566 



Journal of Agricultural Research 



Vol. X, No. II 



REACTION BETWEEN SODIUM SALTS AND CALCIUM CARBONATE IN 



THE SOIL 



By reference to the tables it will be noticed in every case that con- 

 siderably more lime went into solutions in the soils to which calcium 

 carbonate had been added than in the untreated soils. With the sodium 

 nitrate, Table XXV, this difference amounted to 448 parts per million; 

 with sodium chlorid, Table XXVI, to 525 parts per million; with sodium 

 sulphate, Table XXVII, to 335 parts per million; and with a mixture 

 of sodium chlorid and sodium sulphate. Table XXVIII, to 130 parts per 

 million at the maximum concentration. The increase in the soluble 

 lime can be accounted for by the action of the sodium salts upon cal- 

 cium carbonate and the formation of the normal carbonate, or black 

 alkali, and the subsequent formation of sodium bicarbonate — for exam- 

 ple, Na2S04 + CaC03<^Na2C03 + CaS04. With the development of car- 



^o so ^o 



Fig. 18. — Graphs showing the solubility of organic matter in soil in solutions of sodium nitrate. 



bon dioxid in the solution the normal carbonate was converted into 

 bicarbonate; however, at one time in the reaction, sodium carbonate 

 existed, and when in this condition it was capable of reacting and did 

 react upon the organic matter and the silica of the soil. It was noticed 

 that the color of the solutions, owing to soluble organic matter, increased 

 in intensity as the strength of the sodium salt increased, showing the 

 action of the sodium carbonate formed in the reaction upon the organic 

 matter. 



ACTION OF SODIUM CARBONATE UPON ORGANIC MATTER IN THE 



SOIL 



In order to have a soil which contained no carbonates, a quantity of 

 the Station soil was mixed with dilute acetic acid until the soil extract 

 was distinctly acid. This required about 4 c. c. of normal acetic acid to 

 every 100 gm. of soil. After being thoroughly mixed, the soil was allowed 

 to dry in the sun and the excess of acetic acid driven off in this way. 



