Sept. 10, 1917 



Formation of "Black Alkali 



585 



The solubility of organic matter in varying amounts of sodium car- 

 bonate when sodium chlorid was in the solution is also given. 



Table XLVI. — Solubility of organic matter in sodium-carbonate solutions 



From the above table it will be noted that after the organic matter of 

 the soil has once been brought into solution by the sodium carbonate, 

 approximately one-half can be reprecipitated with sodium chlorid. 



From all the results so far obtained it would seem that the injurious 

 effect of sodium carbonate in its action upon the organic matter of the soil 

 rests in that portion of the salt which is hydrolyzed into sodium hydrate. 

 The rate of hydrolysis of sodium carbonate in pure solution and in the 

 presence of sodium salts may be measured by means of the saponification 

 of ethyl acetate. Ten c. c. of ethyl acetate were therefore put into 150 

 c. c. of 0.4 per cent of sodium carbonate, using pure water and increasing 

 amounts of sodium, chlorid. After standing with frequent shaking, for 20 

 minutes, a portion of the solution was withdrawn and titrated against 

 standard acid, using phenolphthalein as an indicator. This titration was 

 repeated after 40, 60, and 100 minutes, respectively. The amount of 

 unsaponified sodium carbonate was thus determined, and by subtracting 

 this from the total amount in the original solution, the quantity of saponi- 

 fied sodium carbonate was determined. This experiment was repeated 

 with sodium sulphate, using a 0.49 per cent sodium carbonate. The 

 results are shown in Tables XLVII and XLVIII and in figures 25 and 26. 



Table XLVII. — Saponification of ethyl acetate by sodimn carbonate in the presence of 



sodium chlorid 



