330 



GASOMETRIC-VOLUMETRIC METHODS 



blood gases, oxygen and carbon monoxide can be determined in 40 

 fx\. blood samples with an accuracy of 0.15 to 0.20 volume per cent, 

 nitrogen in 120 fA. samples to 0.05 volume per cent, and carbon 

 dioxide in 13 [A. samples to about 1 volume per cent. The time 

 required for a determination is 6-10 min. In these methods the blood 

 is drawn into a capillary attached to a 1 ml. tuberculin syringe, the 

 gas is liberated by a suitable reagent, the gas volume is noted, 

 specific absorbents are used to remove the gases separately, and the 

 volume change produced by the removal of each component is 

 recorded. 



20 



30 



Fig. 104. Shaking of syringe 



and extraction of gas. 



From Roughton and Scholander (1943) 



Fig. 105. A and B, syringe showing the tech- 

 nique for absorption of the carbon dioxide used 

 for extraction. C, temperature equihbration of 

 gas bubble in capillary before the reading is 

 made. From Roughton and Scholander (1943) 



The apparatus, which was slightly modified by Roughton and 

 Scholander (1943), consists of a 1 ml. Pyrex tuberculin syringe with 

 an arresting clip on the plunger to prevent its slipping, and with a 

 standard bore precision 0.5 mm. Pyrex capillary fused to its nozzle 

 (Fig. 105). The top of the capillary is expanded to a cylindrical cup 

 of about 1.5 cm. length and 2.5 mm. bore. The capillary, which is 



