1962 Volume 11 Issue 4 Pages 426-431
Micro-determination of metals by diethyldithiocarbamate-chloroform extraction with subsequent polarography was investigated. The extraction of Tl (I), Tl (III), Pb, Cd, and Bi was examined in the presence of the masking agents such as EDTA or KCN and buffering agents such as Na-tartrate, Na-citrate, Na-phosphate or glycine. The metals were extracted from the solution of pH 213, the chloroform extracts were evaporated with mineral acid to syrup or to dryness, but not to carbonization of organic substances, and the metals in the residual solution were determined polarographically after the addition of suitable supporting electrolytes.
The masking effects of EDTA on the extraction of Tl (III) and Bi were not recognized and pH range for the quantitative extraction of them were 213. On the contrary, the masking effects of EDTA on the extraction of Tl (I), Cd and Pb were obvious, while the pH range for the quantitative extraction of them were considerably restricted as follows ; Tl (I) between Cd between and Pb between 45.
By the use of EDTA solutions containing the buffering agents, the pH range for the quantitative extraction of Tl(I) and Cd, was the same as those in case of the absence of buffering agents, or varied within pH 1.5. Meanwhile the reco-veries of Pb were lowered to 5075 per cent of the amounts added, even at its optimum pH value of 4, probably owing to the multiple effects. of EDTA and Na-citrate or Na-tartrate.
