NITRATES. 311 



785. USES OF NITRE. Nitre is exten- 



Mention some 



of the uses sively employed by the chemist and in the 

 arts, as an oxidizing agent. A few grains 

 of it introduced into a solution of green vitriol, or sul- 

 phate of iron, to which some free sulphuric acid has 

 been added, will immediately change its color. The 

 sulphuric acid sets nitric acid at liberty, to which the 

 oxidation and change of color are to be attributed. 

 Nitre, when heated, yields part of its oxygen, as before 

 stated. If heated with metals, it converts them into 

 oxides. The principal use of nitre, is in the manufac- 

 ture of gun-powder. 



Howareni- - NlTRATE OF AMMONIA. - LAUGHING 



trate of am- GAS. Nitrate of ammonia may be prepared 



monia and ,, 



laughing gas irom the carbonate, by evaporation with 

 produced? nitric acid When heatedj the hydrogen 



of the ammonia, and an equivalent quantity of the ox- 

 ygen of the nitric acid, unite to form water, and the 

 residue of both passes off as protoxide of nitrogen, or 

 nitrous oxide. The compound is also called laughing 

 gas, from the exhilarating effects which it occasions, 

 when breathed in considerable quantity. Impurity 

 of material or excess of heat occasion the production 

 of an impure and deleterious gas. In view of these 

 facts, the preparation, and inhalation of laughing gas 

 is not to be recommended to the student. 

 Ex lain the ^^ ' GUN-POWDER. Gun-powder is a 



action of the mixture of nitre, charcoal, and sulphur. 

 o/ When ignited, the carbon burns instanta- 

 neO usly, by help of the oxygen of the nitre, 

 thus producing a large volume of carbonic acid gas. To 



