Refratometric study of ternary mixtures formed by water,glucose and acetonitrile at temperatures ranging from 293 K to 333 K

The study of thermodynamic properties of solutions provides important information on existing molecular interactions between the components present in a solution. These studies are critical for testing, validation and development of theories and mathematical models. The refractometric study of a solution is a simple assessment that can contribute to the understanding of these interactions. In this context, the behaviour of the binary water and glucose mixture was studied as well as ternary mixtures of water, glucose and acetonitrile at five different temperatures in the range 293–333 K by the determination of the refractive index of the solution. Due to the weakening of the molecular interactions with the increasing of the temperature, a decreasing dependence of refractive index with temperature was observed. The addition of acetonitrile provides an increase in the refractive index indicating the formation of clusters in the solution.     

Solubility in the system constituted by acetic acid, n-propanol, water, and n-propyl acetate

Experimental data on the solubility in the system constituted by acetic acid, n-propanol, water, and n-propyl acetate at 313.15 K are presented. The position of the critical curve for the liquid-liquid equilibrium, including that of the critical points on the chemical equilibrium surface, is discussed.     

A kinetic study of the reactions of vanadium, iron, and cobalt with sulfur dioxide

A kinetic study of the reactions of ground state V, Fe, and Co with SO2 is reported. V, Fe, and Co were produced by the 248 nm photodissociation of VCl4, ferrocene, and Co(C5H5)(CO)2, respectively, and were detected by laser-induced fluorescence. V + SO2 proceeds by an abstraction reaction with rate constants given by k=(2.33 +/- 0.57)x 10(-10) exp[-(1.14 +/- 0.19) kcal mol(-1)/RT] cm3 molecule(-1) s(-1) over the temperature range 296-571 K. Fe + SO2 was studied in the N2 buffer range of 10-185 Torr between 294 and 498 K. The limiting, low-pressure third-order rate constants are given by k(0)=(3.45 +/- 1.19)x 10(-30) exp[-(2.81 +/- 0.24) kcal mol(-1)/RT] cm6 molecule(-2) s(-1). Co + SO2 was studied in the CO2 buffer range of 5-40 Torr between 294 and 498 K. This reaction is independent of temperature over the indicated range and has a third-order rate constant of k0=(5.23 +/- 0.28)x 10(-31) cm6 molecule(-2) s(-1). Results of this work are compared to previous work on the Sc, Ti, Cr, Mn, and Ni + SO2 systems. The reaction efficiencies for the abstraction reactions depend on the ionization energies of the transition metal atoms and on the reaction exothermicities, and the reaction efficiencies of the association reactions are strongly dependent on the energies needed to promote an electron from a 4s2 configuration to a 4s1 configuration.     

The Gas-Solid Interface the adsorption of nitrogen,argon, neopentane,sulfur dioxide,carbon dioxide and sulfur hexafluoride on rhombic sulfur

Physical adsorption of the title compounds on rhombic sulfur of 0.4 to 0.5 m²/g is reported. The isotherms are of type II for N₂, Ar and C₅H₁₂, of type III for SO₂ and CO₂, and linear for SF₆. There is no hysteresis. The method of Ross & Olivier shows that the surface is relatively heterogenous (γ 17). Isosteric heats of adsorption and c values of the B.E.T. equation are also reported.     

Kinetics of sulfur oxide, sulfur fluoride, and sulfur oxyfluoride anions with atomic species at 298 and 500 K

The rate constants and product-ion branching ratios for the reactions of sulfur dioxide (SO2-), sulfur fluoride (SFn-), and sulfur oxyfluoride anions (SOxFy-) with H, H2, N, N2, NO, and O have been measured in a selected-ion flow tube (SIFT). H atoms were generated through a microwave discharge on a H2/He mixture, whereas O atoms were created via N atoms titrated with NO, where the N had been created by a microwave discharge on N2. None of the ions reacted with H2, N2 or NO; thus, the rate constants are <1 x 10(-12) cm3 s-1. SOxFy- ions react with H by only fluorine-atom abstraction to form HF at 298 and 500 K. Successive F-atom removal does not occur at either temperature, and the rate constants show no temperature dependence over this limited range. SO2- and F- undergo associative detachment with H to form a neutral molecule and an electron. Theoretical calculations of the structures and energetics of HSO2- isomers were performed and showed that structural differences between the ionic and neutral HSO2 species can account for at least part of the reactivity limitations in the SO2- + H reaction. All of the SOxFy- ions react with O; however, only SO2- reacts with both N and O. SOxFy- reactions with N (SO2- excluded) have a rate constant limit of <1 x 10(-11) cm3 s-1. The rate constants for the SOxFy- reactions with H and O are < or =25% of the collision rate constant, as seen previously in the reactions of these ions with O3, consistent with a kinetic bottleneck limiting the reactivity. The only exceptions are the reactions of SO2- with N and O, which are much more efficient. Three pathways were observed with O atoms: F-atom exchange in the reactant ion, F- exchange in the reactant ion, and charge transfer to the O atom. No associative detachment was observed in the N- and O-atom reactions.     

Enthalpies of transfer of Mebicarum from water to aqueous solutions of carbamide and its methyl-substituted derivatives at 298.15 K

The standard molar enthalpies of solution of Mebicarum (MbCA) in aqueous solutions of carbamide (CA), 1,3-dimethylcarbamide (1,3-DMCA), and 1,1,3,3-tetramethylcarbamide (TMCA) of various molalities, as well as the enthalpies of dilution of solutions of these compounds, were measured at 298.15 K. The enthalpy of transfer of MbCA from water to aqueous solutions of 1,3-DMCA exhibits an unusual dependence on the concentration of 1,3-DMCA. An analysis of the McMillan-Mayer enthalpy parameters of pair interactions revealed that the hydration of MbCA should be regarded as a superposition of the hydrophobic and hydrophilic mechanisms, with the latter one being predominant.     

Reactions of dioxygenyl hexafluoroantimonate with water,carbon monoxide,methane, sulfur dioxide,nitric oxide,and nitrogen dioxide

The following gaseous products are released, in addition to oxygen, in reactions of O₂SbF₆ with water, CO, CH₄ and SO₂, respectively: O₃, COF₂, CHF₃ and SO₂F₂. Nitrogen dioxide forms the solid complex NO₂SbF₆, and nitric oxide forms a mixture of NOSbF₆ and NO₂SbF₆. No reaction of CO₂ with O₂SbF₆ has been observed.     

Crystal Structure of D-Valine at the Temperature of 293, 270, 223 and 173K

1 INTRODUCTION D-amino acids are universally present and play different biological roles in various organisms in- cluding those in the human body. Milton[1] has shown that the D and L forms of the enzyme HIV-1 protease were equally affected by the achiral inhi- bitor but displayed reciprocal chiral specificity in their biochemical interactions. D-proteins may also be nonimmunogenic. Senility and some diseases are related to D-amino acids, such as renal disease[2], Alzheimer disease[3…     

Phase separation conditions in systems constituted by a nonionogenic surfactant,water, and sodium carbonate

Dependence of the viscosity of aqueous solutions containing a nonionogenic surfactant, OP-10, and sodium carbonate on temperature and concentrations of OP-10 and sodium carbonate was studied. The phase-separation conditions were found for the systems under study.     

A long-lived intermediate product in the oxidation of monosilane and dichlorosilane at low pressures and 293 K

An electron-vibration structure of the UV spectrum of a long-lived intermediate is detected during oxidation of SiH₄ and SiH₂Cl₂. This product is common to both reactions and exhibits the same promoting effect on them. It is shown that the formation of this promoting compound in the course of a branched chain reaction accounts for nonthermal flame propagation in reacting mixtures outside of the self-ignition region     

Experimental study of the density and viscosity of polyethylene glycols and their mixtures at temperatures from 293 K to 473 K and at atmospheric pressure

A new apparatus to measure simultaneously the density and viscosity of liquids has been designed and constructed based on the hydrostatic weighing and falling-body principles. The density and viscosity of monoethylene glycol (MEG), diethylene glycol (DEG), and triethylene glycol (TEG) and their binary, (50%MEG + 50%DEG), (50%MEG + 50%TEG), (50%DEG + 50%TEG), and ternary (33.33%MEG + 33.33%DEG + 33.34%TEG) mixtures have been measured over the temperature range from 293 K to 473 K and at atmospheric pressure. The expanded uncertainty of the density, pressure, temperature, and viscosity measurements at the 95% confidence level with a coverage factor of k = 2 is estimated to be 0.15% to 0.30%, 0.05%, 0.06 K, and 1.5% to 2.0% (depending on temperature and pressure ranges), respectively. The theoretically based Arrhenius–Andrade and Vogel–Tamman–Fulcher type equations were used to describe the temperature dependence of measured viscosities for pure polyethylene glycols and their mixtures.     

Equilibrium in the liquid-liquid system and critical phenomena in the ternary system constituted by water,pyridine, and butyric acid in the temperature range 5–55°C

Visual-polythermic method was used to study the mutual solubility of the components and critical phenomena in the system constituted by water, pyridine, and butyric acid in the temperature range 5.0–55.0°C. The temperature dependence of the composition of the critical solubility point was determined.     

Reactions of sulfur dioxide on calcium carbonate single crystal and particle surfaces at the adsorbed water carbonate interface

Sulfur dioxide reactions with calcium carbonate interfaces at 296 K in the presence and absence of adsorbed water result in the formation of adsorbed sulfite and sulfate. The extent of reaction is significantly enhanced, approximately five- to ten-fold for particulate and single crystal CaCO(3) (calcite), respectively, in the presence of adsorbed water between 30 and 85% RH. Atomic force microscopy following the reaction shows that adsorbed water facilitates surface reactivity by enhancing the mobility of surface ions, giving rise to the formation of nanometer sized product crystallites approximately 1 nm in height. Simultaneous with the formation of these crystallites is pitting and etching of the underlying substrate, which occurs preferentially in the vicinity of monoatomic surface steps. In the absence of water, there is little pitting and no evidence for the formation of crystallites. X-Ray photoelectron core and valence band spectra confirm the presence of two sulfur adsorbed species, SO and SO, with nearly equal amounts of SO and SO in the absence of adsorbed water and approximately five times more SO relative to SO in the presence of adsorbed water. From these data, it is proposed that the nanometer-sized crystallites are composed primarily of CaSO(3).     

Extraction of polychlorinated biphenyl with supercritical carbon dioxide, sulfur hexafluoride and subcritical water

In the extraction of spiked PCB from soil, three extracting fluids were investigated: supercritical carbon dioxide (CO2), supercritical sulfur hexafluoride (SF6) and subcritical water. Among the tested fluids SF6 appeared to be appropriate especially for the extraction of low polar PCB. CO2 and water were found to be suitable for the quantitative extraction of all PCB. Water was judged as the best because of its low price, good availability and environmental safety.     

Extraction of polychlorinated biphenyl with supercritical carbon dioxide, sulfur hexafluoride and subcritical water

In the extraction of spiked PCB from soil, three extracting fluids were investigated: supercritical carbon dioxide (CO₂), supercritical sulfur hexafluoride (SF₆) and subcritical water. Among the tested fluids SF₆ appeared to be appropriate especially for the extraction of low polar PCB. CO₂ and water were found to be suitable for the quantitative extraction of all PCB. Water was judged as the best because of its low price, good availability and environmental safety.     

A study of the intersystem crossing reaction induced in gaseous sulfur dioxide molecules by collisions with nitrogen and cyclohexane at 27°C

The quantum yields of the sulfur dioxide triplet (³SO₂)-sensitized phosphorescence of biacetyl (Φ_sens) were determined in experiments with N₂–SO₂–Ac₂ and c-C₆H₁₂–SO₂–Ac₂ mixtures excited at 2875 Å at 27°C. The fraction of the biacetyl triplets which reacts homogeneously by radiative or nonradiative decay reactions was determined in a series of runs at constant [SO₂]/[M] and [SO₂]/[Ac₂] ratios but at varied total pressure. A kinetic treatment of the Φ_sens results and singlet sulfur dioxide (¹SO₂) quenching rate constant data gave the following new kinetic estimates: ¹SO₂ + M → (SO₂–M) (1b) ¹SO₂ + M → ³SO₂ + M (2b); for ¹SO₂–N₂ collisions, k_2b/(k_1b + k_2b) = 0.033 ± 0.008; for ¹SO₂–c-C₆H₁₂ collisions, k_2b/(k_1b ± k_2b) = 0.073 ± 0.024; previous studies have shown this ratio to be 0.095 ± 0.005 for ¹SO₂–SO₂ collisions. It was concluded that the inter-system crossing ratio in ¹SO₂ induced by collision is relatively insensitive to the nature of the collision partner M. However, the individual rate constants for the collision-induced spin inversion of ¹SO₂ (k_2b) and the total ¹SO₂-quenching constants (k_1b + k_2b) are quite sensitive to the nature of M: k_2b/k_2a varies from 0.10 ± 0.03 for M = N₂ to 1.11 ± 0.37 for M = c-C₆H₁₂, and (k_1b + k_2b)/(k_1a + k_2a) varies from 0.29 for M = N₂ to 1.44 for M = c-C₆H₁₂; k_1a and k_1b are the rate constants for the reactions ¹SO₂ - SO₂ → (2SO₂) (1a) and ¹SO₂ + SO₂ → ³SO₂ + SO₂ (2a), respectively.     

A thermodynamic study on the complexation between riboflavin and a diaminotriazine derivative mediated by triple hydrogen bonds at water/oil interfaces

The changes in Gibbs free energy (ΔG _int), enthalpy (ΔH _int) and entropy (TΔS _int) upon complexation between riboflavin (RF) and N,N-dioctadecyl-[1,3,5]triazine-2,4,6-triamine (DTT), mediated by triple hydrogen bonds at water/carbon tetrachloride, trichloroethylene and chloroform interfaces, were determined via temperature-controlled interfacial tension measurements. It was shown that hydrogen bonding interactions between RF and DTT were best characterized by large and negative ΔH _int values, unlike those predicted from either the polarity in each phase or the arithmetic average of the polarities in the two phases. Furthermore, the ΔH _int values became more positive as the dielectric constant of the oil phase was increased. These results strongly indicate that ΔH _int is governed by the dielectric properties of the oil phase. Adsorption of RF, DTT and the RF-DTT complex at the water/oil interface gave rise to restrictions on the translational and rotational motions of these species, as demonstrated by the ΔS _int values observed, which is another characteristic of interfacial complexation. The thermodynamic parameters evaluated in the present study revealed the characteristic complexation behavior that occurs at a water/oil interface, as mediated by hydrogen bonding.     

Phase stability in the system constituted by ammonium nitrate,potassium dichromate,and alkaline-earth metal nitrates

Methods for modification of ammonium nitrate as an oxidizing agent for ecologically safe solid propellants were sought for and the influence exerted on phase transitions in ammonium nitrate by three-component inorganic additives in which a synergic effect lowering the transition energy is manifested was determined.