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The aim of the current study is to investigate the dissolution process of alkaline-earth metal sulfides SrS and CaS in ultrapure MilliQ water and define the size dependence of the formed particles on the amount of added salt due to the similarity of their chemical properties (e.g. a cubic crystal structure, ion radius). The pH values of SrS and CaS aqueous solutions increased when an additional amount of salt was added into these closed equilibrium systems, as the average quantity and size of the formed particles rose respectively in the measured range of 10−1500 nm. The nanoparticles (detected by Nanosight® LM10) appeared in the prepared aqueous solutions containing 0.092 ± 0.01 mM of SrS(s) (pH = 9.97 ± 0.02) and 0.097 ± 0.01 mM of CaS(s) (pH = 9.94 ± 0.02) or above the aforesaid salt amount, which was about 18 times lower concentration than our previously determined values for [SrS] = 1.671 mM and [CaS] = 1.733 mM (pH = 11.22 ± 0.04). Up to these amounts of added salt in the closed equilibrium systems of H2O–SrS and H2O–CaS, all particles had dissolved due to the better solubility of smaller ones, which is related to their larger specific surface area, and thus, to the increase in solubility. Therefore, this principle allows to calculate the value of the solubility product (KSP) for nanoscale particles in different equilibrium systems by using the nanoparticle tracking analysis (NTA) method.

This study investigates the H2O–SrS (strontium sulphide) equilibrium system at [SrS] between 0.125 and 88.064 mM (mmol·L−1) in a closed oxygen-free test system at 25 ºC (the measured system’s pH being in the range of 10.0–13.1). The distribution of ions and molecules in this system is described in a structural scheme. A proton transfer model was developed to calculate the pH, concentrations of formed ions and molecules in the system by using an iteration method. In the formation of the basic equilibrium system of H2O–SrS, the dissociation of SrS in aqueous media causes the release of the S2− ions that will accept a certain quantity of protons (∆[H+]S2–), originating from the reversible dissociation of water (∆[H+]H2O). In the final closed system of H2O–SrS, after adding larger amounts (≥10 g·L−1) of salt into MilliQ water, strontium hydroxide was formed as a precipitate. Proton transfer parameters, pH, and equilibrium concentrations of ions and molecules in the liquid phase were calculated and experimentally validated.

Biomolecular condensates are formed by liquid-liquid phase separation (LLPS) of multivalent molecules. LLPS from a single (\"homotypic\") constituent is governed by buffering: above a threshold, free monomer concentration is clamped, with all added molecules entering the condensed phase. However, both experiment and theory demonstrate that buffering fails for the concentration dependence of multicomponent (\"heterotypic\") LLPS. Using network-free stochastic modeling, we demonstrate that LLPS can be described by the solubility product constant (Ksp): the product of free monomer concentrations, accounting for the ideal stoichiometries governed by the valencies, displays a threshold above which additional monomers are funneled into large clusters; this reduces to simple buffering for homotypic systems. The Ksp regulates the composition of the dilute phase for a wide range of valencies and stoichiometries. The role of Ksp is further supported by coarse-grained spatial particle simulations. Thus, the solubility product offers a general formulation for the concentration dependence of LLPS.

This work mainly explores whether the solubility product principle has a guiding role in regulating the composition of micro-arc oxidation (MAO) coatings. The MAO process was conducted on AZ31 Mg alloy in silicate electrolyte. Varying amounts of Potassium fluoride (KF) and Ammonium fluoride (NH4F) were separately added to the basic electrolyte to regulate the OH− and F− contents in the electrolyte. The microstructure, phase composition and corrosion resistance of the MAO coatings prepared in different electrolytes were analyzed. Results showed that regardless of KF content, MgO was the main component for the MAO coatings obtained in electrolytes with KF. This was because the addition of KF not only elevated the F− concentration in the electrolyte but also enhanced the OH− concentration as a result of F− hydrolysis. Based on the solubility product constants (Ksp) of MgO and MgF2, a relatively lower concentration of Mg2+ was sufficient for the formation of MgO. Hence, Mg2+ consistently exhibited preferential reactivity with OH−, leading to the formation of MgO. The findings of the study demonstrated that the presence of KF electrolyte resulted in an enhancement of conductivity and an increase in the concentration of OH−. Conversely, the growth rate of the coating was observed to be low, and the coating-forming phases of the coating were identified as MgO and Mg2SiO4, and the coating had better corrosion resistance. NH4F electrolyte with the increase in NH4F concentration, conductivity decreases and then increases, OH− concentration decreases, the growth rate of the coating is faster, the concentration of F−/OH− is higher, the coating-forming phase is transformed into MgF2, and the corrosion resistance of the coating is reduced.

PurposeTo predict the aqueous solubility product (Ksp) and the solubility enhancement of cocrystals (CCs), using an approach based on measured drug and coformer intrinsic solubility (S0API, S0cof), combined with in silico H-bond descriptors.MethodA regression model was constructed, assuming that the concentration of the uncharged drug (API) can be nearly equated to drug intrinsic solubility (S0API) and that the concentration of the uncharged coformer can be estimated from a linear combination of the log of the coformer intrinsic solubility, S0cof, plus in silico H-bond descriptors (Abraham acidities, α, and basicities, β).ResultsThe optimal model found for n:1 CCs (−log10 form) is pKsp = 1.12 n pS0API + 1.07 pS0cof + 1.01 + 0.74 αAPI·βcof − 0.61 βAPI; r2 = 0.95, SD = 0.62, N = 38. In illustrative CC systems with unknown Ksp, predicted Ksp was used in simulation of speciation-pH profiles. The extent and pH dependence of solubility enhancement due to CC formation were examined. Suggestions to improve assay design were made.ConclusionThe predicted CC Ksp can be used to simulate pH-dependent solution characteristics of saturated systems containing CCs, with the aim of ranking the selection of coformers, and of optimizing the design of experiments.

Knowledge of the values of the thermodynamic functions of natural minerals of transition elements has important applications in the study of the processes of their formation and geochemical migration with groundwater; when developing methods to prevent corrosion of non-ferrous alloys in fresh and sea water; when immobilizing heavy metals in mine drainage and industrial waters, etc. Also, these values are in demand when calculating reactions and developing methods for producing synthetic analogs of minerals, many of which exhibit magnetic, catalytic, photochemical, and other properties. However, in scientific literature, there is a lack of detailed data on the thermodynamic properties of nickel hydroxysalts. A sample of basic nickel carbonate with the theoretical formula Ni 3 [CO 3 ](OH) 4 ·3H 2 O was obtained using the hydrothermal synthesis method. The structure of the compound was verified by X-ray diffraction and infrared spectroscopy. Experiments were carried out on sample dissolution in order to measure the solubility constant (solubility product): log 10  K SP  =  − 45.8 ± 1.8. Based on the data obtained, the thermodynamic parameters of the reaction of dissolution of the compound were determined and the main thermodynamic functions were determined: Gibbs free energy of formation Δ f G ° =  − 1554 ± 6 kJ·mol −1 ; enthalpy of formation Δ f H ° =  − 1798 ± 9 kJ·mol −1 ; standard entropy S ° = 260.6 ± 7.8 J·mol −1 ·K −1 .

Minerals from the phosphate groups are used in environmental engineering as thermodynamically stable vehicles for heavy metals such as zinc. The hopeite Zn3(PO4)2·4H2O was synthesized and characterized by X-ray diffraction and scanning electron microscopy. The solubility of the hopeite was measured at 25°C. The average solubility product, log Ksp, for the reaction Zn3(PO4)2·4H2O ⇔ 3Zn2+ + 2PO43- + 4H2O at 25°C is –35.72 ± 0.03. The free energy of formation, ΔG°f,298, calculated from this measured solubility product is –3597.4 ± 1.0 kJ mol-1. The immobilization of zinc in the hopeite structure offers the possibility of developing an effective method for removing Zn from wastewater, water and soils.

ABSTRACT Introduction: How fluoride (F-) protects dental enamel from caries is here conveyed to dental health-care providers by making simplifying approximations that accurately convey the essential principles, without obscuring them in a myriad of qualifications. Materials and Methods: We approximate that dental enamel is composed of calcium hydroxyapatite (HAP), a sparingly soluble ionic solid with the chemical formula Ca10(PO4)6(OH)2. Results: The electrostatic forces binding ionic solids together are described by Coulomb's law, which shows that attractions between opposite charges increase greatly as their separation decreases. Relatively large phosphate ions (PO43-) dominate the structure of HAP, which approximates a hexagonal close-packed structure. The smaller Ca2+ and OH- ions fit into the small spaces (interstices) between phosphates, slightly expanding the close-packed structure. F- ions are smaller than OH- ions, so substituting F- for OH- allows packing the same number of ions into a smaller volume, increasing their forces of attraction. Dental decay results from tipping the solubility equilibrium Ca10(PO4)6(OH)2 (s) ⇔ 10Ca2+ (aq) + 6PO42- (aq) + 2OH- (aq) toward dissolution. HAP dissolves when the product of its ion concentrations, [Ca2+]10×[PO43-]6×[OH-]2, falls below the solubility product constant (Ksp) for HAP. Conclusion: Because of its more compact crystal structure, the Ksp for fluorapatite (FAP) is lower than the Ksp for HAP, so its ion product, [Ca2+]10×[PO43-]6×[F-]2, must fall further before demineralization can occur. Lowering the pH of the fluid surrounding enamel greatly reduces [PO43-] (lowering the ion products of HAP and FAP equally), but [OH-] falls much more rapidly than [F-], so FAP better resists acid attack.

Critically assessed data regarding Sn(IV) dioxides and hydroxy complexes have recently been challenged. Differences as large as nine orders of magnitude occur in certain of the published solubility products and other equilibrium constants, despite supposedly being derived from the same ‘reliable’ measurements. We show how these differing conclusions depend on the assignments of uncertainty in the respective experimental observations and that the divergence is due to error propagation in identifiable thermodynamic analyses. The use of Sn 4+ as a ‘basis’/‘master’ species in thermodynamic modelling is deprecated. Automatic methods which enable the necessary calculations to be properly evaluated, as well as easily repeated, help uncover such mistakes. The results from the comprehensive NEA review are substantially confirmed.