New synthetic method and thermochemistry of szaibelyite

A new synthetic method of szaibelyite (2MgO·B₂O₃·H₂O) has been reported. The enthalpy of solution of 2MgO·B₂O₃·H₂O in 2.9842 mol dm⁻³ HCl (aq) was determined. From a combination of this result with measured enthalpies of solution of H₃BO₃ in 2.9842 mol dm⁻³ HCl (aq) and of MgO in (HCl+H₃BO₃) solution, together with the standard molar enthalpies of formation of MgO (s), H₃BO₃ (s), and H₂O (l), the standard molar enthalpy of formation of −(2884.36±1.82) kJ mol⁻¹ of 2MgO·B₂O₃·H₂O was obtained.     

Study on the interaction of nucleic acids with silver nanoparticles—Al(III) by resonance light scattering technique and its analytical application

It is found that Al(III) can further enhance the intensity of resonance light scattering (RLS) of the silver nanoparticles (AgNPs) and nucleic acids system. Based on this, a novel method of determination of nucleic acids is proposed in this paper. Under optimum conditions, there are linear relationships between the enhancing extent of RLS and the concentration of nucleic acids in the range of 1.0 × 10⁻⁹-1.0 × 10⁻⁷ g mL⁻¹, 1.0 × 10⁻⁷-2.0 × 10⁻⁶ g mL⁻¹ for fish sperm DNA (fsDNA), 1.0 × 10⁻⁹-7.0 × 10⁻⁸ g mL⁻¹ for calf thymus DNA (ctDNA) and 1.0 × 10⁻⁹-1.0 × 10⁻⁷ g mL⁻¹ for yeast RNA (yRNA). The detection limits (S/N = 3) of fsDNA, ctDNA and yRNA are 4.1 × 10⁻¹⁰ g mL⁻¹, 4.0 × 10⁻¹⁰ g mL⁻¹ and 4.5 × 10⁻¹⁰ g mL⁻¹, respectively. The studies indicate that the RLS enhancement effect should be ascribed to the formation of AgNPs-Al(III)-DNA aggregations through electrostatic attraction and adsorption bridging action of Al(III). And the sensitivity and stability of the AgNPs-fsDNA system could be enhanced by Al(III).     

Thermal properties of Ga<Subscript>2</Subscript>O<Subscript>3</Subscript>–PbO–P<Subscript>2</Subscript>O<Subscript>5</Subscript> glass system

Thermal behavior of xGa₂O₃–(50 − x)PbO–50P₂O₅ (x = 0, 10, 20, and 30 mol.% Ga₂O₃) and xGa₂O₃–(70 − x)PbO–30P₂O₅ (x = 0, 10, 20, 30, and 40 mol.% Ga₂O₃) glassy materials were studied by thermo-mechanical analysis (TMA) and differential thermal analysis (DTA). Replacement of PbO for Ga₂O₃ is accompanied by increasing glass-transition temperature (263 ≤ T _g/°C ≤ 535), deformation temperature (363 ≤ T _d/°C ≤ 672), crystallization temperature (396 ≤ T _c/°C ≤ 640) and decreasing of coefficient of thermal expansion (5.1 ≤ CTE/ppm K⁻¹ ≤ 16.7). Values of Hruby parameter were determined (0.1 ≤ K _H ≤ 1.3). The thermal stability of prepared glasses increases with increasing of concentration of Ga₂O₃.     

Thermal behavior of 3,4,5-triamino-1,2,4-triazole dinitramide

The thermal decomposition behavior of 3,4,5-triamino-1,2,4-triazole dinitramide was measured using a C-500 type Calvet microcalorimeter at four different temperatures under atmospheric pressure. The apparent activation energy and pre-exponential factor of the exothermic decomposition reaction are 165.57 kJ mol⁻¹ and 10^18.04 s⁻¹, respectively. The critical temperature of thermal explosion is 431.71 K. The entropy of activation (ΔS ^≠), enthalpy of activation (ΔH ^≠), and free energy of activation (ΔG ^≠) are 97.19 J mol⁻¹ K⁻¹, 161.90 kJ mol⁻¹, and 118.98 kJ mol⁻¹, respectively. The self-accelerating decomposition temperature (T _SADT) is 422.28 K. The specific heat capacity of 3,4,5-triamino-1,2,4-triazole dinitramide was determined with a micro-DSC method and a theoretical calculation method. Specific heat capacity (J g⁻¹ K⁻¹) equation is C _p = 0.252 + 3.131 × 10⁻³  T (283.1 K < T < 353.2 K). The molar heat capacity of 3,4,5-triamino-1,2,4-triazole dinitramide is 264.52 J mol⁻¹ K⁻¹ at 298.15 K. The adiabatic time-to-explosion of 3,4,5-triamino-1,2,4-triazole dinitramide is calculated to be a certain value between 123.36 and 128.56 s.     

On the variation of the distances of Nd3+−Cl− and Tm3+−Cl− in mixed system of dimethyl sulfoxide and water

The stability constants, β₁, of each monochloride complex of Ln(III) (Ln=Nd or Tm) have been determined in the mixed system of dimethyl sulfoxide (DMSO) and water with 1.0 mol·dm⁻³ ionic strength using a solvent extraction technique. The values of β₁ of Ln(III) decrease to about 0.2 mole fraction of DMSO (X _s) in the mixed solvent system and then increase withX _s (>about 0.2). However, the variation mode of β₁ of Nd(III) withX _s somewhat differs from that of Tm(III). Calculation of Ln³⁺−Cl⁻ distance using a Born-type equation of the Gibbs' free energy derived from the β₁ evealed the followings: (1) For Tm³⁺ with coordination number 8, the estimated distance between Tm³⁺ and Cl⁻ (d _Tm-Cl) increases linearly withX _s in 0.00≤X _s≤0.17. This means an enlargement of the primary solvation sphere size of Tm³⁺ withX _s. On the other hand, thed _Tm-Cl shows a decrease withX _s in 0.17<X _s<0.28. (2) The estimatedd _Nd-Cl increases linearly withX _s in 0.00≤X _s<0.06 and 0.06<X _s≤0.17, but their slopes are different. The larger slope againstX _s in 0.06<X _s≤0.17 is attributable to a lowering of the β₁ by a coordination of ClO₄ ⁻ into the secondary solvation sphere of Nd³⁺ and/or by an increase in the solvation number of the primary solvation sphere of Nd³⁺.     

Thiourea-isothiouronium conjugate for strong and selective binding of very hydrophilic H2PO4 anion at the 1,2-dichloroethane-water interface

Potential use of a surfactant-like receptor is demonstrated at the 1,2-dichloroethane-water interface for strong and selective binding of H₂PO₄⁻ over Br⁻ and Cl⁻. The analysis by interfacial tensiometry reveals that the interfacial adsorption of a thiourea-isothiouronium conjugate, BT-C₁, is significantly stabilized by the binding of H₂PO₄⁻ with the adsorption constant of 1.7 × 10⁵ M⁻¹ while the interfacial adsorptivity of this receptor is relatively moderate for Br⁻ (0.81 × 10⁵ M⁻¹) and Cl⁻ (0.63 × 10⁵ M⁻¹). Such complexation-induced interfacial adsorption behaviors of BT-C₁ are discussed as a basis for the development of receptor-based chemical sensors for phosphate anions.     

Thermodynamic properties of Ni-Ga melts

The partial mixing enthalpies of the components (Δ_m $ \bar H $ \bar H _i ) of the Ni-Ga melts were measured using the high-temperature isoperibolic calorimetry at 1770 ± 5 K in wide concentration interval. The limiting partial mixing enthalpy of gallium in a liquid nickel (Δ_m $ \bar H $ \bar H _Ga^∞) is −95.5 ± 19.8 kJ mol⁻¹, and similar function of nickel in liquid gallium (Δ_m $ \bar H $ \bar H _Ni^∞) is −74.5 ± 16.4 kJ mol⁻¹. The integral mixing enthalpy of liquid alloys of this system was calculated from partial enthalpies for the whole concentration area (Δ_m H _min = −32.1 ± 2.7 kJ mol⁻¹ at x _Ni = 0.5). The Δ_m H value of liquid nickel-gallium alloys independence of the temperature is confirmed. Enthalpies of formation of liquid (Δ_m H) phases of Ni-Ga system were compared with ones for solid (Δ_f H) phases of this system. An analysis of d-metals influence on formation energy of Ga-d-Me melts was made using the values of Δ_f H for intermediate phases of these systems. The article was translated by the authors.     

Batch and hydrodynamic monitoring of vitamin C using novel periodate selective sensors based on a newly synthesized Ni(II)-Schiff bases complexes as a neutral receptors

A highly selective membrane electrodes based on a two newly synthesized nickel (II) Schiff bases, [NiL¹] and [NiL²] where L¹ and L² are N,N/bis(salicylaldehyde)4,5-dimethyl-1,2-phenylenediamine (H₂L¹) and N,N/bis(salicylaldehyde)4,5-dichloro-1,2-phenylenediamine (H₂L²) were used as a neutral carrier ionophores for static and hydrodynamic potentiometric mode of operations for the determination of periodate. Under static mode of operation, the sensors displayed a near-Nernstian slope of −66.1 ± 0.8 and −59.9 ± 1.1 mV decade⁻¹ of activity and detection limits to 5.2 × 10⁻⁶ and 7.3 × 10⁻⁶ mol L⁻¹ for the sensors based on [NiL¹] and [NiL²], respectively. Under hydrodynamic mode of operation (FIA), the slope of the calibration plot, limit of detection, and working linear range were −71.1 mVdecade⁻¹ of activity, 7.3 × 10⁻⁶ and 1.0 × 10⁻⁵ to 1.0 × 10⁻³ mol L⁻¹, respectively. The response time of the sensors in whole concentration ranges was very short (<10 s). The response of the sensors was independent on the pH range of 3-8. A tubular version was further developed and coupled to a flow injection system for ascorbic acid (AA) determination in beverages and pharmaceutical preparations. This approach was achieved by selecting a 50-cm reactor and an overall flow of 3 mL min⁻¹, and injecting volume 100 μL of AA standards in a 1.0 × 10⁻⁴ mol L⁻¹ IO₄⁻ solution. Under these conditions, a linearity range of 2-13 μg mL⁻¹, with a slope of 4.97 mV (mg/L)⁻¹ (r² = 0.9995), detection limit 0.9 mg L⁻¹ and a reproducibility of ±1.1 mV (n = 5) was recorded. This simple and inexpensive flow injection analysis manifold, with a good potentiometric detector, enabled the analysis of ∼50 samples h⁻¹ without requiring pretreatment procedures. An average recovery of 98.8% and a mean standard deviation of 1.3% were obtained.     

Kinetics of reduction of iron oxides by H2: Part II. Low temperature reduction of magnetite

This study deals with the reduction of Fe₃O₄ by H₂ in the temperature range of 210-950 °C. Two samples of Fe₃O₄ produced at 600 and 1200 °C, designated as Fe₃O₄₍₆₀₀₎ and Fe₃O_4(1200), have been used as starting material.Reduction of Fe₃O₄₍₆₀₀₎ by H₂ is characterized by an apparent activation energy ‘E_a’ of 200, 71 and 44 kJ/mol at T < 250 °C, 250 °C < T < 390 °C and T > 390 °C, respectively. The important change of E_a at 250 °C could be attributed to the removal of hydroxyl group and/or point defects of magnetite. This is confirmed during the reduction of Fe₃O_4(1200). While transition at T ≈ 390 °C is probably due to sintering of the reaction products as revealed by SEM.In situ X-rays diffraction reduction experiments confirm the formation of stoichiometric FeO between 390 and 570 °C. At higher temperatures, non-stoichiometric wüstite is the intermediate product of the reduction of Fe₃O₄ to Fe.The physical and chemical modifications of the reduction products at about 400 °C, had been confirmed by the reduction of Fe₃O₄₍₆₀₀₎ by CO and that of Fe₃O_4(1200) by H₂. A minimum reaction rate had been observed during the reduction of Fe₃O_4(1200) at about 760 °C. Mathematical modeling of experimental data suggests that the reaction rate is controlled by diffusion and SEM observations confirm the sintering of the reaction products.Finally, one may underline that the rate of reduction of Fe₃O₄ with H₂ is systematically higher than that obtained by CO in the explored temperature range.     

Flow injection analysis of ethyl xanthate by gas diffusion and UV detection as CS2 for process monitoring of sulfide ore flotation

A sensitive and robust analytical method for spectrophotometric determination of ethyl xanthate, CH₃CH₂OCS₂⁻ at trace concentrations in pulp solutions from froth flotation process is proposed. The analytical method is based on the decomposition of ethyl xanthate, EtX⁻, with 2.0 mol L⁻¹ HCl generating ethanol and carbon disulfide, CS₂. A gas diffusion cell assures that only the volatile compounds diffuse through a PTFE membrane towards an acceptor stream of deionized water, thus avoiding the interferences of non-volatile compounds and suspended particles. The CS₂ is selectively detected by UV absorbance at 206 nm (? = 65,000 L mol⁻¹ cm⁻¹). The measured absorbance is directly proportional to EtX⁻ concentration present in the sample solutions. The Beer's law is obeyed in a 1 × 10⁻⁶ to 2 × 10⁻⁴ mol L⁻¹ concentration range of ethyl xanthate in the pulp with an excellent correlation coefficient (r = 0.999) and a detection limit of 3.1 × 10⁻⁷ mol L⁻¹, corresponding to 38 μg L⁻¹. At flow rates of 200 μL min⁻¹ of the donor stream and 100 μL min⁻¹ of the acceptor channel a sampling rate of 15 injections per hour could be achieved with RSD < 2.3% (n = 10, 300 μL injections of 1 × 10⁻⁵ mol L⁻¹ EtX⁻). Two practical applications demonstrate the versatility of the FIA method: (i) evaluation the free EtX⁻ concentration during a laboratory study of the EtX⁻ adsorption capacity on pulverized sulfide ore (pyrite) and (ii) monitoring of EtX⁻ at different stages (from starting load to washing effluents) of a flotation pilot plant processing a Cu-Zn sulfide ore.     

Behavior of cadmium(II) in irradiated aqueous solutions

Behavior of cadmium(II) in aqueous solutions irradiated by accelerated electrons was studied. A concentration of 8.8 × 10⁻⁴ mol L⁻¹ of cadmium dissolved from Cd(NO₃)₂ requires dose of 15 kGy to be effectively removed from the system containing 1 × 10⁻² mol L⁻¹ of HCOOK as a scavenger of OH radicals. The positive effect of deaeration with N₂O or N₂ was observed in the range of lower doses. The addition of solid modifiers (bentonite, active carbon, zeolite, Cu₂O, NiO, TiO₂ and CuO) reduced the effectivity of radiation removal of cadmium. Product of irradiation is CdCO₃. On the contrary, in the system with cadmium dissolved from CdCl₂ radiation reduction takes place. Systems contained organic complexants (ethylene diamine tetraacetic acid–EDTA, citric acid) were also studied. The solutions of Cd(NO₃)₂ containing initial concentration 2.37 × 10⁻⁴ mol L⁻¹ of Cd^II were mixed with 3 × 10⁻⁴ mol L⁻¹ EDTA. In this system the efficient degradation proceeds up to 90% at a dose of 45 kGy with addition of 5 × 10⁻³ mol L⁻¹ carbonate (pH 10.5). The product of irradiation is CdCO₃. The presence of 1 × 10⁻² mol L⁻¹ of HCOOK in the solution is necessary for radiation removal of cadmium complexed with citric acid (1 × 10⁻³ mol L⁻¹) at pH 8. With increasing concentration of HCOOK (up to 5 × 10⁻² mol L⁻¹) decreases the pH value necessary for the radiation induced precipitation of cadmium. The best result was obtained in the system containing zeolite as a solid modifier.     

Calorimetric investigation of the effect of hydroxyanthraquinones in Rheum officinale Baill on Staphylococcus aureus growth

The inhibitory effects of five hydroxyanthraquinones (HAQs) from root and rhizoma of Rheum officinale Baill, a traditional Chinese medicinal (TCM) herb, on Staphylococcus aureus growth were investigated by calorimetry. The power-time curves of S.aureus with and without HAQ were acquired and the extent and duration of inhibitory effects on the metabolism evaluated by growth rate constants (k₁, k₂), half inhibitory ratio (IC₅₀), maximum heat output (P_max) and peak time (t_p). The value of k₁ and k₂ of S. aureus in the presence of the five HAQs decreased with the increasing concentrations of HAQs. Moreover, P_max was reduced and the value of t_p increased with increasing concentrations of the five drugs. The inhibitory activity varied for different drugs. IC₅₀ of the five HAQs was 4 μg ml⁻¹ for emodin, 3.5 μg ml⁻¹ for rhein, 10 μg ml⁻¹ for aloe-emodin, 1000 μg ml⁻¹ for chrysophanol, 1600 μg ml⁻¹ for physcion. The sequence of antimicrobial activity of the five HAQs: rhein > emodin > aloe-emodin > chrysophanol > physicion.     

Determination of noradrenaline and dopamine in pharmaceutical injection samples by inhibition flow injection electrochemiluminescence of ruthenium complexes

Two maximal potential-resolved flow injection-electrochemiluminescent (FI-ECL) peaks were observed for Ru(bpy)₃²⁺/TPrA system at 0.90 and 1.05 V, and for Ru(phen)₃²⁺/TPrA at 1.01 and 1.25 V (vs. Ag/AgCl) in pH 8.0 phosphate buffer solutions. Sensitive ECL inhibition effects were observed in the presence of noradrenaline and dopamine for both of these systems. Therefore, an FI-ECL inhibition method for determination of noradrenaline and dopamine has been developed. Under optimal conditions, linear responses between logarithm of ECL intensity changes and logarithm of sample concentration were found for noradrenaline in the linear range (LR) of 4×10⁻⁸-1×10⁻⁵ mol l⁻¹ with theoretical detection limit (DL) of 2.5×10⁻⁸ mol l⁻¹ for Ru(bpy)₃²⁺/TPrA system, and in LR of 2×10⁻⁸-2×10⁻⁵ mol l⁻¹ with DL of 7.1×10⁻⁹ mol l⁻¹ for Ru(phen)₃²⁺/TPrA system; and for dopamine in LR of 8×10⁻⁸-2×10⁻⁵ mol l⁻¹ with DL of 5.2×10⁻⁸ mol l⁻¹ for Ru(bpy)₃²⁺/TPrA system, in LR of 4×10⁻⁸-2×10⁻⁵ mol l⁻¹ with DL of 1.5×10⁻⁸ mol l⁻¹ for Ru(phen)₃²⁺/TPrA system. It was applied for determination of commercial pharmaceutical injection samples with satisfied results. The mechanism of the inhibition effects was proposed in the preliminary way.     

Effect of oxygen nonstoichiometry on kinetics of oxygen exchange and diffusion in lanthanum-strontium cobaltites

The method of isotopic exchange was used to study the kinetics of oxygen exchange and diffusion in complex oxides of La_{1 − x} Sr _x Co_{1 − y} Fe _y O_{3 − δ} (x = 0.0, y = 0.0; x = 0.6, y = 0.2, 0.4). The rates of oxygen interfacial exchange and its diffusion coefficient were determined for LaCoO_{3 − δ} at the pressure of 5 torr in the temperature range of 600–850°C and at the temperature of 700°C in the pressure range of 1–70 torr. The contributions of the three exchange types were calculated. The order of the dependence of the interfacial exchange rate on the oxygen pressure was 0.51 ± 0.01. In the case of La_0.4Sr_0.6Co_{1 − y} Fe _y O_{3 − δ} (y = 0.2, 0.4) in the temperature range of 600–900°C at the oxygen pressure of 10 torr, the oxygen exchange rates and diffusion coefficients were determined in the material bulk and in the subsurface region; contributions of the three types of exchange were calculated. The paper considers the mechanism of oxygen exchange and diffusion as compared to nonstoichiometry in the oxygen sublattice of the La_{1 − x} Sr _x Co_{1 − y} Fe _y O_{3 − δ} oxides.     

The photodecomposition of platinacycloalkanes in solution: II. 1,4-butanediylplatinum(II) and (IV) compounds

The products of the photolysis of a number of platinacyclopentanes in solution at 25°C under a variety of conditions have been determined. With [I₂P$\text{tCH}{}_2\text{CH}{}_2\text{CH}{}_2\text{C}$H₂(L₂)] (L = PMe₂Ph, PPh₃) in CH₂Cl₂, CH₂Br₂ and (CH₃)₂SO the hydrocarbon products are exclusively ethylene and but-1-ene. Formation of the latter through a 1,3-hydrogen shift is preceded by phosphine ligand dissociation. The photolysis of [ICH₃P$\text{tCH}{}_2\text{CH}{}_2\text{C}$H₂(L₂)] gave methane, ethylene, but-1-ene and n-pentane together with a little n-butane, the methane being formed from internal hydrogen abstraction by the CH₃ group in the excited reactant molecule. Photodecomposition of the platinum(II) compounds [P$\text{tCH}{}_2\text{CH}{}_2\text{CH}{}_2\text{C}$H₂(L₂)] (L = (PMe₂Ph)₂, (PPh₃)₂, Ph₂PCH₂CH₂PPh₂) gave ethylene, but-1-ene, pent-1-ene (with the halogenated solvents) and with some systems appreciable yields of n-butane, the latter being the results of internal abstraction of two hydrogen atoms by the C₄H₈ moiety. The formation of pentene is probably preceeded by the addition of CH₂Cl₂ or CH₂Br₂ to the excited reactant molecule. Addition of diphenylphosphine promotes the production of n-butane.     

Thermodynamic characteristics of hydrated acrylamide and polyacrylamide complexes of cobalt nitrate at <Emphasis Type="Italic">T</Emphasis> → 0 to 380 K

The temperature dependences of the heat capacities of hydrated acrylamide and poly(acrylamide) complexes of cobalt nitrate are studied via high-precision adiabatic calorimetry at 6 to 300–380 K. The energy of combustion is estimated via isothermic calorimetry. This evidence makes it possible to calculate thermodynamic functions C _p ^ℴ(T), H ^ℴ(T) − H ^ℴ(0), S ^ℴ(T), G ^ℴ(T) − H ^ℴ(0) at 0 to 300–380 K; the standard enthalpy of combustion, ΔcH ^ℴ; and the thermodynamic parameters of formation, Δ _f H ^ℴ, Δ _f S ^ℴ, and Δ _f G ^ℴ, of monomer and polymer complexes composed of simple compounds at 298.15 K. The results are used for the estimation of enthalpy Δ_pol H ^ℴ, entropy Δ_pol S ^ℴ, and Gibbs function Δ_pol G ^ℴ of bulk polymerization for hydrated acrylamide complexes of cobalt nitrate at 0–300 K.     

The surface tension of liquid copper

The surface tension of liquid copper of 99.999 mass per cent purity has been measured by the sessile drop method in the temperature range 1373 to 1861 K. The least-squares equation expressing the surface tension σ as a function of temperature T is:

$\text{σ(}\text{Cu}\text{)/}\text{mN m}{}^{\mathrm{?}}\text{= (1552±35) ? (0.176±0.023)T/}\text{K}$

The linear correlation of excess surface enthalpy $\text{H}{}^{\mathrm{\sigma }}\text{A}{}^{\mathrm{\sigma }}$ and excess surface entropy $\text{S}{}^{\mathrm{\sigma }}\text{A}{}^{\mathrm{\sigma }}$ per unit area among σ(T) from the literature is also demonstrated. Estimation of $\text{S}{}^{\mathrm{\sigma }}\text{A}{}^{\mathrm{\sigma }}$ via the statistical electron-gas theory of Zadumkin and Pugachewich yields an equation for the calculation of recommended values for the surface tension of molten copper as a function of temperature:

$\text{σ(}\text{Cu}\text{)/}\text{mN m}{}^{\mathrm{?}}\text{= 1497 ? 0.174(T/}\text{K}\text{)}$

.     

Thermochemical study of the solid complex Ho(PDC)3 (o-phen)

A novel solid complex, formulated as Ho(PDC)₃ (o-phen), has been obtained from the reaction of hydrate holmium chloride, ammonium pyrrolidinedithiocarbamate (APDC) and 1,10-phenanthroline (o-phen·H₂O) in absolute ethanol, which was characterized by elemental analysis, TG-DTG and IR spectrum. The enthalpy change of the reaction of complex formation from a solution of the reagents, Δ_rH_m^θ (sol), and the molar heat capacity of the complex, c_m, were determined as being –19.161±0.051 kJ mol^–1 and 79.264±1.218 J mol^–1 K^–1 at 298.15 K by using an RD-496 III heat conduction microcalorimeter. The enthalpy change of complex formation from the reaction of the reagents in the solid phase, Δ_rH_m^θ(s), was calculated as being (23.981±0.339) kJ mol^–1 on the basis of an appropriate thermochemical cycle and other auxiliary thermodynamic data. The thermodynamics of reaction of formation of the complex was investigated by the reaction in solution at the temperature range of 292.15–301.15 K. The constant-volume combustion energy of the complex, Δ_cU, was determined as being –16788.46±7.74 kJ mol^–1 by an RBC-II type rotating-bomb calorimeter at 298.15 K. Its standard enthalpy of combustion, Δ_cH_m^θ, and standard enthalpy of formation, Δ_fH_m^θ, were calculated to be –16803.95±7.74 and –1115.42±8.94 kJ mol^–1, respectively.     

Hydrothermal synthesis and thermodynamic properties of 2ZnO · 3B2O3 · 3H2O

The important zinc borate of 2ZnO · 3B₂O₃ · 3H₂O has been synthesized and characterized by means of chemical analysis, XRD, FT-IR, and DTA–TG techniques. The molar enthalpies of solution of H₃BO₃(s) in HCl · 54.561H₂O, of ZnO(s) in the mixture of HCl · 54.561H₂O and calculated amount of H₃BO₃, and of 2ZnO · 3B₂O₃ · 3H₂O(s) in HCl · 54.604H₂O were measured, respectively. With the use of the standard molar enthalpies of formation for ZnO(s), H₃BO₃(s), and H₂O(l), the standard molar enthalpy of formation of ?(5561.7 ± 4.9) kJ · mol^?1 for 2ZnO · 3B₂O₃ · 3H₂O(s) was obtained. Thermodynamic properties of this compound were also calculated by a group contribution method.     

The Ethanol Tolerance of <Emphasis Type="Italic">Pachysolen tannophilus</Emphasis> in Fermentation on Xylose

The influence of ethanol on fermentation by Pachysolen tannophilus was studied. When xylose utilization rate was 80%, ethanol concentration began to decline. Fermentation of P. tannophilus was affected by ethanol addition in the beginning of fermentation; average xylose consumption rate was 0.065 g·l⁻¹·h⁻¹, and maximum specific growth rate was 0.07 h⁻¹ at 28 g·l⁻¹ ethanol, comparing with the average xylose consumption rate of 0.38 g·l⁻¹·h⁻¹ and maximum specific growth rate of 0.14 h⁻¹ in fermentation with no ethanol addition; P. tannophilus stopped growth at 40 g·l⁻¹ ethanol. When the initial ethanol concentration was 30 g·l⁻¹, the addition of glucose in xylose media made the growth of P. tannophilus better, and the most favorable glucose concentration was 15 g·l⁻¹ with the highest biomass of 1.51 g·l⁻¹ as compared with that of 0.95 g·l⁻¹ in pure xylose media.