Titration of Nitrous Acid and Nitrites

Nitrous acid and nitrites oxidize iodide ions, as can be predicted by examining the 

It must be achieved under very precise experimental conditions in order to avoid the formation of nitrogen dioxide NO2 from nitric oxide NO by reaction with the air dioxygen. Nitric acid itself is formed by the oxidation reaction of iodide ions. Nitrogen oxides, present in the medium, catalyze the oxidization of iodide ions by dioxygen and result in too great a release of iodine. 

In terms of determining nitrites by indirect iodometry, the oxidization of iodide ions by nitrous acid may be used to indicate the equivalence point of a titration reaction involving nitrous acid. This is the case with one of the general methods of analysis in the french pharmacopeia named nitritometrie. It concerns the determination of primary aromatic amines with nitrous acid. The reaction is achieved at pH = 0 

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