HYDROGEN AND NITROGEN. 409 



Ammonia, in Libya. It is produced in the destructive distilla- 

 tion of all organic matters containing nitrogen, which has given 

 rise to one of its popular names, the spirits of hartshorn. It is 

 also produced during the putrefaction of the same matters in 

 the atmosphere. In the mineral kingdom, it appears often to 

 be formed in oxidation, when effected by the simultaneous ac- 

 tion of air and water, as in the rusting of iron, and a trace of it 

 is always found in the native oxides of iron, in the varieties of 

 clay, and in some other minerals. 



Preparation. In a state of purity, ammonia is a gas, of which 

 the liquor or aqua ammonia is a solution in water. This solu- 

 tion, which is of constant use as a reagent, is prepared by mixing 

 intimately sal ammoniac (hydrochlorate of ammonia) with an 

 equal weight of slaked lime, and distilling the mixture in a glass 

 retort, by the diffused heat of a chauffer or sand-pot. Ammo- 

 niacal gas comes off, which should be passed through a small 

 quantity of water, to arrest a little dust of lime that is carried 

 along with it, and afterwards be conducted into a quantity of 

 distilled water, to condense it, equal to the weight of the salt 

 employed. Chloride of calcium and the excess of lime remain 

 in the retort, and a considerable quantity of water is liberated 

 in the process, and distils over with the ammonia. This impor- 

 tant reaction is explained in the following diagram : 



PROCESS FOR AMMONIA. 



Before decomposition. After decomposition. 



669 Hydrochlorate 



of ammonia chlorme ^ 



[Oxygen . 100 -^ I12 2 Water. 

 Lime . . .j Cal ' cium< 256 _\,698 Chloride of 



calcium. 



1025 1025 1025 



Or in symbols : N H 4 , Cl and Ca O = N H 3 and H O and CaCl. 



To obtain ammoniacal gas, the solution prepared by the pre- 

 ceding process may be boiled by a gentle heat, when the gas is 

 first expelled from its superior volatility ; or the gas may be 

 derived at once from sal ammoniac, mixed with twice its weight 

 of quicklime in a small retort, and collected over mercury. 



Properties. Ammonia is a colourless gas, of a strong and 



