FORMATION OF SOLUBLE CARBONATES 29 



in a water-logged condition and to which nitrates were 

 added, concluded that sodium carbonate is readily formed 

 from the nitrates in a water-logged soil. 



Treitz (22) concluded from his studies of alkali soils 

 of Hungary that the soluble salts found in them are derived 

 from the ash constituents of the plants produced on the 

 soil and that the first and most necessary condition for 

 the formation of sodium compounds, particularly the 

 carbonates, is a calcareous subsoil, carbonates of the 

 alkali being formed by the action of calcium carbonate on 

 the humates, sulphates, and chlorides of the alkalies. 



From a study of water extracts of typical alkali soils 

 and of soils to which various salts were added, Cedroits (5) 

 concluded that sodium carbonate is not formed in the soil 

 by direct reaction between sodium chloride and calcium 

 carbonate, but that the sodium of the chloride replaces 

 other bases potassium, calcium, and magnesium -- in 

 humates and silicates, and the latter give up soda to the 

 soil solution when the excess of soluble sodium salts is 

 removed. 



Kelley (13) and Breazeale (2) have concluded that 

 sodium nitrate reacts with calcium carbonate in the for- 

 mation of small quantities of sodium carbonate. In dis- 

 cussing this reaction Breazeale has the following to say: 

 "In the reaction between sodium nitrate (or sodium 

 chloride or sodium sulphate) and calcium carbonate, 

 resulting in the formation of sodium carbonate, the presence 

 of relatively small amounts of calcium nitrate or calcium 

 chloride in the reaction impedes and may prevent the 

 formation of sodium carbonate. The presence of a satu- 

 rated solution of calcium sulphate in this reaction does 

 not entirely stop the formation of sodium carbonate. 

 Sodium nitrate, sodium chloride, and sodium sulphate in 



