130 METHODS FOR THE ANALYSIS OF BLOOD 



that, if sterile, it may be kept for over a week without alteration 

 of its carbon dioxide capacitjO are transferred to a 300 c.c. sepa- 

 ratoj-y funnel, arranged as in Fig. 11, and the air within the funnel 

 is displaced by either alveolar air from the lungs of the operator or 

 a 5.5. per cent carbon dioxide-air mixture from a tank. In either 

 case the gas mixture must be passed over moist glass beads before 

 it enters the funnel. 



When alveolar air is used the operator, without inspiring more 

 deeply than normal, expires as quickly and as completely as pos- 

 sible through the glass beads and separatory funnel. The stopper 

 of the funnel should be inserted just before the expiration is 

 finished, so that there is no opportunity for air to be drawn back 

 into the funnel. In order to saturate the plasma the separatory 

 funnel is turned end over end for two minutes, the plasma being 

 distributed in a thin layer as completely over the surface of the 

 funnel's interior as is possible. After saturation is completed the 

 funnel is placed upright and allowed to stand for a few minutes 

 until the fluid has drained from the walls and gathered in the 

 contracted space at the bottom of the funnel. 



Determination of Carbon Dioxide. A sample of 1 c.c. (or 0.5 

 c.c. in case the amount of plasma available is very small) accu- 

 rately pipetted, is allowed to run into the cup b in the apparatus 

 represented in Fig. 3, the tip of the pipette remaining below the 

 surface of the plasma as it is added. The cup should have been 

 previously washed out with carbonate-free ammonia, and together 

 with the entire apparatus should have been filled with mercury 

 to the top of the capillary tube by placing the leveling bulb of 

 mercury in position 1: 



With the mercury bulb at position 2 and the cock / in the posi- 

 tion shown in the figure the plasma is admitted from the cup into 

 the 50 c.c. chamber, leaving just enough above the cock e to fill 

 the capillary so that no air is introduced when the next solution 

 is added. The cup is washed with two portions of about 0.5 c.c. 

 of water, each portion being added to the pipette in turn. A small 

 drop of caprylic alcohol is then added to the cup and is permitted 

 to flow entirely into the capillary above e. Finally 0.5 c.c. of 5 

 per cent sulphuric acid is run UL (It is desirable to keep the amount 

 of caprylic alcohol small, as larger amounts may appreciably 

 increase results. With plasma 0.02 c.c. is sufficient to prevent 

 foaming and is measured most conveniently from a burette made 



