Henry’s law constants (IUPAC Recommendations 2021)

Henry’s law states that the abundance of a volatile solute dissolved in a liquid is proportional to its abundance in the gas phase. It applies at equilibrium and in the limit of infinite dilution of the solute. For historical reasons, numerous different definitions, names, and symbols are used in the literature to express the proportionality coefficient, denoted the “Henry’s law constant”. Here, a consistent set of recommendations is presented. An important distinction is made between two new recommended reciprocal quantities: “Henry’s law solubility constant” (H s) and “Henry’s law volatility constant” (H v). Eight recommended variants of H s and H v are described and relations among them presented.

Solubility Product of Vanadinite Pb5(VO4)3Cl at 25 °C—A Comprehensive Approach to Incongruent Dissolution Modeling

Although vanadinite (Pb5(VO4)3Cl) occurs in abundance in various terrestrial geochemical systems of natural and anthropogenic origin and is seriously considered as a potential nuclear waste sequestering agent, its actual application is severely limited by a lack of understanding of its basic thermodynamic parameters. In this regard, the greatest challenge is posed by its incongruent dissolution, which is a pivotal hurdle for effective geochemical modeling. Our paper presents an universal approach for geochemical computing of systems undergoing incongruent dissolution which, along with unique, long-term experiments on vanadinites’ stability, allowed us to determine the mineral solubility constant. The dissolution experiments were carried out at pH = 3.5 for 12 years. Vanadinite has dissolved incongruently, continuously re-precipitating into chervetite (Pb2V2O7) with the two minerals remaining in mutual equilibrium until termination of the experiments. The empirically derived solubility constant Ksp,V,298 = 10–91.89 ± 0.05 of vanadinite was determined for the first time. The proposed modeling method is versatile and can be adopted to other mineral systems undergoing incongruent dissolution.

A Review for Consistent Analysis of Hydrogen Permeability through Dense Metallic Membranes

The hydrogen permeation coefficient (ϕ) is generally used as a measure to show hydrogen permeation ability through dense metallic membranes, which is the product of the Fick’s diffusion coefficient (D) and the Sieverts’ solubility constant (K). However, the hydrogen permeability of metal membranes cannot be analyzed consistently with this conventional description. In this paper, various methods for consistent analysis of hydrogen permeability are reviewed. The derivations of the descriptions are explained in detail and four applications of the consistent descriptions of hydrogen permeability are introduced: (1) prediction of hydrogen flux under given conditions, (2) comparability of hydrogen permeability, (3) understanding of the anomalous temperature dependence of hydrogen permeability of Pd-Ag alloy membrane, and (4) design of alloy composition of non-Pd-based alloy membranes to satisfy both high hydrogen permeability together with strong resistance to hydrogen embrittlement.

Synthesis and characterization of cadmium chlorapatite Cd5(PO4)3Cl

One of the most effective methods for the immobilization of toxic metals involves the use of minerals from the apatite supergroup. The formation of cadmium chlorapatite may lead to successful entrapping of cadmium; thus, it is important to examine the solubility constant to determine the stability of cadmium in the the apatite structure. Cadmium chlorapatite was synthetized and characterized by X-ray diffraction, infrared spectroscopy, Raman spectroscopy, and scanning electron microscopy. The solubility constant (log) Ksp of cadmium chlorapatite was -65.58. The Gibbs free energy of formation of cadmium chlorapatite reached -3950.48 kJ mol−1. The solubility constant turned out to be low but was enough for cadmium chlorapatiteto be considered a very stable compound..