124 METHODS FOR THE ANALYSIS OF BLOOD 



Simultaneous Determination of Oxygen and CC>2 



There appears no reason (except that just mentioned) why 

 both gases should not be determined on a single sample of blood 

 by first liberating the oxygen and then the CO2. This can in fact 

 be done (using half quantities of blood and reagents or in diffusion 

 tubes of 20 c.c. capacity) if a small glass rod or some lead shot is 

 put into the tube to assist in breaking up the heavy masses of the 

 precipitate formed by the addition of the acid after the ferricyanide. 

 Practically, however, unless the quantity of blood available is 

 extremely limited it is easier and more accurate to make the two 

 determinations separately. Duplicate determinations for both 

 gases independently can be made by this method in half an hour. 



OXYGEN-BINDING CAPACITY OF BLOOD 



Method of Van Slyke 1 



Principle. Blood is laked and oxygen combined with hemo- 

 globin is set free. The oxygen is then collected and measured. 

 From this volume of gas the oxygen bound by the hemoglobin is 

 calculated. 



Procedure. Five to 10 c.c. of blood is introduced into a sepa- 

 ratory funnel or bottle and distributed in a thin layer about the 

 inner wall, so that maximum contact with the air is assured. 

 The vessel is rotated for three or four minutes so that the blood 

 is kept in a thin layer, or it may be shaken fifteen or more minutes 

 on a mechanical shaker. The blood is then transferred to a cylinder 

 or heavy-walled tube. The blood gas apparatus is now prepared 

 by introducing into it 5 drops of redistilled caprylic alcohol and 

 6 c.c. of ammonia solution made by diluting 4 c.c. of concentrated 

 ammonia to a liter. If saponin is available the diluted ammonia 

 should be made to contain about 1 mg. per cubic centimeter. 

 The apparatus is evacuated and the air extracted from the ammonia 

 by shaking for about fifteen seconds. The extracted air is expelled 

 and the process repeated to make sure that no air is left in the 

 solution. Just before the blood is introduced about 2 c.c. of the 

 air-free ammonia is forced up into the cup of the apparatus. The 

 aerated blood is now thoroughly stirred with a rod to assure even 

 distribution of the corpuscles, and 2 c.c. is drawn into a pipette 

 1 Medical War Manual; No. 6, 1918, p. 129. 



