44 METHODS FOR THE ANALYSIS OF URINE 



AMMONIA 



Microchemical Method of Folin and MacCallum 1 



Principle. This method is a combination of the aeration 

 procedure for ammonia with its colorimetric determination by 

 means of Nessler-Winkler solution. It gives satisfactory results, 

 but is probably not as accurate as the regular Folin procedure 

 where the amount of substance for analysis is not limited. 



Procedure. By means of Ostwald pipettes introduce 1 to 5 

 c.c. of urine into a Jena test-tube (20 to 25 mm. by 200 mm.) 

 and add to the urine a few drops of a solution containing 10 

 per cent of potassium carbonate and 15 per cent of potassium 

 oxalate. To prevent foaming add a few drops of kerosene or 

 heavy, crude machine oil. Pass a strong air current (see page 42) 

 through the mixture until the ammonia has been entirely removed. 

 Collect the ammonia in a 100 c.c. volumetric flask containing 

 about 20 c.c. of ammonia-free water and 2 c.c. of N/10 acid. 



Nesslerize as described in the method for total nitrogen, 

 page 36, and compare with 1 mg. of nitrogen obtained from a 

 standard ammonium sulphate solution and similarly Nesslerized. 



It has been noted that a trace of something capable of giving 

 a color with the Nessler-Winkler solution continues to come along 

 after all the ammonia has been removed from the urine. The 

 nature of this substance has not yet been determined. In actual 

 determinations by this method, the influence of this unknown 

 substance, because of the small volume of urine used, is entirely 

 negligible, 



CREATININE 



Folin' s Colorimetric Method 2 



Principle. This method is based upon the characteristic 

 property possessed by creatinine of yielding a certain definite 

 color-reaction in the presence of picric acid in alkaline solution. 



Procedure. Place 10 c.c. of urine in a 500 c.c. volumetric 

 flask, add 15 c.c. of a saturated solution of picric acid and 5 c.c. 

 of a 10 per cent solution of sodium hydroxide, shake thoroughly 



1 Folin and MacCallum: Jour. Biol. Chem., 1912, 11, 523. 

 'Folin: Am. Jour. Physiol., 1905, 13, 45. 



