75 



water is affected importantly by the presence of other 

 substances in the solution, including salts of potas- 

 sium, sodium and calcium which are usually present in 

 soil solutions. In particular, the solubility of the 

 gas is greatly increased by the presence in the solution 

 of alkaline carbonates or hydroxides with which the carbon 

 dioxide can combine .to form carbonates or bicarbonates. 

 Accordingly the solubility of carbon dioxide in the 

 soil solution will vary widely in response to differences 

 in the chemical composition of the solution and may rise 

 considerably above the values for pure water. 1 How much 

 practical effect the absorption of carbon dioxide by 

 the soil solution may have on the composition of the soil 

 air it is impossible to say but it seems not improbable 

 that such absorption, followed by removal in the drainage- 

 water, may assist significantly in the removal of carbon 

 dioxide from the soil. 



1. Of the voluminous literature concerning the 

 effects of dissolved substances on the solubility of car- 

 bon dioxide see: Mackenzie,- Ann. Physik (Wied.) (2) 1: 

 450 (1877); Geffcken,- Zeits. physik. Ghemie 49: 271 

 (1904); Stieglitz,- Gar. Inst, of Wash., Pub. 107 ; 

 235- (1909); Pox,- Trans. Paraday 3oc. 5: 68-67 

 (1909); Johnston,- Jour. Amer. Ghem. Soc. 37 : 2001- 

 2020 (1915); Johnston and Williamson,- Jour. Amer. Ghem. 

 Soc. 38: 975-983 (1916). 



