Flow Microcalorimeter Research Articles

Excess Enthalpies of Ethyl tert-Butylether + 2,2,4-Trimethylpentane + Decane or Dodecane at 25°C

Measurements of excess molar enthalpies at 25°C in a flow microcalorimeter, are reported for the two ternary mixtures ethyl tert-butylether + 2,2,4-trimethylpentane + n-decane and ethyl tert-butylether + 2,2,4-trimethylpentane + n-dodecane. Smooth representations of the results are described and used to construct constant-enthalpy contours on Roozeboom diagrams. It is shown that useful estimates of the ternary enthalpies can be obtained from the Liebermann–Fried model using only the physical properties of the components and their binary mixtures.

Excess Enthalpies of 2-Methyltetrahydrofuran + 2,2,4-Trimethylpentane + (Decane or Dodecane) at 25°C

Measurements of excess molar enthalpies at 25°C in a flow microcalorimeter, are reported for the two ternary mixtures 2-methyltetrahydrofuran + 2,2,4-trimethylpentane + n-decane and 2-methyltetrahydrofuran + 2,2,4-trimethylpentane + n-dodecane. Smooth representations of the results are described and used to construct constant-enthalpy contours on Roozeboom diagrams. It is shown that useful estimates of the ternary enthalpies can be obtained from the Liebermann–Fried model using only the physical properties of the components and their binary mixtures.

Water Adsorption on Lubricated Surfaces for Magnetic Storage Devices

In order improve the design of tribologically reliable magnetic storage devices, the fundamental properties of adsorption - molecular mobility and interaction energy between lubricants, water, and overcoats — are investigated for perfluorinated polyether (PFPE) lubricants on carbon surfaces. The interaction between the PFPE molecules and water molecules on the carbon surfaces in dry and humid environments is analyzed by using Nuclear Magnetic Resonance (NMR). Two NMR spectrum peaks of water on carbon surfaces on which the PFPE diol is coated are observed when humid air of 90% RH is introduced. One peak at a low chemical shift corresponds to the adsorbed water on the carbon surface. The other peak at a high chemical shift shows sorbed water molecules in the PFPE diol film. Minimum molecular mobility is observed for OH groups, i.e. adsorption sites, in the dry air. However, the molecular mobility increases because of the lubricant desorption when the humid air is introduced. Adsorption energies between the adsorbates (lubricants and water) and the adsorbent (carbon powder) are measured by using a flow micro-calorimeter. When water vapor is introduced, the negative heat of adsorption is observed, which indicates the lubricant desorption caused by the water molecules. Presented as a Society of Tribologists and Lubrication Engineers Paper at the STLE/ASME Tribology Conference in Orlando, Florida, October 11–13, 1999

Excess molar enthalpies of (acetonitrile + butan-2-one) and (methanol + acetonitrile + butan-2-one) atT = 298.15 K

The excess molar enthalpies of (acetonitrile + butan-2-one) and (methanol + acetonitrile + butan-2-one) were measured atT= 298.15 K and atmospheric pressure using a flow microcalorimeter. The experimental results are correlated with polynomial equations and compared with those calculated from associated solution models taking account into self-association of methanol and acetonitrile as well as solvation between unlike molecules and a non-polar interaction term.

Apparent Molar Volumes and Heat Capacities of Aqueous Trifluoromethanesulfonic Acid and Its Sodium Salt from 283 to 328 K

Apparent molar heat capacities $$C_{{\text{p}},\phi }$$ and volumes $$V_\phi$$ of aqueous trifluoromethanesulfonic (triflic) acid, HCF3SO3 (aq.) were determined with a Picker flow microcalorimeter and vibrating-tube densimeter at temperatures from 283 to 328 K and molalities from 0.05 to 9.5 mol-kg-1. Values of $$V_\phi$$ and $$C_{{\text{p}},\phi }$$ display a maximum near 0.8 mol-kg-1. $$V_\phi$$ also displays a shallow minimum at ∼5 mol-kg-1, while $$C_{{\text{p}},\phi }$$ continues to decrease smoothly up to the limit of our measurements at 9.5 mol-kg-1. We attribute this behavior to ion–ion interaction between triflate and the hydrated proton to form the aqueous complex H2n+1O n + CF3SO 3 - (aq.), n = 5. Standard partial molar properties C p o and Vo are consistent with results obtained from NaCF3SO3 (aq.) and yield values for the triflate anion CF3SO 3 - (aq.), over this range.

Excess Molar Enthalpies and Excess Molar Volumes of Binary Mixtures Containing Dialkyl Carbonates + Pine Resins at (298.15 and 313.15) K

Excess molar enthalpies, , and excess molar volumes, , of binary mixtures containing dimethyl carbonate (DMC), or diethyl carbonate (DEC) + α-pinene, + β-pinene, or + p-cymene have been determined using a flow microcalorimeter and a digital density meter at atmospheric pressure and at (298.15 and 313.15) K. All and data are positive and show symmetrical curves versus composition. The influence of temperature is marked for volumetric measurements while almost negligible for enthalpic data. Results have been correlated using the Redlich−Kister polynomial to estimate the binary interaction parameters. The calculated quantities have been qualitatively discussed in terms of thermodynamic interactions between the mixing compounds.

Amino Acids under Hydrothermal Conditions: Apparent Molar Heat Capacities of Aqueous α-Alanine, β-Alanine, Glycine, and Proline at Temperatures from 298 to 500 K and Pressures up to 30.0 MPa

The apparent molar heat capacities Cp° of aqueous α-alanine, β-alanine, glycine, and proline have been determined using a differential flow calorimeter and a Picker flow microcalorimeter at temperatures of 298 K ≤ T ≤ 500 K and at pressures from steam saturation to 30 MPa. Comprehensive equations to describe the standard-state properties over this range are reported. Values of the standard partial molar heat capacities Cp° for the aqueous amino acids increase with temperature and then deviate toward negative values at temperatures above about 390 K, consistent with increasing the critical temperature in the solutions relative to water, i.e., negative Krichevskii parameters. This is opposite to the behavior predicted by correlations reported in the geochemical and chemical literature. The temperature dependence of Cp° predicted using the very recent functional group additivity model of Yezdimer et al. (Chem. Geol. 2000, 164, 259−280) is only in qualitative agreement with the experimental results. The resul...

Excess molar enthalpies of binary mixtures containing phenetole+α-pinene or β-pinene in the range (288.15–313.15) K, and at atmospheric pressure: Application of the extended cell model of Prigogine

Excess molar enthalpies, H m E , of binary mixtures containing phenetole (ethoxy benzene)+α-pinene, or β-pinene have been determined in the range (288.15–313.15) K, and at atmospheric pressure using a flow microcalorimeter. H m E curves are symmetrical with positive values over the entire concentration range and show higher values for the mixture containing α-pinene (the maximum value for H m E is 1072 J mol −1). Only a slight influence of temperature on excess molar enthalpies has been observed for both systems. Experimental results have been correlated using the Redlich–Kister polynomial and the adjustable parameters have been evaluated by least-squares analysis. Results have also been interpreted by an extended modified cell model of Prigogine.

Excess molar enthalpies of binary mixtures containing propylene carbonate + some n-alkoxy- and n-alkoxyethoxy-ethanols at 288.15, 298.15, and 313.15 K

Excess molar enthalpies, H m E, of binary mixtures containing propylene carbonate + six n-alkoxyethanols have been determined using an LKB flow microcalorimeter at 288.15, 298.15, and 313.15 K and at atmospheric pressure. The alkoxyethanols were 2-methoxyethanol, 2-ethoxyethanol, 2-butoxyethanol, 2-(2-methoxyethoxy)ethanol, 2-(2-ethoxyethoxy)ethanol, and 2-(2-butoxyethoxy)ethanol. From the experimental data, deviations in H m E have been determined and fitted to the Redlich–Kister polynomial to estimate the binary interactions parameters.

Excess enthalpies of cyclohexane+ n-hexane+( n-octane or n-dodecane) ternary mixture at 298.15 K

Excess molar enthalpies, measured at 298.15 K in a flow microcalorimeter, are reported for the ternary mixtures (cyclohexane+ n-hexane+ n-octane) and (cyclohexane+ n-hexane+ n-dodecane). Smooth representations of the results are described and used to construct constant excess molar enthalpy contours on Roozeboom diagrams. It is shown that reasonable estimates of the excess enthalpies of the ternary mixtures can be obtained from the Flory theory, using only the physical properties of the components and their binary mixtures.

Excess enthalpies of { 2,2-dimethylbutane + hexane + (octane or dodecane)} at the temperature 298.15 K

Measurements of excess molar enthalpies at the temperature 298.15 K in a flow microcalorimeter are reported for the ternary mixtures {x1(CH3)3CCH2CH3+x2CH3(CH2)4CH3+(1 −x1−x2)CH3(CH2)6CH3} and {x1(CH3)3CCH2CH3+x2CH3(CH2)4CH3+(1 −x1−x2)CH3(CH2)10CH3}. Smooth representations of the results are described and used to construct constant-enthalpy contours on Roozeboom diagrams. It is shown that useful estimates of the ternary enthalpies can be obtained from the Flory theory using only the physical properties of the components and their binary mixtures.

From guinea pigs to cutting fluids — a microcalorimetric journey

This paper is a partial and selective review of the development of biological microcalorimetry with particular emphasis on kinetic aspects. The review describes, in outline, the concerns expressed for the determination of kinetic parameters in previous publications (mostly drawn from the author’s own interests) and concludes with a new kinetic analysis of the output from flow microcalorimeters.

Excess enthalpies of (2,2,4-trimethylpentane + cyclohexane + dodecane) at the temperature 298.15 K

Measurements of excess molar enthalpies at the temperature 298.15 K in a flow microcalorimeter are reported for the ternary mixture {x1(CH3)3CCH2CH(CH3)2+x2c- (CH2)6+ (1 −x1−x2)CH3(CH2)10CH3}. A smooth representation of the results is described and used to construct constant-enthalpy contours on a Roozeboom diagram. It is shown that useful estimates of the ternary enthalpies can be obtained from the Flory theory using only the physical properties of the components and their binary mixtures.

Excess molar enthalpies for (propan-1-ol or propan-2-ol + acetonitrile + 1,1-dimethylethyl methyl ether) at the temperature 298.15 K

The excess molar enthalpies of {propan-1-ol or propan-2-ol + acetonitrile + 1,1-dimethylethyl methyl ether (MTBE)} have been measured at T= 298.15 K and atmospheric pressure using a flow microcalorimeter. The experimental results are correlated with polynomial equations and used to test the workability of an association model.

Thermodynamic properties of aqueous diethanolamine (DEA),N,N-dimethylethanolamine (DMEA), and their chloride salts: apparent molar heat capacities and volumes at temperatures from 283.15 to 328.15 K

Apparent molar heat capacities Cp,ϕand apparent molar volumes Vϕfor aqueous diethanolamine (HOC2H4)2NH, diethanolammonium chloride (HOC2H4)2NH2Cl, N,N'-dimethylethanolamine (HOC2H4)(CH3)2N, and N,N'-dimethylethanolammonium chloride (HOC2H4)(CH3)2NHCl were determined from 283.15 to 328.15 K with a Picker flow microcalorimeter and vibrating tube densimeter. The experimental results have been analyzed in terms of Young's Rule with the Guggenheim form of the extended Debye-Hückel equation and appropriate corrections for chemical relaxation effects. These calculations lead to standard partial molar heat capacities and volumes for the neutral amines, (HOC2H4)2NH(aq) and (HOC2H4)(CH3)2N(aq), and the ions (HOC2H4)2NH2+(aq) and (HOC2H4)(CH3)2NH+(aq) over the experimental temperature range. Key words: standard partial molar volumes, standard partial molar heat capacities, diethanolamine, dimethyethanolamine, aqueous alkanolamine ionization.

Excess Enthalpies of 2,2-Dimethylbutane + Cyclohexane + (Octane or Dodecane) at 25°C

Measurements of excess molar enthalpies at 25°C in a flow microcalorimeter,are reported for the two ternary mixtures 2,2-dimethylbutane + cyclohexane +n-octane and 2,2-dimethylbutane + cyclohexane + n-dodecane. Smoothrepresentations of the results are described and used to construct constant enthalpy contourson Roozeboom diagrams. It is shown that useful estimates of the ternary enthalpiescan be obtained from the Flory theory using only the physical properties of thecomponents and their binary mixtures.

Thermodynamics of 1:1 electrolyte solutions in water + N, N-dimethylformamide mixed solvent system at 25°C : Molar excess enthalpy of mixing

The molar excess enthalpies of mixing for the six possible binary combinationsof solutions of NaCl, KCl, NaBr, and KBr as a function of ionic strength fractionhave been measured at 25°C. The experiments were performed at constant ionicstrengths of 1.000 and 2.000 mol-kg−1 with an LKB flow microcalorimeter inthe mixed solvent water + dimethylformamide. The equations of Friedman'sModel were fitted to the results. Our parameters differ appreciably from thecorresponding results in water and Young's cross square rule does not apply.While Pitzer's ion-interaction model was able to represent the enthalpy data forcommon ion mixings, it was unable to model the data of the noncommon ionmixtures. The data suggests that the problem may arise from variations in solvationof the ions and ion clusters including preferential solvation of certain species.

Excess Molar Enthalpies and Excess Molar Volumes of Diethyl Carbonate + Some n-Alkoxyethanols at (298.15 and 313.15) K

Excess molar enthalpies and excess molar volumes of diethyl carbonate + some alkoxyethanol mixtures have been determined by an LKB flow microcalorimeter and an Anton Paar density meter as a function of mole fraction of diethyl carbonate at (298.15 and 313.15) K. The alkoxyethanols are 2-methoxyethanol, 2-ethoxyethanol, 2-buthoxyethanol, 2-(2-methoxyethoxy)ethanol, 2-(2-ethoxyethoxy)ethanol, and 2-(2-butoxyethoxy)ethanol, respectively.

Excess molar heat capacities and excess molar volumes of (ann-alkylalkanoate + 2,2,4-trimethylpentane, or 2,2,4,4,6,8,8-heptamethylnonane) atT = 298.15 K

Excess molar heat capacities Cp, mEat constant pressure have been measured, as a function of mole fraction x at the temperature T= 298.15 K and atmospheric pressure, for eight liquid mixtures consisting of an n -alkylalkanoate and a highly-branched alkane {i.e. 2,2,4-trimethylpentane (isooctane) and 2,2,4,4,6,8,8-heptamethyl- nonane}: [xHCOO(CH2)3CH3+ (1 −x){(CH3)3CCH2CH(CH3)2, or (CH3)3CCH2C(CH3)2CH2CH(CH3)CH2C(CH3)3} ], {xCH3COOCH2CH3+(1 −x)(CH3)3CCH2CH(CH3)2}, {xCH3COO(CH2)3CH3+ (1 −x)(CH3)3CCH2CH(CH3)2}, {xCH3CH2COOCH3+ (1 −x)(CH3)3CCH2CH(CH3)2}, [xCH3CH2COOCH2CH3+(1 −x){(CH3)3CCH2CH(CH3)2, or (CH3)3CCH2C(CH3)2CH2CH(CH3)CH2C(CH3)3}], {xCH3CH2COO(CH2)2CH3+ (1 −x)(CH3)3CCH2CH(CH3)2}. Excess molar volumes VmEhave been determined, as a function of mole fraction x at the same temperature and pressure, for the same eight mixtures. The instruments used were a Picker flow microcalorimeter and a vibrating-tube densimeter, respectively. All the mixtures show positive excess volumes with a more or less parabolic composition dependence, with the maximum values of VmEranging between c. 0.3 cm3· mol−1and 0.9 cm3· mol−1. Most of the Cp, mEagainst x curves show a pronounced W-shape. However, for {xCH3CH2COO(CH2)2CH3+ (1 −x)(CH3)3CCH2CH(CH3)2}, the Cp, mEcurve has degenerated to one with a virtually flat portion extending from about x= 0.2 to x= 0.8, and Cp, mEof {xHCOO(CH2)3CH3+ (1 −x)(CH3)3CCH2CH(CH3)2} is S-shaped with the negative part situated at small mole fractions of n -butylmethanoate.

Measurement and correlation of excess molar enthalpies for (ethanediol, or 1,2-propanediol, or 1,2-butanediol + water) at the temperatures (285.65, 298.15, 308.15, 323.15, and 338.15) K

The excess molar enthalpies for (ethanediol, or 1,2-propanediol , or 1,2-butanediol + water) have been measured at five different temperatures over the whole composition range in an LKB flow microcalorimeter. A flow-mix cell has been developed and used for the measurements. All the mixtures exhibit negative excess enthalpies. The model parameters of the two group-contribution models EBGCM and modified UNIFAC of Weidlich and Gmehling were fitted with the experimental data and the calculated results are compared with the experimental data.