Acid-base equilibria in ethylenediamine

Ethylenediamine (en), NH2C2H4NH2, a strongly basic substance, may be considered to represent solvents that are weakly acidic compared with water. Ethylenediamine is therefore useful as a solvent for the titration of weakly acidic substances. It is a leveling solvent for adds whose ionization constants are larger than about 10 in water thus acetic add and hydrochloric acid are leveled to about equal strength. The titrant base normally used in en is sodium ethanolamine. The autoprotolysis constant of en is 5 x 10 for the equilibrium 

Activity coefficients in en Schaap and others reviewed the application of equations of the Debye-Huckel type to solutions of electrolytes in en. The appropriate modification of the limiting law (DHLL) becomes 

On the basis of this equation a 1 1 electrolyte with a dissociation constant of 10 has an activity coefficient appreciably less than unity when the total salt concentration is in excess of about 10 M. 

Acidity in a solution of weak acid In the determination of acidity of a solution of acid HA in en. Equation (4-29) can be written to include activity coefficients of the ionic species  

With the assumption that autoprotolysis and homoconjugation are negligible, 

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