Sept. 10, 1917 



Formation of "Black Alkali 



579 



Four samples of these crusts were collected by scraping the surface 

 soil, and extracts were made by shaking them with distilled water and 

 filtering off the soil through Pasteur filters. These solutions were then 

 evaporated to dryness, the residue was dried at 100° F., and portions 

 were taken for analysis. These analyses are given in Table XLII 

 expressed as ions, and also empirically combined as salts, on the basis 

 of the dry water-soluble material. 



Table XLII. — Percentage composition of water-soluble material 



When the bases are combined with the acids, beginning with calcium, 

 and following with magnesium, potassium, and sodium in order, it will 

 be noticed that there is some sodium left over uncombined. This prob- 

 ably existed in part in combination with the organic acids, which were 

 not determined. The sodium no doubt at one time existed as sodium 

 carbonate and had attacked the organic matter of the soil; therefore, at 

 the time of the analysis, it was partly locked up in organic combination. 

 A high percentage of soluble organic matter was to be expected. A 

 high percentage of calcium nitrate is also noticeable. This is due to the 

 fact that active nitrification had been going on in the soil with the for- 

 mation of nitric acid, which had combined with the calcium carbonate 

 of the soil, with the formation of calcium nitrate. Theoretically these 

 crusts could not form in a soil containing no carbonates. 



