Water Activity In Solutions Research Articles

Produção, caracterização e propriedades tecnológicas de um biopolímero produzido por Agrobacterium radiobacter k84

In this study, a biopolymer composed of carbohydrates (35%), protein (15%) and minerals (40%) was obtained through fermentation using sugar cane molasses as the sole carbon source for Agrobacterium radiobacter k84. The process yield was 10 gL-1 of biopolymer, which showed high solubility in water, neutral pH in aqueous solution and low water activity (0.52). The analysis in Scanning Electron Microscopy revealed microstructure characteristic of an amorphous solid, with particles of irregular shapes and sizes. In the evaluation of technological properties, the biopolymer showed formation of viscous solutions at room temperature from concentration of 0.5% in aqueous solution, gelling activity in solution at 2%, emulsifying (56.11±1.39%) and stabilizing activity (98.02±0.78%). The results suggest that the biopolymer from Agrobacterium radiobacter k84 is a promising candidate for industrial use.

Joint effect of organic acids and inorganic salts on cloud droplet activation

Abstract. We have investigated CCN properties of internally mixed particles composed of one organic acid (oxalic acid dihydrate, succinic acid, adipic acid, citric acid, cis-pinonic acid, or Nordic reference fulvic acid) and one inorganic salt (sodium chloride or ammonium sulphate). Surface tension and water activity of aqueous model solutions with concentrations relevant for CCN activation were measured using a tensiometer and osmometry, respectively. The measurements were used to calculate Köhler curves and critical supersaturations, which were compared to measured critical supersaturations of particles with the same chemical compositions, determined with a cloud condensation nucleus counter. Surfactant surface partitioning was not accounted for. For the aqueous solutions containing cis-pinonic acid and fulvic acid, a depression of surface tension was observed, but for the remaining solutions the effect on surface tension was negligible at concentrations relevant for cloud droplet activation. The surface tension depression of aqueous solutions containing both organic acid and inorganic salt was approximately the same as or smaller than that of aqueous solutions containing the same mass of the corresponding pure organic acids. Water activity was found to be highly dependent on the type and amount of inorganic salt. Sodium chloride was able to decrease water activity more than ammonium sulphate and both inorganic salts are predicted to have a smaller Raoult term than the studied organic acids. Increasing the mass ratio of the inorganic salt led to a decrease in water activity. Water activity measurements were compared to results from the E-AIM model and values estimated from both constant and variable van't Hoff factors. The correspondence between measurements and estimates was overall good, except for highly concentrated solutions. Critical supersaturations calculated with Köhler theory based on measured water activity and surface tension, but not accounting for surface partitioning, compared well with measurements, except for the solutions containing sodium chloride and oxalic acid or one of the more surface active organic compounds. In such cases, significantly lower values were obtained from Köhler theory than the measured critical supersaturations with deviations above 50% for a 60 nm particle containing 50% (dry mass) of Nordic reference fulvic acid, suggesting that surfactant partitioning and/or an effect of sodium chloride on solubility of the organic component is important.

Decomposition reactions of magnesium sulfate hydrates and phase equilibria in the MgSO 4–H 2O and Na +–Mg 2+–Cl −–SO 42−–H 2O systems with implications for Mars

We report new measurements of equilibrium relative humidities for stable and metastable hydration–dehydration equilibria involving several magnesium sulfates in the MgSO 4· nH 2O series. We also report a comprehensive thermodynamic treatment of the system including solution properties and experimental data from the published literature, i.e. solubilities, heat capacities and additional decomposition humidities. While for some magnesium sulfate hydrates solubility data in the binary system MgSO 4–H 2O are sparse, there is a reasonable database of solubility measurements of these hydrates in the ternary MgCl 2–MgSO 4–H 2O and the quaternary reciprocal Na +–Mg 2+–Cl − –SO 4 2 − –H 2O systems. To make these data suitable for the determination of solubility products, we parameterized a Pitzer ion interaction model for the calculation of activity coefficients and water activities in mixed solutions of these systems and report the ion interaction parameters for the Na +–Mg 2+–Cl − –SO 4 2 − –H 2O system. The model predicted solubilities in the reciprocal system are in very good agreement with experimental data. Using all available experimental data and the solution model an updated phase diagram of the MgSO 4–H 2O system covering the whole temperature range from about 170 to 473 K is established. This treatment includes MgSO 4·H 2O (kieserite), MgSO 4·4H 2O (starkeyite), MgSO 4·5H 2O (pentahydrite), MgSO 4·6H 2O (hexahydrite), MgSO 4·7H 2O (epsomite) and MgSO 4·11H 2O (meridianiite). It is shown that only kieserite, hexahydrite, epsomite and meridianiite show fields of stable existence while starkeyite and pentahydrite are always metastable. Due to sluggish kinetics of kieserite formation, however, there is a rather extended field of metastable existence of starkeyite which makes this solid a major product in dehydration reactions. The model predicted behavior of the magnesium sulfates is in excellent agreement with observations reported in the literature under terrestrial temperature and relative humidity conditions. We also discuss the implications of the new phase diagram for sulfates on Mars.

10.2478/s11814-009-0286-4

In this work an equation of state applicable to the system containing electrolytes has been developed by coupling the perturbed chain statistical associating fluid theory (PC-SAFT) with the primitive mean spherical approximation. The resulting electrolyte equation of state is characterized by 4 ion parameters for each of the cation and anion contained in aqueous solutions, and 4 ion specific parameters for each of six cations (Li+, Na+, K+, Rb+, Mg2+ and Ca2+) and six anions (Cl−, Br−, I−, HCO 3 − , NO 3 − and SO 4 2− ) were estimated, based upon the individual ion approach, from the fitting of experimental densities and mean ionic activity coefficients of 26 aqueous single-salt solutions at 298.15 K and 1 bar. The present equation of state with the estimated individual ion parameters has been found to satisfactorily describe not only the densities and mean ionic activity coefficients, but also osmotic coefficients and water activities of single-salt aqueous solutions. Furthermore, the present model was extended to two-salt aqueous solutions, and it has been found that thermodynamic properties such as mentioned above, of two-salt solutions, can be well predicted with the present model, without any additional adjustable parameters.

Vapor−Liquid Equilibria, Density, and Speed of Sound of Aqueous Solutions of Sodium Dihydrogen Citrate or Disodium Hydrogen Citrate

Vapor−liquid equilibrium data (water activity, vapor pressure, osmotic coefficient, and activity coefficient) of binary aqueous sodium dihydrogen citrate or disodium hydrogen citrate solutions were obtained through the isopiestic method at T = 298.15 K. Density and speed of sound measurements were carried out on the aqueous solutions of the mentioned electrolytes at T = (288.15 to 308.15) K at atmospheric pressure. From the experimental density and speed of sound data, the apparent molar volume and isentropic compressibility values were evaluated and fitted to the Pitzer equation from which the apparent molar volume and apparent molar isentropic compressibility of the solutions at infinite dilution were calculated at each temperature within the above-mentioned range.

Ammonium in aqueous fluids to 600 °C, 1.3 GPa: A spectroscopic study on the effects on fluid properties, silica solubility, and K-feldspar to muscovite reactions

The behavior of ammonium, NH 4 +, in aqueous systems was studied based on Raman spectroscopic experiments to 600 °C and about 1.3 GPa. Spectra obtained at ambient conditions revealed a strong reduction of the dynamic three-dimensional network of water with addition of ammonium chloride, particularly at small solute concentrations. The differential scattering cross section of the ν 1-NH 4 + Raman band in these solutions was found to be similar to that of salammoniac. The Raman band of silica monomers at ∼780 cm −1 was present in all spectra of the fluid at high temperatures in hydrothermal diamond-anvil cell experiments with H 2O ± NH 4Cl and quartz or the assemblage quartz + kyanite + K-feldspar ± muscovite/tobelite. However, these spectra indicated that dissolved silica is less polymerized in ammonium chloride solutions than in comparable experiments with water. Quantification based on the normalized integrated intensity of the H 4SiO 4 0 band showed that the silica solubility in experiments with H 2O + NH 4Cl was significantly lower than that in equimolal NaCl solutions. This suggests that ammonium causes a stronger decrease in the activity of water in chloridic solutions than sodium. The Raman spectra of the fluid also showed that a significant fraction of ammonium was converted to ammonia, NH 3, in all experiments at temperatures above 300 °C. This indicates a shift towards acidic conditions for experiments without a buffering mineral assemblage. The estimated pH of the fluid was ∼2 at 600 °C, 0.26 GPa, 6.6 m initial NH 4Cl, based on the ratio of the integrated ν 1-NH 3 and ν 1-NH 4 + intensities and the HCl 0 dissociation constant. The NH 3/NH 4 + ratio increased with temperature and decreased with pressure. This implies that more ammonium should be retained in K-bearing minerals coexisting with chloridic fluids upon high- P low- T metamorphism. At 500 °C, 0.73 GPa, ammonium partitions preferentially into the fluid, as constrained from infrared spectroscopy on the muscovite and from mass balance. The conversion of K-feldspar to muscovite proceeded much faster in experiments with NH 4Cl solutions than in comparable experiments with water. This is interpreted as being caused by enhancement of the rate-limiting alumina solubility, suggesting complexation of Al with NH 4. Nucleation and growth of mica at the expense of K-feldspar and NH 4 +/K + exchange between fluid and K-feldspar occurred simultaneously, but incorporation of NH 4 + into K-feldspar was distinctly faster than K-feldspar consumption.

Transformation Pathways of Cocrystal Hydrates When Coformer Modulates Water Activity

An important attribute of cocrystals is that their properties can be tailored to meet required solubility and stability specifications. But before such practical uses can be realized, a better understanding of the factors that dictate co-crystal behavior is needed. This study attempts to explain the phase behavior of anhydrous/hydrated cocrystals when the coformer modulates both water activity and co-crystal solubility. Stability dependence on solution composition and water activity was studied for theophylline-citric acid (THP-CTA) anhydrous and hydrated cocrystals by both suspension and vapor equilibration methods. Eutectic points and associated water activities were measured by suspension equilibration methods to determine stability regions and phase diagrams. The critical water activity for the anhydrous-hydrate co-crystal was found to be 0.8. It is shown that (a) both water and coformer activities determine phase stability, and (b) excipients that alter water activity can profoundly affect the hydrate/anhydrous eutectic points and phase stability. Vapor phase stability studies demonstrate that cocrystals of highly water soluble coformers, such as citric acid, are predisposed to conversions due to moisture uptake and deliquescence of the coformer. The presence of such coformers as trace level impurities with co-crystal will alter hygroscopic behavior and stability.

Water and Mean Ionic Activities of Aqueous HNO3 Solutions Calculated from an Extension of the Brunauer-Emmett-Teller (BET) Model

The objective for this research was to employ the extended adsorption isotherm (EAI) to develop a predictive relationship between the activity of H2O (aw) and the mean ionic activity (a±) of aqueous HNO3. The EAI model is a calculative approach to the estimation of solutions for activities of highly non-ideal chemical systems and is the collective efforts of Stokes and Robinson, Abraham, and Ally and Braunstein. From previous works of the HNO3-H2O system by Rains et al., a predictive model of relevant aqueous phase activities was developed that only needs knowledge of composition and temperature of the HNO3 solution.

Experimental Measurement and Thermodynamic Modeling of the Mixed CH4 + C3H8 Clathrate Hydrate Equilibria in Silica Gel Pores: Effects of Pore Size and Salinity

We measured hydrate phase equilibria for the ternary CH(4) (90%) + C(3)H(8) (10%) + water mixtures in silica gel pores with nominal diameters of 6.0, 15.0, 30.0, and 100.0 nm and for the quaternary CH(4) (90%) + C(3)H(8) (10%) + NaCl + water mixtures of two different NaCl concentrations (3 and 10 wt %) in silica gel pores with nominal diameters of 6.0, 15.0, and 30.0 nm. The CH(4) (90%) + C(3)H(8) (10%) hydrate-water interfacial tension (sigma(HW)) of 42 +/- 3 mJ/m(2) was obtained through the Gibbs-Thomson equation for dissociation within cylindrical pores. With this value, the experimental results were in good agreement with the calculated ones based on the van der Waals and Platteeuw model. A correction term for the capillary effect and a Pitzer model for electrolyte solutions were adopted to calculate the activity of water in the aqueous electrolyte solutions within silica gel pores. At a specified temperature, three-phase H-L(W)-V equilibrium curves of pore hydrates were shifted to higher-pressure regions depending on pore sizes and NaCl concentrations. From the cage-dependent (13)C NMR chemical shifts of enclathrated guest molecules, the mixed CH(4) (90%) + C(3)H(8) (10%) gas hydrate was confirmed to be structure II.

Water activity of aqueous solutions of ethylene oxide-propylene oxide block copolymers and maltodextrins

Abstract - The water activity of aqueous solutions of EO-PO block copolymers of six different molar masses and EO/PO ratios and of maltodextrins of three different molar masses was determined at 298.15 K. The results showed that these aqueous solutions present a negative deviation from Raoult's law. The Flory-Huggins and UNIFAC excess Gibbs energy models were employed to model the experimental data. While a good agreement was obtained with the Flory-Huggins equation, discrepancies were observed when predicting the experimental behavior with the UNIFAC model. The water activities of ternary systems formed by a synthetic polymer, maltodextrin and water were also measured and used to test the predictive capability of both models. Keywords : Water activity; Excess Gibbs energy; Phase equilibrium; Flory-Huggins; UNIFAC. INTRODUCTION The water activity (a w ) of an aqueous solution is the ratio between the fugacity of water in this solution and the fugacity of pure liquid water at the same temperature and pressure. This property is the most directly accessible measure of liquid-phase non-ideality of aqueous solutions of non-volatile solutes, since there are either well documented techniques or electronic devices to accomplish it. Besides its scientific importance, water activity is also related to the stability of foodstuffs, for it represents the amount of water available to microbial or chemical spoilage. In other words, high a

Observations of ice nucleation by ambient aerosol in the homogeneous freezing regime

We measured the freezing activation curves for ambient particles as a function of relative humidity with respect to water over the temperature range of −40° to −50°C using a continuous flow diffusion chamber, and compared the observations with those for ammonium sulfate particles and predictions from a parametric representation of homogeneous freezing of solution particles as a function of water activity and temperature. Since it has been proposed that the rate of homogeneous freezing depends on solution water activity, we made separate measurements of the hygroscopicity (κ) of the ambient aerosol. Observed κ ranged from 0.1 to 0.2, lower than that of ammonium sulfate (0.6) and representative of a continental aerosol. As predicted for this difference in κ, there was no significant difference between the homogeneous freezing conditions of size‐selected ammonium sulfate and the apparent homogeneous freezing conditions of same‐sized ambient aerosol. Further, the parameterization predicted freezing fraction‐relative humidity relationships for non size‐selected ambient aerosol that differed by only 0.5 to 1.5% relative humidity from observed relations at the tested temperatures, well within experimental uncertainty. Our findings confirm that the tested ambient aerosols, with hygroscopicities typical of continental regions, freeze homogeneously as expected based on present understanding for single component solution drops in the laboratory. Results also confirm that freezing is more sensitive to particle size than to composition, for particles containing at least a few percent by volume of hygroscopic species.

Verification of accuracy of standard thermodynamic data of inorganic electrolytes

Accuracy of standard thermodynamic data for some inorganic electrolytes of the types 1-1, 1-2 and 2-1 at 25 °C, in the solid state or aqueous standard solutions, presented in NBS Tables (1982), has been checked. For the purpose, the condition for the pure solid–saturated solution equilibrium and reliable values of solubilities, mean activity coefficients and water activity in saturated solution at the given temperature were used. In most cases, a very good reliability and consistency of all relevant data have been found. On the other hand, some discrepancies have been observed for NaNO3, NaClO4/NaClO4 pair, Na2HPO4·12H2O/Na2HPO4 pair, K2CrO4, K2Cr2O7, (NH4)2SO4 and SrCl2·6H2O/SrCl2 pair the reason of which is not yet known. The verification method can be used for the determination of lacking thermodynamic data. The method has been applied to ΔGşf,cr of NaCNS·2H2O, NaH2PO4·2H2O, Na2CrO4·6H2O, Na2WO4·2H2O, MgI2·8H2O and CaCl2·6H2O at 25 °C. A suitable method has been used for the determination of the most probable solubility in the case when the values scatter. The used methods are applicable to all types of electrolytes and nonelectrolytes.

Modeling of aqueous electrolyte solutions based on perturbed-chain statistical associating fluid theory incorporated with primitive mean spherical approximation

In this work an equation of state applicable to the system containing electrolytes has been developed by coupling the perturbed chain statistical associating fluid theory (PC-SAFT) with the primitive mean spherical approximation. The resulting electrolyte equation of state is characterized by 4 ion parameters for each of the cation and anion contained in aqueous solutions, and 4 ion specific parameters for each of six cations (Li+, Na+, K+, Rb+, Mg2+ and Ca2+) and six anions (Cl−, Br−, I−, HCO3−, NO3− and SO42−) were estimated, based upon the individual ion approach, from the fitting of experimental densities and mean ionic activity coefficients of 26 aqueous single-salt solutions at 298.15 K and 1 bar. The present equation of state with the estimated individual ion parameters has been found to satisfactorily describe not only the densities and mean ionic activity coefficients, but also osmotic coefficients and water activities of single-salt aqueous solutions. Furthermore, the present model was extended to two-salt aqueous solutions, and it has been found that thermodynamic properties such as mentioned above, of two-salt solutions, can be well predicted with the present model, without any additional adjustable parameters.

Synthesis of ethyl acetate employing celite-immobilized lipase ofBacillus cereusMTCC 8372

A wide range of fatty acid esters can be synthesized by esterification and transesterification reactions catalyzed by lipases in non-aqueous systems. In the present study, immobilization of a purified alkaline extra-cellular lipase of Bacillus cereus MTCC 8372 by adsorption on diatomaceous earth (celite) for synthesis of ethyl acetate via transesterification route was investigated. B. cereus lipase was deposited on celite (77% protein binding efficiency) by direct binding from aqueous solution. Immobilized lipase was used to synthesis of ethyl acetate from vinyl acetate and ethanol in n -nonane. Various reaction conditions, such as biocatalyst concentration, substrates concentration, choices of solvents ( n -alkanes), incubation time, temperature, molecular sieves (3A x 1.5 mm), and water activity(a w ), were optimized. The immobilized lipase (25 mg/ml) was used to perform transesterification in n -alkane(s) that resulted in approximately 73.7 mM of ethyl acetate at 55 degrees C in n -nonane under shaking (160 rpm) after 15 h, when vinyl acetate and ethanol were used in a equimolar ratio (100 mM each). Addition of molecular sieves (3A x 1.5 mm) as well as effect of water activity of saturated salt solutions (KI, KCl and KNO 3 ) to the transesterification efficiency has inhibitory effect. Batch operational stability tests indicated that immobilized lipase had retained 50% of its original catalytic activity after four consecutive batches of 15 h each.

Vapor−Liquid Equilibria, Density, Speed of Sound, and Refractive Index of Sodium Tungstate in Water and in Aqueous Solutions of Poly(ethyleneglycol) 6000

Vapor−liquid equilibrium data (water activity, vapor pressure, osmotic coefficient, and activity coefficient) of binary aqueous sodium tungstate solutions and ternary aqueous sodium tungstate−poly(ethyleneglycol) (PEG) solutions were obtained through the isopiestic method at T = 298.15 K. Density and speed of sound measurements were carried out on sodium tungstate in pure water and in aqueous solution of mass fraction 0.02 PEG at T = (288.15 to 308.15) K at atmospheric pressure. From the experimental density and speed of sound data, the apparent molar volume and isentropic compressibility values were evaluated and fitted to the Pitzer equation from which the apparent molar volume and apparent molar isentropic compressibility of the solutions at infinite dilution were calculated at each temperature. The results show a positive transfer volume and isentropic compressibility of sodium tungstate from pure water to an aqueous PEG solution. Furthermore, experimental refractive index data were measured for solutions of sodium tungstate in pure water and in aqueous solution of mass fractions 0.02 and 0.04 PEG as well as those for solutions of PEG in pure water and in aqueous solutions of mass fractions 0.02 and 0.04 sodium tungstate at T = 308.15 K.

Experimental investigation of the stability and evaporation of sulfate and chloride brines on Mars

We have investigated the evaporation of concentrated magnesium and ferrous sulfate, and magnesium and ferric chloride brines as possible sources for liquid water on the surface of Mars, with special emphasis on the effect of freezing and crystallization of solutions. Experimental evaporation rates range from 0.04 mm h − 1 for 25 wt.% MgSO 4 at 271.9 K, to 0.19 mm h − 1 for 18 wt.% FeSO 4 at 270.5 K. For chloride solutions, evaporation rates range from 0.09 mm h − 1 for 40 wt.% FeCl 3 at 261.34 K, to 0.43 mm h − 1 for 20 wt.% MgCl 2 at 267.2 K. These evaporation rates are significantly lower than for pure water, i.e. 1.35 mm h − 1 at 273 K. Using the Pitzer ion interaction model, we show that the decrease in evaporation rate is due to lower water activity in concentrated solutions, down to 0.91 for saturated MgSO 4 and 0.97 for saturated FeSO 4, at their eutectic temperatures. For saturated MgCl 2 and FeCl 3, the calculated water activities are 0.57 and 0.60 at their respective eutectic temperatures. In addition, we show that the water activity drops significantly when salts are crystallizing, down to 0.17 and 0.21 for MgSO 4 and FeSO 4, respectively. Our experiments and calculations show that the water activity and evaporation rate are dependent on the hydration state of the precipitating salt, which is in turn controlled by the temperature and the relative humidity. Low-hydration state salts precipitate at lower humidity, with lower evaporation rates. Our study suggests that martian brines could remain stable for longer periods of time, at low temperatures and low humidity, than previously thought. Brines formed from these salts would be a more stable source of water on Mars, thus beneficial for any putative martian life, past and/or present.

A model for the Gibbs energy of aqueous solutions of polyelectrolytes

A new model for the excess Gibbs energy of aqueous solutions of polyelectrolytes is presented and applied for the correlation of the activity of water in aqueous solutions of polyelectrolytes without as well as with an added (single) salt. The model considers the phenomenon of counterion condensation, i.e., the partial dissociation of highly charged polyelectrolytes in water. Three parameters (a binary interaction parameter between polymer segments, the equilibrium constant of the dissociation reaction and a parameter which accounts for the polymer configuration) were fitted to the experimental results. The model allows for a reliable correlation of experimental results for the osmotic coefficient of aqueous solutions of a single polyelectrolyte (without as well as with an added salt).

Influence of Copolymer Molar Mass on the Thermodynamic Properties of Aqueous Solution of an Amphiphilic Copolymer

The osmotic coefficients and water activities in binary solutions of water-soluble DMAM−TBAM copolymer (the abbreviation for N,N-dimethylacrylamide and t-butylacrylamide copolymer) with different molar masses were determined by isopiestic method using NaCl(aq) as the reference standard at 308.15 K. From these measurements, values of the vapor pressure of solutions were determined, and the effect of molar mass on the vapor−liquid equilibrium of DMAM−TBAM copolymer has been studied. The experimental water activities data have been correlated using the Flory−Huggins equation, the modified Flory−Huggins equation, and the Freed Flory−Huggins equation + the nonrandom two-liquid model (NRTL). Better agreement with the experimental data was obtained using the Freed Flory−Huggins equation + NRTL model.

Parameterizations for ice nucleation in biological and atmospheric systems

Ice nucleation is an important process in numerous environmental systems such as atmospheric aerosol droplets or biological tissues. Here we analyze two widely used approaches for describing homogeneous ice nucleation in aqueous solutions with respect to their applicability to heterogeneous ice nucleation processes: the lambda approach and the water-activity-based approach. We study experimentally the heterogeneous ice nucleation behaviour of mineral dust particles and biological ice nuclei (Snomax; Pseudomonas syringae) in aqueous solutions as a function of solute concentration for various solutes (sulfuric acid, ammonium sulfate, glucose, and poly(ethylene glycol) with two different molar masses of 400 and 6000 g mol(-1)). We show that the ice nucleation temperature and the corresponding lambda values depend on both the type of ice nucleus and the type of solute, while the water-activity-based approach depends only on the type of ice nucleus when the solution water activity is known. Finally, we employ both approaches to the study of ice nucleation in biological systems such as the supercooling point of living larvae and insects. We show that the behaviour of freeze tolerant and freeze avoiding species can be described using the two approaches and we discuss how the analysis can be used to interpret experimental results of the freezing behaviour of living species.

The properties of water in solutions of hydrophilic polymers

The properties of water in solutions of hydrophilic polymers were compared with those in solutions of their monomeric analogues. The properties of polar groups grafted to polymeric molecules were known to remain unchanged. A comparison of the properties of water in solutions of polymers and the corresponding monomers under equal conditions therefore allowed us to obtain information about the influence of polymeric bonds on the properties of water in solutions of polymers. Proceeding from this, we analyzed the influence of polymeric chains and three-dimensional polymeric network on the activity and concentration of water in solutions of polymers.