Thermodynamics of nucleic acid bases and nucleosides in water from 25 to 55°C

Specific heat capacities, apparent molar heat capacities, densities, and apparent molar volumes have been determined for cytosine, uracil, thymine, adenine, cytidine, 2-deoxycytidine, uridine, thymidine and adenosine at temperatures from 25°C to 55°C. The results of these measurements have been used to calculate for the first time, the thermodynamic quantities:C _p,2 ^o , (C _p,2 ^o /T)_p, (² C _p,2 ^o T ²)_p,V ₂ ^o , (V ₂ ^o /T)_p, and (² V ₂ ^o /T ²)_p. The-CH₂-group contribution has been calculated at different temperatures. It has also been observed from the data for the nucleic acid bases and nucleosides that the additivity ruleC _p,2 ^o (nucleoside)-C _p,2 ^o (base) +C _p,2 ^o (water)=C _p,2 ^o (ribose) does not hold in these cases.     

Volumetric properties of cyclic hydrocarbons in tetrachloromethane at 25°C

By means of a vibrating-tube densimeter, the densities at 25°C have been determined for binary mixtures of tetrachloromethane with a liquid (cyclodecane, cis-decahydronaphthalene, trans-decahydronaphthalene, bicyclohexyl, pentane) or a solid hydrocarbon (cyclododecane, cyclopentadecane, norbornane, adamantane, octahydro-4,7-methano-1H-indene). Excess molar volumes have been obtained in the whole mole fraction range for mixtures containing a liquid hydrocarbon. For solid cycloalkanes, apparent molar volumes have been evaluated in the whole range of miscibility. The partial molar volumes at infinite dilution have been calculated for all examined cycloalkanes and compared with those of n-alkanes. The dependence of upon the size and shape of the ring or cage structure of the solute is discussed. The capability of the Flory theory to reproduce V^E for these mixtures is also tested.     

The solubility of indium hydroxide in acidic and basic media at 25°C

The solubility of In(OH)₃ was measured in NaOH and HClO₄ solutions. Possible reactions of In(OH)₃ in dilute NaOH and HClO₄ are indicated along with the calculated constants. The result indicated conclusively that In(OH)₃ is only slightly amphoteric, being much more basic than acidic.     

Volumetric Properties of Binary Mixtures of Acetonitrile and Chloroalkanes at 25°C and Atmospheric Pressure

Excess molar volumes for binary mixtures of acetonitrile + dichloromethane, acetonitrile + trichloromethane, and acetonitrile + tetracloromethane at 25°C have been used to calculate partial molar volumes , excess partial molar volumes , and apparent molar volumes of each component as a function of composition. The V _m ^Evalues are negative over the entire composition range for the systems studied. The applicability of the Prigogine–Flory–Patterson theory was explored. The agreement between theoretical and experimental results is satisfactory for the systems with dichloromethane and tetrachloromethane. For the unsymmetrical behavior of the system with trichloromethane, however, the agreement is poor.     

Conductance of Lithium and Sodium Perchlorates and Tetraphenylborates in 2-Butanone from −35 to 25°C

Conductances of dilute solutions of LiClO₄, NaClO₄, LiBPh₄ and NaBPh₄ in 2-butanone were measured at seven temperatures from ?35 to 25°C. The limiting molar conductivities and association constants were evaluated using the conductance equation of Fuoss and Justice (including the Chen effect). The distance parameter was fixed at the Bjerrum distance. The limiting ionic conductivities, determined by assuming equal ionic conductivities of the i-Am₃ BuN⁺ and BPh ₄ ^? ions at all temperatures, were related to the crystallographic ionic radii using the Hubbard–Onsager model of dielectric friction corrected for the inhomogeneity of the electric field. The activation enthalpy of ionic transport in 2-butanone is almost independent of the nature of the electrolyte. The Walden products do not vary with the temperature. The correction to the conductance parameters for dielectric saturation computed for M⁺ClO ₄ ^? associates was found to be small. Thermodynamic functions characterizing the association process were evaluated from K _A data and their dependences on the temperature. The short-range, noncoulombic contributions to the Gibbs energy were estimated using Bjerrum's theory.     

A Volumetric Study of Water–Decyltrimethylanimonium Bromide–Pentanol Ternary System from 25 to 130°C at 2 and 19 MPa

Density measurements on decyltrimethylammonium bromide (DeTAB)–water and pentanol (PentOH)–DeTAB–water systems as functions of both alcohol and surfactant m_S concentrations were carried out at 2 and 19 MPa from 25 to 130°C. From experimental data for the water–DeTAB binary system, the standard (infinite dilution) partial molar volumes, expansibilities, and compressibilities of DeTAB, and the corresponding properties in the micellar phase are calculated. The trends of the standard partial molar volumes of PentOH V_R^o in DeTAB micellar solutions as functions of m_S reflect the transfer of PentOH from the aqueous to the micellar phase, except at 130°C and 19 MPa. On the basis of an equation previously used, the distribution constant of PentOH between the aqueous and the micellar phases and the standard partial molar volume of alcohol in the aqueous and the micellar phases are obtained from V_R^o data. Comparisons with data for PentOH in dodecyltrimethylammonium bromide are made.     

Comparative conductimetric studies of salicylic acid in methanol-water mixtures at 25 °C

The conductivity of salicylic acid in methanol-water mixtures was measured at 25 °C. Experimental data were analyzed using the Hsia-Fuoss and Fuoss-78 conductance equations and a comparison was made. The Hsia-Fuoss and Fuoss-78 methods were also used to deter-mine the thermodynamic association constants and the limiting molar conductivities for all solvent compositions. The limiting equivalent conductance decreases with an increase in the methanol content in the binary mixtures over the whole range of solvent compositions, but the variation does not give a constant value of Walden product. The electrolytes were found to be practically completely associated in all solvent mixtures studied. The association constant of salicylic acid decreases as the dielectric constants of the mixtures increase.     

Raman Spectroscopic Study of Aluminum Silicate Complextion in Acidic Solutions from 25 to 150°C

Raman spectroscopic measurements were performed on aqueous acid to neutral silica-bearing solutions (0.005 ≤ m _Si ≤ 0.02, 0 ≤ pH ≤ 8) and Al–silica solutions at temperature from 20 to 150°C. At 20°C, the spectrum of silica-bearing solutions exhibits only the bands of water and a completely polarized band at 785 cm^?1. This band is attributed to the ν₁ band of the tetrahedral Si(OH)₄ molecule. In ${\text{Si(OH)}}_{\text{4}} {\kern 1pt} {\kern 1pt} - {\kern 1pt} {\text{AlCl}}_3 {\kern 1pt} - {\kern 1pt} {\text{HCl}}$ solutions, the intensity of this band decreases with increasing Al concentration, temperature, and pH. This decrease can be explained by the formation of an inner sphere complex between Al³⁺ and Si(OH)₄ according to the reaction: ${\text{Al}}^{{\text{3 + }}} {\text{ + H}}_{\text{4}} {\text{SiO}}_{\text{4}}^{\text{0}} ({\text{aq}}){\text{ }} \Leftrightarrow {\text{ AlH}}_{\text{3}} {\text{SiO}}_{\text{4}}^{{\text{2 + }}} {\text{ + H}}^{\text{ + }} $ The fraction of complexed silica deduced from raman spectroscopic measurements is in good agreement with that calculated for the similar solution compositions and temperatures using the complexation constant generated by Pokrovski et al. ⁽²³⁾ from potentiometric measurements. At ambient temperature, the formation of aluminum silicate complex is weak and does not account for more than ca. 5 % of the total Al in most natural waters. As temperature increases, this complex becomes more significant and can dominate Al speciation in acid (pH ≤ 2) hydrothermal solutions.     

Ultrasonic Velocities and Isentropic Compressibilities of Electrolytes in 2-Methoxyethanol from 15 to 35°C

The ultrasonic velocities of lithium tetrafluoroborate (LiBF₄), sodium tetrafluoroborate (NaBF₄), tetraphenylphosphonium chloride (Ph₄PCl), tetraphenylphosphonium bromide (Ph₄PBr), and tetraphenylarsonium chloride (Ph₄AsCl) in 2-methoxyethanol (ME) have been measured at 15, 25, and 35°C. Apparent molar isentropic compressibilities κ_φ of these electrolytes were derived from these data supplemented with their densities. Infinite dilution partial molar compressibilities κ_φ ^o were obtained by extrapolation from the plot of κ_φ vs. the square root of the molarity. The κ_φ ^o values of the electrolytes were split into approximate limiting ionic compressibilities κ_φ± ^o on the basis of the assumption that κ_φ ^o (BF^? ₄) = 0. The results have been interpreted in terms of specific constitutional and structural factors of the solvent molecules and of solute ions.     

Phase diagram of the ethylene glycol-dioxane system in the temperature range from ?90 to 25°C

The ethylene glycol-1,4-dioxane system is studied by means of differential scanning calorimetry over a wide range of temperatures (?90 to 25°C) and is found to be a simple eutectic with the eutectic point at 10 mol % of dioxane (?16.5°C). Unlike a water-dioxane system, in which the clathrate with dioxane: H₂O = 1: 34 ratio is formed, the observed phase diagram showed no evidence of clathrate formation, due presumably to its hydrogen bond geometry and the intermolecular interaction properties of ethylene glycol.     

Volumetric Properties of Some α-Amino Acids in Aqueous Guanidine Hydrochloride at 5, 15, 25, and 35°C

The infinite-dilution apparent molar volumesV ₂ ^o for glycine, DL-alanine, DL--amino-n-butyric acid, DL-valine, DL-leucine, and L-serine in 6 mol-kg^–1 aqueous guanidine hydrochloride were determined at 5, 15, 25, and 35°C from precise density measurements. Using these data, the standard volumes of transfer, _t V°, from water to 6m> aqueous guanidine hydrochloride solution were calculated. A linear relationship was found between V ₂ ^o and temperature. Both V ₂ ^o and _t V° vary linearly with increasing number of carbon atoms in the alkyl chain of the amino acids. The results show that the apparent molar volumes at infinite dilution for (NH ₃ ⁺ ,COO^-) groups increase with increasing temperature and those for CH₂ and the other alkyl chains are almost constant. These results also shows that guanidine hydrochloride has stronger interactions with amino acids than urea. These phenomena are discussed in terms of the cosphere overlap model.     

Viscosities of n-Alkyl Chlorides from 15 to 80°C

The viscosities of n-alkyl chlorides from pentyl to hexadecyl chloride were determined at temperatures between 15 to 80°C at 5°C intervals. The intrinsic volumes of the n-alkyl chlorides were determined by extrapolation of the plot of fluidity against molar volume to zero fluidity. Plots of the logarithm of viscosity vs. reciprocal absolute temperature were almost linear. The energies of activation for viscous flow for the n-alkyl chlorides were calculated and found to increase with increase in chain length. The fluidities, , of the n-alkyl chlorides were found to obey the modified form of Hildebrand's equation. = D[(V-V_o/V_o]\exp(-E_B/RT) where D is a constant, V and V _o are the molar volume and the intrinsic molar volume, respectively, and E _B is an energy term corresponding to the energy required for disrupting the association of the molecules. The activation energy for viscous flow consists of the sum of the energy required for the expansion of the void volume and the energy required to overcome intermolecular interactions. These energies were calculated and discussed.     

Viscosities of long chainn-alcohols from 15 to 80°C

Viscosities of five n-alcohols from 1-hexanol to 1-tetradecanol were determined from 15 to 80°C at 5°C intervals. Plot of the logarithm of viscosity vs. reciprocal absolute temperature were almost linear. The energies of activation for viscous flow were determined for each of the alcohols and found to increase with increase in chain length. The intrinsic molar volumes V_o were determined by extrapolation to zero fluidities. The fluidities of the alcohols were found to obey the equation

Orientation order in monoethanolamine at 25–75°C, according to data from dielcometry

The static permittivity (?_s) of monoethanolamine (MEA) is measured at a frequency of 1 MHz in the temperature range of 20–90°C. The found data were analyzed in the context of the Onsager-Kirkwood-Fröhlich theory. The values of the correlation factor (g) are calculated in the investigated temperature range. Similar calculations using literature data are performed for 3-amino-1-propanol (AP) and N,N-dimethylethanolamine (DMEA) (temperature range, 15–35°C). The difference between the correlation factors of MEA, AP, and DMEA and their temperature dependences are explained by the structures of these amino alcohols and their molecules. A conclusion is drawn on the orientation order in liquid MEA, based on the obtained results made. In addition, the data from our study of the equilibrium dielectric properties of MEA are compared to the similar properties of ethylene glycol (EG), and a conclusion is drawn on features of the structure of amino alcohol relative to diol.     

Effect of Ammonium Salts on the Volumetric and Viscometric Behavior of D(+)-Glucose,D(−)-Fructose and Sucrose in Aqueous Solutions at 25°C

Apparent molar volumes, V _φ, and viscosity, η, of D(+)-glucose, D(−)-fructose and sucrose in water and in 0.02, 0.05, 0.5, 1.0 and 2.0 mol·kg⁻¹ aqueous solutions of ammonium bromide, tetraethylammonium bromide and tetra-n-butylammonium bromide have been determined at 25 °C from density and efflux time measurements by using a vibrating-tube digital densimeter and a capillary viscometer, respectively. Partial molar volumes, , at infinite dilution that were extrapolated from the V _φ data were used to obtain the corresponding transfer volumes, , for saccharides from water to different aqueous solutions of co-solutes. The Jones-Dole equation viscosity B-coefficients were obtained from the viscosity data. Positive values of were obtained for the saccharides in the presence of ammonium bromide, whereas both positive and negative values were obtained in the presence of tetraethylammonium and tetra-n-butylammonium bromides. The negative values at very low concentrations have small magnitudes. Volumetric interaction coefficients have been calculated by using the McMillan-Mayer theory and Gibbs energies of activation of viscous flow have been calculated by using Feakin’s transition-state theory equation. The parameters obtained from the volumetric and viscometric studies were used to understand various mixing effects due to the interactions between saccharides and ammonium salts in aqueous solutions.     

Pressure Dependence of the Solubilities of Anthracene and Phenanthrene in Water at 25°C

Solubilities of anthracene and phenanthrene in water were measured at 298.15K at pressures to 200 MPa and were found to decrease with increasing pressure.From the pressure coefficients of the solubilities, the volume changesaccompanying the dissolution were estimated to be 15.1±0.6 cm³-mol–1 for anthraceneand 12.4±0.3 cm³-mol–1 for phenanthrene. The partial molar volumes of thesesolutes in water are presumed to decrease with increasing pressure, contrary to thenegative compressibility of alkylbenzenes previously observed in water. Volumechanges accompanying hydrophobic hydration are also estimated to be 1.4cm³-mol–1 for anthracene and 4.1 cm³-mol–1 for phenanthrene, respectively. Thesepositive values are opposite to the negative ones usually observed for hydrophobichydration. The hydration structure of these hydrocarbons is discussed.     

Hydrolysis of thorium carbides between 25 and 99°C

The reactions with water of arc-cast thorium carbides with total-C/Th atom ratios varying from 0·8 to 2·1 were investigated. Thorium monocarbide produced mostly methane (and also hydrogen if carbon-deficient). Thorium dicarbide yielded C₂ to C₈-hydrocarbons, hydrogen, and a nonvolatile wax. Varying the reaction temperature between 25 and 99°C caused no change in the hydrolysis products, although the reactions were considerably faster at the higher temperatures. Hydrolysis of monocarbide-dicarbide mixtures gave the products expected from simple ThC-ThC_1·95 binaries. Tungsten (2·4 atom%) as an impurity in thorium dicarbide catalysed the polymerization of the C₂ units to wax which markedly changed the gas composition.The maximum combined-C/Th atom ratio obtainable by arc-melting with graphite electrodes was 1·95 rather than the theoretical 2·00. There was no indication of any significant range of composition for the dicarbide. The lattice parameter for ThC_1·0 was 5·346Å, and for the carbon-deficient ThC_0·81 5·340 Å.     

Determination of enthalpy of ionization of water from 250 to 350° C

The enthalpy changes at zero ionic strength (H°) for the ionization of water (H₂O=H⁺+OH^–) were determined by flow calorimetry from the heats of mixing of aqueous NaOH and HCl solutions in the temperature range 250 to 350°C. Pitzer ion-interaction models developed by other workers were used to calculate enthalpies of dilution of aqueous NaOH, HCl, and NaCl solutions for the extrapolation of H values from the conditions of the experiment to infinite dilution. Equations are derived for thermodynamic quantities (log K, H°, S°, C _p ^° and V°) for the ionization of water using the H° values determined in this study from 250 to 350°C and literature log K and H° values from 0 to 225°C. Smoothed values of log K, H°, S°, C _p ^° , and V° are presented at rounded temperatures from 0 to 350°C and at the saturation pressure of water for each temperature. The equations in the present study provide a better representation of experimental thermodynamic data from 0 to 350°C than the Marshall-Franck equation.