§ 107. THE PHYSICAL QUALITIES OF THE SOIL. 191 



100 parts of soil dried at 100° C. contain of clay AlaOg 2Si02, 

 2H.jO, estimated from tlie alumina and silica dissolved by acids 

 (See Table III). 



a. In the hydrochloric acid solutions 4.50 



&. " " sulphuric acid solution 4.41 



100 parts of soil dried at 100° contain of 



a. Fotassa feldspaVj KsOjSSiOa, AlaOgjoSiOa, estimated from the 



potassa in the solution by hydrofluoric acid. (See Table III,).18.94 



b. Soda feldxpar, NagOjSSiOo, AlaOsjSSiOa, estimated from the 



soda in the solution by hydrofluoric acid 17.85 



c. Clay, imdccomposed by the previous treatment with sulphuric 



acid, estimated from the alumina in the solution by hydro- 

 fluoric acid in excess of what is required for the feldspars 0.30 



d. Pure quartz sand, estimated from the silica in excess over what 



is required for the feldspars and clay 19.11 



(Estimated also from the determination made with the aid of 

 phosphoric acid). 

 100 parts of soil dried at 100" C. yielded to water }{ saturated 

 with carbonic acid 

 Volatile matter, expelled on ignition of the residue left by evaj^o- 



ration of the extract 0.15 . 



Mineral matters 0.19 



0.34 

 THE PHYSICAL QUALITIES OF THE SOIL. 



107. Experiments for testing the physical qualities of 

 the soil, and for comparing different soils in respect to 

 these qualities, should be made with soils of the same de- 

 gree of dryness and mechanical division, and Avith tolera- 

 bly large quantities, and the observations should be made 

 under circumstances resembling those as closely as possi- 

 ble, by which the soil is affected in the field. The fol- 

 lowing methods have been carefully tested by Wolff 

 himself, and he vouches for their reliability. 



The soil must be completely air-dried, pulverized in a 

 porcelain mortar with a wooden pestle, or rubbed between 

 the hands to break up the lumps that were formed in 

 drying, and passed through a sieve with meshes 3 mm. 

 wide. 



