CAEBON MONOXIDE AND NITROGEN 335 



Other Reagents. The other reagents required are those listed for 

 the oxygen method (page 331) with the exception of the 10% 

 sodium hydroxide. The distilled water is aerated. 



PROCEDURE 



1-10. Same as for oxygen (pages 332-333). 



11. Substitute pyrogallol soln. for the 10% sodium hydroxide, 

 but otherwise same as for oxygen (page 333). 



12-14. Same as for oxygen (pp. 333-4). Read vol. of bubble (Fi). 



15. Flush the glass cup clean with water and leave filled. Quickly 

 pull about three fourths of the water in the cup down into the 

 syringe to form a layer over the blood mixture. Then immediately 

 run the bubble with the clean water below it up into the top of the 

 capillary. 



16. Empty the water from the glass cup and fill it with Winkler 

 soln. 



17. Incline the syringe so that the cup points downward at a 

 slight angle from the horizontal. Cautiously screw in the plunger to 

 drive the gas bubble out into the glass cup where it can rest near 

 the junction of the capillary and the cup. Suck in the Winkler soln. 

 behind the bubble to half fill the capillary, and rotate the instru- 

 ment gently for a few sec. to complete the absorption of the carbon 

 monoxide. Then turn the syringe to the vertical position with the cup 

 down and suck the gas bubble back into the capillary. Measure the 

 gas vol. (72) in the usual fashion, and calculate the carbon mon- 

 oxide content from the formula: 



Carbon monoxide = (Fj — Fg)/ 



where / is the correction factor (page 334), 



NITROGEN 



The adaptation of the syringe analyzer to the measurement of 

 nitrogen in fluids was made by Edwards, Scholander, and Roughton 

 (1943). Their method calls for a pipette with two marks, calibrated 

 to deliver not only the usual volume (page 331) but also three 

 times this. The principle of the method depends on extraction of 

 all the nitrogen and part of the oxygen from the sample with carbon 

 dioxide, absorption of the oxygen and carbon dioxide with alkaline 

 hydrosulfite, and measurement of the nitrogen which remains. 



