NITROGEN. 169 



being simply dissolved. By boiling, all the ammonia is finally driven 

 out of solution. 



It has a strong alkaline action on litmus and has basic properties 

 like those of sodium and potassium hydroxide. It neutralizes acids 

 forming salts, thus : 



NH 4 OH + HC1 = NH 4 C1 + H 2 O. 



Ammonia gas also unites with acids directly without elimination of 

 water. For example, with hydrochloric acid gas, a dense white cloud 

 of ammonium chloride is formed : 



NH 3 + HC1 = NH 4 C1. 



The union of water or hydrochloric acid directly with ammonia is 

 explained by the increase of valence of the nitrogen atom from 3 to 

 5. In the hydroxide and all the salts, there is a group of atoms, 

 (NH 4 ) , which acts exactly like an atom of metal. It has, therefore, 

 been called ammonium. This radical and its analytical reactions will 

 be discussed under Ammonium compounds. 



Experiment 7. To about 20 c.c. of dilute ammonia water, add concentrated 

 hydrochloric acid until litmus-paper is just turned from blue to red by the 

 liquid. Evaporate to dryness in a porcelain dish over a small flame. Note 

 appearance of residue and compare its taste with that of the ammonia water, 

 and dilute hydrochloric acid and also that of ammonium chloride. What is 

 the residue? This is an example of the formation of a salt by neutralization 

 of an acid by an alkali. 



Ammonia "water, Aqua ammoniae (Spirit of hartshorn). This is 

 a solution of ammonia gas in water or ammonium hydroxide in water. 

 The common ammonia water contains 10 per cent, by weight, equal 

 to 125 volumes of ammonia, and has a specific gravity of 0.958 at 

 25 C. ; the stronger ammonia water, aqua ammonias fortior, contains 

 28 per cent., and has a specific gravity of 0.897 at 25 C. Ammonia 

 water has the odor, taste, and reaction which characterize the gas. 



Hydrazine, N 2 H 4 (Diamine], is a compound obtainable from organic com- 

 pounds by processes which cannot be considered here. It is a colorless gas at 

 summer heat, readily liquefying at a somewhat lower temperature, and solidi- 

 fying at the freezing-point of water. 



Exposed to the air it takes up oxygen, forming water and nitrogen. In its 

 chemical properties hydrazine resembles ammonia, forming a hydrate of 

 the composition N 2 H 4 .H 2 O, and salts with acids, such as N 2 H 4 .H 2 SO 4 and 

 N 2 H 4 (HC1) 2 . The constitution of hydrazine may be represented by the 



H \ / H 



formula >N NC 



H/ \H 



Hydroxylamine, NH 2 OH. The term amine is used to designate com- 



