Deniges’ modification

The only difficulty in obtaining a sharp end point lies in the fact that silver cyanide, precipitated by local excess concentration of silver ion somewhat prior to the equivalence point, is very slow to re-dissolve and the titration is time-consuming. In the Deniges modification, iodide ion (usually as KI, ca 0.01 M) is used as the indicator and aqueous ammonia (ca 0.2M) is introduced to dissolve the silver cyanide. 

The essential difference between Liebig s and Deniges methods lies in the fact that the constants that govern the phenomena occurring in Deniges modification exhibit values different from those found in Liebig s titration since silver ions stand as ammine complexes, above all as the diamminesilver(I) complex. 

Spindler O (1905) New modification of the reaction of Denige s. Proof of tartaric acid in citric acid. Chem Ztg 28 15-13... 

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