Band 2, Heft 4 1964 M. PEISACH, Reactor-Produced Carrier-Free by such solvents as TBP, MIBK etc., that are able also to extract various metal nitrates from nitric acid media, so that selectivity of extraction method described is appreciably lowered. The curves obtained by plotting the logarithms of distribution ratios of ruthenium against the nitric acid concentration (Fig. 6) have indistinct maxima in the ränge of 0.2 to O.4M-HNO3, just as has been found for the extraction by naphthols [2, 3]. Lower yields of extraction obtained from nitric acid of lower concentrations than 0.2 M are presumably connected with hydrolytic reactions of nitrosylruthenium nitrato complexes, whose products probably form less extractable complexes with the reagent.
Separation of Ruthenium from Naphthol ExtractsThe possibility of Separation of ruthenium from the naphthol extracts has also been investigated, either using the oxidation to ruthenium tetroxide or the back-extraction in the presence of hydrochloric and oxalic acid of various concentrations. The first method mentioned is highly selective for ruthenium and allows US to separate this element from any other. The most suitable procedure has been found to be the combustion of the solidified naphthol extract followed by conversion of the ruthenium dioxide obtained to tetroxide by energic oxidation in a hot acid medium (for instance using a mixture of dilute sulphuric acid (2:1) and saturated potassium permanganate Solution). The yields after heating in a boiling water bäth for 2 hours were about 60 to 75% of the theory. The backextraction of ruthenium is based on the decomposition of complexes dissolved in the naphthol phase by various acids. The Variation of the percentage of the ruthenium reextracted with the extraction time Urne Fig. 7. Percentage of reextracted ruthenium versus heating time in the presence of HCl and C2H2O2 (time in hours). The naphthol phase contained 8.6 • 10"' mgat Ru; volume of aqueous phase = 10 ml., t = 98 °C; HCl concentration: curve 1-1M;2-3M;3-5M;4-10M. C2H2O4 concentration: curve 5 -1 M (determined at 98 °C) is shown in Fig. 7. (Total amounts of ruthenium in naphthol phase were always 8.6 • 10"' mgat Ru, the volume of the aqueous phase = 10 ml.). It has also been found that the backextraction becomes more efficient with increasing acid concentration. Also better results were obtained by the use of oxalic acid than with the back-extraction in the presence of hydrochloric acid. This may probably be attributed to the formation of relatively stable oxalato complexes of ruthenium. This method seems to be less convenient for the Separation of ruthenium than the oxidation due to the fact that simultaneous back-extraction of various ions (for instance zirconium) may take place, especially in the presence of oxalic acid.