54 § 47. BASES AXD ACIDS WITH EEAGENTS. 



manner (§ 59), and the respective amounts of sodic and 

 potassic sulphate estimated by the following formulas, in 

 which X = the amount of the sodic sulphate, Y that of 

 the potassic sulphate, A the weight of the mixed sul- 

 phates, and S that of the sulphuric acid contained therein. 



S-(A X 0.45919) 

 ^ = 0.10419. ' Y - A - X. 



In determining potassium and sodium by either of these 

 indirect methods, it is absolutely essential that all other 

 metals be carefully removed. 



AMMONIUM. NH4 18. AMMONIA. NH3. 



47. All the salts of ammonium are either volatilized by 

 heat or decomposed with expulsion of the ammonia, and 

 their solubility is the same as that of the potassium salts, 

 except that the tartrate is more 'soluble. 



Reactions. — Salts of ammonium behave like salts of 

 potassium, with platinic chloride, except that when am- 

 monic platinic chloride is ignited, nothing but metallic 

 platinum is left behind. 



When salts of ammonium are gently heated with baric 

 or sodic hydrate, ammonia is expelled and gives a blue 

 color to a piece of moistened red litnius-j)aper held in the 

 tube above the liquid, or a brown color to a piece of tur- 

 meric-paper. To make this reaction as delicate as possi- 

 ble, put the substance to be tested in a small beaker, with 

 baric or calcic hydrate in a dry form, moisten the mixture 

 with water, cover the beaker with a watch-glass on the 

 under side of which is a slip of the moistened test-paper, 

 and heat the whole gently. Sooner or later, the presence 

 of ammonium will be manifested by a change in the color 

 of the paper, if any is present in the substance. 



The test is a delicate one, as thus performed, and none 

 of the metals interfere with it, if present. 



