146 THE FITNESS OF THE ENVIRONMENT 



if the amount of acid be ten times the amount 

 of salt (ll^j = loY the hydrogen ion concentra- 

 tion must be 0.000003 N, and if the reverse 



be the case ( =f = — ) the value must be 



VBA 10/ 



0.00000003 N. 



The range of variation of concentration of 

 hydrogen ions in the usual solutions of the 

 chemical laboratory considerably surpasses 

 the limits 1.0 N and 0.00000000000001 N. In 

 comparison with such enormous differences 

 those between 0.000003 N and 0.00000003 N are 



J_ . 1 



100 * 100,000,000,000,000, 

 Hence ordinarily it is quite accurate enough 

 to speak of any solution containing both 

 free carbonic acid and a bicarbonate, when 

 the disparity between the concentrations of 

 the two substances is not very great, as of 

 constant neutral reaction. For, obviously, 

 the neutral point, which at a temperature of 

 25° amounts to a concentration of hydrogen 

 and hydroxyl ions 0.0000001 N, falls well 

 within the narrow range of reaction of such 

 solutions, being characterized by a ratio of 

 carbonic acid to bicarbonate of about 1:3. 



Thus carbonic acid, like the almost equally 

 weak acids sulphuretted hydrogen and phos- 



almost negligible (-J- : nOO.OOo) 



