92 BULLETIN 846, U. S. DEPARTMENT OF AGRICULTURE. 
ammonium sulphate 1 (containing about 3 mg. of nitrogen) and 25 ce. 
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.? 
The essential features of the method consist of rendering a small 
sample alkaline, removing the liberated ammonia 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 
ec. 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 14 inch test tube of strong glass connected 
to the wash bottle, to serve as a trap to remove any spray of dilute 
acid. (8) Asmall Kjeldahl flask of about 125 ce. capacity for holding 
the sample. (4) A 10 by 14 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 ce. 
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 ce. 
oraduated 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 ce. 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 ce. 
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. 
