92 BULLETIN 846, U. S. DEPARTMENT OF AGRICULTURE. 



ammonium sulphate J (containing about 3 mg. of nitrogen) and 25 cc. 

 of water, instead of the egg. The recovery should be over 95 per 

 cent. It is also essential to run blank experiments with the reagents 

 and water used. 



The nesslerization method is an adaptation of the micro-method 

 of Folin and Macallum for the determination of ammonia in urine. 2 

 The essential features of the method consist of rendering a small 

 sample alkaline, removing the liberated a mm onia by aeration, and 

 catching it in dilute sulphuric acid. This is then nesslerized, and 

 the ammonia determined quantitatively by comparing the intensity 

 of the color with a known standard in a Duboscq colorimeter. 



The apparatus employed is as follows: (1) An ordinary acid bottle, 

 fitted with a 2-hole rubber stopper, and containing from 200 to 300 

 cc. of 35 per cent sulphuric acid, to serve as a wash bottle for remov- 

 ing any ammonia that may be present in the air which passes through 

 the system. (2) A 10 by 1| inch test tube of strong glass connected 

 to the wash bottle, to serve as a trap to remove any spray of dilute 

 acid. (3) A small Kjeldahl flask of about 125 cc. capacity for holding 

 the sample. (4) A 10 by 1^ inch test tube, to serve as a trap to 

 catch any foam which may be formed in the sample and carried over 

 mechanically. (5) A 100 cc. volumetric sugar flask containing 2 cc. 

 of approximately N/20 sulphuric acid and about 20 cc. of ammonia- 

 free water. (6) A means of passing air through the system, like 

 that described for the titration method (p. 91). Blast at 10 pounds 

 pressure is preferred; suction may be used. Each of the first five 

 parts enumerated is fitted with a 2-hole rubber stopper, and all are 

 connected by glass tubes of suitable shape and length to permit the 

 proper passage of air through the apparatus. The tube leading into 

 the acid wash bottle should contain a stop cock for regulating the 

 air supply. It is essential that the tube leading into the 100 cc. 

 graduated flask receiving the volatile ammonia be bulb-shaped on 

 the end and perforated with small holes to insure thorough dispersion. 



Weigh approximately 3 grams of sample on a watch glass and add 

 a few drops of water at a time, mixing into a homogeneous mass with 

 a rubber-tipped glass rod, until about 3 cc. of water have been added. 

 Then wash into the Kjeldahl flask with about 10 cc. of ammonia- 

 free water. Add 6 cc. of a solution containing 10 per cent of 

 sodium carbonate and 15 per cent of potassium oxalate. Add 

 enough very heavy cylinder oil to make a layer over the liquid. 

 Pass through this mixture a current of air of sufficient strength to 

 cause a slight spray in the receiving flask, which contains about 20 cc. 

 of ammonia-free water made acid with 2 cc. of approximately N/20 

 sulphuric acid. Aerate for 1 hour and dilute the liquid in the flask 



1 For method of preparing pure ammonium sulphate, see Folin and Farmer, J.Biol. Chem. (1912), 11 : 496. 

 * J. Biol. Chem. (1912), 11 : 523. 



