Boiling Point Parameters of Di- and Trichlorostannane

The boiling point, molar volume of liquid at the boiling point, and enthalpy of vaporization at the boiling point were found by calculation for little-studied tin compounds SnH₂Cl₂ and SnHCl₃.     

Evaluation of thermal analysis equipment for the determination of vapor pressure and heat of vaporization

A rapid, relatively simple method for determining vapor pressure and heat of vaporization on small amounts of organic compounds is described. A DuPont 900 differential thermal analyzer (DTA), a Perkin—Elmer Model DSC-1B differential scanning calorimeter (DSC), and a Thomas—Hoover (TH) melting point apparatus were evaluated in this work. Vapor pressure data for a wide variety of organic liquids were obtained by measuring the boiling points of the liquids at pressures ranging from 20 to 735 torr. A computer was used to rapidly plot the experimental data. The average deviations of boiling points from the literature values were 2.3°C for the DTA 1.2°C for the DSC, and 1.5°C for the TH. The vapor pressure data were used to solve the Haggenmacher equation for heat of vaporization (ΔH_v). The deviations of the experimental values for ΔH_v. from the literature values were 5.5%, 8.3%. and 3.3% for the DTA, DSC, and TH methods, respectively.     

Solubility of pentane, 2-methylbutane,and cyclopentane in liquid nitrogen at 77.4 K

The solubilities of pentane, 2-methylbutane (isopentane) and cyclopentane were measured in liquid nitrogen at 77.4 K by the filtration method. The solubilities of the C₅ hydrocarbons in liquid nitrogen at 77.4 K vary from 1.8×10^–8 mole fraction for cyclopentane, to 3.0×10^–8 mole fraction for pentane and 3.2×10^–7 mole fraction for 2-metylbutane. Correlations between the solubilities of alkanes, alkenes and cyclic hydrocarbons in liquid nitrogen, and some properties of solutes [normal boiling point T _b , enthalpy of vaporization at normal boiling point H _b and the mean of the enthalpy of vaporization and the enthalpy of melting [(H _b +H _m )/2] are presented.     

Group vector space method for estimating enthalpy of vaporization of organic compounds at the normal boiling point

The specific position of a group in the molecule has been considered, and a group vector space method for estimating enthalpy of vaporization at the normal boiling point of organic compounds has been developed. Expression for enthalpy of vaporization Delta(vap)H(T(b)) has been established and numerical values of relative group parameters obtained. The average percent deviation of estimation of Delta(vap)H(T(b)) is 1.16, which show that the present method demonstrates significant improvement in applicability to predict the enthalpy of vaporization at the normal boiling point, compared the conventional group methods.     

Fast method for the experimental determination of vaporization enthalpy by differential scanning calorimetry

A simple method is proposed to estimate the vaporization enthalpy of the palmitic acid (hexadecanoic acid) at its normal boiling temperature. Differential scanning calorimetry (DSC) was the technique used to directly measure these thermodynamic properties. The advantages of this method are its speed and small amount of sample required. In order to avoid evaporation and to ensure equilibrium conditions, the experiments were carried out including a-alumina in contact with the fatty acid. The effect of the alumina concentration is discussed. The obtained experimental data (T_bp=625.4±0.5 K, D_vap H=237.6±5.9 J g^-1) is compared with that obtained by using thermodynamic equations. This revised version was published online in August 2006 with corrections to the Cover Date.     

Vapor pressure and heat capacities of perfluoro-<Emphasis Type="Italic">N</Emphasis>-(4-methylcyclohexyl)piperidine

Heat capacities of perfluoro-N-(4-methylcyclohexyl)piperidine (PMCP) have been measured by low-temperature adiabatic calorimetry. The purity of the compound, its triple-point temperature, and its enthalpy and entropy of fusion have been determined. The saturated vapor pressure was determined by comparative ebulliometry as a function of temperature in the 6.2–101.6 kPa pressure range and 374.2–460.9 K temperature range. The calorimetric enthalpy of vaporization at T = 298.15 K has been measured. The following thermodynamic properties were calculated for PMCP: normal boiling temperature, enthalpy of vaporization Δ_vap H _m ⁰ (T) as a function of temperature, and critical parameters. The enthalpies of vaporization at 298.15 K obtained experimentally and by calculation methods match within their error limits, which validates their adequacy and the adequacy of the Δ_vap H _m ⁰ = f(T) equation as an extrapolation.     

Determination of heat of mixing and heat of vaporization with a differential scanning calorimeter

A simple method is presented for measuring the heat of mixing and the heat of vaporization of volatile liquids at temperatures below their boiling point. It consists in introducing liquids by a microsyringe into a nearly closed cell of the DSC. The relative standard deviation for 4 to 5 runs is ca. 5% for heat of mixing and ca. 2% for heat of vaporization.     

Prediction of the enthalpy of vaporization of metals and metalloids

A simple correlation equation without adjustable parameters is used to obtain the enthalpy of vaporization of 10 metals and 2 metalloids as a function of the temperature. Besides the critical temperature, this equation requires knowing of the enthalpy of vaporization at two reference temperatures: the lowest available temperature and the normal boiling temperature. Average relative deviations are less than 0.75% for the available ranges of temperature. A comparison is made with three other well-known empirical equations based only on the normal boiling point.     

Corresponding states theory and thermodynamic properties of liquid alkali metals

According to phenomenological scaling and the law of corresponding states, reduced coordinates F ^*-T ^*, where F* represents the reduced thermodynamic properties (enthalpy of vaporization, speed of sound, surface tension, saturated liquid density) and T ^* is the reduced temperature, are introduced for the prediction of the thermodynamic properties of alkali metals. Values of the thermodynamic properties from the melting point up to boiling point are correlated. It has been shown that the correlation between reduced thermodynamic properties, as well as with the reduced temperature, can be expressed as a unique straight-line plot with a linear correlation coefficient of 0.9998. The proposed correlation has a simple form for easy calculation, requires only the melting and boiling point parameters, which are usually easy to acquire, and can predict the thermodynamic properties from the melting temperature up to the boiling temperature accurately.     

Thermodynamic parameters of phase transitions of perfluoro-N-(4-methylcyclohexyl)piperidine

The heat capacity of perfluoro-N-(4-methylcyclohexyl)piperidine (PMCP) was measured by low-temperature adiabatic calorimetry. The purity of the substance (N ₁ = 99.66 mol %), triple point temperature (T _tp = 293.26 K), and enthalpy of fusion (Δ_fus H _m ^° = 8.32 kJ/mol) were determined. The enthalpy of vaporization was measured by calorimetry at 298.15 K (Δ_vap H _m ^° (298.15 K) = 56.56 kJ/mol). The temperature dependence of the saturated vapor pressure of PMCP over the pressure range 6.2–101.6 kPa was determined by comparative ebulliometry. The normal boiling point (T _n.b. = 460.74 K), ehthalpies of vaporization (at various temperatures), and critical parameters of PMCP were calculated. The calculated and experimental values of Δ_vap H _m ^° (298.15 K) agree to within measurement errors, which proves the reliability of these values and pT parameters used in calculations.     

Thermal Analysis and Non-isothermal Kinetic Study of Some Pesticides. Part II. Chlorinate derivatives

The thermal behaviour of some commercial pesticides was studied by simultaneous TG/DSC measurements. Kinetic parameters, related to solid-gas phase transition processes, were also carried out by using dynamic TG technique. The kinetics were analysed by using Arrhenius, Satava and Harcourt-Esson equations. The choice of the mathematical expression to insert in these equations was influenced by the shape of the TG plot and other thermal analysis signals. The compounds studied undergo a fusion process followed by a single vaporization process. The latter is well represented by a diffusive process (D₁, D₂ or D₃). The variation of the activation energy values within the range of temperature where the vaporization processes occur was calculated. The enthalpy values of vaporization were also evaluated by using the Clausius-Clapeyron equation. This revised version was published online in August 2006 with corrections to the Cover Date.     

Relation between the vaporization heat and the first ionization potential in series of liquids at normal boiling point

It is shown that a general relationship exists between the latent heat of vaporization and the first ionization potential for liquids at the normal boiling point. The generalized parabolic relation is:

where Y = In(hcωT_B) and X = In(ΔH_v/RT_B), such that ω is the first ionization potential expressed in reciprocal centimeters; while ΔH_v is the latent heat of vaporization at the normal boiling point temperature T_B.     

Thermochemistry of Solvated Crystals of C60> and C70> with o-Xylene

Differential scanning calorimetry (DSC) was used to study the binary systems of C₆₀-o-xylene and C₇₀-o-xylene and the ternary system C₆₀-C₇₀-o-xylene. Fullerene C₆₀ formed solvated crystals C₆₀·2C₈H₁₀ with incongruent melting point 320 K and with enthalpy of decomposition 31±3 kJ (mol of C₆₀)^-1. Two solvated crystals of C₇₀ with incongruent melting points 283 and 369 K, and with decomposition enthalpies 18.5±2.2 and 23.0±1.5 kJ (mol of C₇₀)^-1, were formed from o-xylene solutions. Three ternary compositions with C₆₀/C₇₀ mole ratios of 3:1, 1:1 and 1:3 were scanned by DSC. This revised version was published online in July 2006 with corrections to the Cover Date.     

1-烷基-4-氨基-1,2,4-三唑硝酸盐含能离子液体的蒸气压及其摩尔汽化焓的理论研究

合成了1-烷基-4-氨基-1,2,4-三唑硝酸盐含能离子液体([RATZ]NO₃),并通过核磁和红外进行了结构表征;采用Gaussian09/B3LYP/6-311+G(d,p)密度泛函理论,计算了[RATZ]NO₃的离子间相互作用能及摩尔体积;在298 K-323 K温度范围内,测定了不同配比[RATZ]NO₃-EtOH混合溶液的饱和蒸气压,其中乙醇摩尔分数分别为0.984、0.996、0.999以及1.000。系统研究了[RATZ]NO₃-EtOH混合溶液的饱和蒸气压、[RATZ]NO₃的蒸气压及摩尔汽化焓与温度、离子间相互作用能以及结构之间的关系。结果表明：[RATZ]NO₃-EtOH混合溶液的饱和蒸气压随着温度的升高、离子间作用能的减小以及阳离子体积的增大而增大,其沸点比纯溶剂高,且在298 K-323 K温度范围内[RATZ]NO₃的平衡蒸气压均低于250 mPa,因此说明含能离子液体具有不挥发性,蒸气压极低,并通过理论计算得到的离子间相互作用能及体积,解释了[RATZ]NO₃的摩尔汽化焓随烷基链增长而降低的原因。     

The enthalpies of vaporization of some hydrocarbons with three-membered rings

The enthalpies of vaporization of four compounds with three-membered rings (bicyclopropyl, 1,2-bicyclopropylacetylene, 1-cyclopropylpentadiine-1,3, and 1,2,2-trimethylcyclopropene) were determined calorimetrically. The temperature dependence of saturated vapor pressure of 1,2,2-trimethylcyclopropene was studied by ebulliometry, and the results were approximated by the equation lnp = A + B/T. The enthalpy of vaporization, normal boiling temperature, critical parameter, and similarity criterion according to the law of corresponding states in the variant suggested by Filippov were calculated. The calculated corrections to the enthalpy of vaporization (kJ/mol) for the cyclopropene ring containing methyl substituents are discussed in comparison with the data on related compounds.     

Prediction of vapor pressures and enthalpies of vaporization of organic compounds from the normal boiling point temperature

Recently, our Laboratory proposed a model for the prediction of vapor pressures of organic compounds that requires only the knowledge of the normal boiling point of the compound involved, and a compound specific K_f for which generalized expressions for several classes of organic compounds as functions of the normal boiling point and the molecular weight were developed.In this work our model is compared with the one proposed in Lyman's book, which is similar to our model but uses different K_f values. The results indicate that our model provides very satisfactory results in the temperature range from the melting up to the normal boiling point and up to the critical, where no hydrogen-bonding is involved. Also, it is proven that the accuracy of our model is much better than that proposed by Lyman, especially for the high molecular weight compounds.Finally, our model is used for the prediction of enthalpies of vaporization at the normal boiling point. Excellent results are obtained that are comparable or better than those obtained with two recommended models in “The Properties of Gases and Liquids” book, where the latter, however, require as input information except from the normal boiling point the critical properties of the compound involved as well.     

Prediction of phase equilibria and thermodynamic properties of refrigerant/oil solutions

A method for estimation of the phase equilibrium, density, enthalpy, heat of vaporization and molecular weight of refrigerant/oil solutions (ROS) is proposed in this paper. The method is based on the theory of thermodynamic similarity, since refrigerant/oil solutions appear to be thermodynamically similar in the region of the refrigerant mass concentrations: 0.3≤w_R≤1.0. The initial information is the concentration dependence of the temperature of the normal boiling point, the concentration dependence of the density in very narrow temperature ranges, and the temperature dependence of the isobaric heat capacity of the liquid phase of the pure oil. On the basis of this information, the proposed method allows calculation of all the above-mentioned properties. Modeling of thermodynamic properties of the ROS requires data on pseudocritical properties and molar weight. Hence, the method of estimation of these properties is proposed.     

Thermal Analysis Studies on Isopropylnitrate

Isopropylnitrate (IPN) is described as a detonable material used in propellants and explosives. While there is considerable information available on its sensitivity and compatibility with other materials, very little is known about its thermochemical properties. This paper will describe the results obtained from some DSC, heat flux calorimetry (HFC) and accelerating rate calorimetry (ARC) measurements. The ASTM DSC method using a hermetic aluminum pan having a lid with a laser-produced pin hole was used to determine the vapour pressure of IPN₁. Results calculated from an Antoine equation are in substantial agreement with those determined from DSC measurements. From the latter measurements, the enthalpy of vaporization was determined to be 35.32±0.62 kJ mol⁻¹. Attempts to determine vapour pressures above about 0.8 MPa resulted in significant decomposition of IPN_g. The enthalpy change for decomposition in sealed glass systems was found to be -3.43±0.09 kJ g⁻¹ and -3.85±0.03 kJ g⁻¹, respectively from DSC and HFC measurements on IPN₁ samples loaded in air. Slightly larger exotherms were observed for the HFC results in air than those in inert gas, suggesting some oxidation occurs. In contrast, no significant difference in the observed onset temperature of about 150°C was observed for both the HFC and ARC results. From DSC measurements, an Arrhenius activation energy for decomposition of 126±4 kJ mol⁻¹ was found. These measurements were also conducted in sealed glass systems and decomposition appeared to proceed primarily from the liquid phase. This revised version was published online in August 2006 with corrections to the Cover Date.     

Estimation of Physico-chemical Properties of Ionic Liquid EPReO_4 Using Surface Tension and Density

An ionic liquid (IL) EPReO₄ (N‐ethylpyridinium rheniumate) was prepared. The density and surface tension values of the IL were determined in the temperature range of 293.15–343.15 K. The ionic volume and surface entropy of the IL were estimated by extrapolation, respectively. In terms of Glasser's theory, the standard molar entropy and lattice energy of the IL were estimated, respectively. Using Kabo's and Rebelo's methods, the molar enthalpy values of vaporization of the IL, Δ^g_lH⁰_m (298 K), at 298 K and, Δ^g_lH⁰_m (T_b), at hypothetical normal boiling point were estimated, respectively. According to the interstice model, the thermal expansion coefficient of IL EPReO₄ (α) was calculated and compared with experimental value, finding their magnitude order is in good agreement by 8.98%.