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GEOLOGY AND CHEMISTRY OF SOILS. 



min. The quantity of this acid, contained in any given por- 

 tion of soil, may be determined, very nearly, by the proportion 

 of vegetable matter, dissolved by the application of alkalies. 



The following is the proportion of the soluble matter, 

 called soluble geine, nearly identical with humic acid, and of 

 insoluble geine (humin), contained in the soils of Massachu- 

 setts, from the different geological formations. 



The soluble geine, of course, is not all humic acid, as other 

 acids and salts are dissolved by the alkalies ; still, there is not 

 much reason to doubt, but that there is from 1 to 3 per cent, 

 of this acid in all fertile soils. 



2. Crenic acid was first discovered by Berzelius, in 1832, 

 in the water of Porla well, near Orebro, in Sweden. It exists 

 in all our soils, and in the waters of rivers and ponds, and is 

 generally associated with apocrenic acid, and combined with 

 bases. 



Both of these acids may be precipitated from their neu- 

 tral solutions by means of subacetate of lead, and may be 

 separated from each other by the salts of copper. 



It is difficult to determine the quantity of this acid. Soils, 

 analyzed by Berzelius, contained two per cent. 



