

By E. CLEMINSHAW, Es^., M.A., F.C.S., 

 F.G.S 



UEING combustion in air, elements combine mth the 

 Oxygen of the air, the combinations so formed being 

 called Oxides, and supposed to consist of a certain 

 number of atoms of the element united with a certain number 

 of atoms of Oxygen. 



These Oxides have, in many cases, the power of combining 

 directly with water, and these compounds are divided into two 

 classes — Acids and Bases. As familiar examples may be mentioned , 

 Sulphuric, Nitric, and Carbonic Acids, and Potash, Soda, and 

 Lime. The majority of acids may be supposed to consist of an 

 oxide combined with water ; others, as Hydrochloric or Muriatic 

 Acid, consist of Hydrogen combined with another element. Acids 

 and Bases have the power of acting on each other, forming a salt 

 and water, e.g., Carbonic Acid and Soda from Carbonate of Sodaand 

 water, Sulphuric Acid and Oxide of Iron form Sulphate of Iron 

 and water. Salts, which contain Oxygen, may be regarded as a 

 combination of the two Oxides, e.g., Carbonate of Soda, as Oxide 

 of Sodium and Carbon Dioxide, or as metal and Chlorine in the 

 case of Ohorides, or Salts of Hydrochloric Acid. These salts 



