POTASH AND PHOSPHORUS 31 



the fertility of his fields, therefore, the farmer need 

 not give a thought to the stfbject of carbon ; with no 

 assistance from him his growing crops find in the air 

 all the carbonic acid gas they require. There re- 

 mains for our consideration, then, the residue left 

 after combustion, the ashes in fact, a mixture of vari- 

 ous substances of which we will now examine the 

 most important. 



"Let us put a few handfuls of ashes to boil in a 

 pot of water. After boiling a little while we will 

 let the contents cool. The ashes settle to the bottom 

 and the liquid at the top becomes clear. Well, we 

 shall find this liquid emitting a peculiar odor, exactly 

 like that which comes from the lye obtained by pass- 

 ing water through a barrel of ashes. We shall also 

 find that it has an acrid, almost burning taste. This 

 smell of lye, this acrid taste were not in the water at 

 first ; they come from the ashes, which have yielded 

 a certain constituent to the water. 



"Hence we see that ashes must contain at least 

 two substances of different kinds, of which the prin- 

 cipal one cannot dissolve in water, but settles at the 

 bottom as an earthy deposit, while the other, form- 

 ing but a very small part of the whole, dissolves 

 easily in water and gives it its properties, espe- 

 cially its odor and its acrid taste. ■ 



"If we wish to obtain this latter element by itself, 

 we can very easily do so. All that is necessary is to 

 put the clear liquid into a pot over the fire and boil 

 it until all the water has evaporated. There will be 

 left a very small quantity of whitish matter resem- 



