SCIENTIFIC AGRICULTURE. 229 



The first process in the analysis of a soil is to weigh a given 

 quantity with apothecaries' scales; it should then be spread 

 out on a piece of clean paper and subjected to a heat not suffi- 

 ciently high to burn the vegetable matters which it contains, 

 until thoroughly dried : after drying, the soil should be again 

 accurately weighed, and the second weight subtracted from 

 the first, when the remainder will show the amount of water 

 lost 



To find the amount of organic matter which it contains, put 

 the dried soil into an earthen crucible and heat it over a fire 

 to "redness, till the organic matter is burned out and the ash 

 only remains ; after cooling, it should be again weighed, the 

 loss by burning shows the amount of organic matter it con- 

 tained, allowing a trifle for the charcoal which remains with 

 the earthy part If a black soil loses nothing by burning, it 

 probably derives it color from black oxide of iron or graphite. 



To detect humic acid, boil a small quantity of peat or muck 

 in a solution of carbonate of soda, until it attains a brown 

 color, then add muriatic acid till the solution has a distinctly 

 sour taste, when brown flocks of humic acid will fall to the 

 bottom. 



Ulmic acid may be obtained from the same soil, after the 

 humic acid is separated, by digesting it over a gentle heat in a 

 solution of caustic ammonia, and then adding muriatic acid as 

 before ; brown flocks are precipitated, which are ulmic acid. 



To detect crenic and apocrenic acids, digest a quantity of 

 soil in hot water until organic matter is dissolved out sufficient 

 to give the water a yellow color. When this solution is evapo- 

 rated to dryness, there remains a brown residue, which con- 

 tains the soluble saline matters of the soil, some extractive 

 matter, humic and ulmic acids, and the crenic and apocrenic 

 acids: these four acids are all in combination with alumina 

 and other bases. When this residue is dried at 220 F., the 

 compounds of the humic and ulmic acids become insoluble, 



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