CHEMISTEY OF SOILS 



97 



water, chiefly in the form of hydrates. This requires a 

 much higher temperature to drive it off. The last traces 

 can only be expelled at a red heat. The proportions of 

 mixed and combined water found in three samples of soil 

 were as follows : 



The solvent action of water has also been referred to. 

 The majority of substances are soluble in water to some 

 extent. The several forms in which some bodies can exist 

 often exhibit very different degrees of solubility. 



The dissolving power of water is greatly increased by 

 the presence of carbonic acid. A [thousand par.ts of 

 pure water can dissolve, at the utmost, only 0*013 parts of 

 carbonate of lime. When saturated with carbonic acid it 

 can dissolve 0'99 parts, i.e., 76 times as much. 



Soil water is never saturated with carbonic acid but is 

 always more or less charged with it, and contains both 

 mineral and organic matters in solution. 



There is every reason to believe that these solutions must 

 be very dilute, but it is impossible to determine their exact 

 concentration or the amount of substances present in a 

 soluble state at any particular time. Soluble salts cannot 

 be completely washed out of the soil with water. On the 



1 This does not include organic matter, which was estimated 

 separately and deducted from the total loss on ignition. 



S.M. H 



