Titrimetric determination of iron(II), molybdenum(V), and thallium(I) with potassium chlorate using redox indicators

Abstract Accurate and convenient procedures have now been devised for the titrimetric determination of iron(II), molybdenum(V), and thallium(I) with potassium chlorate using visual indicators. These procedures are more advantageous than the procedures involving bromate. Further, chlorate is to be preferred as it is more inexpensive than bromate or iodate. Potassium chlorate is now obtainable at the purity required of a primary standard at a nominal cost. The chlorate titration procedure for iron(II) works satisfactorily even in the presence of organic materials such as oxalic acid, tartaric acid, and citric acid, so that it can be used for the determination of ferrous iron in pharmaceutical preparations or of ferric iron after reduction. It has been observed by us that oxygen of the air interferes in the titration of iron(II) in 6–7m hydrochloric acid medium using naphthol blue black or methyl orange as a redox indicator but not in the titration of iron(II) in sulphuric acid medium using ferroin as an indicator. An inert atmosphere is not necessary for the titration of molybdenum(V) and thallium(I) in hydrochloric acid medium.