134 METHODS FOR THE ANALYSIS OF BLOOD 



perature at which saturation and analysis are performed, the 

 table gives the volume (reduced to 0, 760 mm.) of carbon dioxide 

 that 100 c.c. of plasma are capable of binding when saturated at 

 20 with carbon dioxide at approximately 41 mm. tension. If the 

 figures in the table are multiplied by 0.94 they give, within 1 or 

 2 per cent of the carbon dioxide bound at 37. 



TITRATION OF THE BICARBONATE CONTENT OF 

 BLOOD PLASMA 



Method of Van Slyke, Stillman and Cullen l 



Principle. The bicarbonate content of serum or oxalate 

 plasma is determined by adding an excess of standard acid, 

 removing the carbon dioxide by rotating the solution, and titrat- 

 ing back with standard alkali to the original hydrogen ion con- 

 centration of the blood with neutral red as indicator. 



Procedure. In drawing and centrifugating the blood the 

 precautions outlined by Van Slyke and Cullen for preventing loss 

 or accumulation of carbon dioxide and consequent change in the 

 distribution of bicarbonate between corpuscles and plasma, are 

 to be observed. Oxalate plasma is used. Up to the beginning 

 of the analysis, the blood and plasma are handled exactly as 

 described for the carbon dioxide method. 



For the analysis, 2 c.c. of plasma are pipetted into a round- 

 bottomed flask of 150 to 200 c.c. capacity, and 5 c.c. of 0.02 N 

 hydrochloric acid are added (this is about 2 c.c. of 0.02 N acid in 

 excess of the bicarbonate normally present). In order to remove 

 the carbon dioxide set free by the acid, the flask is shaken vigor- 

 ously with a rotary motion, so that the solution is whirled in a 

 thin layer about the inner wall. One minute of this treatment is 

 sufficient to remove carbonic acid so completely that not enough- 

 is left to affect the results measurably. The solution is now poured 

 as completely as possible into a 50 c.c. Erlenmeyer flask and the 

 walls of the larger flask are rinsed with 20 c.c. of water. The 

 water is measured within 1 c.c. in a cylinder, and approximately 

 a third is used for each of three washings. 



When the solution, measuring about 26 c.c., has been trans- 

 ferred to the 50 c.c. flask, 0.3 c.c. of a 0.1 per cent solution of 



1 Van Slyke, Stulman and Cullen: Jour. Biol. Chem., 1919, 38, 167. 



