S. Siekierski

Bio: S. Siekierski is an academic researcher. The author has contributed to research in topics: Lanthanide. The author has an hindex of 1, co-authored 1 publications receiving 41 citations.

The coordination (hydration) of rare earth ions in aqueous chloride solutions from x‐ray diffraction. III. SmCl3, EuCl3, and series behavior

Abstract: The inner sphere water coordination of Sm3+ and Eu3+ in concentrated (3.23 m) aqueous chloride solutions was obtained from x‐ray diffraction measurements at 25 °C. The average water coordination is 8.8 for Sm3+ and 8.3 for Eu3+. The average RE3+–H2O distances are 2.474 A for Sm3+ and 2.450 A for Eu3+. The average RE3+⋅⋅⋅Cl− ion pair distances occur near 4.9 A. A careful examination of the x‐ray diffraction results for ten rare earth chloride solutions indicates that the inner sphere water coordination of the rare earth ions in aqueous solutions decreases from nine to eight due to the decreasing rare earth ionic radii. The ions La3+ through Nd3+ are nine coordinated, those between Nd3+ and Tb3+ are transitional between nine and eight, and those from Tb3+ to Lu3+ are eight coordinated.

Thermodynamic properties of lanthanide and actinide ions in avueous solution

Abstract: This paper reports systematics on the thermodynamic properties of lanthanides and actinides in avueous solution. It includes comparisons between the 4f and 5f series. We will limit our review to non-compleved avuo ions, mainly divalent, trivalent and tetravalent ions. Special attention is drawn to crystallographic radii since they are basic parameters in the interpretation of thermodynamic properties. A consistent set of data is presented for M2+, M3+ and M4+ ions. Effect of coordination number is discussed and estimates are given for unusual ovidation states. The structure of trivalent avuo ions is described from different evperimental lanthanide data and actinide transport number determinations. Then entropies of avuo ions are re-estimated and the problem of hydration enthalpy calculations is discussed. Finally, we compare the stability of the different ovidation states of the actinides.

Lanthanide tetrad effect observed in the Oklo and ordinary uraninites and its implication for their forming processes

Abstract: The abundances of fourteen rare earth elements (REE) were precisely determined for hydrothermal and sedimentary uraninite (UO2) ore samples, including those from the Oklo natural nuclear reactor. A lanthanide tetrad effect is recognized from the REE patterns of all uraninite samples, irrespective of their origin of occurrence and uranium contents. The REE patterns of Oklo uraninites are characterized by the shape of W-type tetrad effect, distinct from the patterns of hydrothermal uraninites with M-type effects. One uraninite ore in sandstone from the Orphan deposit, Arizona, U.S.A., shows M-type tetrad effect, indicating that the uraninite may be detrital, and not precipitated during or shortly after the deposition of the enclosing sediment. These results suggest that lanthanide tetrad effect in uraninites closely relates to conditions and processes of their formation.

Recent Advances in the Chemistry of the Less-Common Oxidation States of the Lanthanide Elements

Abstract: Publisher Summary At one time, a reviewer of the less-common oxidation states of the lanthanide elements would have defined these states as +2 and +4, and then covered all of their chemistry. A modern article with this brief could hardly be kept to a manageable size, such that further restrictions are necessary. In this review, the restrictions are of two kinds. The first restriction is concerned with species that have an oxidation state of + 2 as computed from their stoichiometry in the usual way (in this article we shall always use the term “oxidation state” in this sense). Such species can be divided into two distinct groups. In this article, one concentrates our attention on di-f and tetra-f species and make no attempt to treat tri-f dipositive species, comprehensively. In Section V, one discusses the factors that affect the distribution of dipositive species between the di-f and tri-f states. However, detailed reviews of the chemistry of compounds or ions are confined to di-f systems only.