OXIDES. 285 



OXIDES. 



Define an ox- 710. The compounds of the metals with 



terms ere- ox yg en j wit h tne exception of those which 

 ferent oxides have decided Iv acid properties, are called 



distinguished? _ J 



oxides. When a metal unites with oxy- 

 gen in several different proportions, forming different 

 oxides, these a"re distinguished as protoxide, deutoxide 

 or binoxide, tritoxidc or teroxide : terms signifying 

 first, second, and third ^oxides. The highest oxide is 

 also called peroxide. An oxide containing three atoms 

 of oxygen to two atoms of metal, is called a sesquiox- 

 ide. The names of chlorides, sulphurets, &c. are simi- 

 larly modified, to indicate the proportion of chlorine, 

 sulphur, &c. which they respectively contain. Com- 

 pounds of non-metallic substances with oxygen which 

 do not possess acid properties, are also called oxides. 

 There are, for example, oxides of nitrogen and phos- 

 phorus. 



711. PROPERTIES OF OXIDES. The 



What is said 



of add and lower oxides are generally strong bases, 

 basic proper- w ^{\ e tne higher oxides exhibit basic or 



tics in oxides ? 



acid properties, according to circumstances. 

 Binoxide of tin, for example, described in a previous 

 chapter, acts as a base in combining with sulphuric 

 acid to form 'a sulphate, while, if fused with potassa, it 

 acts as an acid, and forms a stannate. On account of 

 its acid property, the binoxide of tin is also called stan- 

 nic acid. The name is derived from Stannum, which 

 is the Latin word for Tin. 



