THE CHEMISTRY OF FARM PRACTICE 



CHAPTER I 



ELEMENTS ATOMIC WEIGHTS MOLECULES SYMBOLS- 

 MOLECULAR WEIGHTS OXIDATION REDUCTION 



1. Chemistry. Chemistry deals with the composition 

 and properties of substances and the changes which sub- 

 stances undergo. Agricultural chemistry has to do with 

 the application of the knowledge gained through chemistry 

 to the art of agriculture and to the problems which the 

 farmer has to solve. To understand agricultural chemistry 

 we must gain first a knowledge of some of the underlying 

 principles of General Chemistry. 



2. Elements. Matter is made up either of simple ele- 

 ments or of these elements combined into compounds of 

 unvarying composition. An element is a simple substance 

 which has certain definite properties and which has not 

 been separated into substances having different properties. 

 Iron is an element. However minutely the piece of iron 

 may be divided, the smallest particle will always have 

 properties identical with the iron before its division. 



Somewhat more than eighty elements have been isolated 

 which have resisted all the attempts of present chemical 

 methods at further separation. Each element has certain 

 distinctive properties that prevent it being classed with 

 other elements, although certain elements which are closely 

 related have some of their properties in common. 



Only ten elements are necessary to sustain the life of 



