552 



Journal of Agricultural Research 



Vol. X, No. II 



Table XII. — Titrations with oxalic acid of the sodium nitrate-calcium carbonate solutions 



The oxalic acid titration of the sodium carbonate formed in this re- 

 action is represented as follows: Na2C03 + H2C204<=^Na-,C204 + H20 + C02, 

 or sodium carbonate and oxalic acid in equilibrium with sodium oxalate, 

 water, and carbon dioxid. The sodium oxalate thus formed would react 



/SO 



/so 

 %//o 

 \/oo 



\ 



< so 



\^o 



a ■ 



/o /s ^o 



ss 



30 



Fig. 6. — Graphs showing the sodium carbonate formed by reaction of calcium carbonate (solid phase 

 present) and sodium chlorid. Sodium carbonate titrated out with hydrochloric acid, allowing equi- 

 librium to be established between successive titrations. Numbers refer to titrations. Each graph 

 represents the total sodium carbonate neutralized up to and including that titration. 



with the soluble calcium nitrate produced by the first reaction and the 

 insoluble calcium oxalate would be precipitated: Na2C204-f Ca(N03)2^ 

 CaC204 + 2NaN03. 



A noticeable feature of these curves is their tendency to elongate in 

 the meridian where the formation of sodium carbonate is most pro- 



