Determination of Metallic Salts at Their Maximum

Metallic salts at their maximum may be determined by indirect iodometry. 

Cupric ions oxidize iodide ions according to the equation 

As the examination of this equation shows, this is not a simple redox reaction. There is also a precipitation reaction together with the redox one. Half of the iodide ions added are indeed oxidized into iodine, while the other half remains at state-I. The part that the latter plays is to precipitate Cu +1 as cuprous iodide. Cu +1 is formed by the redox reaction between Cu + and I  

The precipitation of cuprous as cuprous iodide permits its stabilization (see Fig. 15.14 of Chap. 15). The cuprous ions that are not precipitated (or complexed) do not exist in aqueous solution. They disproportionate according to 

Moreover, the precipitation makes the redox reaction possible from a thermodynamic standpoint. Indeed, the simple consideration of the standard potentials of both 

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