[295] SCIENTIFIC MANUAL. 9 



are called sulphates ; with nitric acids, nitrates ; with car- 

 bonic acid, carbonates, etc. They are generally neutral, 

 possessing neither acid nor alkaline character. 



The strength of the union of acids with bases varies, 

 the acid possessing the stronger affinity for a given base, 

 having the power of displacing the weaker, and taking its 

 place in combination with the base. 



This principle is utilized by the manufacturer of super- 

 phosphate to liberate phosphoric acid from its union with 

 lime, and thus make it available for plant nutrition. When 

 the pulverized phosphate of lime is treated with sulphuric 

 acid, the sulphuric acid, having a stronger affinity for lime 

 than the phosphoric acid, displaces a portion of the latter 

 from its union with the lime, forming super-phosphate of 

 lime, together with sulphate of lime. 



About half of every acid phosphate, or commercial su- 

 per-phosphate, js sulphate of lime. 



Chemistry is divided into two general departments : 

 Organic, which treats of those compounds which have 

 organized structure, whether vegetable or animal ; and x 



Inorganic, which includes all substances which have not 

 organic structure, embracing the mineral kingdom, and 

 such other compounds as have not been formed by life. 



Inorganic compounds can be formed in the chemical 

 laboratories, while organic are the result only of life in 

 conjunction with other forces. 



In the following pages the elements, with their chief 

 compounds, will be briefly described, that the reader may 

 obtain a general idea of those substances which, by their 

 different combinations with each other, constitute the solid, 

 liquid and gaseous substances of the world, so far as they 

 may be deemed of interest to farmers. 



Oxygen is a colorless, inodorous, tasteless gas. It exists 

 free in the air, and has a powerful chemical affinity for 

 other elementary substances. It is the most abundant and 

 most widely distributed of all the elements. " In its free 



