Determination of Henry’s constant using a photoacoustic sensor

We present a simple method for measuring Henry’s constant k_Hof ethanol using photoacoustic spectroscopy. At T =  298.1 K the measured value fork_H is (0.877  ±  0.039)kPa · kg · mol ^− 1. Our data show that Henry’s law is valid at ethanol molalities between 0.1mol · kg ^− 1 and 1.4 mol · kg ^− 1. The temperature dependence of Henry’s constant was carefully examined by measuring the ethanol vapour pressure of six different aqueous solutions between T =  273.1 K and T =  298.1 K. By analysing the gas phase concentration and applying Henry’s law, an ethanol molality of 0.864 mol · kg ^− 1in the liquid phase can be measured with an error of  ± 0.038mol · kg ^− 1. The detection limit of the photoacoustic sensor is a gaseous ethanol pressure of 10 ^− 3kPa. Ethanol molality changes as low as 1.10 ^− 3mol · kg ^− 1can be measured.     

Mechanisms and solubility equations of gas dissolving in water

The two mechanisms of gas dissolving in water, interstice filling and aquation, are proposed. General equations of gas solubility have been deduced from the mechanisms and experimental observations. Dependence of Henry's coefficient on temperature, pressure, aquation equilibrium constant and gas molecular wlume is discussed. The theoretical equations were verified by experimental data, which shows that the theoretical results of the solubility of methane are in good agreement with the experimental data in the range of 20 -160℃ and under a pressure of less than 60 MPa.     

Determination of Henry’s law constant of light hydrocarbon gases at low temperatures

The solubility of i-butane in water at the low temperatures was measured (274 K to 293 K). Additionally, Henry’s law constants of light hydrocarbons (methane, ethane, propane, i-butane, and n-butane) in water at the low temperatures are reported. A modified equation based on Krichevsky–Kasarnovsky equation is proposed to consider the effect of pressure and temperature on the equation parameters. Results show that Henry’s law constant of the selected components depends on temperature. It is deduced that pressure has a considerable effect on Henry’s law constant for methane, ethane, and propane, whereas this dependency for butanes is negligible.     

A generalized correlation for Henry’s Law constants of nonpolar solutes in four polymers

In this work, Henry’s Law constants of nonpolar solutes in four polymers were obtained by extrapolation of finite concentration vapor–liquid equilibrium (VLE) data using the UNIQUAC equation to infinite dilution condition. The consistency of the results was confirmed by comparing them with infinite dilution data through the linear relationship between logarithm of Henry’s Law constants and inverse of temperatures. This verification provided good method for crosschecking a reliability of finite concentration VLE data with infinite dilution data. Henry’s Law constants were correlated based on both types of data as a function of temperature using the classical van’t Hoff equation. Generalized correlations of the Henry’s Law constants of solutes were proposed for polyisoprene (PI), polyisobutylene (PIB) and poly(n-butyl methacrylate) (PBMA).     

Determination of the emanation coefficient and the Henry’s law constant for the groundwater radon

The radon emanation coefficient (ε) from aquifer rock and the Henry’s law constant (H) of radon were determined by measuring activity concentrations using liquid scintillation counter (LSC). For the evaluation of the method, the coefficients were measured at 0, 10 and 20 °C and the temperature dependency of the coefficients was compared with others. The radon emanation coefficients from the rock particles used in this work are 0.0845, 0.1007 and 0.1308 at 0, 10 and 20 °C, respectively. The dimensionless Henry’s law constants for the groundwater used in this work are 0.994, 1.153 and 2.641 at 0, 10 and 20 °C, respectively. The results show a good agreement with those in literatures.     

Correct derivation of a combined version of the Jouyban–Acree and van’t Hoff model and some comments on ‘Determination and correlation of the solubility of myricetin in ethanol and water mixtures from 288.15 to 323.15 K’

The experimental data reported in the paper by Cai and co-workers [DOI: 10.1080/00319104.2016.1163560] pertaining to the solubility of myricetin dissolved in binary aqueous–ethanol solvent mixtures has been reanalysed. A correct mathematical derivation is provided for the correlation expression from a combination of the van’t Hoff and Jouyban–Acree models. Cai et al. who used the expression in their study, however, erroneously implied that the expression resulted from a simple transformation of the Jouyban–Acree model. No mention was made that one needed to assume a van’t Hoff-type mathematical representation for how the solute solubility varied with temperature in the two mixture co-solvents.     

Comparison of hydrophobicity studies of silica aerogels using contact angle measurements with water drop method and adsorbed water content measurements made by Karl Fischer’s titration method

Hydrophobic silica aerogels possesses potential applications as insulating materials for refrigerators, furnaces and thermos flasks. In such applications, aerogel materials may get exposed for longer time to atmosphere and the adsorbed water content from surroundings may deteriorate its properties. Therefore, hydrophobicity of the arogels becomes crucial parameter and needs to be evaluated critically. In the present works, silica alcogels were prepared using the mixture of tetramethoxysilane and methyltrimethoxysilane (MTMS) as precursor chemicals for silica. The concentration of MTMS, which is used as hydrophobic reagent, in the said mixture of silicon alkoxide was varied between 0 and 100% in steps of 25%. After gelation, the alcogels were dried supercritically by solvent extraction method. Resulted aerogels were exposed to relative humidity of 90% for a period of one month which were then characterized to assess hydrophobicity by the contact angle using water drop method and adsorbed water content measurements by Karl Fischer’s Titration method. Observed contact angle and water content measurements were compared and the results are reported in the present research paper.     

Sommerfeld’s fine structure constant approximated as a series representation in e and $$\pi $$

Sommerfeld in 1916 introduced the dimensionless fine structure constant, \(\alpha \), in to the context of atomic physics, in the course of working out the relativistic theory of the H atom, under the old quantum theory of Bohr. He was able to account for the fine structural detail of the atomic line spectrum of H by introducing this dimensionless constant which emerged naturally from his relativistic theory of the H atom. Since this time, the fine structure constant has emerged in several other contexts within experimental and theoretical physics. It has attained a status of being a mysterious number in physics that defies understanding as to its experimentally verified magnitude and identity. Being physically dimensionless, such a number invites a suggestion (or approximation) of its value in terms of mathematical constants in some formulation. Feynman most famously has conjectured that it might be possible to account for \(\alpha \) in some type of series or product expression in “e”, the base of natural logarithms, and “\(\pi \)” the familiar circular constant. Here we propose an infinite series in the product \(\mathrm{e} \cdot \pi \) that converges, within a few terms, to better than 9999 parts in 10,000 of the true value of \(\alpha \).     

Deprotonation energetics of adenine,adenosine, 5′-adenosine monophosphate and adenosine triphosphate in water from EMF and spectrophotometric measurements

The deprotonation constants of adenine (ADE) [K₁ and K₂], adenosine (ADO) [K₁ and K₂], 5-adenosine monophosphate (5-AMP) [K₁, K₂ and K₃] and adenosine triphosphate (ATP) [K₃ and K₄] have been obtained for aqueous soutions from emf measurements on cells such as Pt, H₂ (g, 1 atm)/HA(m₁), NaA(m₂), KI(m₃)/AgI-Ag (where HA is the corresponding acid of ADE, ADO, 5-AMP and ATP) at different temperatures. The pK values were fitted by the temperature equation: pK=AT¹+B+CT by the least squares method and the related thermodynamic quantities viz. G ^o , TS ^o and H ^o were calculated from the coefficients A, B and C.     

Experimental determination and correlation of bosentan solubility in (PEG 200 + water) mixtures at T= (293.15–313.15) K

The solubility of bosentan (BST) in the aqueous mixtures of polyethylene glycol 200 (PEG 200) at the temperature range, T = (293.15–313.15) K, has been studied using a shake-flask method. The experimental solubility data were correlated with Jouyban–Acree, Jouyban-Acree-van’t Hoff, modified Wilson and Yalkowsky models. Deviations of the calculated solubility from experimental one were determined by percent average relative deviations and relative deviations. In addition, to represent the thermodynamic behaviour of BST in PEG 200 solutions, the apparent thermodynamic functions, Gibbs energy, enthalpy and entropy of dissolution were obtained by using the van’t Hoff and Gibbs equations.     

Correlation equations for solubility of NaHS in water and organic solvents at 297–323 K

The solubility of NaHS in different solvents had been determined from 297.85 to 342.55 K by an analytical method. A solubility model is proposed and the solubilities calculated by the model show good agreement with experimental data. It provided the basic data for the synthesis of isopropyl mercaptan in industry.     

Henry’s constants and infinite dilution activity coefficients of propane,propene, butane,isobutane, 1-butene,isobutene, trans-2-butene,and 1,3-butadiene in isobutanol and tert-butanol

The Henry’s constants and the infinite dilution activity coefficients of propane, propene, butane, isobutane, 1-butene, isobutene, trans-2-butene and 1,3-butadiene in isobutanol at T = (250 to 330) K and tert-butanol at T = (300 to 330) K are measured by a gas stripping method. The rigorous formula for evaluating the Henry’s constants from the gas stripping measurements is used for data reduction of these highly volatile mixtures. The accuracy of the measurements is about 2% for Henry’s constants and 3% for the estimated infinite dilution activity coefficients. In the evaluations for the infinite dilution activity coefficients, the nonideality of the solute such as the fugacity coefficient and the Pointing correction is not negligible, especially at higher temperatures, and the estimation uncertainty in the infinite dilution activity coefficients includes 1% for nonideality.     

Synthesis, structure, and properties of a new phosphorus-containing Schiff’s base, a derivative of pyrazole-5-one

A new Schiff’s base and its salt have been prepared from 2-aminophenyl(triphenyl)phosphonium chloride and 5-hydroxy-3-methyl-1-phenyl-4-formylpyrazole. The products structures have been proved by IR, ¹H NMR, and UV spectroscopy, mass spectrometry, X-ray diffraction analysis, and quantum-chemical modeling. Possible tautomerism and some properties of the products have been studied.     

Development and validation of a liquid chromatography tandem mass spectrometry method for the analysis of β-agonists in animal feed and drinking water

A reproducible, sensitive and selective multiresidue analytical method for seven β-agonists: clenbuterol (CBT), clenpenterol (CPT), ractopamine (RTP), brombuterol (BBT), mabuterol (MBT), mapenterol (MPT), and hydroxymethylclenbuterol (HMCBT) was developed and validated by using liquid chromatography tandem mass spectrometry (LC–MS/MS) in feed and drinking water samples. The validation was achieved according to the criteria laid down in the Commission Decision 2002/657/EC, however it was necessary to use minimum required performance limits (MRPLs) proposed by the Community Reference Laboratories (CRLs) due to the lack of maximum residue limits (MRLs) for β-agonists. By setting up these MRPLs, allows controlling their use in safe mode, since β-agonists are commonly used in veterinary medicine sometime in a fraudulent manner, for increasing the weigh of animals. Values set for both matrices studied are 50 μg/kg for animal feed, and a range from 0.2 to 10 μg/L for drinking water. CCα values calculated were under the MRPLs suggested; for drinking water the lowest value obtained was 0.12 μg/L, and for animal feed 0.87 μg/kg. Values for CCβ were ranged from 0.08 to 0.13 μg/L in drinking water and from 0.5 to 0.92 μg/kg in animal feed samples. The excellence values obtained, allowed us to conclude that the proposed analytical method is capable to control the β-agonists studied in both matrices and that it can be successfully applied and used as a routine method in laboratories of residue analysis of veterinary food control.     

Molecular interpretation of Trouton’s and Hildebrand’s rules for the entropy of vaporization of a liquid

The entropy of vaporization at a liquid’s boiling point is well approximated by Trouton’s rule and even more accurately by Hildebrand’s rule. A cell method is used here to calculate the entropy of vaporization for a range of liquids by subtracting the entropy of the gas from that of the liquid. The liquid’s entropy is calculated from the force magnitudes measured in a molecular dynamics simulation based on the harmonic approximation. The change in rotational entropy is not accounted for except in the case of liquid water. The predicted entropies of vaporization agree well with experiment and Trouton’s and Hildebrand’s rules for most liquids and for water except other liquids with hydrogen bonds. This supports the idea that molecular rotation is close to ideal at a liquid’s boiling point if hydrogen bonds are absent; if they are present, then the rotational entropy gain must be included. The method provides a molecular interpretation of those rules by providing an equation in terms of a molecule’s free volume in a liquid which depends on the force magnitudes. Free volumes at each liquid’s boiling point are calculated to be ～1 Å³ for liquids lacking hydrogen bonds, lower at ～0.3 Å³ for those with hydrogen bonds, and they decrease weakly with increasing molecular size.