absorption bulbs must also be freed of CO a and 2 . This can be a m- 



plished by making a ilniiiiny analysis of atmospheric air before the real 

 analysis. Great care must be taken to have atmospheric pressure in all 

 the tubes at the start of the analysis. This is accomplished by opening 

 the stopcock in the burette first to atmospheric air and then to the ab- 

 sorption bulbs, until no further change in the level of the fluids in 

 stems of the absorption bulbs occurs. This level is then marked and 

 used as the standard. A small amount of water in the burette over tlm 

 mercury assures saturation of the air with water vapor. Time for drain- 

 age must be allowed before making readings. 



A very serviceable sampling tubi for the transfer of air can be made 

 from a 30 c.c. ground-glass syringe, to which is attached a two-way 

 stopcock. A cut of this is shown in Fig. L81. The dead Bpace in tl 

 syringes is washed out by working the piston back and forth several 

 times, a thin coating of vaseline prevents leakage of the gas. We have 

 found that these sampling tidies will retain a sample of expire. 1 air with- 

 out change up to eighl hours. 



Manipulation of Apparatus. The sampling syringe [20 is attached 

 to opening 2 of the burette, and its stopcock opened to spheric air. 



The level of the mercury is raised to the level of the stopcock of the syr 

 and is then turned so that syringe and burette are in communication. 

 hulb of mercury is lowered so thai the mercury falls in the burette. This 

 draws the piston of the syringe with it. and tills the burette with air 

 from the Byringe. It is advisable to put a little positive pressure on the 

 piston of the Byringe in the maneuver to prevenl possible leakage. When 

 all of the air is in the burette a slight positive pressure is produced in 

 the burette by gently pressing on the piston, and immediately there- 

 after the stopcock on the syrii gain tun riginal 

 position. This allows the pr< of aii- in the b 'hat 



