Solubilities and vapour pressures of saturated aqueous solutions of sodium peroxydisulfate and potassium peroxydisulfate

Solubilities of sodium peroxydisulfate and potassium peroxydisulfate in water and vapour pressures of saturated solutions were determined as a function of temperature. The vapour pressures served to evaluate the water activities, osmotic coefficients and molar enthalpies of vaporization. The molar enthalpy of solution of sodium peroxydisulfate was determined calorimetrically.     

The molar enthalpies of solution and vapour pressures of saturated aqueous solutions of some cesium salts

Vapour pressures of water over saturated solutions of cesium chloride, cesium bromide, cesium nitrate, cesium sulfate, cesium formate, and cesium oxalate were determined as a function of temperature. These vapour pressures were used to evaluate the water activities, osmotic coefficients and molar enthalpies of vapourization. Molar enthalpies of solution of cesium chloride, Δ_solH_m(T = 295.73 K; m = 0.0622 mol · kg⁻¹) = (17.83 ± 0.50) kJ · mol⁻¹; cesium bromide, Δ_solH_m(T = 293.99 K; m = 0.0238 mol · kg⁻¹) = (26.91 ± 0.59) kJ · mol⁻¹; cesium nitrate, Δ_solH_m(T = 294.68 K; m = 0.0258 mol · kg⁻¹) = (37.1 ± 2.3) kJ · mol⁻¹; cesium sulfate, Δ_solH_m(T = 296.43 K; m = 0.0284 mol · kg⁻¹) = (16.94 ± 0.43) kJ · mol⁻¹; cesium formate, Δ_solH_m(T = 295.64 K; m = 0.0283 mol · kg⁻¹) = (11.10 ± 0.26) kJ · mol⁻¹ and Δ_solH_m(T = 292.64 K; m = 0.0577 mol · kg⁻¹) = (11.56 ± 0.56) kJ · mol⁻¹; and cesium oxalate, Δ_solH_m(T = 291.34 K; m = 0.0143 mol · kg⁻¹) = (22.07 ± 0.16) kJ · mol⁻¹ were determined calorimetrically. The purity of the chemicals was generally greater than 0.99 mass fraction, except for HCOOCs and (COOCs)₂ where purities were approximately 0.95 and 0.97 mass fraction, respectively. The uncertainties are one standard deviations.     

An empirical correlation for the calculation of vapour pressures of pure compounds

A four-parameter equation for vapour pressure is derived by integrating the Clapeyron equation with the aid of an empirical expression for the ΔH/Δ a wide range of reduced temperatures for 21 liquids which are representative of different classes of compounds: polar compounds, non-polar compounds, hThree methods for the application of the new equation are discussed. The best of these is more accurate than the Thek-Stiel equation although it does nAn equation for calculating vaporization enthalpies is also derived.     

The vapour pressures over saturated aqueous solutions of sodium and potassium acetates,chlorates, and perchlorates

Vapour pressures of water over saturated solutions of sodium acetate, potassium acetate, sodium perchlorate, and potassium perchlorate were determined over the (278 to 318) K temperature range and compared with available in the literature data. The cases of saturated solutions of sodium chlorate and potassium chlorate are also considered. The determined vapour pressures were used to obtain the water activities, the osmotic coefficients, and the molar enthalpies of vaporization in considered systems.     

The vapour pressures and saturated volumes of benzotrifluoride in the temperature range 460–530K.

A sample of benzotrifluoride was degassed in a high vacuum train, and the vapor pressure was measured in the temperature range 460 – 53OK. Also the saturated vapour and saturated liquid volumes were measured. Two simple equations were used to fit the vapour pressure data by the least square method. The heat of vaporization was calculated using Clapeyron equation.     

Reference values of vapour pressure the vapour pressures of benzene and hexafluorobenzene

The vapour pressures of benzene and hexafluorobenzene in the range 10 to 100 kPa were measured in the course of developing a comparative ebulliometric apparatus, and the results of four sets of measurements on benzene and of one on hexafluorobenzene are given. There is excellent agreement between the measurements made in this laboratory and those made at the Bartlesville laboratory of the U.S. Department of Energy and equations are given that reproduce the results of the work in the two laboratories within 0.01 per cent of the pressure in a range around atmospheric pressure, corresponding to differences in temperature of not more than 0.005 K.     

Representation of the vapour pressures of sulfur

The Wagner equation coefficients for representing the vapour pressures of sulfur at temperatures ranging from the melting temperature to the critical temperature are reported. With a relative root-mean-square deviation of 0.87 per cent and an average percentage absolute deviation of 0.58 per cent, the representation by the Wagner equation with the optimal coefficients determined in this study are generally more accurate than those by means of the equations found in the literature.     

Study and prediction of alkylbenzenes’ vapour pressures

Vapour pressures of 1,4-di-tert-butylbenzene (379–1647 Pa), 1,3,5-tri-tert-butylbenzene (203.9–241 Pa), 1-methyl-3,5-di-tert-butylbenzene (16.7–435.8 and 1318–103,880 Pa), and 1,2,2-trimethylpropybenzene (36.3–287.4 Pa) have been measured using a transpiration method and an ebuliometric method. Based on the literature and obtained by the authors experimental data a comparative study of prediction capabilities of the following methods has been carried out: Ambrose–Walton's, Lee–Kesler's, Riedel's and the modification of Riedel's method made by Vetere.     

The vapour pressures over saturated aqueous solutions of cadmium chloride,cadmium bromide,cadmium iodide,cadmium nitrate,and cadmium sulphate

Vapour pressures of water over saturated solutions of cadmium salts (chloride, bromide, iodide, nitrate, and sulphate) were determined over the temperature range 280 K to 322 K and compared with the literature data. The vapour pressures determined were used to obtain the water activities, osmotic coefficients and the molar enthalpies of vaporization in the (cadmium salt + water) systems.     

Antimicrobial activities of single aroma compounds

Commercially available aroma samples were evaluated for their olfactory quality by professional perfumers and tested for their antimicrobial activity. Agar diffusion and agar-dilution were used as test methods and a set of two Gram-positive (Staphylococcus aureus and Enterococcus faecalis) and four Gram-negative bacterial strains (Escherichia coli, Pseudomonas aeruginosa, Proteus vulgaris G, Klebsiella pneumoniae and Salmonella abony) and a yeast, Candida albicans, were the test microorganisms. All the investigated compounds were active against Gram-positive bacteria, especially beta-caryophyllene against Enterococcus faecalis (MIC 6 ppm), but only few substances showed activity towards Gram-negative bacteria, except for cinnamic acid, which was active against all (MIC 60 ppm) and Candida albicans, against which cinnamic acid and caryophyllene oxide showed high activity (MIC < 60 ppm).     

Fluorescence decay kinetics of acetone vapour at low pressures

Acetone-h₆ and -d₆ were excited by a short UV laser pulse to the nπ* state. Using pressures of 10^?4-10 ^?3 Torr, two distinct decay components were observed - the faster with a decay time of less than 20 ns and the slower of about 5 μs. Increasing the pressure leads to the appearance of two longer-lived decay components, which are apparently absent in the case of isolated molecules. Based on the deuteration effect, excitation wavelength dependence, quenching kinetics and analogy with other molecules, the four decay components are assigned as follows. The fastest component is due to dephasing of the initially excited state, forming a quasi-stationary eigenstate. The second component is due to the radiative decay of the latter states. The third, to decay of triplet states not directly coupled to the initially excited singlet states, and the last to the thermalized triplet state.     

Determination of saturated organic vapour concentrations by a spectroscopic method

A spectroscopic method for determination of organic saturated vapour concentrations is presented. From absorption spectra, an empirical equation is established relating absorbance with the temperatures of the cell and its side arm. Application to determination of benzene vapour concentrations, as well as the heat of vaporization referred to 0 K is described: the value 47.90 ± 0.03 kJ mol⁻ was obtained.     

Dairy aroma compounds recovery by pervaporation

Original pervaporation experiments with two dairy aroma compounds diluted in model aqueous solutions through GFT silicalite-filled silicone composite membrane and GKSS PEBA homogeneous membrane (0.1 m² effective area) were carried out on a pilot-plant. A systematic approach was done, studying the influence of various operating parameters (feed temperature and permeate pressure). The permeabilities of the membranes were calculated for each permeant, based on the estimation of the driving force as a fugacities difference. The pervaporation membranes tested showed a good selectivity for the extraction of methylthiobutanoate (hydrophobic molecule with cheese fragrance) at high dilution rate. However, these membranes proved to be less selective for the recovery of diacetyl (hydrophilic butter aroma). For this component, the coupling of pervaporation and two-stage condensation improved significantly the selectivity of the whole process. The thermodynamic properties in the liquid feed (real dairy media) as well as in the permeate (vapour-liquid equilibria at low pressure) have to be well known in order to optimize the recovery of the aroma compounds     

The vapour pressures over saturated aqueous solutions of dl-2-aminobutyric acid, 4-aminobutyric acid,sodium-d-gluconate,sodium hippurate,and potassium magnesium-l-aspartate

Vapour pressures of water over saturated solutions of dl-2-aminobutyric acid, 4-aminobutyric acid, sodium-d-gluconate, sodium hippurate, and potassium magnesium-l-aspartate were determined over the (278 to 322) K temperature range. The determined vapour pressures were used to obtain the water activities, the molar enthalpies of vaporization, and the osmotic coefficients of sodium-d-gluconate.     

Decomposition temperatures and vapour pressures of selected ionic liquids for electrochemical applications

Journal of Thermal Analysis and Calorimetry - The thermal behaviour of selected ionic liquids, potentially useful as electrolyte components in electrochemical devices, formed by ammonium or...     

Solubilities and vapour pressures of saturated aqueous solutions of sodium tetraborate,sodium carbonate,and magnesium sulfate and freezing-temperature lowerings of sodium tetraborate and sodium carbonate solutions

Solubilities and vapour pressures of water over saturated solutions of sodium tetraborate, sodium carbonate, and magnesium sulfate and freezing-temperature lowerings of sodium tetraborate and sodium carbonate solutions were determined and compared with the literature data. These results permitted the evaluation of osmotic and activity coefficients and molar enthalpies of vaporization.     

Characteristic aroma compounds from different pineapple parts

Characteristic aroma volatile compounds from different parts of cayenne pineapple were analyzed by headspace-solid phase microextraction (HS-SPME) and gas chromatography-mass spectrometry (GC/MS). The main volatile compounds were esters, terpenes, ketones and aldehydes. The number and content of aroma compounds detected in pulp were higher than those found in core. In pulp, the characteristic aroma compounds were ethyl 2-methylbutanoate, ethyl hexanoate, 2,5-dimethyl-4-hydroxy-3(2H)-furanone (DMHF), decanal, ethyl 3-(methylthio)propionate, ethyl butanoate, and ethyl (E)-3-hexenoate; while in core the main compounds were ethyl 2-methylbutanoate, ethyl hexanoate and DMHF. The highest odor units were found to correspond to ethyl 2-methylbutanoate, followed by ethyl hexanoate and DMHF. The odor units found for pulp were higher than those for core.