INTEODUCTOEY. 21 



from some fanciful idea of its nature. Thus nitric acid was 

 called aqua fortis (strong water), because it is a liquid of 

 such powerful acid properties ; and sulphuric acid was 

 named oil of vitriol, because it flows like oil, and was ob- 

 tained from what was called green vitriol. Then the sul- 

 phates of iron, copper, and zinc were respectively named 

 green, blue, and white vitriol, because, from their translu- 

 cency, they somewhat resemble glass of these colors. Oth- 

 er examples might be given, but these are sufficient. In 

 chemical books all these old names have given place to the 

 new nomenclature introduced by Lavoisier and his com- 

 peers, though a few of them are yet retained in common 

 language. This nomenclature, which, though it has been 

 extended with the progress of chemical discovery, has not 

 been essentially altered since it was first promulgated, is 

 worthy of admiration for its beautiful clearness and simplic- 

 ity. There is nothing arbitrary but the names of the ele- 

 ments. All the compounds have names which indicate their 

 ingredients ; and if any new compound be discovered, the 

 discoverer gives to it a name which expresses its chemical 

 character in accordance with the general plan of the nomen- 

 clature. Examples of the method of naming compounds 

 will be given in the next paragraph ; and as we proceed in 

 the examination of various substances, you will have con- 

 stant illustrations of this language of chemical science. 



1 8. Naming of Chemical Compounds. The names of com- 

 pound bodies are derived from the elements of which they 

 are composed ; many of these names have been anticipated, 

 but some explanation is necessary. In general, when two 

 elements unite, the name of the compound is formed by 

 writing the name of one element in full and placing the name 

 of the other element after it, giving to the latter the termi- 

 nation ide. Usually the non-metallic element follows the 

 metallic ; thus potassium and oxygen form potassium oxide; 



