Solubility of 1-Butene in Water and in a Medium for Cultivation of a Bacterial Strain

Solubility measurements of 1-butene in water, from 20 to 50°C and at atmospheric pressure, were carried out using a Ben-Naim/Baer-type apparatus. The experimental results have a precision of about ±0.3%. Using accurate thermodynamic relations, the Ostwald coefficients at the experimental conditions and at infinite dilution, the mole fractions of the dissolved gas at the gas partial pressure of 101.325 kPa and the Henry coefficients at the water vapor pressure were calculated. The mole fraction of dissolved gas were fitted to the Clarke, Glew, and Weiss equation and thermodynamic quantities, standard molar Gibbs energy, entropy, and enthalpy changes, for the process of transferring the 1-butene molecules from the gaseous to the water phase, were computed. Moreover, solubility measurements of 1-butene in an aqueous medium for the cultivation of Xanthobacter Py2 in the same temperature range were also performed at atmospheric pressure. These solubility data are approximately 2.6% lower than those observed in pure water.     

Experimental and theoretical determination of the saturation vapor pressure of silicon in a wide range of temperatures

Reference books and original studies devoted to the determination of the saturation vapor pressure of silicon in a wide range of temperatures have been analyzed. It has been established that no reliable experimental data in the range of high temperatures (above 2000 K) are available in the literature. It has been demonstrated that there is a need to perform additional theoretical and experimental investigations with the use of different methods. The total pressure and partial pressures of Si _n (n = 1−6) molecules over liquid silicon are calculated in the temperature range 1700–3400 K. The calculation of the composition of the gas phase over the “Si(l)-container” systems is performed. Materials of the crucibles intended for the use in experimental investigations of the temperature dependence of the saturation vapor pressure of silicon over the liquid phase are recommended.     

Thermodynamic study of Ag<Subscript>8</Subscript>GeSe<Subscript>6</Subscript> by EMF with an Ag<Subscript>4</Subscript>RbI<Subscript>5</Subscript> solid electrolyte

The Ag–Ge–Se system was studied in the range of compositions Ag₂Se–GeSe₂–Se by measuring the EMF of the concentration (relative to the silver electrode) circuits with a solid electrolyte Ag₄RbI₅ in the temperature range 290–430 K. The polymorphic transition temperature of Ag₈GeSe₆ (320 K) was determined and the partial molar functions of silver were calculated for both crystal modifications of this compound based on the EMF measurements. The thermodynamic functions of formation and entropy of both modifications of Ag₈GeSe₆ and the thermodynamic functions of its polymorphic transition were calculated.     

A novel method for estimation of transition temperature for polymorphic pairs in pharmaceuticals using heat of solution and solubility data

A novel method for thermodynamic stability studies of polymorphic drug substances has been developed. In order to estimate the transition temperature for an enantiotropic polymorphic pair, a formula for calculating the temperature at which the solubilities of each polymorph become equal has been derived with heat of solution and solubility as the variables. This formula is based on the assumption that van't Hoff plots (logarithmic solubility versus reciprocal of absolute temperature plots) of each polymorph show a straight line (heat of solution is independent of temperature) whose slope can be expressed as a function of heat of solution. The transition temperatures for seratrodast, acetazolamide and carbamazepine polymorphic pairs calculated by the formula were in good agreement with the results of previous studies. Furthermore, the calculated transition temperature for the indomethacin polymorphic pair was above the melting point, an unrealistic temperature range, suggesting that these polymorphs are monotropically related. Since this formula requires solubility data at only one arbitrary temperature other than heat of solution data for both polymorphs in a polymorphic pair, the proposed method is much faster than the conventional method requiring solubility data at five or more different temperatures for the preparation of van't Hoff plots.     

Experimental Vapor Pressures and Derived Thermodynamic Properties of Aqueous Solutions of Lithium Nitrate from 423 to 623 K

Vapor pressures of six aqueous lithium nitrate solutions with molalities of (0.181, 0.526, 0.963, 1.730, 2.990, and 5.250) mol-kg^–1 have been measured in the temperature range 423.15–623.15 K with a constant-volume piezometer immersed in a precision liquid thermostat. The static method was used to measure the vapor pressure. The total uncertainty of the temperature, pressure and composition measurements were estimated to be less than 15 mK, 0.2%, and 0.014%, respectively. The vapor pressures of pure water were measured with the same apparatus and procedure to confirm the accuracy of the method used for aqueous lithium nitrate solutions. The results for pure water were compared with high-accuracy P_S–T_S data calculated from the IAPWS standard equation of state. Important thermodynamic functions (activities of water and lithium nitrate, partial molar volumes, osmotic coefficient, excess relative partial molar entropy, and relative partial molar enthalpy values of the solvent) were derived using the measured values of vapor pressure for the solution and pure water. The measured and derived thermodynamic properties for solutions were compared with data reported in the literature. The present results are consistent with most previous reported thermodynamic data for the pure water and H₂O + LiNO₃ solutions at low temperatures.     

In Situ Direct Measurement of Vapor Pressures and Thermodynamic Parameters of Volatile Organic Materials in the Vapor Phase: Benzoic Acid,Ferrocene, and Naphthalene

We report the direct determination of vapor pressures and optical and thermodynamic parameters of powders of low‐volatile materials in their vapor phase using a commercial UV/Vis spectrometer. This methodology is based on the linear proportionality between the density of the saturated gas of the material and the absorbance of the gas at different temperatures. The vapor pressure values determined for benzoic acid and ferrocene are in good agreement with those reported in the literature with ～2–7 % uncertainty. Thermodynamic parameters of benzoic acid, ferrocene, and naphthalene are determined in situ at temperatures below their melting points. The sublimation enthalpies of the investigated organic molecules are in excellent agreement with the ICTAC recommended values (less than 1 % difference). This method has been used to measure vapor pressures and thermodynamic parameters of organic volatile materials with vapor pressures of ～0.5–355 Pa in the 50–100 °C temperature range.     

Synthesis,structure, and conductivity of BIMEVOX oxide ceramics

The methods using solid-phase synthesis or liquid precursors converted compounds of BIMEVOX family (ME is a bi- to pentavalent cation) into stable materials in a sufficiently wide concentration and temperature ranges. The crystal structure of various BIMEVOX polymorphic modifications was refined and their behavior was analyzed with respect to temperature and oxygen partial pressure. The phase transition temperature ranges were fixed. The particle size distribution was determined by means of laser diffraction and optical microscopy. The impedance measurements of BIMEVOX electroconductivity against temperature, composition, oxygen partial pressure detected the most promising compositions with respect to the absolute conductivity value and linear conductivity relationship to temperature and Po₂. Different conductivity of specimens was noted with respect to method of synthesis.     

Solid-state characterization of chloroprocaine hydrochloride

Summary Chloroprocaine hydrochloride (2-CPCHC) is a local anaesthetic agent of the ester type preferentially used for epidural anaesthesia. The compound, official in the USP, was found to exist in two polymorphic crystal forms which have been characterized by thermomicroscopy, differential scanning calorimetry (DSC), pycnometry, FTIR-, FT-Raman-spectroscopy as well as X-ray powder diffractometry. Based on these data the relative thermodynamic stability of the two forms was determined and is represented in a semi-schematic energy/temperature diagram. Mod. I° is the thermodynamically stable form at room temperature. This form is present in commercial products and can be crystallized from ethanol. Mod. II can be obtained by annealing the supercooled melt in a temperature range between 100 and 130°C. Upon heating mod. II exhibits an exothermic phase transition (Δ_trsH_II-I: -5.0±0.5 kJ mol^-1) at about 134°C to mod. I° (melting point 175°C, Δ_fusH_I: 46.6±0.6 kJ mol^-1). The exothermic transformation of mod. II to mod. I° confirms that mod. I° is thermodynamically stable in the entire temperature range (heat of transition rule) whereas mod. II is monotropically related to mod. I°, i.e. is metastable at all temperatures below its melting point. Mod. II is of low kinetic stability at room temperature and the transformation to mod. I° starts within a few minutes at room temperature. The N-H band in the infrared spectrum of mod. I° (3433 cm^-1) lies at significantly higher wavenumbers than that of mod. II (3413 cm^-1) indicating differences in the hydrogen bonding arrangement. Furthermore, the measured density of mod. I° is lower than the density of mod. II and thus both, the IR- and the density-rule are violated in this polymorphic system.     

Poly(aquachlorobis(1,10–phenanthroline)copper(II)iodidemonohydrate)/GCE for simultaneous determination of caffeine and theophylline in human serum,tea, and tablet samples

This paper presents metal complex based polymer film modified electrode for simultaneous determination of caffeine, and theophylline. Potentiodynamic fabrication of poly(aquachlorobis(1,10– phenanthroline)copper(II)iodidemonohydrate) modified glassy carbon electrode (poly(ACP₂CuIH)/GCE) was verified using cyclic voltammetric and electrochemical impedance spectroscopic techniques. In contrast to the unmodified glassy carbon electrode, the poly(ACP₂CuIH)/GCE in equi-molar mixture of theophylline and caffeine revealed sufficiently separated oxidative peaks with much enhanced peak current showing electrocatalytic property of the polymer film towards the oxidation of theophylline and caffeine. Under optimized solution pH and square wave voltammetric parameters, oxidative peak current response of poly(ACP₂CuIH)/GCE showed linear dependence on the concentration of caffeine and theophylline in the concentration range 1.0–200.0 µM with limit of detection 8.92 × 10^-3 µM for theophylline, and 1.02 × 10^{-2 µ}M for caffeine. Spike recovery in the range 97.0-102.4% for theophylline, and 95.4-100.0% for caffeine, interference recovery in the range 96.0–101.0% for theophylline, and 95.7–104.3% for caffeine, agreement of the detected amounts of theophylline and caffeine in tablet samples with the nominal values, and stability of the modified electrode all validated the developed method for simultaneous determination of theophylline and caffeine in wide range of real samples. The method was applied for simultaneous determination of both theophylline and caffeine in three tea brands (Black lion, Addis, and Wush wush), pharmaceutical tablet brands (Panadol extra, and Theodrine), and human blood serum samples making the method an excellent candidate.     

Electroconductivity of Cesium Orthophosphate in Dry Air

The electroconductivity and thermal behavior of cesium orthophosphate is studied in dry air. The differential scanning calorimetry and dilatometry data show it to experience a phase transition at 450–620°C. The transition occurs in a wide temperature range, is accompanied by perceptible hysteresis, and shifts towards lower temperatures with rising air humidity.     

On the polymorphism of dicarboxylic acids: I pimelic acid

The results of solid-state analytical studies on pimelic acid demonstrate that the compound occurs in three polymorphic modifications. The modifications have been characterized by means of thermal analysis (videosupported thermomicroscopy, DSC, TGA), temperature-controlled FTIR microscopy and X-ray powder diffractometry, FT Raman and¹³C NMR spectroscopy, as well as pycnometry. The thermodynamic relationships are illustrated in a semi-schematic energy/temperature-diagram, which gives information about the relative stabilities and physical properties of the three modifications. Mod. III (commercial product, density 1.315 g cm^–3) is the thermodynamically stable form between absolute zero and nearly 57 °C (transition point with mod. II 55 to 59 °C). Mod. II (density 1.276 g cm^–3) is thermodynamically metastable in ambient conditions, but resistant. The transition point of mod. II with I (m.p. 105 °C) was determined to be 97.0 to 97.6 °C.Part of this work was presented at the 8th Österreichische Chemietage, Graz, Austria, September 28–30, 1994     

Thermodynamics of sodium chloride solutions at high temperatures

Osmotic coefficients are reported from vapor-pressure-lowering measurements on sodium chloride solutions at concentrations from approximately 4m to saturation and at temperatures from 75° C to 300° C. In combination with previously reported measurements at lower concentrations, these results allow a correlation of free energies for the system NaCl–H₂O over a range of concentrations and temperatures that is unprecedented for any aqueous electrolyte. Activity coefficients and other thermodynamic quantities for both salt and water have been calculated for the complete range of concentrations and temperatures. Calculated heats of solution and standard partial molal entropies agree well with calorimetric determinations where comparison is possible. The excess partial molal entropy of the salt is informative concerning structural effects and their changes with temperature and concentration.Presented in part at the 160th National Meeting of the American Chemical Society, Chicago, Illinois, September 1970.     

Polymorphism of paracetamol

The thermodynamic relationship between crystal modifications of paracetamol was studied by alternative methods. Temperature dependence of saturated vapor pressure for polymorphic modifications of the drug paracetamol (acetaminophen) was mea sured and thermodynamic functions of the sublimation process calculated. Solution calorimetry was carried out for the two modifications in the same solvent. Thermodynamic parameters for sublimation for form I (monoclinic) were found: ΔG _sub²⁹⁸=60.0 kJ mol⁻¹; ΔH _sub²⁹⁸=117.9±0.7 kJ mol⁻¹; ΔS _sub²⁹⁸=190±2 J mol⁻¹ K⁻¹. For the orthorhombic modification (form II), the saturated vapor pressure could only be studied at 391 K. Phase transition enthalpy at 298 K, ΔH _tr²⁹⁸(I→II)=2.0±0.4 kJ mol⁻¹, was derived as the difference between the solution enthalpies of the noted polymorphs in the same solution (methanol). Based on ΔH _tr²⁹⁸ (I→II), differences between temperature dependencies of heat capacities of both modifications and the vapor pressure value of form II at 391 K, the temperature dependence of saturated vapor pressure and thermodynamic sublimation parameters for modification II were also estimated (ΔG _sub²⁹⁸=56.1 kJ mol⁻¹; ΔH _sub²⁹⁸=115.9±0.9 kJ mol⁻¹; ΔS _sub²⁹⁸=200±3 J mol⁻¹ K⁻¹). The results indicate that the modifications are monotropically related, which is in contrast to findings recently reported found by classical thermochemical methods.     

Polymorphism and solvatomorphism of bicalutamide

Single crystals of the crystallosolvate [bicalutamide + DMSO] with 1:1 stoichiometry were grown, and their structures were solved by X-ray diffraction methods. Polymorphic modifications I and II, the amorphous state, and the DMSO crystallosolvate of bicalutamide were prepared and thermochemistry of fusion processes was studied by DSC technique. The temperature dependence of the saturated vapor pressure of polymorphic form I was obtained and the thermodynamic characteristics of the sublimation process including the crystal lattice energy were calculated. The solution enthalpies of the forms under consideration and the crystallosolvate were acquired by the solution calorimetry procedure. The phase transition enthalpies estimated for form I, form II, and the amorphous state followed the rank order: form I— > form II, form I— > amorphous state, and form II— > amorphous state. The crystal lattice energy of polymorphic form II was determined using the results of sublimation and solution calorimetric experiments. The difference between the crystal lattice energy of the crystallosolvate and unsolvated phases was observed. The dissolution kinetics of forms I, II, the amorphous state, and DMSO solvate in water were investigated.     

The kinetics of tritium-hydrogen exchange between xanthine,theophylline,caffeine and water

Isotopic hydrogen exchange at C-8 of xanthine, theophylline and caffeine in water has been studied at several temperatures and constant pH. The rates of detritiation of these compounds have been determined over a pH range at constant temperature. The rate-pH profiles for theophylline and caffeine are interpreted in terms of rate determining attack by hydroxide ion on protonated substrate. For caffeine and xanthine at high pH an additional mechanism involving hydroxide catalysed exchange of the neutral compound is suggested.     

The ionization of aqueous ammonia to 300°C in KCl media

A potentiometric technique using a hydrogen electrode concentration cell with flowing solutions was employed to study the ionization of ammonia over the temperature range 50–295°C in KCl media from 0.04 to 3.3m. The isothermal pressure coefficient of the ionization reaction was obtained at pressures up to 100 bars and temperatures to 250°C in these same media, and was found to vary as the square root of the ionic strength within the experimental error. Smoothing functions have been presented which also fit selected published data on the ammonia ionization reaction with a standard error of fit of 1.8 times the assigned uncertainties. Thermodynamic parameters for the reaction have been tabulated at rounded temperatures, and ionic strengths at the saturation vapor pressure. A limit is given for the association quotient of HCl at 300°C in 3m KCl based on these data.     

咖啡因、茶碱和氨茶碱的低温热容和热分析

咖啡因、茶碱和氨茶碱是临床应用中广泛使用的三种重要的甲基化的黄嘌呤.采用绝热量热、热重分析(TG)和差示扫描量热法(DSC)研究了这三种药物的热力学性质.采用绝热量热法测定了β型-咖啡因、茶碱和氨茶碱在80-370K温度范围内的摩尔热容值,结果显示氨茶碱的摩尔热容值最大,茶碱的摩尔热容值最小.采用最小二乘法对这三种药物热容的测量值和温度进行了拟合,得到了热容与折合温度的多项式,计算了咖啡因、茶碱和氨茶碱在298.15K时的热容分别为226.49、218.13和554.78J·K-1·mol-1;并计算了它们相对于298.15K时的焓和熵.采用热综合分析仪对这三种药物的热稳定性进行了评价,结果表明它们的热稳定顺序为氨茶碱咖啡因茶碱.通过DSC分析,得到了咖啡因和茶碱的相转变温度、相转变焓和熵.基于密度泛函理论的第一性原理,计算了咖啡因和茶碱分子的结构稳定性,结果显示咖啡因分子的稳定性低于茶碱,与实验结果吻合.     

Spreading and compression of n-hexadecyl acrylate at liquid-air interface

Usingn-hexadecyl acrylate, surface pressure-area (F-A) curves and equilibrium spreading pressuresF ^e were measured at various temperatures (5.7°–46°C) by the Langmuir balance (F-A) and the Wilhelmy-plate method (F ^e). At low temperatures (T<13 °C) condensed films and the liquid-condensed/solid condensed transition can be observed. At high temperatures (T>30 °C) liquid-expanded films occur. In the intermediate range the compression curves have two transition points. The transition pressureF ₁ between liquid-expanded and condensed film has a marked temperature dependence. The transition enthalpiesH ₁ decrease with increasing temperature and become zero at 29.2 °C. The second transition is related to a transition between the condensed films (F ₂). The slight temperature dependence of this transition is accompanied by an increasing change of area as well as by increasing transition enthalpiesH ₂.TheF ^e-T curve has two distinct breaks, at the melting pointT _m and atT=30 °C. The break atT _m is due to the melting process and the break atT=30 °C is caused by a phase transition between a liquid-expanded film and a condensed film.The phase diagram was constructed from the transition pressures. It can be demonstrated that the highest pressures of the thermodynamic stable film occurs atT _m. At temperaturesT>T _m equilibrium spreading pressure and equilibrium collapse pressure are identical whereas atT _m supercompression of the monolayer occurs. The film in this state behaves like a supercooled liquid. Obviously, rupture and collapse of such a film lead to a thermodynamically metastable bulk phase.     

Effects of melting and ordering on the isosteric heat and monolayer density of argon adsorption on graphite

The aim of this paper is to study the effects of temperature on the state of the adsorbed argon on an uniform graphite surface. We applied the kinetic Monte Carlo scheme to simulate adsorption over a very wide range of temperature, which allows us to model the vapor–solid, the vapor–liquid and the order–disorder transition of the monolayer. The main distinction of our methodology is that it accounts for the lattice constant change with loading in the case of formation of an ordered molecular layer by appropriately changing the simulation box size. To do this we enforced the equality of the tangential pressures obtained by the virial and thermodynamic routes, which corresponds to the minimum Helmholtz free energy of a system at a given number of molecules and volume. This criterion is a consequence of the Gibbs–Duhem equation. A significant result obtained by application of the new simulation method was a sharp contraction of the monolayer just after its completion and the onset of the second layer. It manifests itself in an additional heat release. We re-determined the 2D-melting and 2D-critical temperatures of the molecular layer of argon. We also analyzed the order–disorder transition above the 2D-melting and showed that it could occur at some temperatures above the 2D-critical temperature. In this case, a hexagonal lattice appears at a sufficiently large tangential pressure. The effects of loading on the lattice constant, the 2D-critical temperature of the order–disorder transition and the differential heat of adsorption are thoroughly discussed.     

On-line FT-MIR/NIR process analysis

FT-IR spectrometers designed for laboratory operation are generally not suited for plant production areas where ambient temperatures often exceed 120° F and noise levels are extremely high. The Nicolet Pro-IR 5 process FT-IR spectrometer can operate in hostile environments over the spectral range from 10 000 to 250 wavenumbers. We have evaluated the performance of this system using a set of commercial detergent samples and a wide range of gas mixtures. The detergent samples were simultaneously analyzed for twelve components using a sophisticated partial least-squares statistical analysis software package. The concentrations ranged from 0.1 to over 50 wt.-%, with water being the major component. A comparison will be made between the NIR and MIR results using flow-through ATR (attenuated total reflectance) and transmission cells.