Sept. 10, 1917 



Formation of "Black Alkali" 



575 



place outside the soil. The sodium carbonate was changed into sodium 

 bicarbonate, and the action of the bicarbonate upon the organic matter 

 of the soil was only a little more than that of sodium nitrate alone. 



4. When calcium carbonate was mixed with the soil and the sodium- 

 nitrate solution introduced into it, the reaction which involved the forma- 

 tion of the sodium carbonate took place in contact with the soil. The 

 action of the sodium carbonate upon the organic matter is clearly brought 

 out. 



Another sample of acetic-acid-treated soil was taken, treated, first with 

 sodium sulphate, second with sodium sulphate and calcium carbonate, 

 and third with sodium sulphate and calcium carbonate and then the solu- 

 tion saturated with carbon-dioxid gas. These were shaken until equi- 

 librium was established. Determinations were then made of the soluble 

 organic matter (Table XXXVIII). 



Table XXXVIII. — Solubility of the organic matter in acetic-acid-treated soil with the 



addition of salts 



The fact that the presence of calcium carbonate increases the solu- 

 bility of the organic matter indicates that the sodium sulphate is acting 

 upon calcium carbonate with the formation of the normal sodium car- 

 bonate, and this is acting upon the organic matter of the soil. When 

 carbon dioxid is present in excess, the reaction forms sodium bicarbo- 

 nate, which shows little action upon organic matter. This experiment 

 was repeated with sodium chlorid, with practically the same results. 



ACTION OF SODIUM CARBONATE AND SODIUM BICARBONATE UPON 



ORGANIC MATTER 



Having demonstrated the fact that in the soil sodium salts react with 

 lime to form sodium carbonate and this attacks the organic matter of 

 the soil, the pure salts sodium carbonate and sodium bicarbonate were 

 added in varying concentrations to the station soil and brought to 

 equilibrium. Portions of the solutions were withdrawn and titrated 

 for carbonates and bicarbonates, and determinations were made of the 



