Sept, lo, 1917 



Formation of "Black Alkali" 



551 



Tabl^ XI. — Titrations with acetic acid of the sodium nitrate-calcium carbonate solution 



conditions existing in the. field, 

 the solutions, they were tightly 



y^Or 



this was an imitation of the probable 

 When the color was titrated out of all 

 stoppered and shaken 

 until they had again 

 reached equilibrium. 

 This usually required 

 about three days. 

 The color was then 

 titrated out a second 

 time. This was re- 

 peated seven times. 

 The results are shown 

 in Tables XI and XII 

 and figures 4 and 5. 



In the reaction be- 

 tween sodium nitrate 

 and calcium carbon- 

 ate, sodium carbonate 

 was formed, and this 

 was titrated out by 

 the acetic acid as rep- 

 resented by the fol- 

 lowing reaction : 

 Na2C03^-2HC2H30,,^ 

 2NaC2H302-fH,6-f 

 CO2. 



If under field con- 

 ditions some sodium 

 carbonate is formed by the action of sodium nitrate upon calcium 

 carbonate and is neutralized by some weak soil acid, more sodium 

 carbonate will be formed. This reaction wall therefore continue until 

 enough of the soluble lime salt, calcium nitrate, is formed to put an 

 end to the reaction, as shown in Table V. 



O S /O /S ^O ^5 30 3S ^lO '^S so SS (SO 



Fig. 5.— Graphs showing the sodium carbonate formed by reaction of 

 calcium carbonate (solid phase present) with sodium nitrate. Sodium 

 carbonate titrated out with oxaUc acid, allowing equilibrium to be 

 established between successive titrations. Numbers refer to titrations. 

 Each graph represents the total sodium carbonate neutraUzed up to 

 and including that titration. 



