82 



SUBSTANCES SOLUBLE IN WATER. 



ence the amount of ammonia may be calculated in the usm 

 way. 



(b) The ammonia may be distilled into hydrochloric acid; th( 

 liquid evaporated to dryness, the residue alternately moistem 

 and dried two or three times, and the chlorine estimated volu- 

 metrically by nitrate of silver and chromate of potash. From th( 

 chlorine found the amount of ammonia may be calculated. 



Another method for the estimation of ammonia is that pro- 

 posed by Schloessing. A few grams of the material made into a 

 paste with water, or better, a concentrated aqueous extract, is 

 mixed with milk of lime and placed over a measured quantity of 

 volumetric sulphuric acid under a bell jar. The ammonia liberated 

 by the lime is absorbed by the sulphuric acid, and after standing 

 two or three days at a temperature as nearly constant as possible 

 (8 to 10), the amount of acid thus neutralized may be ascertained 

 by estimating the excess with volumetric solution of soda, and 

 from this the ammonia may be calculated. 



It must be admitted 1 that in all these experiments the action 

 of the lime or magnesia on albuminous substances may result in 

 the formation of ammonia. It is advisable, therefore, to remove 

 such substances by precipitation with basic acetate of lead before 

 distilling. Glutamine and asparagine, however, remain in solu- 

 tion. These substances, when pure, are not acted upon by either 

 lime or magnesia, but Schulze believes that they undergo a partial 

 decomposition in mixtures, and therefore recommends boiling 

 with hydrochloric acid for one to two hours (compare remarks 

 on asparagine, 191), by which they are completely resolved 

 into the corresponding amido-acids and chloride of ammonium. 

 The estimation of ammonia now includes the total ammonia 

 derived from the asparagine and glutamine. These two sub- 

 stances may, however, be determined by Sachsse's method, and 

 the ammonia they yield calculated and deducted. 



If the precautions mentioned have been observed, the first 

 method (a) will generally yield satisfactory results. 



98. Amido-Compounds, etc. The foregoing estimation will be 

 inaccurate if the material under examination contains amido-com- 

 pounds, etc., or volatile alkaloids, as the former yield ammonia and 

 the latter distil over and saturate part of the acid. Many amines, 



1 Compare E. Schulze, Zeitschr. f. anal. Chem. xvii. 171 (1878) ; Journ. 

 Chem. Soc. xxxiv. 308. 



