194 WALL'S MANUAL 



a hissing or effervescence, when poured on pearl ash. 

 This action ceasing, there is neither acid taste or 

 alkaline properties; the character of the vinegar and 

 pearl ash has disappeared ; the substances have united ; 

 they have formed a new substance, termed a salt-. 

 The fact to be observed in the above experiment 

 is, that an alkali and an acid mutually neutralize 

 each other. The vinegar is popularly said in this 

 case, to "kill" the pearl ash. So, soda, potash, lime, 

 magnesia, etc., would all be "killed" or neutralized by 

 vinegar, they would all be dissolved by it, and lose 

 their distinguishing character. In either case, a 

 neutral salt would be formed. Such a class of salts 

 are called acetates, being formed by alkalies, alkaline 

 earth, and metallic oxydes, united with acetic acid, or 

 vinegar. 



Silex or silica, or the earth of flints, is in its pure 

 state, is a perfectly white, insipid, tasteless powder. 

 It unites with bases in the form of silicic acid, form- 

 ing neutral salts, termed silicates. Thus, are formed 

 a large class, in which are found silicates, potash, 

 soda, lime, magnesia, etc. This class forms the great 

 bulk of all the rocks and soil. 



METALLOID COMPOUNDS SALTS. 



The substances last mentioned are all metals, 

 united with oxygen v They are metallic oxides. If 

 the oxygen is removed and replaced by carbon, 

 sulphur, or phosphorus, the combinations are called 

 carburids, sulphids, phosphids. 



Metalloid compounds are combinations of metal- 

 loids with metals, in their pure or unoxydized state. 



Salts are combinations of metalloids with oxygen 

 and the metals, in their rusted or oxydized state. 



