Sept. 10, 1917 



Formation of "Black Alkali'' 



557 



Table XVII. — Titrations with carbon-dioxid solutions of the sodium chlorid calcium 



carbonate solutions 



Table XVIII. — Titrations with carbon-dioxid solutions of the sodium sulphate calcium 



carbonate solutions 



By considering the curves, one after another, a very definite idea is 

 obtained of what might happen in the soil when a minimum amount of 

 carbon dioxid is present and being generated continuously. The sodium 

 salts, acting upon the calcium carbonate, would form a small amount of 

 sodium carbonate, and this would combine with the carbon dioxid being 

 generated in the soil and form sodium bicarbonate. Equilibrium would 

 be upset and more sodium carbonate would be formed, which in its turn 

 would be converted into sodium bicarbonate, and the reactions would 

 continue until equilibrium was established. Equilibrium would depend 

 upon the amount of the soluble lime salt formed in the reaction. 



EQUILIBRIUM UNDER ^OIL CONDITIONS 



Cameron and Seidell, in studying the reaction of sodium chlorid and 

 sodium sulphate with calcium carbonate, drew air through the solutions 

 until equilibrium was established with atmospheric air. In applying 

 their results to soil conditions one is apt to fall into error, for soil air 

 contains a great deal more carbon dioxid than atmospheric air. Carbon 

 dioxid will hold calcium carbonate in solution in a fairly stable form until 

 an inert gas is bubbled through the solution. This bubbling process will 

 effectually wash out the carbon dioxid and precipitate the salt. In the 

 4599°— 17 2 



