24 AGRICULTURAL CHEMISTRY. 



38. In Table II. are arranged the principal salts 

 (salts having special relation to agriculture), which 

 are derived from the compounds, in the second col- 

 umn of TabJe I., aiTd from other compounds at the 

 bottom of that table. The figures placed after them 

 show from which two compounds each salt is formed. 



EXPLANATION OP THE POREGOING TABLES. 



39. Two things are essential to success in learning 

 chemistry : 1st, to become able to infer from the name 

 of a substance what it is composed of; and 2nd, to 

 know how to name a compound from the names of its 

 ingredients. You would suppose that if a chemist 

 discovers a new compound, he may call it what he 

 pleases. But it is not so ; he must give it a name, 

 which will indicate its ingredients, so that others may 

 know, as soon as they hear its name, what it is made 

 up of. Chemists have proceeded on this principle for 

 the last half century ; and it is due in no small degree 

 to the excellence of their nomenclature, that they 

 have achieved so many and so valuable discoveries. 

 It is for the purpose of explaining the nomenclature 

 of chemistry, that I have introduced the foregoing ta- 

 bles. The reader will notice that at the head of the 

 table of oxygen compounds, we have six acids, each 

 named after the element that combines with oxygen to 

 form it ; as sulphuric acid, from sulphur and oxygen ; 

 carbonic acid from carbon and oxygen ; and so of the 

 others. Besides these six acids there is another, which 

 has intimate relations to agriculture, viz., hydrochloi'ic 



