ABSTRACT Saturated salt solutions produce environments with specific relative humidities used in several applications, such as determining water sorption isotherms of foods. However, the preparation of saturated solutions requires knowledge of solubility data. Thus, the objective of this work was to determine the solubility of 14 salts: lithium bromide (LiBr), lithium chloride (LiCl), lithium iodide (LiI), magnesium chloride (MgCl2), sodium iodide (NaI), potassium carbonate (K2CO3), magnesium nitrate (Mg(NO3)2), sodium bromide (NaBr), potassium iodide (KI), sodium chloride (NaCl), ammonium sulfate ((NH4)2SO4), potassium chloride (KCl), potassium nitrate (KNO3), and potassium sulfate (K2SO4) in the temperature range of 275.15 to 363.15 K at 101.3 kPa. The apparatus for the solubility determination consists of a jacketed glass cell and a magnetic stirrer. Furthermore, polynomial and exponential empirical models were fitted to the observed data to determine salt solubilities. Salt solubilities ranged from 7.39 to 80.41 g of salt·(100 g of solution)-1. Sodium iodide (NaI) presented the highest (p<0.05) solubility, up to 343.15 K, and lithium iodide (LiI) up to 363.15 K. The specific equilibrium moistures afforded by saturated saline solutions were associated with water activity data. A general mathematical model to determine the solubility of different salts was not obtained because the dissolution behaviors of each salt are distinct. However, the availability of solubility data of saline solutions covering a wide range of temperatures is helpful since the salts have different behavior.

Issues regarding deficiencies of the database, types and uncertainties of experimental data, and limitations of the model, are discussed. The challenging parameter optimization problem is solved with a novel combination of powerful global minimization algorithms. A number of exemplary calculations for systems containing atmospherically relevant aerosol components are shown. Amongst others, we discuss aqueous mixtures of ammonium sulfate with dicarboxylic acids and with levoglucosan. Overall, the new parameterization of AIOMFAC agrees well with a large number of experimental datasets. However, due to various reasons, for certain mixtures important deviations can occur. The new parameterization makes AIOMFAC a versatile thermodynamic tool. It enables the calculation of activity coefficients of thousands of different organic compounds in organic-inorganic mixtures of numerous components. Models based on AIOMFAC can be used to compute deliquescence relative humidities, liquid-liquid phase separations, and gas-particle partitioning of multicomponent mixtures of relevance for atmospheric chemistry or in other scientific fields. Published in Atmospheric Chemistry and Physics

Accelerated salt-induced deterioration occurs by frequent changes across the equilibrium relative humidity (RHeq). Therefore, knowledge of the actual RHeq of a salt mixture has a major impact on preventive conservation to ensure that the relative humidity (RH) does not cause a salt-phase transition. In addition, knowledge of the RHeq is essential in relation to in situ desalination as the dissolution of salt is an essential criterion to enable transport of salt (ions) in materials. For decades, it has been possible to determine the RHeq in salt mixtures with thermodynamic-based ECOS-Runsalt software. However, the ECOS-Runsalt model is challenged by the influence of kinetics along with some limitations in regard to possible ion types and combinations. A dynamic vapor sorption (DVS) instrument is used for the direct measurement of RHeq and to deduce knowledge on the physicochemical nonequilibrium process related to the phase changes in salt mixtures. The experimentally measured RHeq values in this study of NaCl-Na2SO4-NaNO3, NaNO3-Na2SO4, NaCl-NaNO3, NaCl-Na2SO4, and (NH4)2SO4-Na2SO4 are in agreement with values from the literature. A comparison with thermodynamically calculated results makes it probable that the phase transition for some salts is significantly influenced by nonequilibrium conditions. The present work bridges some of the existing gaps in regard to improving the accuracy of ECOS-Runsalt, including the effects of kinetics and the possible ions and combinations th

Abstract Inorganic species such as ammonium sulfate (AS) and ammonium nitrate (AN), which significantly affect air quality, visibility degradation, and climate change, occupy 20–50% among ambient fine aerosol mass. In the present study, laboratory generated, micrometer sized, pure AS, AN, and AS-AN mixture aerosol particles at 9 mixing ratios (mole fraction of AS, X AS =0.02, 0.035, 0.1, 0.15, 0.2, 0.28, 0.5, 0.6, and 0.8) were examined systematically to observe their hygroscopic behavior, to derive experimental phase diagrams for efflorescence and deliquescence, and to obtain chemical micro-structures using in-situ Raman microspectrometry (RMS). All the nebulized AS-AN mixture particles experienced only one-stage efflorescence at 15–40% relative humidity (RH) during dehydration process, revealing that all the compounds in the particles crystallized nearly simultaneously. Nebulized AS-AN mixture particles of eutonic composition ( X AS =0.035) showed singlestage transition at a mutual deliquescence relative humidity (MDRH) of 63.6%, whereas the others exhibited two-stage deliquescence transitions during humidification process, i.e., the eutonic component dissolved at MDRH, and the remainder in the solid phase dissolved completely at their DRHs, resulting in a phase diagram composed of four different phases, as predicted thermodynamically. The measured MDRH and second DRHs of mixture particles with mixing ratios of 0.035< X AS <0.33 are either higher or lower than the theoretic