554 



ILL USTRA TI VE EXPERIMENTS 



plasma is then transferred to sampling tubes (Fig. 112), 3-4 c.c. of plasma to 

 each tube. These tubes (3UU c.c), or separating funnels of the same capacity, 

 are filled with alveolar air (of the subject, if possible). This may be done by 

 holding the tube horizontally, opening both taps and, without inspiring more 

 deeply than normal, expire as quickly and as completely as possible through 

 the tube, closing the further tap just before the -expiration is finished. A 

 bottle containing large glass beads must be interposed between mouth and 

 funnel in order to prevent dilution of the plasma by condensation of vapour 

 from the breath. With both taps closed, the funnel is rotated (not shaken) 

 so that the plasma forms a thin layer over the walls, and so readily comes into 



equilibrium as regards COg tension 

 with the alveolar air. 



(3) Procedure. The apparatus is 

 entirely filled with mercury, including 

 the two capillaries (a and stem of b) 

 at the top. The cup b is washed with 

 COo-free NH3. 1 c.c. of plasma is run 

 into the cup from an Ostwald-Folin 

 pipette, keeping the tip of the pipette 

 immersed in the fluid. Placing the 

 mercury reservoir in the second ring 

 (Fig. Ill) and with cock/ open to d, 

 open e and admit the plasma to the 

 pipette, leaving sufficient in b to fill the 

 capillary. Wash the cup twice into 

 the pipette, using about 0-5 c.c. of 

 water each time, adding a very small 

 quantity of caprylic acid to the second 

 wash water. Finally run in 0-5 c.c. 

 of 5 per cent. HoSOj and seal the 

 capillary with mercury. The fluid 

 must come to the 2-5 c.c. mark. Wash 

 out the cup with water and then with 

 carbonate-free ammonia till acid-free. 

 The mercury bulb is now taken to a 

 position (about 80 cm. below the 

 second ring) so that a Torricellian 

 vacuum is formed in the gas pipette. 

 Allow the mercury to run down almost 

 to (but not below) the 50 c.c. mark. 

 Close / and replace the bulb on the 

 upper ring. Slacken the milled head of the screw that controls the central 

 swivel. Holding the pipette at the bulb with the right hand and gathering 

 up the loose rubber tubing with the left, rotate the bulb through 

 180° some 15 times. Set vertically and tighten the milled head. Lower 

 reservoir and, with / open to d, rapidly empty the water solution into d 

 without however allowing any of the gas to follow it. Now open /to c and, 

 by raising the reservoir, fill the body of the pipette with clean mercury. 

 Hold the reservoir in such a position that pressure inside the reservoir is 

 atmospheric and rapidly take a reading. If thought desirable, re-extraction 

 may be carried out. 



Cleanivg. Lower the reservoir and run )i)ost of the mercury back through c. 

 Open/ to d and, by raising the reservoir, run the water back into the pipette. 



''10. 113. — Van Slyke mii-ro apparatus 



