Heat Conduction Microcalorimeter Research Articles

Immersion enthalpy of activated carbons with different oxygen content in toluene-hexane mixtures

The immersion enthalpies of three activated carbons (G, G1173 and O), subjected to chemical (oxidation with HNO3) and thermal modifications (treatment at 1173 K) into hexane (H) and toluene (T) as pure solvents and mixtures of the liquids with a ratio T/H = 0.2/0.8, 0.4/0.6, 0.6/0.4 and 0.8/0.2 were determined to evaluate both, the effect of the solid and the modification of the liquid phase in the adsorbate–adsorbent interaction. For this, the physicochemical characterization of the solids was carried out through N2 adsorption isotherms and Boehm titrations. Immersion enthalpies were evaluated using a heat conduction microcalorimeter designed and assembled in the laboratory. The enthalpy values for the pure solvents were between −59.06 and −126.10 J g−1 for toluene and between −16.36 and −66.14 J g−1 for hexane. For the mixtures, the values were between −26.15 and −94.38 J g−1. The interaction was favored if toluene was the pure solvent and the sample had lower oxygenated groups content, since the interactions of the dispersive type increased by the interaction between the π electrons present in activated carbon and the aromatic structure of toluene. For the mixtures T/H ratio = 0.2/0.8 and 0.4/0.6 where hexane was the solvent, the interaction of the mixture with the solid was favored with respect to the pure solvent, while for T/H ratio = 0.6/0.4 and 0.8/0.2 (solvent: toluene), the interaction was disfavored, given the lower affinity of hexane with activated carbon.

Synthesis, characterization and determination of standard molar enthalpies of formation of two zinc borates with higher ratio of ZnO/B2O3 by solution calorimetry

Two pure phases of zinc borates with high ratio of ZnO/B2O3, Zn8[(BO3)3O2(OH)3] and Zn6O(OH)(BO3)3, have been synthesized and characterized by XRD, FT-IR, TG and chemical analysis. The molar enthalpies of solution of Zn8[(BO3)3O2(OH)3](s) and Zn6O(OH)(BO3)3(s) in 1 mol dm−3 HCl(aq) were measured at 298.15 K by using a heat conduction microcalorimeter, respectively. With the incorporation of the previously determined enthalpies of solution of H3BO3(s) in 1 mol dm−3 HCl(aq) and ZnO(s) in the mixture solvent of [1 mol dm−3 HCl(aq) + H3BO3(aq)], together with the standard molar enthalpies of formation for ZnO(s), H3BO3(s) and H2O(l), the standard molar enthalpies of formation of −(5243.8 ± 3.9) kJ mol−1 for Zn8[(BO3)2O3(OH)3](s) and −(4248.5 ± 3.3) kJ mol−1 for Zn6O(OH)(BO3)3(s) at 298.15 K were obtained on the basis of the appropriate thermochemical cycles.

RD496微热量计的研制及其应用

This paper briefly reviewed the establishment and development of heat conduction microcalorimeter and introduced the research process of RD496 microcalorimeter. Summarized and introduced the application of RD496 microcalorimeter in chemistry and materials research, including the determination of crystalline transformation temperature, enthalpy of conversion, enthalpy of dissolution, enthalpy of mixing and enthalpy of formation, the reseach of chemical reaction thermokinetics and dilution crystallization kinetics, determination of the specific heat and thermal conductivity of solid materials, the calorimetric study of in situ growth and trace adsorption of materials. Meanwhile, the application of RD496 microcalorimeter in polymer chemistry and physics, biology chemistry and agricultural science had been metioned.

Synthesis, characterization, and thermochemical property of a novel mixed alkali metal borate: NaCs[B10O14(OH)4

A novel mixed alkali metal hydrated borate NaCs[B10O14(OH)4] was synthesized under hydrothermal conditions. Its structure was determined by single-crystal X-ray diffraction and further characterized by FT-IR spectroscopy, TG-DTA, powder X-ray diffraction, and chemical analysis. NaCs[B10O14(OH)4] crystallizes in monoclinic space group P2/c with a = 7.6588(3) A, b = 9.0074(3) A, c = 11.8708(6) A, and β = 115.682(3)°. The crystal structure of NaCs[B10O14(OH)4] consists of Na–O, Cs–O polyhedral, and [B10O14(OH)4]2− polyborate anions. [B10O14(OH)4]2− units are connected together through common oxygen atoms forming a 1D helical chain-like structure, which are further connected by O–H···O hydrogen bonds forming a 3D supramolecular structure. Through a designed thermochemical cycle, the standard molar enthalpy of formation of this borate was determined to be −7888.6 ± 8.1 kJ mol−1 by using a heat conduction microcalorimeter.

Enthalpy of the formation of natural hydrous aluminum hydroxosulfate (aluminite)

A thermochemical study of natural aluminum hydroxosulfate Al2[(OH)4SO4] · 7H2O, aluminite (Nakhodka deposit, West Chukotka, Russia) is performed on a Tian-Calvet “Setaram” high-temperature heat-conducting microcalorimeter (France). The enthalpy of aluminite formation from simple compounds is obtained via the melt calorimetry of dissolution, ΔfH○(298.15 K) = −4986 ± 21 kJ/mol.

Synthesis, Structure and Thermodynamic Property of a New Lithium Borate: Li4[B8O13(OH)2]·3H2O

AbstractA new hydrated lithium borate, Li4[B8O13(OH)2]·3H2O, has been hydrothermally synthesized and characterized by single crystal X‐ray diffraction, FT‐IR spectroscopy, simultaneous TGA‐DTA and chemical analysis. It crystallizes in the triclinic, space group $ P {\bar 1} $, a=8.4578(5) Å, b=8.7877(5) Å, c=10.8058(7) Å, α=87.740(3)°, β=71.819(3)°, γ=61.569(3)°, Z=2, V=665.26(7) Å3, Dc=2.043 g/cm3. Its crystal structure features polyborate anionic layers with the larger odd 13‐membered boron rings constructed by [B8O13(OH)2]4− FBBs. Through designing the thermochemical cycle, the standard molar enthalpy of formation of this borate was determined to be −(7953.8±6.6) kJ·mol−1 by using a heat conduction microcalorimeter.

Design, construction, and calibration of an isothermal titration calorimeter and its application in the study of the adsorption of phenolic compounds

An isothermal calorimetric titration was designed and built, and some of the results obtained are presented here. For this purpose, a Calvet heat-conducting microcalorimeter was developed and connected to a titration unit built for this experiment to record titration thermograms. The microcalorimeter was electrically calibrated to establish its sensitivity and reproducibility, obtaining K = 13.56 ± 0.21 W V(-1). Additionally, the equipment was tested using the heat of neutralisation for the tris-hydroxymethyl-aminomethane-HCl (THAM-HCl) system, obtaining ΔH = -30.92 ± 0.03 kJ mol(-1). The unit was assembled to obtain titration heats and the corresponding thermodynamic variables (ΔH, ΔG, ΔS, and K(e)) with a system of phenolic derivatives-activated carbon (synthesised from potato peel).

Study on the enthalpy of solution and enthalpy of dilution for the ionic liquid [C 3mim][Val] (1-propyl-3-methylimidazolium valine)

A new amino acid ionic liquid (AAIL) [C 3mim][Val] (1-propyl-3-methylimidazolium valine) was prepared by the neutralization method. Using the solution-reaction isoperibol calorimeter, molar solution enthalpies of the ionic liquid [C 3mim][Val] with known amounts of water and with different concentrations in molality were measured at T = 298.15 K. In terms of standard addition method (SAM) and Archer’s method, the standard molar enthalpy of solution for [C 3mim][Val] without water, Δ s H m ∘ = (−55.7 ± 0.4) kJ · mol −1, was obtained. The hydration enthalpy of the cation [C 3mim] +, Δ H + ([C 3mim] +) = −226 kJ · mol −1, was estimated in terms of Glasser’s theory. Using the RD496-III heat conduction microcalorimeter, the molar enthalpies of dilution, Δ D H m( m i → m f), of aqueous [C 3mim][Val] with various values of molality were measured. The values of Δ D H m( m i → m f) were fitted to Pitzer’s ion-interaction model and the values of apparent relative molar enthalpy, φL , calculated using Pitzer’s ion-interaction model.

Determination of optimal glucose concentration for microcalorimetric metabolic evaluation of equine spermatozoa

The heat conduction microcalorimeter can be used to evaluate the metabolic rates of the sperm cell. Two ejaculates of four stallions were cooled to +5ºC and checked for sperm motility (bright field microscopy), viability (eosin 3%), functional membrane integrity (hyposmotic swelling test), and heat production (microcalorimetry). Glucose and sperm cell concentrations were determined in order to measure the heat outputs resulting from sperm metabolism. Sperm viability, membrane integrity and sperm motility did not differ among the different glucose concentrations tested. Nevertheless, the highest heat output detected by the microcalorimeter was obtained with 6 mM glucose and 10(8) spermatozoa/mL. Since conduction microcalorimetry offered additional information on equine sperm metabolism, it could be used as a method to study equine semen preservation.

The thermodynamic properties of natural margarite

Thermal, IR spectroscopic, and thermochemical studies of natural brittle mica, margarite Ca1.00Na0.10Mg0.02Al3.89Fe0.013+Si2.03Ti0.01O10(OH)1.74F0.26, were performed. The enthalpy of formation of natural margarite from the elements (−6269 ± 12 kJ/mol) was determined by melt solution calorimetry on a high-temperature heat-conducting Calvet microcalorimeter (Setaram, France). Enthalpy growth over the temperature range 298.15–973 K was determined by the drop method. Equations for the temperature dependences of the enthalpy and heat capacity were obtained, H°(T)−H°(298.15 K), J/mol = 435.21T + 36.46 × 10−3T2 + 109.91 × 105/T − 169863 and C°p, J/(mol K) = 435.21 + 72.92 × 10−3T − 109.91 × 105/T2. The experimental data were used to estimate the thermodynamic properties of margarite of the theoretical composition, CaAl2[Al2Si2O10](OH)2.

A new microcalorimeter of adsorption for the determination of differential enthalpies

An adsorption microcalorimeter for the determination of the differential heat of adsorption is designed and built, and some of the results are presented here. For this purpose, a Calvet heat-conducting microcalorimeter is developed and is connected to a gas volumetric unit built in stainless steel to record adsorption isotherms. The microcalorimeter is electrically calibrated to establish its sensitivity and reproducibility, obtaining K = 154.34 ± 0.23 W V −1 and, chemically, it is examined with a THAM–HCL system, obtaining Δ f = −30.49 ± 0.05 kJ mol −1.The adsorption microcalorimeter is used here to obtain adsorption isotherms and the corresponding differentials heats, using as reference solid, a zeolite ZSM-5 type.

Determination of Differential Enthalpy and Isotherm by Adsorption Calorimetry

An adsorption microcalorimeter for the simultaneous determination of the differential heat of adsorption and the adsorption isotherm for gas-solid systems are designed, built, and tested. For this purpose, a Calvet heat-conducting microcalorimeter is developed and is connected to a gas volumetric unit built in stainless steel to record adsorption isotherms. The microcalorimeter is electrically calibrated to establish its sensitivity and reproducibility, obtaining K=154.34±0.23 WV−1. The adsorption microcalorimeter is used to obtain adsorption isotherms and the corresponding differential heats for the adsorption of CO2 on a reference solid, such as a NaZSM-5 type zeolite. Results for the behavior of this system are compared with those obtained with commercial equipment and with other studies in the literature.

Deuterium isotope effect on molar heat capacities and apparent molar heat capacities in dilute aqueous solutions: A multi-channel heat-flow microcalorimeter study

The molar heat capacities of chloroform, dichloromethane, methanol, acetonitrile, acetone, dimethyl sulfoxide, benzene, dimethylformamide, toluene, and cyclohexane, as well as their deuterated isotopologues, were measured using a multi-channel heat conduction TAM (Thermal Activity Monitor) III microcalorimeter. In addition, the apparent molar heat capacities of some of the associated dilute aqueous solutions (0.0039 < solute mole fraction, x i < 0.0210) were also measured. A temperature drop method from (298.15 to 297.15) K at 0.1 MPa was employed. The corresponding heat capacities were determined from the integration of the measured heat flow. The heat capacity results are shown to be in good to very good agreement with the available literature values. In addition, good correlations were obtained for the effect of isotopic substitution on both molar heat capacity and apparent molar heat capacity in aqueous solutions. These correlations should be useful in the prediction of the molar heat capacities or the apparent molar heat capacities of other deuterated compounds. Since these measurements were conducted with ampoules, the effects of heat of condensation and/or vapor space on the accuracy of the heat capacity determinations are discussed. The overall results from this study demonstrate the utility of a multi-channel heat conduction microcalorimeter in obtaining good reproducibility and good accuracy for molar heat capacities as well as apparent molar heat capacities from simultaneous samples.

Phase Equilibrium CsBr-CeBr3-HBr(12.52 wt %)—H2O at 298 ± 0.1 K and a New Solid Phase Compound

The equilibrium solubility of the quaternary system CsBr-CeBr3-HBr(12.52 wt %)—H2O was determined at 298K and the corresponding equilibrium diagram was constructed. The quaternary system is complicated by three equilibrium solid phases: CsBr, Cs5Ce2Br11 · 22H2O (5: 2 type), and CeBr3 · 7H2O, of which the new compound Cs5Ce2Br11 · 22H2O was found to be incongruently soluble in the system. The new compound obtained was identified and characterized by the method of X-ray diffraction and the thermal analysis methods of thermogravimetry-differential thermogravimetry (TG-DTG), and it loses its crystal water in two steps from 325 to 511 K. The standard molar enthalpy of solution of Cs5Ce2Br11 · 22H2O in deionized water was measured to be (129.105 ± 0.150) kJ mol−1 with a heat conduction microcalorimeter. The standard molar enthalpy of formation was calculated as (−10438.215 ± 0.150) kJ mol−1.

Novel physically structured lipid matrices of beeswax and a homolipid from Capra hircus (goat fat): a physicochemical characterization for application in drug delivery

Lipid based materials are fast becoming the carrier of choice for delivery of new chemical entities and active agents. It is important to know the thermal characteristics, crystal habit, texture and appearance of a new lipid matrix when determining its suitability for use in pharmaceutical formulations. In this study, physically structured lipid matrices containing various proportions (25% w/w, 50% w/w and 75% w/w) of beeswax in a novel homolipid from Capra hircus (goat fat) were prepared by fusion, and subjected to thermal treatments in a differential scanning calorimeter (DSC) to obtain the thermal characteristics. Further characterization of the lipid matrices was performed by X-ray diffraction, polarized light microscopy (PLM) and transmission electron microscopy (TEM). Kinetics of crystallization of the molten lipid matrices was studied in an isothermal heat conduction microcalorimeter (IMC). Analysis of thermal data from DSC indicated that the physically structured lipid matrices revealed varied melting peaks between those of the pure lipids. PLM observation exhibited qualitatively different textures for the different structured lipid matrices. The lipid matrix containing 50% w/w of beeswax presented an interference at 2θ = 1.2° d = 73.63 A different from those of the two pure lipids. The lipid matrix containing 75% w/w of beeswax showed a change in crystallization behavior after 34 h. Crystallization kinetic analysis indicated that the structured lipid matrix containing 50% w/w beeswax possessed the highest Avrami kinetic exponent n. Results obtained indicated that mixtures of beeswax and goat fat produced matrices composed of mixtures of crystals alongside mixed crystals with imperfections necessary for increased drug loading and retention capacities. The matrix containing 50% w/w of beeswax possessed ideal crystal properties for the formulation of colloidal and microparticulate lipid drug carrier systems of drug delivery.

Thermodynamic investigation on the reactions of formation of the compounds RE(C 5H 8NS 2) 3(C 12H 8N 2) (RE = Eu, Tb)

The reactions of ammonium pyrrolidinedithiocarbamate (APDC) and 1,10-phenanthroline ( o-phen · H 2O) by hydrated lanthanide chlorides in the presence of absolute ethanol yield two novel lanthanide derivatives represented with the empirical formula RE(PDC) 3(phen) (RE = Eu, Tb). The resulting compounds were characterized by elemental analysis, TG-DTG and i.r. spectrum. The enthalpy change of the reaction of complex formation from a solution of the reagents, Δ r H m θ ( l ) , and the molar heat capacities of the compounds, c m, were determined at T = 298.15 K by using an RD496-III heat conduction microcalorimeter, which were (−22.21 ± 0.08) kJ · mol −1 and (61.68 ± 0.65) J · mol −1 · K −1 for Eu(PDC) 3(phen) and (−21.04 ± 0.05) kJ · mol −1 and (67.74 ± 0.60) J · mol −1 · K −1 for Tb(PDC) 3(phen), respectively. On the basis of the appropriate thermochemical cycles and other auxiliary thermodynamic data, the enthalpy changes of formation of the compounds from the reactions of the regents in solid phase, Δ r H m θ ( s ) , were calculated as being (54.53 ± 0.31) kJ · mol −1 for Eu(PDC) 3(phen) and (40.20 ± 0.36) kJ · mol −1 for Tb(PDC) 3(phen). The thermodynamics of reactions of formation of the compounds were investigated by the reactions in ethanol. Fundamental parameters, the activation enthalpy ( Δ H ≠ θ ) , the activation entropy ( Δ S ≠ θ ) , the activation free energy ( Δ G ≠ θ ) , the apparent reaction rate constant ( k), the apparent activation energy ( E), the pre-exponential constant ( A) and the reaction order ( n), were obtained by combination of the thermochemical data of the reaction and kinetic equations with the data of thermokinetic experiments.

Thermochemical study of the solid complex Ho(PDC)3 (o-phen)

A novel solid complex, formulated as Ho(PDC)3 (o-phen), has been obtained from the reaction of hydrate holmium chloride, ammonium pyrrolidinedithiocarbamate (APDC) and 1,10-phenanthroline (o-phen·H2O) in absolute ethanol, which was characterized by elemental analysis, TG-DTG and IR spectrum. The enthalpy change of the reaction of complex formation from a solution of the reagents, ΔrHmθ (sol), and the molar heat capacity of the complex, cm, were determined as being –19.161±0.051 kJ mol–1 and 79.264±1.218 J mol–1 K–1 at 298.15 K by using an RD-496 III heat conduction microcalorimeter. The enthalpy change of complex formation from the reaction of the reagents in the solid phase, ΔrHmθ(s), was calculated as being (23.981±0.339) kJ mol–1 on the basis of an appropriate thermochemical cycle and other auxiliary thermodynamic data. The thermodynamics of reaction of formation of the complex was investigated by the reaction in solution at the temperature range of 292.15–301.15 K. The constant-volume combustion energy of the complex, ΔcU, was determined as being –16788.46±7.74 kJ mol–1 by an RBC-II type rotating-bomb calorimeter at 298.15 K. Its standard enthalpy of combustion, ΔcHmθ, and standard enthalpy of formation, ΔfHmθ, were calculated to be –16803.95±7.74 and –1115.42±8.94 kJ mol–1, respectively.

Enthalpies of solution of paracetamol and sodium diclofenac in phosphate buffer and in DMSO at 298.15 K

We have been using a heat conduction microcalorimeter to measure enthalpies of dissolution of slightly soluble solids. Recently we did report the testing of the prototype and we are now extending the previous investigation to measurements with organic solvents. In the present work we use DMSO due to its importance in the pharmaceutical industry. The importance of the applications of enthalpies of solution in organic solvents calls for the need to find a substance that can be used in the future for chemical calibration in these solvents. Attempts for proposing such a substance have also been a goal for our research group. The enthalpies of solution of paracetamol and sodium diclofenac were measured in DMSO and in phosphate buffer (pH 6.91) at 298.15 K. We show that it is possible to obtain very good results with DMSO as solvent for these two drugs on our dissolution microcalorimeter. Nevertheless, due to their slow and low enthalpy of dissolution in this solvent, they cannot be seen as good candidates for test substances.

Standard Molar Enthalpies of Formation for the Two Hydrated Calcium Borates xCaO·5B2O3·yH2O (x = 2 and 4, y = 5 and 7)

Two pure calcium borates of 2CaO·5B2O3·5H2O (I) and β-4CaO·5B2O3·7H2O (II) have been synthesized under hydrothermal condition and characterized by X-ray diffraction, infrared spectra, and thermogravimetric analysis as well as by chemical analysis. All the enthalpies of solution were measured at 298.15 K by using a heat conduction microcalorimeter. The molar enthalpies of solution of (I) and (II) in 2.00 cm3 of 1 mol·dm-3 HCl(aq) were measured to be −(60.30 ± 0.78) kJ·mol-1 and −(158.63 ± 0.72) kJ·mol-1, respectively. The molar enthalpies of solution of H3BO3(s) in 2.00 cm3 of 1 mol·dm-3 HCl(aq) and of CaO(s) in 2.00 cm3 of (HCl + H3BO3) aqueous solution were measured to be (21.84 ± 0.05) kJ·mol-1 and −(188.59 ± 0.42) kJ·mol-1, respectively. The enthalpies change of borates (I) and (II) formation from the reaction of reagents in the solid phase, −(98.3 ± 1.3) kJ·mol-1 and −(377.2 ± 1.9) kJ·mol-1 were calculated respectively on the basis of the appropriate thermochemical cycles. From these data and the stan...

The thermodynamic properties of 1-bromoadamantane in the gaseous state

The saturated vapour pressure over two crystalline phases (crI and crII) of 1-bromoadamantane in the temperature range from 288 to 323 K was measured by the integral Knudsen effusion method with the use of a modified effusion cell with an enlarged surface of sublimation. The temperature dependences of p sat are the following: for crII between T = 288.4 and 309.9 K: ln { p sat ( crII ) ( Pa ) } = ( 30.33 ± 0.44 ) − ( 8608 ± 137 ) ⋅ ( T ( K ) ) − 1 , for crI from 309.9 to 323.0 K: ln { p sat ( crI ) ( Pa ) } = ( 27.07 ± 0.81 ) − ( 7600 ± 252 ) ⋅ ( T ( K ) ) − 1 . The sublimation enthalpy for the compound at T = 303.0 K was measured in a differential heat-conducting microcalorimeter of the Calvet type, Δ sub H m ° ( 303.0 K ) = 71.77 ± 0.31 kJ mo l − 1 , which agrees with the value obtained by the effusion measurements, Δ sub H m ° ( 298.1 K ) = 71.6 ± 1.1 kJ mo l − 1 , within the experimental errors. The molar thermodynamic functions of 1-bromoadamantane in the ideal gaseous state were calculated by the statistical thermodynamic method. The complete set of the fundamentals necessary for the above calculations was made up from the experimental IR and Raman spectral data and the results of DFT calculations (B3LYP/6-31G*). The enthalpy of formation for 1-bromoadamantane was evaluated in terms of three different approaches. The thermodynamic analysis of some reactions with 1-bromoadamantane was performed.