Water Activity Data Research Articles

New thermodynamic data for KNO3-sucrose-water ternary system: Water activity, osmotic coefficient, activity coefficient, excess Gibbs energy, solubility and transfer Gibbs energy at 298.15 K

On the basis of the measurement of relative humidity, the hygrometric method is used to determine the new thermodynamic data of water activity and osmotic coefficient of water-sucrose-potassium nitrate system in the wide range of KNO3 molality, varying from 0.10 to 3.00 mol kg−1 and for various contents of sucrose (0.10, 0.30, 0.5, 1.00, 2.00, 4.00, and 6.00 mol kg−1). The experimental results are compared with the predictions of the extended composed additivity (ECA) rule, the Lin et al. equation, and Lietzke and Stoughton (LS II) models. The Pitzer-Simonson-Clegg model is employed to correlate these data and calculate the other thermodynamic properties such as, the stoichiometric ionic mean activity coefficient of KNO3, the excess Gibbs energy, the solubility in aqueous solution of the studied system and the transfer Gibbs energy of KNO3 from water (W) to sucrose-water (W + S) mixtures. The different interactions that occur in the ternary solution between water, sucrose and KNO3 are discussed.

Experimental studies and thermodynamic modeling on vapor-liquid equilibrium of aqueous solutions containing 1-butyl-1-methylpyrrolidinium trifluoromethanesulfonate ionic liquid, (d+)-Galactose, (d-)-Fructose, (d+)-Lactose and sucrose at 298.15 K

Vapor-liquid equilibrium for aqueous solutions of 1-butyl-1-methylpyrrolidinium trifluoromethanesulfonate ([bmpl][otf]) + (d+)-galactose, [bmpl][otf] + (d-)-fructose, [bmpl][otf] + (d+)-lactose and [bmpl][otf] + sucrose was investigates at 298.15 K. For this purpose, water activity in these systems was measured using an improved isopiestic method at T = 298.15 K. Osmotic coefficient of ionic liquid and vapor pressure of solutions were calculated from measured water activity data. NRTL, NRF-NRTL, mNRTL, Wilson and TNRF-mNRTL local composition based models were used to correlate the water activity data for binary and ternary aqueous solutions containing ionic liquid and saccharides considered in this work. All of these models predicted satisfactorily water activity data for the systems investigated. Water activity data and vapor pressure decreasing were utilized to highlight the solute-solvent interactions.

Water activity, density, sound velocity, refractive index and viscosity of the {(NH4)6Mo7O24 + poly(ethylene glycol) + H2O} system in the temperature range from 313.15 to 333.15 K: Experiment and modelling

Experimental data of water activity, density, sound velocity, refractive index and viscosity of unsaturated solutions of {ammonium heptamolybdate + poly(ethylene glycol) + water} at (313.15, 323.15 and 333.15) K were obtained. The concentration range of the solutions was from 0 to 0.4 mass fraction of poly(ethylene glycol) with an average molar mass of 4000 g·mol−1 and from 0 to 0.17 mass fraction of (NH4)6Mo7O24. Additionally, water activities and physical properties of the constituent binary systems, {(NH4)6Mo7O24 + H2O and PEG 4000 + H2O}, were measured and modeled at the same temperatures of the ternary system. The modified Pitzer model for the representation of water activity was applied and the physical properties were correlated by the Othmer’s rule. Good agreement between the experimental and correlated data was obtained.

Effect of diphenhydramine-hydrochloride, guaifenesin and naproxen sodium drugs on water activity in aqueous solutions of 1-butyl-1-methylpyrrolidinium trifluoromethanesulfonate ionic liquid at 298.15 K

Water activities for the binary aqueous solution of ionic liquid of 1-butyl-1-methylpyrrolidinium trifluoromethanesulfonate ([BMP][TfO]), and also three ternary aqueous solutions containing ionic liquid of [BMP][TfO] and drugs of diphenhydramine-hydrochloride, guaifenesin and naproxen sodium were measured using an improved isopiestic method to study the medicines effect on water activity of ionic liquid aqueous solution at T = 298.15 K. Vapor pressure values were calculated from the water activity data measured in this work. NRTL, NRF-NRTL, mNRTL, Wilson and TNRF-mNRTL local composition based models were applied for correlating the water activity data for binary and ternary aqueous solutions containing ionic liquid and drugs considered in this work. All of these models satisfactorily predicted the water activity data for the systems investigated. Water activity data and vapor pressure decreasing were utilized to highlight the solute-solvent interactions.

Measurement and modelling of water activity, density and viscosity of the KClO4 + poly(ethylene glycol) + H2O system at various temperatures

The water activities of unsaturated solutions of potassium perchlorate + poly(ethylene glycol) + water at 298.15, 308.15 and 318.15 K and densities and viscosities at 288.15, 298.15 and 308.15 K were measured experimentally. The concentration range of the solutions was from 0.2 to 0.8 mass % of poly(ethylene glycol) with an average molecular weight of 4000 and from 0.25 to 1.25 mass % of KClO4. The water activity data show that in the PEG–salt–water system, KClO4 has a significant effect on the water activities and the vapour pressures; a slight increase in water activities with increasing temperature was also observed. Density and viscosity decrease as temperature increases and both properties increase as KClO4 and PEG-4000 concentrations increase. The electrolyte and polymer non-random two liquid models, extended for the representation of water activity, excess molar volume and dynamic viscosity, were applied. Good agreement between the experimental and correlated data was obtained, since for the ternary system, the average absolute deviations calculated at all temperatures studied for the water activity, density and viscosity were 0.0067, 0.72 and 2.91%, respectively.

Vapor–Liquid Equilibria Study of the Aqueous Systems Containing {Choline Chloride + Glucose or Urea} and Their Deep Eutectic Solvents at 298.15 K and 85 kPa

In this work, to study the vapor–liquid equilibria (VLE) for the aqueous systems containing {choline chloride + glucose} and {choline chloride + urea} at 298.15 K and atmospheric pressure, water activity was measured using the improved isopiestic method. The obtained water activity lines showed that these systems have negative deviation from the semi-ideal solution, and therefore solute–solute interactions are favorable. From the measured water activity data, osmotic coefficient values were calculated and the polynomial method is used to fit these data from which activity coefficients of urea or glucose in ternary and binary solutions were determined. The transfer Gibbs energy values calculated from these activity coefficients were negative for the transfer of urea or glucose from binary to ternary aqueous solutions containing choline chloride, indicating again favorable interaction between choline chloride and urea or glucose. In addition, a comparative isopiestic study was made on the two synthesized deep eutectic solvents (DESs) containing choline chloride + glucose or urea and corresponding mixtures with the same molar ratios, with the addition of different amounts of water to investigate the effect of dilution on the existing hydrogen bonding interactions in these DESs at 298.15 K. The measured water activity and water mass fraction values were used to study the weakening of these interactions by dilution, and it was found that the H-bonding interaction between two components of both DESs disappears at around 75% (g/g) of water.

Relationship between Water Activity and Moisture Content in Floral Honey.

The water activity (Aw) and moisture content (MC) data of floral honey at five temperatures were determined using the Aw method and it was found that temperature significantly affected the Aw/MC data. The linear equation could be used to express the relationship between Aw and MC of honeys. The empirical regression equations between parameters and temperature were established. To evaluate the factors affecting the Aw/MC data, we used categorical tests of regression analysis to assess the effect of the correlation between Aw and MC of honey and examined the factors affecting the regression parameters. Six datasets from five countries were selected from the literature. The significance of the levels of qualitative categories was tested by t-test. The slope of the relationship between Aw and MC was affected by the state of honey (liquid and crystallized). The intercepts were significantly affected by honey type (flower or honeydew), harvesting year, geographical collection site, botanical source and other factors. The outliers in the datasets significantly affected the results. With modern regression analysis, useful information on the correlation between Aw and MC could be found. The results indicated that no universal linear equation for Aw and MC could be used. The Aw value could be used as a criterion for the honey industry; then, the MC of honey could be calculated by the specific linear equation between Aw and MC.

Water Activity and Solubility of the System MgCl2–RbCl–H2O at 323.15 K

The water activities of the MgCl2–RbCl–H2O ternary system and its sub-binary systems have been measured with the isopiestic method at 323.15 K. The measured water activities for the MgCl2–H2O and RbCl–H2O sub-binary systems agree well with the results reported in literature. The measured equal water activity lines of the MgCl2–RbCl–H2O ternary system are not straight lines, which means the mixing behavior of the solutions do not obey Zdanovskii’s rule. The solubility of the MgCl2–RbCl–H2O ternary system has been determined with the Flow-Cloud-Point method at 323.15 K, and the measured results are roughly consistent with values reported in the literature. The Pitzer model was selected to correlate the water activity and solubility data measured in this work. The predicted water activities and solubility isotherm for the MgCl2–RbCl–H2O ternary system at 323.15 K, with binary solution parameters only, both deviated from the experiment values. The ternary solution Pitzer model parameters were obtained by fitting the measured water activities in the ternary system. The water activities and solubility isotherms of the MgCl2–RbCl–H2O ternary system at 323.15 K were calculated including both binary and ternary solution parameters. The calculated water activities are consistent with the experimental values. The calculated solubility isotherms are roughly consistent with experiment values, except they deviate somewhat in the RbCl crystallization region.

Water Activity, Solubility Determination, and Model Simulation of the CaCl2–SrCl2–H2O Ternary System at 323.15 K

Water activities for the CaCl2–SrCl2–H2O ternary system and its sub-binary system were elaborately determined using an isopiestic vapor-pressure method at 323.15 K. The solubility of the titled ternary system at 323.15 K was also determined by the isothermal equilibrium method. The Pitzer–Simonson–Clegg (PSC) model was used for correlating the determined water activity and solubility data, simulating the thermodynamic properties, and predicting the solubility isotherm of the titled system. The reliability of the determined solubility results in this work was evaluated by comparing with the solubility isotherms calculated with the PSC model. The model simulation results showed that the thermodynamic properties and solubility can be predicted with binary parameters only. The experiment and simulation results showed that the equilibrium solid phase in the CaCl2–SrCl2–H2O ternary system are pure salts, and no solid solution was found at 323.15 K.

Water Activity and Freezing Points in Aqueous Solutions of Manganese Nitrate: Experimental and Modeling

The water activities of manganese nitrate solutions were measured using a humidity sensor instrument up to almost the saturation molality at 298.15 K; the thermodynamic properties of the system were described by the Pitzer model and specific interaction theory (SIT). The evaluation of the ion interaction parameters for the Pitzer model and SIT were carried out using experimental freezing points and osmotic coefficients of manganese nitrate aqueous solutions, collected from the open literature, and the water activity data measured in this work. A set of Pitzer and SIT parameters were estimated using a temperature dependency, that enables us to cover wider temperature ranges, and consequently calculate system properties to higher molalities. Both approaches represent very satisfactorily, and with similar accuracy, the experimental data and the calculated manganese nitrate molal activity coefficients are comparable to those already published for analogous systems. Additionally, the Pitzer model was also able to calculate the ice curve and the solubility branch of manganese nitrate hexahydrate up to a salt solution 6.5 mol·kg−1.

Investigation of the solute-solute and solute-solvent interactions in ternary {saccharide + ionic liquid + water} systems

The aim of this work is to investigate the salt effect resulted by addition of ionic liquids to aqueous saccharide solutions. To achieve this goal, systematic studies have been made on ternary {saccharide+ionic liquid+water} system using the available vapor-liquid equilibrium (VLE) data published recently. Vapor pressure depression, osmotic and activity coefficient data for the ionic liquids and saccharides in the binary solutions are used to investigate ionic liquid-water and saccharide–water interactions. For ternary solutions, the calculated activity coefficient of saccharides in presence of ionic liquids, transfer Gibbs energies, pair and triplet interaction parameters and salting constants are used to investigate saccharide-ionic liquid interactions. The variety of ionic liquids based on imidazolium and pyridinium have been considered. To extent the number of systems considered in this work, we have also included vapor-liquid equilibrium studies on the new systems {d-fructose+1-butyl-4-methyl pyridinium bromide+H2O} and {sucrose+1-butyl-4-methyl pyridinium bromide+H2O} from which experimental water activity data are measured. The aforementioned properties were also calculated for these new systems. In this article, the effect of stereochemistry of sugar, cation (imidazolium or pyridinium), chain length and anion of ionic liquids on vapor-liquid equilibrium behavior of these ternary systems and saccharide-ionic liquid interactions have been discussed. Generally, we found that there is a relationship between soluting-in or soluting-out behavior of ionic liquids and their hydration so that soluting-in effect is observed in ionic liquids with longer chain length and with anions having smaller values of osmotic coefficient. Soluting-out effect is observed in ionic liquids with shorter chain length and with anions having larger values of osmotic coefficient. From the VLE results we conclude that soluting-out effect of ionic liquids also depends on the hydration of saccharides and is observed in saccharides with high tendency to interact with water.

Water Activity and Solubility Measurements and Model Simulation of the CsCl–MgCl2–H2O Ternary System at 323.15 K

Water activities in the ternary system CsCl–MgCl2–H2O and its sub-binary systems at 323.15 K were elaborately measured by an isopiestic method. Moreover, the solubility of the CsCl–MgCl2–H2O system at 323.15 K was also measured by the flow-cloud-point method. A Pitzer model was used to predict the measured water activity and solubility data. The binary parameters for the CsCl–H2O system at 323.15 K were obtained by fitting the measured water activities for this binary system. The calculated water activity and solubility isotherms for the CsCl–MgCl2–H2O system at 323.15 K, with binary parameters only, deviated from the experimental values. This means that it is insufficient with binary parameters only to predict the water activity and calculate the solubility isotherms of the CsCl–MgCl2–H2O system at 323.15 K. The calculated solubility isotherms with both binary and mixing parameters, obtained by fitting the measured water activity, also deviated from experimental values. A new set of reasonable ternary pa...

Evaluation of the Spoilage Microbiota Associated with Sliced Pre-Packaged Deli-Style Ham

ObjectivesThe objective of this study was to evaluate the spoilage microbiota of various sliced, case ready deli-style hams and identify differences between their microbiological communities.Materials and MethodsHam samples were procured at local retail stores from products available on the shelf. Three brands (A, B, C) of smoked, sliced, Ham, Water Added were purchased with a brand being considered the same product and establishment number. Replication was defined as having the same sell-by date indicating a common date of production; 3 different sell-by dates for each brand created 3 replications. Multiple packages of each brand and sell-by date were purchased to allow an unopened package to be used for each sampling date and were stored at 4°C. Sampling times were determined as follows: –4, –2 (4 and 2 wk prior to sell-by, respectively), 0 (sell-by date), 2, and 4 (2 and 4 wk after the sell-by day, respectively). Water activity and salt concentration were sampled at –4 only. Objective color (CIE L*, a*, b*), pH, aerobic plate count (APC) and anaerobic plate count (AnPC) were evaluated throughout storage time. Bacterial community analysis was performed using high throughput 16S rRNA gene sequencing on the Illumina MiSeq platform. Sequences were processed using QIIME, binned into operational taxonomic units (OTUs) at 97% similarity and assigned taxonomy using the Greengenes database as reference. Water activity and salt concentration data were analyzed using R. Color, pH, and plate counts were analyzed as a 3 (brand) by 5 (storage time) factorial using R. Alpha and β diversity of bacterial communities were analyzed using QIIME and R. Alpha diversity was estimated using observed OTUs and Chao1 estimates, and β diversity was determined using a weighted UniFrac distance matrix.ResultsSalt and water activity were different between brands (P ≤ 0.007). Brand A had less salt compared to brands B and C, while brand B had a lower water activity than brands A and C. Objective color values for L* and a* were not different (P ≥ 0.182) between brands or storage times, but b* was different between brands (P < 0.001). Brand A had greater b* (yellowness) than brands B and C. There was a brand by storage time interaction for pH (P = 0.021). At wk 0, the pH of brand B was lower than any time during the study. There was a significant main effect of brand on both APC and AnPC (P < 0.001). Brand A had greater APC and AnPC when compared to brands B and C. Observed OTUs and Chao1 diversity estimates indicated there was a brand by storage time interaction for bacterial richness, where brand A wk –4 had the greatest bacterial richness followed by brand A wk 0. There was a main effect of storage time on the bacterial community structure (P < 0.001). Brand B and brand C were more similar in community structure compared to brand A.ConclusionThe lower salt concentration in brand A may affect bacterial spoilage. Furthermore, results from this study indicate that the spoilage community associated with similar types of sliced ham is dependent on brand, implying that spoilage patterns and characteristics are related to environmental bacteria composition of the initial post-lethality contamination.

Evaluation of the effect of ionic-liquids as soluting-out agents on the solubility of carbohydrates in aqueous solutions

In order to study the soluting-effect of ionic liquids on carbohydrates in aqueous solutions and to better understanding of its molecular mechanism, systematic investigations on the vapor–liquid (VLE) equilibria and solid–liquid equilibria (SLE) of ternary ionic liquid + carbohydrate + water systems were carried out at various temperatures. The ionic liquids 1-butyl-3-methylimidazolium bromide ([Bmim][Br]) and 1-butyl-3-methylimidazolium hydrogen sulfate ([Bmim][HSO4]) with different hydrophilicity and seven carbohydrates including monosaccharides (L-(+)-arabinose, D-(+)-xylose, D-(+)-glucose and D-(−)-fructose), disaccharides (maltose and sucrose), and a polyol (maltitol) were selected. The water activity data showed that the hydrophilicity of the investigated solutes obey the following order: [Bmim][HSO4] > [Bmim][Br] ≥ carbohydrates. In these systems, the more hydrophilic solutes [Bmim][Br] and [Bmim][HSO4] acted as soluting-out agent and precipitated the sugars from the aqueous solutions. The negative deviations of the constant water activity lines from the linear isopiestic relation for [Bmim][HSO4]/carbohydrate systems were somewhat larger than [Bmim][Br]/carbohydrate systems. The order of these deviations was agreement with the obtained soluting-out coefficients, ks, from the SLE experiments.

Water Activity and Phase Equilibria Measurements and Model Simulation for the KCl–SrCl2–H2O System at 323.15 K

Water activities for the ternary system of KCl–SrCl2–H2O and its sub-binary system SrCl2–H2O were elaborately measured using an isopiestic method at 323.15 K. The solubility isotherms for the KCl–SrCl2–H2O system were determined by the isothermal equilibrium method. It is found that the measured isopiestic composition lines for the KCl–SrCl2–H2O system deviated from the Zdanovskii rule, especially at a lower water activity. The Pitzer–Simonson–Clegg model was used to correlate the measured water activity and solubility data, simulate the thermodynamic properties, and predict the solubility of the ternary system. The reliability of the solubility data measured in this work was evaluated by comparing with the solubility isotherms calculated with the Pitzer–Simonson–Clegg model. The measured water activity and solubility results are of great importance for predicting the phase diagram of other multicomponent systems that related to this ternary system.

Isopiestic Measurements of Water Activities for an Arsenic Acid Aqueous Solution at 298.15 K

The water activity of the H3AsO4–H2O system is quite important for controlling arsenic in the environment and modeling the hydrometallurgical processing related to arsenic. In this work, the water activity for this binary system, from extremely low concentrations to a molality of 18 mol·kg–1 at 298.15 K was determined by isopiestic measurements. The relative isopiestic molality deviation for parallel samples in each experimental run was better than 0.2%. When these water activity data were combined with the mean ionic activity coefficient (γm,±) calculated by the Gibbs–Duhem equation, the Pitzer model parameters for arsenic acid aqueous solution were fitted. The reliability of the data and the model parameters obtained in this work were also systematically discussed.

Measuring the Pressboard Water Content of Transformers Using Cellulose Isotherms and the Frequency Components of Water Migration

The measurement of water within power transformer insulation is necessary for the unit's reliable operation. Probes can be inserted into the oil of a transformer to measure water activity, and then this water activity is used to determine the water content of transformer cellulosic insulation. The migration of water between the insulation media is driven by differences in water vapor pressure around the insulation system. Over time, this water reaches an equilibrium partition when cellulosic adsorption isotherms are used to calculate the concentration of water absorbed by the cellulose. However, the insulation of a normally operating transformer is highly unlikely to reach this state, as the migration of water between the insulation media is much slower than the rate of change of temperature caused by the varying load of the transformer. This leads to inaccuracies in analyzing water vapor pressure, which is a function of both oil water content and temperature. The frequency spectrum of the oil's water activity data was used to determine whether very slow changes in dissolved water, attributed to long diffusion time constants, could be separated by a filter from fast changes caused by temperature, leading to a better measurement technique. This filter was then used on data from three operating power transformers, which had their insulation water content measured using dielectric response. The results are discussed in this paper.

Vapor pressure osmometry determination of vapor-liquid equilibria behavior of aqueous imidazolium-based ionic liquid + amino acid systems

In this study, in order to get a better understanding about the soluting effect occurring in aqueous amino acid + IL solutions, the experimental measurements of water activity for the ternary amino acid (L-proline, glycine, alanine and L-serine) + IL (1-butyl-3-methylimidazolium chloride, [C4mim]Cl, 1-hexyl-3-methylimidazolium chloride, [C6mim]Cl, and 1-butyl-3-methyl-imidazolium trifluoromethanesulfonate, [C4mim][CF3SO3]) + water systems were taken using the vapor pressure osmometry (VPO) method at 308.15 K. From the obtained water activity data, the values of the vapor pressure, deviations from the semi-ideal behavior, and Gibbs free energy changes were calculated. Due to the unfavorable IL-amino acid interactions, all the studied ternary amino acid + IL + water systems showed negative deviations from the semi-ideal state (soluting-out effect). The soluting-out phenomena in these systems appears by aqueous biphasic systems (ABS) formation for the ternary [C4mim][CF3SO3] + amino acids + water systems and precipitation of the amino acids from the solution for the ternary [C4mim]Cl/[C6mim]Cl + amino acids + water systems. The influences of the nature of the ILs and amino acids on the soluting effects have been discussed.

Water Activity and Solubility Measurements and Pitzer Model Simulation of the MgCl2–RbCl–H2O Ternary System at 298.15 K

Water activities for the MgCl2–RbCl–H2O ternary system and its sub-binary MgCl2–H2O and RbCl–H2O systems at 298.15 K have been measured using the isopiestic method. The measured results for the binary systems agree well with literature data. The measured equal water activity lines for the MgCl2–RbCl–H2O ternary system deviate from Zdanovskii’s rule. The solubilities for the MgCl2–RbCl–H2O ternary system also have been measured using a isothermal visual first/last crystal method, and the results are consistent with one reported set of solubility data. Pitzer’s model was selected to correlate the measured water activity and solubility data and the parameters reported in the literature are re-examined by comparing the model-calculated equal water activity lines and solubilities with experimental values measured in this work. New and reasonable parameters are obtained by fitting the water activity and solubility data measured in this work and those reported in the literature. The water activities and solubilities were simulated with the new parameters and the results show that the Pitzer model can successfully represent the thermodynamic properties and be used to calculate the solubility isotherms.

A Low-Temperature Thermodynamic Model for the Na-K-Ca-Mg-Cl System Incorporating New Experimental Heat Capacities in KCl, MgCl2, and CaCl2 Solutions

Chloride salts and their solutions are common on Earth and perhaps on other solar system bodies. To better understand the effects of freezing and evaporation on mineral formation and the composition of residual brines in chloride salt systems, we developed a comprehensive Pitzer model in the Na-K-Ca-Mg-Cl system valid from 298.15 to <200 K up to saturated salt concentrations. This model improves over previous models because we include new experimental heat capacities for KCl, CaCl2, and MgCl2 solutions that have been measured using differential scanning calorimetry, as well as heat capacities of crystalline phases and enthalpies of solution from literature sources. These thermal properties constrain the temperature dependence of model activity coefficients. We also use water activity data and solubility data covering the full temperature range of equilibrium salt solubilities in binary, ternary, quaternary, and quinary systems. Importantly, our model accurately represents the thermodynamic properties of C...