Constant ionic strength buffers with added electrolyte

2 Constant ionic strength buffers with added electrolyte. 

Calculations are essentially similar for constant ionic strength buffers, initially of ionic strength /, to which an indifferent electrolyte such as NaCl is added to change the ionic strength to /. The value of pATa is obtained from Equations 5.2 or 5.3 by inserting the value of /, and Equations 5.6, 5.7, 5.8 remain as before, with 1 = 1 — [NaCl]. 

A more common situation is one in which the sum of the concentrations of HA and A remains constant and an electrolyte is added in varying amount so as to maintain I at some specified value such as 0.1 or 0.15. As before, pAa is calculated from pAa and the total ionic strength, and hence the value of x can be obtained at the given pH. Then if c is the total concentration of HA - 1) - + A  

Buffer tables are frequently expressed as the titration of the acidic buffer species with alkali, or of the basic buffer species with strong acid, followed by the addition of an 

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