Manfredi Carla, Ferri Diego, Vasca Ermanno, Caruso Tonino, Caruso Vincenzo, Fontanella Cecilia, Palladino Giuseppe, Vero Stefania
Dipartimento di Chimica, Università "Federico II", Complesso di Monte Sant'Angelo, via Cinthia, 80126 Napoli, Italy.
Ann Chim. 2005 May;95(5):313-24. doi: 10.1002/adic.200590036.
The complex formation between the dioxouranium (VI) and the oxalate ions has been investigated by measuring the potential of a glass electrode, at 25.00 degrees C, in 1 and 3 M NaClO4, at lower acidities than 10(-4.5) M, in order to favour the formation of (mixed) ternary species. The upper limits of concentration of all the analytical parameters have been imposed by the modest solubility of Na2C2O4 in the ionic media. The experimental measurements at different ionic strengths have been treated by means of the computerised least square programme LETAGROP - ETITR. Ternary complexes of general composition (p, q, r) are formed according to reaction (1), in addition to the already reported binary complexes. pUO2(2+) + qH2O + rC2O4(2-) <==> (UO2)p(OH)q(C2O4)r(2p-q-2r)(+) + qH+ (1). The stoichiometric compositions of the ternary species are (1, 1, 1), (2, 4, 2), (2, 2, 4). Their formation constants, expressed in molality, obtained in the two ionic media, are listed below. [table: see text]. For reasons discussed in the present work in the last column only the value of the constant in 1 M ionic medium is reported for the species (2, 4, 2). Additional evidence on the stoichiometric composition of the species formed is afforded by the mass-spectrometric measurements, collected in solutions of known composition.
通过在25.00摄氏度下，于1 M和3 M高氯酸钠中、在低于10⁻⁴.⁵ M的较低酸度下测量玻璃电极的电位，研究了双氧铀(VI)与草酸根离子之间的络合物形成情况，以促进（混合）三元物种的形成。所有分析参数的浓度上限均由草酸钠在离子介质中的适度溶解度决定。不同离子强度下的实验测量通过计算机化的最小二乘法程序LETAGROP - ETITR进行处理。除了已报道的二元络合物外，还根据反应(1)形成了一般组成为(p, q, r)的三元络合物。pUO₂²⁺ + qH₂O + rC₂O₄²⁻ ⇌ (UO₂)p(OH)q(C₂O₄)r(2p - q - 2r)⁺ + qH⁺ (1)。三元物种的化学计量组成分别为(1, 1, 1)、(2, 4, 2)、(2, 2, 4)。在两种离子介质中获得的、以质量摩尔浓度表示的它们的形成常数列于下表。[表格：见原文]。由于本工作中讨论的原因，在最后一列中仅报告了物种(2, 4, 2)在1 M离子介质中的常数数值。通过在已知组成的溶液中进行的质谱测量，提供了关于所形成物种化学计量组成的更多证据。
