452 PRINCIPLES OF CHEMISTRY 



like all other ammonium salts, easily decomposes ; for instance, by 

 volatilisation with alkalis, and even partially when its solution is 

 boiled. But at higher temperatures ammonia decomposes with the 

 liberation of hydrogen, and therefore ammonia is then able to act 

 as a reducing agent as, for example, on metallic oxides. The other 

 properties and reactions of sal-ammoniac, especially in solution, fully 

 bring to mind what has been already mentioned in speaking of sodium 

 chloride. Thus, for instance, with silver nitrate it gives a precipitate 

 of silver chloride ; with sulphuric acid it gives hydrochloric acid and 

 ammonium sulphate, and it forms double salts with certain metallic 

 chlorides and other salts. 45 



45 The solubility of sal-ammoniac in 100 parts of water (according to Alluard) is 



10 20 30 40 60 80 100 110 



28-40 32-48 37'28 41'72 46 55 64 73 77 



A saturated solution boils at 115-8. The specific gravity at 15/4 of solutions of sal- 

 ammoniac (water 4 = 10000) = 9991'6 + 31-26^ 0'085p 2 , where p is the amount by weight 

 of ammonium chloride in 100 parts of solution. With the majority of salts the differen- 

 tial dsjdp increases, but here it decreases with the increase of p. For (unlike the 

 sodium and potassium salts) a solution of the alkali phis a solution of acid occupy a 

 greater volume than that of the resultant ammonium salt. In the solution of solid' 

 ammonium chloride a contraction, and not expansion, generally takes place. It may 

 further be remarked that solutions of sal-ammoniac have an acid reaction even when 

 prepared from the salt remaining 'after prolonged washing of the sublimed salt with 

 water (A. Stcherbakoff ). 



