Titrations with extractive end-points: The dichromate titration

A method for the titration of iron(II) with K₂Cr₂O₇ in coloured solutions is reported, using the extraction of Cr₂O₇^-2 ions as (Ph₃MeAs)₂Cr₂O₇ at the end-point. The method is applicable to titration with $\text{N}\text{10}$ K₂Cr₂O₇ in the presence of normally interfering coloured cations in molar concentrations up to 50 times that of the iron (II). The method may be used to estimate iron in ferrous alloys, usually without separation from the other metals present. A stable dichromate, (Ph₃MeAs)₂Cr₂O₇ has been isolated.