4 



BULLETIN 158, U. S. DEPARTMENT OF AGRICULTURE. 



Ammonia. — Considerable difficulty was experienced in obtaining 

 concordant results in the determination of the nitrogen in the form 

 of ammonium salts. Boiling weighed amounts of the base goods with 

 water and magnesium hydroxide, according to the official method, 1 

 for the determination of ammonia in fertilizers, did not give duplicate 

 results sufficiently close for the purpose of this research. Owing to 

 the acidity of the sample, it was impractical to use barium carbonate, 

 but litharge was used with varying results. Finally, the determina- 

 tion was made by using the vacuum distillation method, which gave 

 concordant results. This method, which gives only the nitrogen 

 found as ammonia or as ammonium salts, is used for the determina- 

 tion of amide nitrogen in the products of acid hydrolysis of proteins. 

 A weighed quantity of the fertilizer was placed in a Claisen flask con- 

 nected up with a cooled receiver of 1 liter capacity and a small guard 

 flask of 200 cubic centimeters capacity. Both flasks contained 0.1 N 

 sulphuric acid. To the fertilizer was added 100 c. c. of neutral 95 

 per cent alcohol and 100 c. c. of distilled water, together with enough 

 10 per cent suspension of calcium hydroxide to make the mixture 

 decidedly alkaline in reaction. The ammonia was then distilled 

 under a pressure of from 10 to 12 mm., the temperature of the bath 

 not exceeding 40° C. In the table which follows are given the results 

 obtained by the three methods here used for the determination of 

 ammonia. 



Table III. — Nitrogen in the form of ammonia or, ammonium salts. 



Method. 



Expressed in 



Expressed in 

 per cent of 



total nitrogen 

 in base goods. 



Magnesium hydroxide distillation 



Lead oxide distillation 



Vacuum distillation 



23.60 

 24.16 

 24.47 

 25.09 

 23.23 

 23.23 



An examination of these results shows that by boiling with mag- 

 nesia or litharge, somewhat more nitrogen is found as ammonia than 

 really exists in this form in the base goods. It is therefore probable, 

 that there are in the base goods nitrogenous compounds which are 

 broken down into ammonia by the action of these alkaline reagents 

 at a temperature of 100° C. The use of magnesia at boiling tem- 

 perature for the purpose of determining the amount of ammonia 

 split off by acid hydrolysis from certain proteins which contained 

 cystine, was found to give unreliable results. 2 The reason for this 



1 Bui. 107, 9 (Revised), Bureau of Chem., U. S. Dept. Agr. 



2 Embden, q\:oted by Giimbel, Hofmeister's Beitrage, 5, 297 (1904): Hart, Zeit. physiol. Chem., 33, 354, 

 1901); Eolin,ibid., 39, 476 (1903); Denis, J. Biol. Chem., 8, 427 (1910). 



