The analytical chemistry of thorium up to 1961 has been well documented'*z. Since that time, very many methods for the determination of thorium have been reported. but little seems to have been done on the polarography of thorium. Sancho er ~1.~ have investigated the polarographic behavior of thorium in dimethyl sulfoxide media.
Superchrome Garnet Y has been used by Saylor and Castor to develop an amperometric procedure for determination of fluoride by means of its aluminum complex'. This dye has also been used in the polarographic determination of aluminum, the aluminum-Superchrome GarnetY complex being reduced5,and in an analogous determination of gallium '. Several papers have appeared describing the USC of Superchrome Garnet Y (SGY) for the determination of aluminum, gallium, and indium'l 2.
This paper describes a polarographic determination of thorium in plutonium metal based on anion exchange for preliminary sepanition of plutonium, and then reduction of the thorium-SGY complex.
EXPERIMENTAL
Apparatus
A Davis Differential Cathode Ray Polarotrace, Type A-1660 (Southern Analytical, Ltd., Camberley, England) equipped with an electrode stand and a constant-temperature water bath, was used. This instrument has a voltage sweep rate of 0.25 V see-', a sweep time of 2 set and a delay period of 5 sec. All polarographic measurements were made at 30Β°. A polarographic cell with a mercury pool anode was used throughout the investigation. A single 15-cm long capillary was used for all measurements. The nz* t* value, obtained at zero voltage in a buffer solution containing 1.86.10-3 M SGY, was 1.16. The pH values of the solutions were measured with a Sargent Model DR pH