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The standard molar enthalpies of formation of PbBi12O19(s) and ϕ-Pb5Bi8O17(s) at 298.15 K were determined using an isoperibol calorimeter. The enthalpies of solution of ternary compounds, namely, PbBi12O19(s) and ϕ-Pb5Bi8O17(s) as well as stoichiometric oxide mixtures, namely, {PbO(s) + 6 Bi2O3(s)} and {5 PbO(s) + 4 Bi2O3(s)} in HNO3 (aq., 4.47 mol kg−1) at T = 298.15 K were measured. Using these values, Δ f H m o (298.15 K) of PbBi12O19(s) and ϕ-Pb5Bi8O17(s) were determined as (-3549.6 ± 23.8) kJ mol−1 and (-3239.4 ± 7.6) kJ mol−1, respectively. The given uncertainties were calculated as 2σ of the mean with 0.95 level of confidence.

The enthalpies of solution of ethylacetate (EtOAc) in water, octane and 1-octanol (OctOH) were measured at 298, 308 and 318 K using a precise isoperibol calorimeter. The standard enthalpies and heat capacities of these non-electrolyte solution were computed and compared with the previously obtained ΔsolH∘ and \(\Delta C_{p}^{\circ}\) values in N,N-dimethylformamide (DMF). Partial molal heat capacities of EtOAc in water and in organic solvents were calculated and compared with the available literature values.

The molar enthalpies of solution of VOSO4⋅3.52H2O(s) at various molalities in water and in aqueous sulfuric acid (0.1 mol⋅kg−1), ΔsolHm, were measured by a solution-reaction isoperibol calorimeter at 298.15±0.01 K. An improved Archer’s method to estimate the standard molar enthalpy of solution, \(\Delta_{\mathrm{sol}}H^{0}_{\mathrm{m}}\), was put forward. In terms of the improved method, the values of \(\Delta_{\mathrm{sol}}H^{0}_{\mathrm{m}}=-24.12\pm 0.03~\mbox{kJ}{\cdot}\mbox{mol}^{-1}\) of VOSO4⋅3.52H2O(s) in water and \(\Delta_{\mathrm{sol}}H^{0}_{\mathrm{m}}=-15.38\pm 0.06~\mbox{kJ}{\cdot}\mbox{mol}^{-1}\) in aqueous sulfuric acid were obtained, respectively. The data indicates that the energy state of VOSO4 in aqueous H2SO4 is higher than that in pure water.

The standard enthalpies of formation at 300 K of the RNiAl phases (R=rare earth) have been obtained by using a high temperature direct reaction drop calorimeter and an aneroid isoperibol calorimeter. State and composition of the samples were checked by X-ray diffraction analysis. Metallographic examination was performed and the phases were further identified by electron microscopy and electron probe microanalysis. The results obtained are discussed and compared with those available for the binary RNi 2 and RAl 2 compounds.

The enthalpies of dilution for aqueous solutions of [Co(en)3]Br3, [Co(pn)3]Cl3, and [Co(tn)3]Cl3 (where en = 1,2-diaminoethane, pn = 1,2-diaminopropane, and tn = 1,3-diaminopropane) have been measured at 25°C, and up to m = 1 mol-kg−1, using an isoperibol calorimeter by the “long-jump” method. Relative apparent molar enthalpies Lφ have been extracted as an empirical equation relating Lφ and m. Previously reported experimental data and theoretical predictions in the restricted primitive model (RPM) for 3:1 and 1:3 aqueous electrolytes are shown together with the new experimental material.

The molar enthalpies of solution of SrTeO3, SrTe2O5, TeO2, and SrCO3in HCl (aq,c=11 mol·dm−3) have been measured by using an isoperibol calorimeter. From these results and other auxiliary data, the standard molar enthalpies of formation ΔfHm°(298.15 K) of SrTeO3(cr) and SrTe2O5(cr) have been calculated to be −(1026.0±10.7) kJ·mol−1and −(1381.2±12.9) kJ·mol−1, respectively. These values of enthalpies of formation are consistent with the second-law enthalpies of formation derived from their vapour pressures determined in this laboratory by a transpiration technique.

The molar enthalpies of solution of CaTeO3, CaTe2O5, TeO2, and CaCO3in HCl(aq,c=11 mol·dm−3) have been measured by using an isoperibol calorimeter. From these results and other auxillary data, the standard molar enthalpies of formation ΔfHm°(298.15 K) of CaTeO3(s) and CaTe2O5(s) have been calculated to be −(985.4±4.8) kJ·mol−1and −(1337.4±7.2) kJ·mol−1, respectively. These values are consistent with the second law enthalpies of formation of the compounds determined in this laboratory by a transpiration technique.

The molar enthalpies of solution of ZrTe 3 O 8 , TeO 2 , and ZrF 4 , in HF(aq) of concentration 10 mol.dm −3 have been measured using an isoperibol calorimeter. From the results and other auxiliary quantities, the standard molar enthalpy of formation of ZrTe 3 O 8 (s) has been determined to be Δ f H m °(298.15 K) = −(2119.2 ± 9.6)kJ·mol −1 .

Four compounds in the system Li 2 O-MoO 3 , namely, Li 2 MoO 4 (c), Li 2 Mo 2 O 7 (c), Li 2 Mo 3 O 10 (c) and Li 2 Mo 4 O 13 (c) were synthesized and characterized by both chemical and X-ray diffraction analyses and confirmed to be single-phase compounds. The molar enthalpies of solution of these compounds have been measured at 298.15 K using an isoperibol calorimeter and the respective values at infinite dilution, Δ sol H m α (298.15 K), for the compounds Li 2 MoO 4 (c), Li 2 Mo 2 O 7 (c), Li 2 Mo 3 O 10 (c) and Li 2 Mo 4 O 13 (c) are −(33.88 ± 0.51), −(97.68 ± 0.52), −(167.20 ± 0.30) and −(247.68 ± 0.88) kJ mol −1 respectively. These data were used to calculate the standard molar enthalpies of formation Δ f H m o (298.15 K) and the respective values for the compounds are −(1520.13 ± 0.94), −(2279.29 ± 1.76), −(3032.68 ± 2.53) and −(3775.26 ± 3.46) kJ mol −1 . The results are compared with the available data in the literature.

The important amount of hydration water in the ulexite (NaCaB5O9.8H2O), allows using calcination methods to increase its B2O3 content. This paper analyses the thermal decomposition reaction of a preconcentrated ulexite through weight loss measurements, which occur during the heating of samples until 1000 oC. Determinations of heat content at each temperature were made using an isoperibol calorimeter. The mean specific heat was calculated from these values, and its dependence on temperature was determined. The maximum weight loss was about 32.5 % and the specific heat obtained was 1,13 kJ/kgoC for solid samples and 1,38 kJ/kgoC for fluid samples.The results are useful for the design of the industrial process, in order to determine the thermal requirements for heating calcined ulexite, and to obtain smelted ulexite.

The enthalpies of dilution for aqueous solutions of [Co(en)3]Cl3, where en = 1,2-diaminoethane, have been measured at 25°C, and up to m = 1 mol-kg-1, using a new large isoperibol calorimeter by the >long-jump> method. Relative apparent molar enthalpies Lφ have been extracted as an empirical equation relating Lφ and m. Comparison with other 3:1 and 1:3 aqueous systems confirms the previously suggested hydrophobic character of the [Co(en)3]3+ cation.

Dr. Shyamala Bharadwaj is presently Head, Fuel Cell Materials & Catalysis Section, Chemistry Division, Bhabha Atomic Research Centre, Mumbai, India. She obtained her M.Sc. in Chemistry in 1981 and her Ph.D. in Physical Chemistry in 1991 from Mumbai University. Her main area of work during the past 30 years has been determination of thermodynamic properties of nuclear materials using various techniques such as vapour pressure measurements, thermogravimetry, isoperibol calorimeter, etc. During 2000–2001, she worked as guest scientist at Juelich Research Centre, Juelich, Germany on Solid Oxide Fuel Cell (SOFC) materials. Her current interests are in the fields of Intermediate Temperature Solid Oxide Fuel Cells (ITSOFC) and sulphur–iodine thermochemical cycle for generation of hydrogen from water. She was awarded the NETZSCH–ITAS Award (2006) by the Indian Thermal Analysis Society in the year 2006 for her contributions in the field of thermal analysis. She has more than 95 papers in refereed international journals and more than 100 papers in National and International Symposia. She served two terms (2003–2009) as Hon. General Secretary of Indian Thermal Analysis and during this period she was involved in organizing several national symposia and workshops on Thermal Analysis. She has been one of editors of Proceedings of National Symposium on Thermal Analysis held biennially at various places in India during the period 1991 to 2010.

The enthalpies of solution of crystalline AlCl 3 and KBr were measured successively in one portion of 3.5 mol dm −3 HCl solution as well as AlBr 3 and KCl in another. The measurements were carried out in a 100 cm 3 reaction vessel of the isoperibol calorimeter LKB-8700. The standard enthalpy of the resulting reaction: A l C l 3 ( c ) + 3 K B r ( c ) = A l B r 3 ( c ) + 3 K C l ( c ) , was found to be Δ H r o ( 298.15 K ) = ( 6 3 . 4 ± 1 . 3 ) k J m o l - 1 which leads to Δ H f o ( A l B r 3 , c , 2 9 8 . 1 5 K ) = ( - 5 1 2 . 6 ± 1 . 9 ) k J m o l - 1 . The same measurements were carried out for AlCl 3 and KI and for AlI 3 and KCl. The standard enthalpy of the reaction: A l C l 3 ( c ) + 3 K I ( c ) = A l I 3 ( c ) + 3 K C l ( c ) , was found to be Δ H r o ( 298.15 K ) = ( 8 0 . 1 ± 1 . 4 ) k J m o l - 1 which leads to Δ H f o ( A l I 3 , c , 2 9 8 . 1 5 K ) = ( - 3 0 2 . 9 ± 2. 0 ) k J m o l - 1 .

The enthalpies of the reactions of Zr(cr), ZrCl 1.09 (cr), and ZrCl 4 (cr) with (1.0HF + 2.9HCl) mol · dm −3 solution were measured in 0.1 dm 3 reaction vessel of the isoperibol calorimeter LKB-8700. The following standard molar enthalpies of formation were calculated: Δ f H m o (298.15 K)/(kJ · mol −1 ): ZrCl 1.09 (cr), −330.5 ± 2.4; ZrCl(cr), −303.2 ± 3.4; ZrCl 2 (cr), −531.0 ± 5.0; ZrCl 4 (cr), −980.7 ± 1.0. Heat-capacity measurements between 9 and 315 K were performed on pure samples of ZrCl 0.98 (cr) and ZrCl 4 (cr). The following standard molar thermodynamic quantities of crystal zirconium chlorides are reported at T ′ = 298.15 K: ZrCl ZrCl 2 ZrCl 4 C p, m o (T′)/( J · K −1 · mol −1 ) 47.26 ± 0.10 75 116.80 ± 0.20 S m o (T′)/( J · K −1 · mol −1 ) 60.94 ± 0.12 100 180.40 ± 0.35 “H m o (T′) − H m o (0)’/(J · mol −1 ) 9324 ± 10 14200 24590 ± 50 Δ f G m o (T′)/( kJ · mol −1 ) −276.5 ± 3.4 −482.7 ± 5.0 −889.9 ± 1.0

A more exact method of calculating the heat loss from isoperibol-calorimeter reaction vessels is described. This method involves corrections for changes in the heat-leak constant and the external power input with changes in the calorimeter contents, and is particularly important for reaction vessels with volumes of less than 25 cm3 or with heat-leak constants greater than about 0.005 min−1. The new calculation has been tested by application to results collected with a titration calorimeter of capacity 3 cm3.

Literature values of the enthalpy of formation of perchlorate ion are based solely on measurements of the enthalpy of decomposition of crystalline perchlorates and are in poor agreement. In this paper a new method—measurements of the enthalpies of reaction in solution—was used. The enthalpies of reduction of crystalline KClO4 and KBrO3 by TiCl3 solution were measured in the 100 cm3 reaction vessel of LKB-8700 isoperibol calorimeter. The enthalpies of solution of crystalline KCl and KBr were measured similarly in the same solution. The values ΔHfo(KClO4, c, 298.15 K) = − (431.41 ± 0.87) kJ mol−1, and ΔHfo(ClO4−, aq, 298.15 K) = − (127.79 ± 0.86) kJ mol−1, were calculated from appropriate thermochemical cycles.

The enthalpies of solution of α-Zr(SO 4 ) 2 (c), Zr(SO 4 ) 2 ·4H 2 O(c), ZrCl 4 (c), KCl(c), K 2 SO 4 (c), and H 2 O(l) in 3.0 mol·dm −3 HCl(aq) were measured. The measurements were carried out in the 100 cm 3 reaction vessel of the isoperibol calorimeter LKB-8700. The following values were calculated from these measurements: Δ f H m o {α-Zr(SO 4 ) 2 , c, 298.15 K) = −(2244.2 ± 2.2) kJ·mol −1 ; Δ f H m o {Zr(SO 4 ) 2 ·4H 2 O, c, 298.15 K} = −(3469.3 ± 2.7) kJ·mol −1 . α-Zr(SO 4 ) 2 includes an excess of 0.03 mol of SO 3 and in this paper α-Zr(SO 4 ) 2 means Zr(SO 4 ) 2 ·0.03SO 3 . Using literature enthalpies of solution of Zr(SO 4 ) 2 (c) and of its mono- and tetra-hydrates in water, the value: Δ f H m o {Zr(SO 4 ) 2 ·H 2 O, c, 298.15 K} = −(2576±6) kJ·mol −1 was calculated.

Molar enthalpies of solution at very low molalities of some mono-, di, tri, and tetra-saccharides in water have been measured at 298.15 and 308.15 K using an isoperibol calorimeter. The molar heat-capacity changes ΔsolCp, m∞ on dissolution at 303.15 K were derived from molar enthalpies of solution. A Picker flow microcalorimeter and an Anton Paar digital density meter were used to measure apparent molar heat capacities Cp, 2, φ and apparent molar volumes V2, φ of solute at 298.15 K. The various compounds studied show large positive values of ΔsolCp, m∞ and Cp, 2∞. The experimental Cp, 2∞ values are found to be much higher than values estimated using additivity relations and heat capacities for the constituent groups derived from the heat capacities of monofunctional compounds. Results further indicate that the difference in Cp, 2∞(expt) and Cp, 2∞(est.) per hydroxyl group increases with an increase in the number of hydroxyl groups in a molecule. An attempt has been made to explain the Cp, 2∞ values of stereoisomers in terms of the compatibility of the aqueous-solution conformation of the compound and the tetrahedral order in water.

The enthalpy of oxidation of NaNO2(aq) and KI(c) by K2Cr2O7 in 1 mol·dm−3 H2SO4 solution was measured in a 0.1 dm3 reaction vessel of the isoperibol calorimeter LKB-8700. The enthalpy of the reaction: NaNO2(sln, 43.64H2O)+I2(c)+H2O(l)+K2SO4(c)=NaNO3(c)+2KI(c)+H2SO4(sln, 53.40H2O), was found to be ΔrHmo(298.15 K) = (52.06±0.68) kJ·mol−1, which leads to ΔfHmo(NO2−1,aq,298.15 K) = −(100.0±0.9) kJ·mol−1.

A reaction-solution rotating-bomb isoperibol calorimeter has been developed and tested. It consists of the calorimeter bomb with surrounding can, and accessories including a control box. These units together with an LKB 8710 control unit and a suitable thermostat constitute the calorimeter assembly Potassium chloride and tris , tris(hydroxymethyl)aminomethane, dissolution experiments were carried out between 298 and 390 K and between 298 and 360 K, respectively. The results have been compared with literature data.

The heats of solution of crystalline amino acids and hydroxy acid in water at 298.15 K were measured with a twin isoperibol calorimeter. It was found, as was expected from the theory, that the difference in the heat of solution between optically active compounds and their corresponding racemic compounds was appreciably large compared with the heat of mixing of concentrated aqueous solutions of d- and l-optical isomers.

To measure directly the heat change associated with the extraction of zinc(II) from hydrochloric acid solutions by trioctylmethylammonium chloride (TOMAC) in benzene has been succeeded by using twin type isoperibol calorimeter. It is proved that the heat change depends on the concentration of acid in aqueous phase.