NITROGEN: AMMONIA 87 



It may be supposed that ammonia would unite directly with 

 acids thus : — 



NH3 + HC1 = NH3.HC1 

 2NH3 + H2SO4 = (NH3)2.H2S04. 

 To test the truth of this conjecture, place 20 cubic centimeters 

 of the diluted sulphuric acid of known strength, prepared for 

 Study XVIII., in a weighed dish, add the solution of ammonia, 

 prepared above, in slight excess (the excess will volatilise), 

 evaporate the solution to dryness on the water bath, and 

 weigh. Does the weight of the compound obtained correspond 

 with that calculated from the second of the formulae given? 

 Having found the formulae for sal-ammoniac and the sulphate, 

 write equations representing the action of quicklime upon 

 them. Deduce the formula for calcium chloride from the 

 formulae of calcium oxide and hydrochloric acid. 



Instead of the formulae NH3.HCI and (NH3)2.H2S04, the compounds 

 might be represented as NPI4CI and (NH4)2S04, in which NH4 is regarded 

 as taking the place of hydrogen in the acids and a metal in the salts. The 

 name ammonium is applied to this hypothetical metallic radicle, and the 

 salts are called chloride of ammonium and sulphate of ammonium, like 

 chloride of sodium and sulphate of sodium. In the same way the hydrate 

 of ammonia, produced by dissolving ammonia in water, may be regarded as 

 hydroxide of ammonium. Thus NH4CI, like NaCl, instead of NII3.HCI ; 

 (NH4)2S04, like Na2S04, instead of (NH3)2.H2S04; NH4OH, like NaOH, 

 instead of NHg.HgO. The use in commerce of the term muriate and 

 sulphate of ammonia for chloride and sulphate of ammonium is obviously 

 not justifiable. 



Ammonium compounds are easily recognised, for they 

 decompose when warmed with potash or soda, ammonia gas 

 being set free. The gas can be distinguished by its smell, 

 by its action on red litmus paper, and by the white fumes of 

 sal-ammoniac produced when the mouth of the tube in which 

 the test is made is brought near the mouth (or stopper) of the 

 hydrochloric acid bottle. By this means, test a sample of 

 " nitrogenous guano " and a sample of " barley manure " for 

 ammonium salts. 



