OF VITAL PHENOMENA 



43 



a 



Fig. 14. Hydrogen electrode for fluids containing C0 2 . Hydrogen is 

 shaken with one portion of the fluid in the large compartment and passed 

 into another portion of the fluid in the small compartment without ex- 

 posure to air (from JBC). 



ing the mercury funnel causes the serum to rise in the cock and 

 wash out the air, and when this is done the cock is turned (the 

 two others likewise) so that the serum enters the electrode, the 

 hydrogen bubbling out through the water in the trap, t. The 

 2 cc chamber is completely filled with serum, the 4.5 cc chamber 

 filled until it contains only 1.5 cc of hydrogen and all of the 

 cocks closed. The electrode is shaken or. inverted 200 times, to 

 bring the hydrogen to equilibrium as regards C0 2 . The middle 

 cock is now opened and the electrode held vertically or shaken 

 so that the hydrogen displaces 1.5 cc serum from the smaller 

 chamber. In passing from the large to the small chamber, the 

 hydrogen is in contact with the returning serum spread in a thin 

 film, and so completes C0 2 equilibrium. The middle cock is 

 closed and the electrode shaken or inverted 200 times, connected 

 to the potentiometer by means of a wire hooked into the platinum 

 loop, and to the calomel electrode by dipping the Fresenius cock 

 into the vial filled with a saturated solution of KC1. Clark and 

 Lubs (1916) state that it is better to have the KC1 meet the 

 serum in a wide tube and make this contact immediately before 

 taking the reading. I have not found this precaution necessary 

 for an accuracy of 1 millivolt. If desired, the precaution may 

 be taken by having the opening, a, Fig. 14, wide, lubricating this 

 stopcock with serum before filling the electrode and leaving the 

 outlet filled with serum after filling the electrode. The tempera- 

 ture of the room is controlled or at least noted. A convenient 

 thermoregulator for the room is shown in Fig. 15. The first 



