ALKALI RESERVE 127 



It is advisable after one 2 c.c. portion of a blood sample has 

 been analyzed to aerate the remainder of the sample a second 

 time and repeat the determination in order to make certain that 

 the first sample was completely saturated with oxygen. 



Example 



Observed gas volume = 0.45 c.c. at 20, 760 mm. 

 Correction for dissolved air = 0.034. 

 Corrected gas volume = 0.416 c.c. 

 Hemoglobin = 0.416 X 245 = 102 per cent. 



ALKALI RESERVE 



Direct Method. Carbon Dioxide Capacity of the Plasma 

 (Van Slyke and Culleri) l 



Principle. The plasma from oxalated blood is shaken in a 

 separatory funnel filled with an air mixture whose carbon dioxide 

 tension approximates that of normal arterial blood, by which 

 treatment it combines with as much carbon dioxide as it is able 

 to hold under normal tension. A known quantity of the saturated 

 plasma is then acidified within a suitable pipette, and its carbon 

 dioxide is liberated by the production of a partial vacuum. The 

 liberated carbon dioxide is then placed under atmospheric pressure, 

 its volume carefully measured, and the volume corresponding to 

 100 c.c. of plasma calculated. 



Apparatus. The apparatus used in the estimation of the car- 

 bon dioxide content of the plasma is illustrated in Fig. 9. It is 

 made of strong glass in order to stand the weight of mercury 

 without danger of breaking, and is held in a strong screw clamp 

 the jaws of which are lined with thick pads of rubber. In order 

 to prevent accidental slipping of the apparatus from the clamp, 

 an iron rod of 6 or 8 mm. diameter should be so arranged as to 

 project under cock / between c and d. 



Three hooks or rings at the levels 1, 2, and 3 serve to hold the 

 leveling bulb at different stages of the analysis. The bulb is 

 connected with the bottom of the apparatus by a heavy walled 

 rubber tube. 



*Van Slyke and Cullen: Jour. Biol. Chem., 1917, 30, 289. Van Slyke: 

 Jour. Biol. Chem., 1917, 30, 347. 



