Chemical Classification 309 



termination of the chemical name of such a compound 

 ends in "-ide". To this class belong the oxides, 

 chlorides, bromides, sulphides, and carbides. When 

 three elements were present in a compound, it was 

 termed a " ternary " compound ; the inclusion of four 

 elements produced a " quaternary " compound, and 

 so on. Those acids which contain oxygen and the 

 metallic compounds derived from these acids, are in 

 general members of the ternary group of compounds. 

 Their characteristic termination is " -ate ". Thus we 

 have the sulphates, nitrates, phosphates, chlorates, 

 carbonates, and silicates. 



213. A very important method of arranging 

 inorganic substances has been indicated in a previous 

 chapter. Certain oxides were termed acidic, while 

 others were said to be basic. The bodies formed by 

 the addition of the elements of water to the acidic 

 oxides are known as acids, while those produced simi- 

 larly from basic oxides are the bases. The phrase 

 " addition of the elements of water " should be noted. 

 Solution in water is not necessarily intended by this, 

 for we already know that some basic oxides, e.g. iron 

 oxide, do not dissolve in water. This is also the case 

 with a few acidic oxides. Silicon dioxide, or silica, 

 a common form of which is sand, is quite insoluble, 

 yet we are able to obtain it combined with a certain 

 quantity of hydrogen and oxygen, these elements 

 entering into combination in the same ratio by weight 

 as- that in which they exist in water, the combination 

 being effected by indirect means. The substance 

 produced is known as hydrogen silicate, or silicic acid, 

 and behaves, in most respects, just like those acids 

 we have already obtained by the solution of a non- 

 metallic oxide in water (see Chapter xv). 



