AMMONIA IN THE BLOOD 97 



TOTAL NITROGEN 



The total nitrogen of the blood may be readily determined by 

 the regular Kjeldahl method. One c.c. of the blood accurately 

 measured is used in this method. 



AMMONIA IN THE BLOOD 



Method of Folin and Denis l 



Principle. Same as for ammonia in urine. 



Procedure. 10. c.c. of systemic blood or 5 c.c. portal or 

 mesenteric blood are transferred to a suitable large test-tube. 

 To it are added 2 to 3 c.c. of an oxalate carbonate solution (15 

 per cent potassium oxalate and 10 per cent sodium carbonate) 

 and about 5 c.c. toluene. The air current is then connected and 

 the ammonia is carried over into a standard acid solution. The 

 current is run as fast as possible for twenty to thirty minutes. 

 The ammonia thus collected is Nesslerized in the usual manner 

 for blood nitrogen. 



Note. Ammonia determinations in the blood are not accurate 

 inasmuch as blood decomposes spontaneously (especially in the 

 presence of alkalies capable of setting free the ammonia) at all 

 temperatures even when kept on ice. 



UREA 



The Urease Method, Van Slyke and Cullen's 2 Modification 

 of Marshall's Method 3 



Principle. See Urease Method, page 38. 



Procedure. Run 3 c.c. of fresh blood (carefully measured 

 with an accurate pipette) into a 100 c.c. test-tube containing 1 c.c. 

 of a 3 per cent solution of potassium citrate (to prevent clotting). 

 Add 0.5 c.c. of the urease solution 4 and 2 or 3 drops of caprylic 

 alcohol (to prevent foaming). After ten minutes add 15 c.c. of a 

 saturated solution of potassium carbonate, and drive off the 



1 Folin and Denis: Jour. Biol. Chem., 1912, 11, 532. 



2 Van Slyke and Cullen: J. Am. Med. Assn., 1914, 62, 1558. 



3 Marshall: Jour. Biol. Chem , 1913, 15, 487. 



4 The enzyme solution is prepared as described on page 89. 



