Standard Thermodynamic Properties Research Articles

Solubility of NaCl in water vapor at 400–700 °C

Water significantly impacts the chemical evolution of the Earth’s crust, affecting environments from volcanic settings to hydrothermal systems. These fluids transport elements essential for geological processes, such as metal ore deposit formation. At high temperatures, as water transitions from liquid to vapor, its molecular structure changes, drastically reducing its capacity to dissolve solids and solvate ions. Here, we report experimental results of halite (NaCl(s)) solubility in water vapor at 400–700 °C and 30–300 bar using a novel U-tube flow-through reactor system. The results show that halite solubility is low (xNaCl,tot = 3.2 × 10−9 to 2.9 × 10−4 mol/mol) and increases with temperature and pressure, attributed to the dissolution of NaCl followed by its hydration according to the reaction:NaCl(s)+nH2O(g)⇋NaCl·H2On(g)Thermodynamic modeling of the experimental results indicates a preference for specific hydrated species, including NaClg, NaCl·H2O4g, NaCl·H2O6g and NaCl·H2O8g. The less hydrated gaseous NaCl species become more prevalent with increasing temperature and decreasing pressure. At temperatures below 600 °C and pressures above 50 bar, halite solubility is close to stoichiometric, whereas at higher temperatures and lower pressures, the hydrolysis of NaCl(s) to form NaOH(lq,s) or a NaClxOH(1-x)(lq,s) (x < 1) solid solution is evident, resulting in the formation of HCl(g). The logarithm of the halite equilibrium solubility constant (logKn) ranges from −10.18 to −4.19 for NaCl(g), and from −13.12 to −11.94, −15.90 to −17.28, and −19.67 to –22.73 for NaCl·H2O4(g), NaCl·H2O6(g) and NaCl·H2O8(g), respectively. Standard thermodynamic properties derived from this data reveal a temperature-independent enthalpy (ΔHn,ro), entropy (ΔSn,ro) and heat capacity (ΔCp,n,ro) of reaction for each NaCl species. While the enthalpy of reaction is nearly constant, the entropy and heat capacity decrease with an increasing degree of hydration, indicating the decreasing stability of these species with increasing temperature. Our thermodynamic model results and gas species stoichiometries are in excellent agreement with previous density functional theory (DFT) calculations (Suleimenov et al., 2006). The halite solubility data obtained here compare well with prior studies and thermodynamic models for the NaCl-H2O system.

Silica solubility and molecular speciation in water vapor at 400–800 °C

Silica solubility and molecular speciation in hydrothermal water vapor have been determined through quartz solubility experiments at 400–800 °C and 50–270 bar using a novel U-tube flow-through reactor system and theoretical calculations. The results demonstrate that silica concentrations are low in water vapor (mSi,tot = 0.11–4.56 mmol/kg or xSi,tot = 8.21 × 10−5–1.98 × 10−6 mol/mol) increase with both temperature and pressure, which is attributed to the dissolution of quartz according to the reaction:SiO2(s) + (n + 2)H2O(g) ⇋ Si(OH)4·(H2O)n(g)Thermodynamic modeling and theoretical calculations employing density functional theory (B3LYP-D3), and MP2 ab initio calculations reveal the stable structures to be Si(OH)4(g), Si(OH)4·(H2O)2(g), Si(OH)4·(H2O)4(g) and Si(OH)4·(H2O)7(g) (n = 0, 2, 4, 7) under the temperature and pressure conditions of interest, with higher-order hydrated structures also present at the lowest temperatures and highest pressures. Various isomers of the gaseous silica species were identified, with the number of energetically favorable structures increasing with hydration level and the motifs shifting from silanol-water bonds to complex water-water networks. Over the temperature range of interest, the logarithm of the quartz equilibrium solubility constant (logKn) rises from −7.40 to −6.55 and −12.23 to −11.65 at 400 to 800 °C for the formation of Si(OH)4(g) and Si(OH)4·(H2O)2(g), respectively, and decreases from −16.20 to −19.15 and –22.61 to −28.74 for Si(OH)4·(H2O)4(g) and Si(OH)4·(H2O)7(g) at the same temperature range, respectively. Standard thermodynamic properties were derived based on the experimental results, revealing temperature-independent enthalpy (ΔHn,ro), entropy (ΔSn,ro) and heat capacity (ΔCp,n,ro) of reaction for each gaseous silica species. The enthalpy of the reaction is nearly constant, whereas the entropy and heat capacity decrease with increasing hydration, resulting in higher-level hydrated species becoming less important with increasing temperature. Our quartz solubility results are in good agreement with previous experimental data and thermodynamic equations, as well as the thermodynamic properties of Si(OH)4(g) at 25 °C and 1 bar.

Unified, Integral Approach to Modeling and Design of High-Pressure Pipelines: Assessment of Various Flow and Temperature Models for Supercritical Fluids

Abstract A unified one-dimensional, steady-state flow and heat transfer model is presented for the pipeline transport of fluids at high pressures, including the supercritical conditions. The model includes a generalized temperature equation, presented here for the first time, and accounts for all of the important effects, including the property variation, viscous dissipation, Joule-Thomson (J-T) cooling, and heat exchange with the surrounding. With appropriate approximations, this model can yield all isothermal and non-isothermal pipe flow solutions reported thus far. A generalized multi-zone integral method is developed which solves the two resulting algebraic equations for pressure and temperature in conjunction with a property database, such as the National Institute of Standard and Technology (NIST) Reference Fluid Thermodynamic and Transport Properties (REFPROP). With appropriately selected number and size of the zones and using property values at the mean temperature and pressure within each zone, this integral method can accurately predict the complex effects of the governing parameters, such as the pipe diameter and length, inlet and exit pressures, mass flow rate, J-T cooling, and inlet and surrounding temperatures. Its accuracy for small-to-large diameter pipes has been ascertained by a comparison with the numerical solutions of the differential form of governing equations that requires a large number of small grids along the pipe and the values of mean properties within each grid. Indeed, this integral model can be used for the pipeline transport at both subcritical and supercritical pressures as long as the fluid does not encounter its anomalous states and the phase-change.

Gold in sulfide fluids revisited

Gold solubility was measured at temperatures of 350, 400, 450, and 490 °C and pressures of 500 and 1000 bar in an ’oxidized sulfide’ system, as a function of pHT (2 – 10) and sulfur concentration (m(Stotal) = 0.03 – 1.2 [mol·(kg H2O)-1]). In this system, sulfur primarily exists as H2S, H2SO3, H2SO4, their dissociation products, and radical species such as S2- and S3-. The complexes Au(HS)2-, Au2S22-, AuHS(aq), AuHS(H2S)3(aq), and AuOH(aq) were identified as the primary gold species in the experimental fluids, varying with pH and m(Stotal). The solubility constants for Au(HS)2-, a critical (hydro)sulfide complex, align excellently with literature for ’reduced sulfide’ fluids, where sulfur predominantly exists in the 2- oxidation state. New experimental data from the ’oxidized sulfide’ system were regressed along with reliable literature data from ’reduced sulfide’ systems to calculate standard thermodynamic properties and parameters of the Helgeson-Kirkham-Flowers (HKF) model. The solubility constants for charged complexes, Au(HS)2- and Au2S22-, increase sharply with temperature, whereas those for neutral species, AuHS(aq) and AuHS(H2S)3(aq), show a pronounced peak near 300 °C. These (hydro)sulfide complexes account for gold solubility ranging from a few tens of ppb to a few tens of ppm in natural sulfide fluids, depending on the fluid pH. Thermodynamic calculations also indicate that, in addition to (hydro)sulfide species and the hydroxide complex, AuCl2- significantly contributes to Au mobility in high-temperature acidic chloride fluids. Based on new experimental data and prior studies using solubility and X-ray absorption spectroscopy methods, other gold complexes including mixed Au-HS-Cl, Au-HS-S3- species, and complexes with alkali metal cations, are deemed redundant. Above 250 °C, the influence of chloride salts on gold solubility can be accurately modeled using a simple extended Debye-Hückel equation with the term bγ·I = 0. The Setchenov coefficient bn = 0 suffices for calculating the activity coefficients of neutral species. This streamlined thermodynamic model aligns closely with earlier experimental work by Terry Seward and his team, effectively describing the state of Au in all types of natural fluids where Au exists in the 1+ oxidation state, under any set of P-T-f(O2)-f(S2)-compositional parameters.

Kinetic, Thermodynamic, and Parametric Studies on Batch Synthesis of 1,1‐Diethoxybutane Catalyzed by Amberlyst‐15 Wet

Abstract1,1‐Diethoxybutane is a high‐potential biofuel additive that enhances various fuel properties, which include cetane number, lubricity, biodegradability, and flash point. This work presents a kinetic and thermodynamic study on the acetalization reaction between butanal and ethanol in the presence of Amberlyst‐15 wet in a batch reactor. The experiments were conducted in the temperature range 313–333 K at atmospheric pressure with three different initial molar ratios of reactants and catalyst loadings. An optimal parameter setting to achieve maximum equilibrium conversion of butanal was derived from a parametric study with these three factors. The equilibrium constant for the reaction was determined. Standard thermodynamic properties of the reaction, such as enthalpy, entropy, and Gibbs free energy, were experimentally evaluated. The activity‐based two‐parameter Langmuir‐Hinshelwood‐Hougen‐Watson rate expression was used for reaction kinetics. The activity coefficients were calculated by the UNIFAC method. The kinetic parameters and the activation energy were evaluated from the experimental data. The experimental data and data predicted by the model were found to be in good agreement.

Celecoxib solubility in two choline chloride-based deep eutectic solvents- Experimental study, thermodynamic modeling, and molecular dynamic simulation

In the present study, we investigated the solubility of celecoxib the in the aqueous solution of two deep eutectic solvents (DESs) at various DES weight fractions within the temperature range of 283.2-323.2 K. Choline chloride (ChCl) as hydrogen bond acceptor (HBA) and ethylene glycol (EG) and 1,2-propanediol (PD) as hydrogen bond donors (HBDs) were used for the preparation of DESs. Experimental results showed that the solubility of celecoxib is significantly enhanced by approximately one million times in DES-contained PD compared to pure water. Also, celecoxib's solubility was enhanced by increasing temperature and the weight fraction of DESs. Besides, DES2 (ChCl + PD) showed a higher solubility for celecoxib compared to DES1 (ChCl + EG) in all experiments. Moreover, two temperature-dependent Buchowski-Ksiazaczak λh and modified Apelblat equations and the local composition models such as Wilson, non-random two-liquid theory (NRTL), and universal quasi-chemical (UNIQUAC) were applied to correlate the experimental solubility data. The correlated solubility was in good agreement with the experimental data. In addition, two-segment-based models, including non-random two-liquid-segment activity coefficient (NRTL-SAC) and universal quasi-chemical segment activity coefficient (UNIQUAC-SAC) models provided relatively good performance in solubility prediction. Furthermore, the calculation of the apparent standard thermodynamic properties showed that enthalpy is the primary contribution term to the apparent standard Gibbs free energy in the dissolution process of celecoxib. Finally, we applied molecular dynamics simulations to describe the drug solubility from the molecular point of view. The radial distribution function (RDF) analysis revealed that the experimental solubility is consistent with the MD simulation results, so the attractive interactions between celecoxib-DES1 and celecoxib-DES2 are much higher than the water-celecoxib.

Cadmium behavior in sulfur-bearing aqueous environments: insight from CdS solubility measurements at 25-80°C

The present experimental study explores the effects of temperature and sulfur in Cd aqueous geochemistry under reduced conditions. Greenockite CdS solubility is measured in H2O-H2S-HClO4-NaHS solutions at 25-80°C as a function of pH and sulfur concentration. Based on solubility product measurements in highly acid solutions, the standard thermodynamic properties of greenockite (CdS) are revised, and the recommended value of ∆fG0298.15 for greenockite CdS(s) is -151.5±0.3 kJ mol-1. The stability of greenockite (CdS) is higher than predicted by calculations using previous literature data. At 80°C, the stability constants for Cd-HS complexes are measured for the first time, the values are 10–5.65±1.00 for CdS(s) + H+ = CdHS+, 10–6.00±0.40 for CdS(s) + H2S0(aq) = Cd(HS)20(aq), 10–3.87±0.10 for CdS(s) + H2S0(aq) + HS- = Cd(HS)3-, and 10–3.53±0.20 for CdS(s) + H2S0(aq) + 2HS- = Cd(HS)42-. Modeling of Cd behavior at 3-200°C shows that Cd-HS species are more important than previously believed. The fraction of Cd(HS)n2-n (n = 1-4) complexes increases with mH2S and decreases with T. Thus, in euxinic marine environments with mH2S ≥ 10-5, Cd speciation changes from Cd-Cl to Cd-HS. This speciation change is expected to affect Cd isotope fractionation and should be accounted for when applying Cd isotopic signature as a paleo tracer in marine sediments. The new thermodynamic data are indispensable for modeling Cd behavior in response to pH, T, and mH2S. As a function of these parameters, sulfur has the main control on Cd geochemistry being the main factor of Cd precipitation at low mH2S and favoring Cd mobilization at high mH2S.

Theoretical and Experimental Studies on the Critical Size Effect on Surface Heat Capacity Using In Situ Microcalorimetry: During the Solid–Liquid Reactions of Cu2O Nanocubes

Phase transition, energy storage, and other activities depend critically on the size variations of nanomaterials for their heat capacity. The size variation of the nanomaterial is also equally important to the thermodynamic properties for chemical reaction processes. Based on this, it will be fascinating to examine how the surface heat capacity of nanomaterials changes with size. Herein, we used an in situ microcalorimeter to report a general approach to obtaining the regular patterns of numerical changes in the surface heat capacity at different sizes and temperatures when the chemical reactions of cuprous oxide (Cu2O) take place in the liquid phase. We synthesized four Cu2O nanocubes with uniform size distributions, which range from 40 to 120 nm, by using the liquid-phase reduction method. Combined with the principle of thermodynamic cycle and transition state theory, the effects of size and temperature changes on the standard molar formation thermodynamic properties, surface thermodynamic properties, and specific surface thermodynamic properties of Cu2O nanocubes were calculated and analyzed. The calculated results are in agreement with the established thermodynamic model. It is inspiring that we find that Cu2O nanocubes also have a critical size in the range of 55–67 nm, and their molar surface heat capacity and specific surface heat capacity are 59.35 and 59.31 nm, respectively. This property allows them to exhibit differences in thermal resistance from bulk materials within an acceptable range of error. This work has important scientific significance and values for enriching and developing the surface physical chemistry and understanding the energy storage and other processes of nanomaterials.

Toward Native Hardwood Lignin Pyrolysis: Insights into Reaction Energetics from Density Functional Theory

Lignin is one of the three structural components of lignocellulosic biomass and the only renewable source for sustainably producing aromatic chemicals. Despite lignin’s promise for targeted valorization to fine chemicals, fuels, and polymer composites, a major roadblock is an ambiguity associated with its molecular structure. Due to the lack of an established molecular structure, all types of computational studies from reaction mechanism to reaction energetics are performed with model lignin compounds. Among several thermochemical conversion techniques, lignin pyrolysis has been an active research area for both experimental and computational investigations. Historically, computational studies on the pyrolysis of lignin have mainly been limited to dimeric or trimeric models using electronic structure methods. Very recently, model oligomers up to the size of decamers have been studied with density functional theory (DFT) calculations. While these studies used very simplified models to study lignin’s pyrolysis behavior, theoretical investigations on a more realistic lignin structure are warranted to advance its state-of-the-art. To address this, we have modeled a native hardwood lignin polymer consisting of 20 repeating units, including all three monolignols, i.e., guaiacyl (G), syringyl (S), and p-hydroxy coumaryl (H) units, and multiple types of linkages, i.e., β-O-4, 4-O-5, β–β, and β-5. This more realistic molecular model for the wild-type poplar lignin is based on a proposed lignin structure reported in a previous experimental study. The initial stage in lignin pyrolysis involves the homolytic cleavage of β-O-4 linkages present in lignin. The activation energy for homolysis of this linkage is considered to be slightly greater than the bond dissociation enthalpy (BDE) required to cleave it. We used a composite method using molecular mechanics-based conformational sampling and quantum mechanically based density functional theory (DFT) calculations to determine the reaction energetics for this reaction, which indicates the activation energy required for the early stage of lignin pyrolysis. In addition, we calculated standard thermodynamic properties for all species, including enthalpy of formation, heat capacity, entropy, and Gibbs free energy of formation as a function of temperature. This study provides the reaction energetics and standard thermodynamic quantities that could be used in kinetic and reactor modeling for biomass conversion. Additionally, these predictions would be particularly helpful in advanced-generation biorefinery, where hardwoods can be used as a potential feedstock. Moreover, the predictions reported in this study will benefit further computational studies and cross-validation with pyrolysis experiments, ultimately contributing to solving the puzzle of the structural ambiguity of lignin.

Strain wars 3: Differences in infectivity and pathogenicity between Delta and Omicron strains of SARS-CoV-2 can be explained by thermodynamic and kinetic parameters of binding and growth

In this paper, for the first time, empirical formulas have been reported of the Delta and Omicron strains of SARS-CoV-2. The empirical formula of the Delta strain entire virion was found to be CH1.6383O0.2844N0.2294P0.0064S0.0042, while its nucleocapsid has the formula CH1.5692O0.3431N0.3106P0.0060S0.0043. The empirical formula of the Omicron strain entire virion was found to be CH1.6404O0.2842N0.2299P0.0064S0.0038, while its nucleocapsid has the formula CH1.5734O0.3442N0.3122P0.0060S0.0033. Based on the empirical formulas, standard thermodynamic properties of formation and growth have been calculated and reported for the Delta and Omicron strains. Moreover, standard thermodynamic properties of binding have been reported for Wild type (Hu-1), Alpha, Beta, Gamma, Delta and Omicron strains. For all the strains, binding phenomenological coefficients and antigen-receptor (SGP-ACE2) binding rates have been determined and compared, which are proportional to infectivity. The results show that the binding rate of the Omicron strain is between 1.5 and 2.5 times greater than that of the Delta strain. The Omicron strain is characterized by a greater infectivity, based on the epidemiological data available in the literature. The increased infectivity was explained in this paper using Gibbs energy of binding. However, no indications exist for decreased pathogenicity of the Omicron strain. Pathogenicity is proportional to the virus multiplication rate, while Gibbs energies of multiplication are very similar for the Delta and Omicron strains. Thus, multiplication rate and pathogenicity are similar for the Delta and Omicron strains. The lower number of severe cases caused by the Omicron strain can be explained by increased number of immunized people. Immunization does not influence the possibility of occurrence of infection, but influences the rate of immune response, which is much more efficient in immunized people. This leads to prevention of more severe Omicron infection cases.

Measurement and correlation of the solubility of kojic acid in pure and binary solvents

The solubility of kojic acid in seven pure solvents (isopropanol, n-butanol, 2-butanol, n-pentanol, acetonitrile, methyl acetate, THF) and two binary solvents (2-methoxyethanol + water, 2-ethoxyethanol + water) were determined from 278.15 K to 323.15 K under 101.3 kPa by the gravimetric method. Besides, the modified Apelblat equation, λh model, van't Hoff model, NRTL model, Wilson model and UNIQUAC model were selected to correlate the experimental data in pure solvents, and the modified Apelblat equation, λh model, van't Hoff model, NRTL model, CNIBS/R-K model and the modified Apelblat-Jouyban-Acree model were applied for binary solvents. The results indicated that in this work the modified Apelblat model had the highest accuracy among those semi-empirical models, while UNIQUAC model was the most representative local component model with the best fitting effect among all models. The solubility of kojic acid in all the tested pure and binary solvent systems monotonously increased with increasing of the temperature. Under the isothermal condition, the solubility value of kojic acid increased first and then decreased with the increase of the mass fraction of 2-methoxyethanol and 2-ethoxyethanol, and reached the maximum value when the mass fraction of 2-methoxyethanol and 2-ethoxyethanol were 0.9 and 0.7, respectively. The solubility parameters of solvents were determined by the improved mixing rule. According to the solubility parameters obtained, the co-solvency in the binary solvent mixtures can be explained. To further explain the observed phenomena, the molecular electrostatic potential surface (MEPS), Hirshfeld surface analysis (HS) and KAT-LSER model were applied. Furthermore, the standard thermodynamic properties of the mixtures, including Gibbs energy, entropy and enthalpy were calculated and discussed, which indicated that the dissolution of the kojic acid in all solvents was spontaneous and entropy-driven. The conductor-like screening model for real solvents (COSMO-RS) was also applied to calculate solvation free energy of kojic acid in the studied solvents. The results showed a reasonable explanation to the dissolution behavior of kojic acid.

A structurally-consistent CASH+ sublattice solid solution model for fully hydrated C-S-H phases: Thermodynamic basis, methods, and Ca-Si-H2O core sub-model

A new thermodynamic model, CASH+, is proposed, aimed at accurately describing equilibrium composition, stability, solubility, and density of C-S-H gel-like phases at varying chemical conditions. Taking advantage from recent atomistic and spectroscopic studies, this sublattice solid solution model allows incremental extensions to accommodate alkali, aluminum and other cations. This incrementality, achieved first time for a C-S-H solid solution model, means that all thermodynamic properties of endmembers and interaction parameters can be kept fixed in further extensions. This paper describes principles of how endmembers of CASH+ solid solution model can be constructed by permutating moieties assigned to different sublattices, and how the structural consistency of the model can be established. Initial standard thermodynamic properties of endmembers were estimated using predictive methods and PSI/Nagra and Cemdata18 chemical thermodynamic databases. The parameterized core CASH+ sub-model in Ca-Si-H2O system is shown to perform well in presence of liquid water at temperatures up to 90 °C.

Unified Gorini-Kossakowski-Lindblad-Sudarshan quantum master equation beyond the secular approximation

Derivation of a quantum master equation for a system weakly coupled to a bath which takes into account nonsecular effects, but nevertheless has the mathematically correct Gorini-Kossakowski-Lindblad-Sudarshan form (in particular, it preserves positivity of the density operator) and also satisfies the standard thermodynamic properties is a known long-standing problem in theory of open quantum systems. The nonsecular terms are important when some energy levels of the system or their differences (Bohr frequencies) are nearly degenerate. We provide a fully rigorous derivation of such equation based on a formalization of the weak-coupling limit for the general case.

Critical assessment of thermodynamic properties of important polycyclic aromatic hydrocarbon compounds (PAHs) in coal tar pitch at typical temperature ranges of the carbonization process

Because of the importance of thermodynamic behavior of Polycyclic Aromatic Hydrocarbon (PAH) compounds in coal tar pitch carbonization process, a thermodynamic model for the prediction of thermodynamic properties of PAH compounds is developed. Heat capacity functions as well as standard thermodynamic properties of PAHs in solid, liquid, and gas states are estimated using modified group additivity algorithms first proposed by Richard and Helgeson and thermal physical data of those PAHs for which enough experimental data exists in the literature. For the first time, initial calculated thermodynamic properties of PAHs are optimized by applying the CALPHAD (CaLculation of PHAse Diagrams) approach where all thermodynamic data are rendered consistent with phase transitions and vapor pressure data. The heat capacity function of PAHs exhibiting thermal anomaly behavior is modeled as a specific case. This modeling is performed using an order-disorder approach with the Compound Energy Formalism (CEF). Good agreement has been obtained between the predicted thermodynamic properties of PAHs and available experimental data. The proposed model has improved the predictive capacity compared to that of the previous models predicting thermodynamic properties of PAHs at typical temperature ranges of the carbonization process. The application of the model to predict the thermodynamic properties of major and high molecular weight PAHs available in coal tar pitch has been discussed.

Standard Thermodynamic Properties, Biosynthesis Rates, and the Driving Force of Growth of Five Agricultural Plants.

Elemental composition of Gossypium hirsutum L. (cotton), Oryza sativa L. (Asian rice), Phaseolus vulgaris L. (common bean), Saccharum spp. L. (sugarcane), and Zea mays L. (corn) was used to calculate their empirical formulas (unit carbon formulas) and growth stoichiometry. The empirical formulas were used to find standard enthalpy of formation, standard molar entropy, standard Gibbs energy of formation, and standard molar heat capacity. A comparison was made between thermodynamic properties of live matter of the analyzed plants and other unicellular and multicellular organisms. Moreover, the growth process was analyzed through standard enthalpy, entropy, and Gibbs energy of biosynthesis. The average standard Gibbs energy of biosynthesis was found to be +463.0 kJ/C-mol. Thus, photosynthesis provides energy and carbon for plant growth. The average intercepted photosynthetic energy was found to be 15.5 MJ/C-mol for the analyzed plants. However, due to inefficiency, a great fraction of the intercepted photosynthetic energy cannot be used by plants. The average usable photosynthetic energy was found to be –2.3 MJ/C-mol. The average thermodynamic driving force for growth is –1.9 MJ/C-mol. Driving forces of growth of C3 and C4 plants were compared. It was found that C4 plants have a greater driving force of growth than C3 plants, which reflects the greater efficiency of C4 photosynthesis. The relationship between the driving force and growth rates was analyzed by determining phenomenological L coefficients. The determined phenomenological coefficients span two orders of magnitude, depending on plant species and environmental conditions. The L coefficient of P. vulgaris was found to be lower than that of other plants, due to additional energy requirements of nitrogen fixation.

Solid-liquid equilibrium behavior, thermodynamic analysis and molecular simulation of dimetridazole in twelve organic solvents

The molecular structure properties of Dimetridazole (DMZ) were investigated both in the solid and liquid phases. Molecular electrostatic potential surface and Hirshfeld surface analysis were respectively used to investigate the overall charge distribution and the intermolecular interaction of DMZ. In addition, the solubility of DMZ in twelve mono organic solvents, including methanol, ethanol, 1-propanol, 2-propanol, 2-butanol, 1-pentanol, acetone, 2-butanone, cyclohexanone, ethyl acetate, propyl acetate and isopropyl acetate, was investigated using the gravimetric method at temperature ranging from 283.15 K to 323.15 K under atmospheric pressure. The solubility of DMZ in all solvents were monotonously rising with increasing temperature as expected. Furthermore, the Apelblat equation, λh equation, van't Hoff equation and NRTL model were selected to check and correlate the experimental solubility data, respectively, in which the Apelblat equation showed the best fitting performance. Besides, the solvent properties including polarity, hydrogen bond and solubility parameter (cohesive energy density) were performed to analyze the solid-liquid equilibrium behavior of DMZ. Meanwhile, the standard thermodynamic properties of mixing (ΔmixG, ΔmixH and ΔmixS) were calculated, and the results indicated that the mixing process of DMZ in different solvents is spontaneous, endothermic and entropy-driving. To further confirm this conclusion, the molecular simulations involving solvation free energy and radial distribution function analysis were employed to successfully analyze the interactions between solute-solvent and solvent-solvent.

Heat capacity and thermodynamic functions of poly(1-(hydroxyimino)trimethylene)

In the present work, the temperature dependence of the molar heat capacity of a partially crystalline poly(1-(hydroxyimino)trimethylene) has been measured over the range of T = (6–500) K using a precise automated adiabatic calorimeter and a heat-flux differential scanning calorimeter. In the above temperature interval, the glass transition has been detected, and the standard thermodynamic characteristics of polyoxime have been determined and analysed. The standard thermodynamic functions of the studied polyoxime, namely, the heat capacity Cpo(T), the enthalpy [H°(T) − H°(0)], the entropy [S°(T) − S°(0)], and the potential Φ°(T) have been calculated for the range from T → (0 to 400) K based on the experimental data. The standard thermodynamic properties of poly(1-(hydroxyimino)trimethylene) have been discussed and compared with the previously studied alternating polyketone (copolymer of ethylene C2H4 and carbon monoxide CO).

Thermodynamic analysis of hydrogen storage: Biphenyl as affordable liquid organic hydrogen carrier (LOHC)

One of the promising directions for accumulating hydrogen is its binding into a liquid organic hydrogen carrier (LOHC). In this concept, a LOHC is loaded with hydrogen (hydrogenation) during production and then discharged again (dehydrogenation) when the hydrogen is needed. Biphenyl is an interesting option as potential LOHC due to its reasonable storage capacity. This paper deals with the experimental chemical equilibrium study and a detailed analysis of the biphenyl hydrogenation reactions. We evaluated the consistent set of vapour pressures and standard molar thermodynamic properties of biphenyl derivatives with help of complementary vapour pressure measurements, and empirical and quantum-chemical calculations. The chemical equilibrium constants of hydrogenation-dehydrogenation and thermodynamic characteristics for the biphenyl system were determined.

Effect of temperature on the chloride binding capacity of cementitious materials

The effect of temperature on the chloride binding capacity (CBC) of cementitious materials was investigated. A reactive transport model including thermodynamic equilibrium, kinetic control and surface complexation was applied to investigate this effect. The surface complexation model was completed by introduction of the equilibrium constant of calcium silicate hydrate (C–S–H) complexation reactions at different temperatures (5, 21 and 35°C). In order to validate the developed numerical model, the results were compared with experimental data obtained from the literature. Good agreement was found between the numerical and experimental CBCs. The effect of temperature on the CBC of cementitious materials was evaluated and is discussed in this paper. The van 't Hoff equation of C–S–H surface complexation reactions (SCRs) and variation of the standard thermodynamic properties of the SCR (ΔrHT0 (kJ/K) and ΔrST00) at the reference temperature of T0 = 25°C and p0 = 1·1013 × 105 Pa are also presented.

Thermodynamic and thermophysical properties of holmium orthovanadate

The current paper reports thermodynamic and thermophysical property data on holmium orthovanadate over a wide temperature range. The heat capacities of HoVO4 have been measured using precision adiabatic calorimetry and differential scanning calorimetry over the temperature ranges of 7–343 K and 337–1097 K, respectively. A broad heat capacity anomaly, centred at 15 K, has been observed. The standard entropy of HoVO4 at 298.15 K, derived from low-temperature heat capacity data, has been estimated. This value, in conjunction with available thermodynamic data, has been used to evaluate the standard Gibbs energy of formation of HoVO4 from the elements. The temperature dependences of standard thermodynamic properties have been calculated from 0 K to 1100 K. Thermal diffusivity measurements for HoVO4 have been conducted from ambient temperature to 1073 K, using a laser flash method. The thermal conductivity has been evaluated on the basis of the heat capacity and thermal diffusivity data obtained.