Electrolytic Separation and Volumetric, Absorptiometric, and Coulometric Estimation of Thallium

Abstract

Thallium may be quantitatively separated on the anode from an ammoniacal solution containing silver ion as a cathodic depolarizer. The mean of 41 determinations gives 116.4 as equivalent weight of the oxide, with a standard deviation of 0.35. Under certain conditions the deposit of silver on the cathode is a precise measure of the thallium.Thallium(III) may be precisely estimated by back-titrating the solution of thallium at pH 3.5 with thorium nitrate and excess EDTA. Thallium(I) may be measured by a spectrophotometric titration at 222 µ with standard EDTA. Thallium-(III) may be estimated absorptiometrically from measurements on the chloroform extracts of thallium dibenzyldithiocarbamate at 430 µ. Thallium(I) may be estimated with an accuracy within 0.3% by direct coulometric oxidation at the anode in an acid solution. EXPERIMENTSwere carried out to determine the best conditions for the electrogravimetric separation of thallium from solution and for its volumetric, absorptiometric, and coulometric estimation. ELECTROGRAVIMETRIC SEPARATION OF THALLIUM

Coulometric Determination of Uranium(IV) by Oxidation at Controlled Potentials

“…The method of controlled-potential coulometric analysis has been applied to the oxidation of iron(II) (9), arsenic (III) (9,10), thallium(I) (3), and plutonium(III) (12) with 100% current efficiency at a platinum anode. With oxidations which involve reversible electrode couples, the potential of the working electrode determines the ratio of the amounts of oxidized and reduced forms that can exist in contact with the electrode, and current is forced to flow until such a ratio is reached.…”

Electroanalysis and Coulometric Analysis

“…According to Foley and Pottle (41) thallium may be quantitatively deposited as thallic oxide on a platinum anode at +0.7 volt vs. N.H.E. from a solution of the thallous sample in ammonia buffer at pH 9.5 containing silver ion as a cathode depolarizer.…”