Determination of phenylmercuric nitrate by potentiometric titration

A procedure was developed for measuring small amounts of phenylmercuric nitrate in aqueous solutions. The method depends on the formation of insoluble phenylmercuric iodide upon titration of phenylmercuric nitrate with potassium iodide. The end-point can be detected using an iodide-sensitive electrode. The method is able to measure down to 0.000125% aqueous solution of phenylmercuric nitrate with a 1% accuracy. Procedural details and dexcriptions of excipient effects on the assay are presented. Naphazoline hydrochloride, phenylephrine hydrochloride, fluroescein sodium, and antipyrine interfered with the method, while the common buffer systems, polyvinyl alcohol, sodium thiosulfate, edetate sodium, and chloramphenicol had no effect.