Abstract
Thallous salt gives precipitation and coloration with various ions and it has been used as a reagent for microscopic analysis.
This report deals with investigations on the volumetric method with thallous salt as the standard solution, especially suitable for determinations of molybdenum(VI), tungsten(VI), and vanadium(V) by amperometric or potentiometric titration.
Since thallous salts of molybdenum, vanadium, and tungsten had innegligible solubilities in water, the pH ranges for complete precipitation of these tallous salts were determined. Each determination was made on the acetone-containing solution, the precipitate was taken up in acid and the amount was determined by a liquid amalgam method.
For the amperometric titration, a dropping mercury electrode was used as an indicating electrode and a saturated calomel electrode as an opposite electrode.
Potentiometric titrations using various bimetal electrodes were tried, and it was found that platinum-lead amalgam for molybdenum and vanadium, and tungsten-lead amalgam for tungsten were most preferable giving satisfactory results.
