HARRISON A vanderlkck] .ESCULTN bile salt MEDIA 149 



As soon as we add alkali the equilibrium is upset and very 

 important changes result. For a better conception of these changes 

 we shall give the physical chemical equations representing the reaction. 



1. H + OH = H2 O K = Constant 



C, X C, = K C, X C2 = K 



2. Fe + citrate = Fe citrate 



C3 X C4 = C, X K, C3 X C, 



= K, 



3. Fe + 3 OH = Fe (OH), 



C3 X C2 = Kj C;, X C2 = K, 



4. 3H + citrate = H citrate Cj x C^ 



Ce 

 C, X C, = K3 X C, 



We add NaOH 



NaOH = Na + OH 



K, X Ce = C- X C2 C, X C2 



- K. 



The addition of NaOH means an increase in Cj 



(1) C, X C = Constant. 



a. Conclusion. Cj decreases as much as Cj increases. 



(3) C3 X C, = Constant. 



h. CuHcJudori. C3 decreases as much as C2 increases. 



From conclusions a. and h. we infer that C3 and Cj decrease to 

 the same extent. 



C3 = Iron ions. Cj = Hydrogen ions. 



The acidity of a liquid is dependent on the number of H ions. 



At neutral point there are no H ions and as C^ = Cj, the number 

 of Fe ions must be also zero. 



The most important result is that there are no Fe ions in a 

 neutral medium. 



Sec. IV., 1909. 9. ' 



