576 



Journal of Agricultural Research 



Vol. X, No. u 



soluble organic matter. These are shown in Tables XXXIX and XL, 

 and in figure 22. 



The difference between the amount of sodium carbonate added to 

 the solution and that shown by the titration after equilibrium has been 

 established is indicated in the column "Lost" in Table XXXIX. By 

 subtracting the control, No. i, fron the others and dividing the sodium 

 carbonate "lost" into the parts per million of organic matter brought 



into solution, the parts 



k3000 



I 



(j /GOO 



\ 



%/^oo 



\ 



^ /^oo 

 ^ /ooo 



\ 



ft GOO 



&00 



<ioo 



<eoo 



per million of organic 

 matter brought into so- 

 lution for every 100 

 parts per million of so- 

 dium carbonate lost are 

 obtained. This shows 

 the relative solvent ac- 

 tion of sodium carbo- 

 nate when acting in 

 weak and in fairly 

 strong solutions. 

 Contrary to what one 

 might expect, this ex- 

 periment seems to 

 show that a unit of so- 

 d i u m carbonate is 

 nearly 10 times more 

 effective in a strong 

 concentration than in 

 a weak one. It is well 

 known, however, that, 

 when sodium carbo- 

 nate is added to the 

 soil, a part of it be- 

 comes fixed — that is, 



Fig. 32. — Graphs showing the solubility of organic matter in a soil j*- jg absorbed bv the 



in sodium-carbonate and sodium-bicarbonate solutions. 



sou grams or is com- 

 bined with the silicates or other like bodies of the soil. This fixation 

 would remove in absolute amounts almost as much from a weak solu- 

 tion as from a moderately strong one, and would, of course, leave rela- 

 tively less free sodium carbonate in the weak solution than in the 

 strong one to act upon the organic matter. The carbon dioxid ex- 

 isting in the soil would also convert a small amount of sodium car- 

 bonate into sodium bicarbonate. This action would be almost equal in 

 the weak and the strong solutions. The sodium bicarbonate thus formed 

 woiild be almost negligible, so far as its action upon the organic matter 

 is concerned. 





