Differential Heat Of Solution Research Articles

The impact of viscosity on the combined heat, mass and momentum transfer in laminar liquid falling films

In this article we present a model describing a laminar film flow over a vertical isothermal plate whilst heat and mass transfer is occurring. We focus on a formulation where most common assumptions, such as constant property data and constant film thickness, have been cancelled. The hydrodynamic model results in longitudinal and transversal velocity components and their evolution in the entrance region. Heat and mass transfer occurs simultaneously and is modelled with respect to release of differential heat of solution as well as heat flow due to interdiffusion. The numerical solution is obtained by utilising a Newton-Raphson method to solve the finite difference formulation of the governing equations. Mass transfer across the film affects the development of both longitudinal and transversal velocity components. The hydrodynamics are modelled using a boundary layer approximation of the Navier-Stokes equations. The significance of simplifications on the hydrodynamic model are illustrated and discussed using a fully developed velocity profile (Nusselt flow) and a plug flow at the inlet for comparison. Even if a Nusselt profile is assumed, it develops further since mass is absorbed or desorbed. It is found that the onset of absorption occurs at shorter flow length when applying a plug flow at the inlet. If the film is initially in equilibrium, this results in a 9.3% increase in absorbed mass over a length of 0.03 m as compared with the Nusselt flow. A fluid with a viscosity five times the one of lithium bromide solution but sharing comparable properties apart from that, leads to lower overall heat and mass transfer rates. If the respective fluids are saturated at the inlet, the accumulated mass flux absorbed by lithium bromide solution is 2.2 times higher than the one absorbed by a high viscous fluid. However, when a plug flow is applied and the fluid is sub-cooled, ab initio the absorbed mass flux is slightly higher for a high viscous fluid. Assuming a sub-cooling of 3 K at the inlet, lithium bromide solution now only performs around 11% better as compared with a high viscous fluid over the considered length of 0.03 m. The code may be downloaded from: https://github.com/mittermaier/hmt.

A New Method to Determine the Half-Life for Penicillin Using Microcalorimeter

The dissolution process of penicillin in normal saline and isotonic glucose solution was reported using a microcalorimeter. Both the integral and differential heats of solution were measured. The quantitative relationships between the amount of heat released and the quantity of dissolved penicillin were established. Meanwhile, the kinetics and the half-life of the dissolution processes as well as the enthalpy of solution, the entropy of dissolution, and the free energy of dissolution were determined. The results showed that a change of the solvent from normal saline to isotonic glucose solution had little effect on the half-life of penicillin in the dissolution process, and there was no significant difference between the stabilities of penicillin in isotonic glucose solution and normal saline. Moreover, the dissolution process of penicillin in isotonic glucose solution followed the first-order kinetics. These results could provide a theoretical basis for the clinical applications of penicillin.

Thermodynamic properties of laburnine in saline and glucose solutions

Laburnine’s dissolution behaviors in glucose and saline solution were studied by a micro-calorimetry method. The measured integral and differential heats of solution were utilized to build equations of the solute and the heat, so that dissolution thermodynamic equations and half-time periods, Δsol H m, Δsol G m, and Δsol S m were obtained. The results show that this study does not only provide a simple method for the determination of the half-life period for a drug but also offer a theoretical reference for the clinical application of laburnine.

Calorimetric determination of differential integral heats of solution for a set of diastereomeric salt pairs

Heats of solution in dimethyl sulfoxide (DMSO) have been determined for the diastereomeric salts (−)-(R)-methamphetammonium (+)-(RR)-bitartrate and (−)-(R)-methamphetammonium (−)-(SS)-bitartrate, (+)-(R)-α-phenethylammonium (−)-(R)-2-phenylbutyrate and (−)-(S)-α-phenethylammonium (−)-(R)-2-phenylbutyrate, and of a new polymorph of (+)-(1S2R)-ephedrinium (−)-(R)-mandelate. The heats of solution for these salts were found to be 11.4 and 10.0 kcal/mol, 15.6 and 14.0 kcal/mol, and 7.4 kcal/mol, respectively. Differential enthalpy contributions to chiral discrimination computed from these numbers are 1.4, 1.6, and 2.1 kcal/mol for the methamphetammonium bitartrates, α-phenethylammonium (−)-2-phenylbutyrates, and ephedrinium mandelates, respectively. The new and previously observed (Zingg et al. J Am Chem Soc 110:1565–1580, 1988) polymorphs of the (+)-(1S2R)-ephedrinium (−)-(R)-mandelate are separated by nearly 1 kcal/mol. Comparison of differential heats of solution with the corresponding differential heats of fusion suggests that heats of fusion differences do not properly represent the energy differences useful for diastereomeric salt separations. Chirality 9:325–328, 1997. © 1997 Wiley-Liss, Inc.

Chromatographic determination of the rate and extent of absorption of air pollutants by sea water

A simple chromatographic method is developed to determine the rate constant for expulsion of an air pollutant from water or its diffusion parameter in the liquid, the rate constant for chemical reaction of the pollutant with water, its mass transfer coefficient in the liquid, and the partition coefficient between liquid water and air. From these physicochemical parameters, the absorption rate by sea water and, therefore, the depletion rate of a polluting substance from the air can be calculated, together with the equilibrium state of this absorption. The method has been applied to nitrogen dioxide being absorbed by triple-distilled water and by sea water, at various temperatures. From the temperature variation of the reaction rate constant and of the partition coefficient, the activation energy for the reaction and the differential heat of solution were determined.

Thermodynamic properties for the quaternary system H 2O + CH 3OH + LiBr + ZnCl 2

The thermodynamic properties (solubility, vapour pressure, density, viscosity, heat capacity and heat of mixing) of the H 2O + CH 3OH + LiBr + ZnCl 2 (9:1 H 2O:CH 3OH and 1:1 LiBr:ZnCl 2 by mass) system using H 2O + CH 3OH as the working media and LiBr + ZnCl 2 as the absorbents were measured. The solubility data were obtained in the temperature range from 270.35 to 389.55 K. The measurements of vapour pressure, density, viscosity and heat capacity were carried out at various temperatures and absorbent concentrations. The differential heat of dilution and differential heat of solution at 298.15 K were measured for solutionw with absorbent concentrations from 0 to 75.2 wt%. The integral heat of mixing data at 298.15 K were obtained from both sets of experimental data. The integral heats of mixing for this quaternary system showed exothermic behaviour. The vapour pressure data were correlated with an Antoine-type equation. An empirical formula for the heat capacity was obtained from experimental data. The experimental data for the basic thermodynamic properties of this quaternary system were compared with those of the basic H 2O + LiBr system.

Differential Enthalpies of Solution of Components in Binary Systems 2 CaO . Al2O3 . SiO2-CaO . Al2O3 . 2 SiO2, CaO . SiO2-CaO . Al2O3 . 2 SiO2 and CaO . SiO2-2 CaO . Al2O3 . SiO2

Differential enthalpies of solution of components in binary systems 2 CaO . Al2O3 . SiO2-CaO . Al2O3 . 2 SiO2, CaO . SiO2-CaO . Al2O3 . 2 SiO2 and CaO . SiO2-2 CaO . Al2O3 . SiO2 as the function of composition and temperature were determined on the base of isothermal composition dependences of enthalpies of mixing and temperature dependences of heats of fusion of their pure components. From the values of the first differential heat of solution of CaO . Al2O3 . 2 SiO2 and 2 CaO . Al2O3 . SiO2 in CaO . SiO2 over temperature range considered we can conclude that the reactions were closed chains of SiO4 tetrahedra in CaO . SiO2 melt break, are exothermic. On the other hand positive values of this quantity for CaO . SiO2 in CaO . Al2O3 . 2 SiO2 and 2 CaO . Al2O3 . SiO2 led us to the conclusion that the progressive breaking originally closed chains in CaO . SiO2 melt has endothermic character.

フェニルブタゾン結晶多形の溶解挙動

The solubilites of phenylbutazone polymorphs, pure α, β and δ, were measured over a temperature range of 35°C, from 50°C to 15°C. Both the Van't Hoff plots of lnX2 against 1/T and the Hildebrand plots of lnX2 against lnT are nonlinear, where X2 is the mole fraction solubility at an abslute temperature, T. The data were treated by multiple regression analysis according to the equation: ln(solubility)=(-Q/R)(1/T)+(b/R)lnT+c, where a, b and c are constant and R is the gas constant. From a, b and c, the heat of solution ΔH*2(soln) may be calculated e. g. ΔH*2(soln)=a+bT, and ΔCp=b, where ΔCpis the difference between the heat capacities of the liquid and the solid forms of the solute. Also, the heat of dissolution, ΔH2(diss), and dissolution activation energy, Ea, for these polymorphs were obtained by using the initial disolution rate at various temperatures. Their ideal mole fraction solubilities (α2) were calculated from the heats of fusion and the melting points of these polymorphs. The activity coefficient, γ2, the partial molal heat of mixing, ΔH2(mix), and the differential heat of solution, ΔH2(soln) may also be calculated from the heat of fusion, the activity coefficient, and the mole fraction solubility. The relationships between these ΔH*2(soln), ΔH2(diss) and Ea were discussed.

Thermodynamic properties of lithium nitrate-ammonia mixtures

In this paper, the thermodynamic properties of lithium nitrate-ammonia mixtures are presented. The vapour pressure-temperature correlations are developed by fitting the experimental P-T-x data. The enthalpy of solution, the latent heat of vaporization, the integral heat of solution and the differential heat of solution are presented in appropriate tabular and graphical forms.

Dicyandiamide analysis and solubility in epoxy resins

AbstractA simple procedure is described for the rapid, quantitative analysis of dicyandiamide in epoxy resins and epoxy resin prepregs. High performance liquid chromatography is used to analyze for dicyandiamide and to investigate the solubility behavior of dicyandiamide and 3‐(p‐chlorophenyl)‐1,1‐dimethylurea (Monuron) in liquid epoxy resins. Solubility expressions and differential heats of solution are determined. The formation of soluble amine‐epoxy reaction products and epoxy resin additives such as Monuron are found to enhance the solubility of dicyandiamide.

A high-sensitivity heat flow calorimeter for the investigation of metal-hydrogen reactions

A new sensitive heat flow calorimeter combined with a hydrogen reactor was developed. Metal-hydrogen reactions can be investigated in the temperature and pressure ranges 243<or=T<or=353K and 1<or=pH2<or=20 MPa, respectively. The calorimeter permits detection of heats of 10 mJ and is suitable for precise measurements of 50 mJ and more in periods of a few seconds up to some 103 s. In its first application the apparatus has been used to determine differential heats of solution of hydrogen in FeTi at 298K.

Solubility and Dissolution of Triamcinolone Acetonide

Available data on the solubility of triamcinolone acetonide in aqueous media are neither complete nor in agreement. Solubility of the steroid in distilled water and in potassium chloride solutions of varying ionic strength was determined at 28, 37, and 50°. Dissolution rates of the steroid in the aqueous media were determined at 28° via a rotating‐disk method. Triamcinolone acetonide solubility in distilled water ranged from 21 mcg. ml.−1 at 28° to 33.6 mcg. ml.−1 at 50°. The differential heat of solution was 4207 cal.mole−1. The intrinsic dissolution rate constant at the maximum agitation intensity employed was 4.51 × 10−3 hr.−1 cm.−2. Solubilities and dissolution rates were markedly lower in potassium chloride solutions. „Salting‐out”︁ coefficients were calculated, for the effect of potassium chloride on triamcinolone acetonide solubility, using the empirical Setschenow equation.

Gas chromatography of bis(triethylsilyl) sulfide and related compounds

1. It was shown that bis(triethylsilyl) sulfide and its isologs can be separated and studied by the GLC method. 2. The values of the specific retained volumes and the differential heats of solution (QS) of these compounds in a nonpolar solvent, and specifically in Apiezon L, were determined. It was found that QS is linearly dependent on the molecular weight of the compounds.

A study on the interaction between surfactants and hydrocarbon liquids by measurement of vapor pressure

The interaction between surfactants and hydrocarbon liquids was studied by measurement of the vapor pressure of hydrocarbons. The differential heat of solution Δ H ̄ and the differential entropy of solution Δ S ̄ of the hydrocarbons in the surfactants were calculated from the temperature dependence of the vapor pressure. The Δ H ̄ ' s and Δ S ̄ ' s decreased with increase in the mole fraction of hydrocarbons and their order corresponded approximately to that of the solubility parameter of hydrocarbons. The activity coefficient of hydrocarbons was obtained for mole fractions of hydrocarbons up to ca. 0.5. The results suggest that the interaction between surfactants and hydrocarbons arises from dispersion forces.

The solubility of amorphous silica at 25°C

Solutions in contact with solid amorphous silica at room temperature tend to become supersaturated. Experiments carried out over long periods of time show that steady states of supersaturation, 120 to 170 ppm, may persist for months. Eventually, however, the colorimetrically detectable dissolved silica in contact with silica gel decreases to about 115 ppm. Dissolved silica in waters collected from hot springs (p;H range 6.0 to 8.5) also slowly polymerizes and approaches 115 ppm. Extrapolation to 25°C of solubility data taken at high temperatures also yields a value of about 115 ppm for the solubility of amorphous silica. It is concluded that in nearly neutral solutions 115 ppm is the solubility of amorphous silica at 25°C, the differential heat of solution, ΔH, is 3.35 kcal/mole, and the standard free energy of solution, ΔF°25°C, is approximately 3.7 kcal/mole.

Concentrated polymer solutions — I. determination of the integral and differential heats of solution and dilution of polyiobutylene and polystyrene

Concentrated polymer solutions — I. determination of the integral and differential heats of solution and dilution of polyiobutylene and polystyrene

Concentrated polymer solutions—I. Determination of the integral and differential heats of solution and dilution of polyisobutylene and polystyrene : A. A. Tager and A. I. Podlesnyak, Vysokomol. soyed. 5: No. 1, 87–93, 1963

Concentrated polymer solutions—I. Determination of the integral and differential heats of solution and dilution of polyisobutylene and polystyrene : A. A. Tager and A. I. Podlesnyak, Vysokomol. soyed. 5: No. 1, 87–93, 1963

Studies on the structure and properties of carbochain polymers in dilute solutions—IV. The integral and differential heats of solution and densities of the polymers : S. G. Zelikman, and N. V. Mikhailov, Vysokomol. soedin. 1: No. 7, 1077–1085, 1959

Studies on the structure and properties of carbochain polymers in dilute solutions—IV. The integral and differential heats of solution and densities of the polymers : S. G. Zelikman, and N. V. Mikhailov, Vysokomol. soedin. 1: No. 7, 1077–1085, 1959

Semiconductor Properties of Recrystallized Silicon in Aluminum Alloy Junction Diodes

This is a study of the basic electrical properties of thin recrystallized regions formed in the fabrication of PN junctions by the alloying of pure aluminum on N-type silicon single crystals. The average aluminum concentration is about 7×1018 cm−3, and varies by a factor of 4 to 5; being largest in the region first recrystallized and decreasing in a linear manner to the surface immediately beneath the aluminum-silicon eutectic. The average Hall-hole mobility is about 55 cm2 volt−1 sec−1 and varies from 35 to 75 cm2 volt−1 sec−1 across a region formed by precipating from 977°C to the eutectic. Across the same region the conductivity varies from 72 to 35 mho cm−1. The built-in field which is both a function of depth and total width can vary from 10 to 200 v per cm in typical cases. The minority carrier (electron) diffusion length ranges from 4 to 12 μ. The temperature dependence of the distribution coefficient corresponds to an enthalpy change (differential heat of solution) of +0.43 ev necessary for the transfer of an atom of aluminum from the liquid to the solid.

Physical Studies of Non-aqueous Solvates. IV. The Solubility of Zinc Bromide in Diethyl Ether1

Solubility determinations of zinc bromide in diethyl ether were made over the temperature range -20 to +35/sup 0/. The existence of two etherates of zinc bromide has been further substantiated and their transition points determined more precisely: probably zinc bromide monoetherate, ZnBr/sub 2/.(C/sub 2/H/sub 5/)/sub 2/O stable below +16-17/sup 0/, and zinc bromide dietherate, ZnBr/sub 2/.2(C/sub 2/H/sub 5/)/sub 2/O which decomposes above +4/sup 0/. The differential heats of solution at saturation were calculated over the entire temperature range studied averaging 3.5 kcal/mole for the monoetherate and 0.60 kcal/mole for the unsolvated zinc bromide. The dietherate gave a value of 6.2 kcal/mole at 0/sup 0/ falling to 4.3 kcal/mole at about -8/sup 0/ and rising to 10.5 kcal/mole at -20/sup 0/.