The Uranyl: Citrate System. II. Polarographic Studies of the 1:1 Complex¹

Abstract

in the form of the complex, Cu^O^". A mechanism which leads to the rate law of equations ( 1) and ( 2) can be obtained by postulating the oxidation of copper in this complex to the tripositive state. Culx(C204)r + &08-->.CuXXI(C204)2~+ so4 -+ S04-( 10)Cu"i(C204)r ->• CuI(C204)" + 2C02 ( 12)It is postulated that the rate-determining step is reaction (12), and therefore the rate is first-order with respect to the copper catalyst and zero-order with respect to oxalate and peroxydisulfate. This accounts for the second term on the right-hand side of equation ( 2), but does not account for the first term. Although it would be convenient to ascribe the first term to the residual copper impurity of the solutions, the spectrographic analyses showed that the impurity was too small for this by a factor of five.One striking effect on the copper catalysis in this region of concentration is inhibition of the uncatalyzed reaction. The curves of Fig. 3 are very straight and show none of the autocatalytic character of the curves of Fig. 2-this despite the fact that the time for 50% reaction is about the same for the uncatalyzed reaction as for the experiment with 1 X 10-7 M CuS04. Apparently the S04-radicals are removed by reactions ( 11) and ( 15) before they can initiate the chain-reaction with reaction (5).The increase in rate obtained with a large increase in peroxydisulfate concentration can be explained as due to the simultaneous uncatalyzed reaction. This seems especially likely as the curves resemble those for the uncatalyzed reaction.The slight decrease in rate observed with an increase in oxalate concentration may be due to a competition between the reactions of the catalyzed and uncatalyzed mechanisms. A more exact explanation of this phenomenon is not readily apparent.Acknowledgments.-I am deeply indebted to Professor Don M. Yost for his aid, encouragement, and for many helpful conversations. I also wish to express my thanks to Professor William H. Cone and Professor Herbert A. Young for their interest and suggestions, and to Mr. John Voth for the spectrographic analyses.Davis, Calif.

Association of uranyl with the cell wall of Pseudomonas fluorescens inhibits metabolism

“…Numerous uranyl-citrate complexes have been proposed in the literature: a 1:1 uranyl-citrate complex (Newman et al, 1951;Rajan and Martell, 1965;Markovits et al, 1972;Nunes and Gil, 1987;Lenhart et al, 2000), a 2:1 complex (Nunes and Gil, 1987), a 2:2 complex (Newman et al, 1951;Feldman et al, 1954;Rajan and Martell, 1965;Markovits et al, 1972;Nunes and Gil, 1987;Allen et al, 1996), a 2:3 complex (Dodge and Francis, 1997), a 3:2 complex (Feldman et al, 1954) and a hexameric complex (Rajan and Martell, 1965). In our speciation calculations, we consider only the complexes for which a formation constant exists: the mononuclear (1:1) and binuclear (2:2) complexes.…”

Formation constants for the mixed-metal complexes between indium(III) and uranium(VI) with malic, citric, and tartaric acids

“…The formation and polymerization of uranyl malate, citrate, and tartrate have been investigated by several workers. [16][17][18][19][20][21] Basically, the technique used in these studies was potentiometry. The interpretation of the resultant data is, however, controversial.…”

Binding constant determination of uranyl–citrate complex by ACE using a multi‐injection method

“…With different binding stoichiometry, the method and data treatment to evaluate binding constant from the shift of electrophoretic mobilities would be different. The complexation between uranyl and citrate has been studied for more than 60 years , and various efforts have been made using different techniques and instruments, such as potentiometry , polarography , UV/Vis spectroscopy , IR and Raman spectroscopy , ion‐exchange method , nuclear magnetic resonance (NMR) , extended X–ray absorption fine–structure spectroscopy (EXAFS) , X–ray absorption spectroscopy (XAS) , etc. In and , some of the results obtained so far have been summarized and compared.…”