Calorimetric solution calorimetry

Randzio S L 1994 Calorimetric determination of pressure effects Solution Calorimetry, Experimental Thermodynamics vol IV, ed K N Marsh and PAG O Hare (Oxford Blackwell)... 

The reactions depicted in Eq. (1) are suitable for calorimetric investigations since they proceed rapidly and quantitatively as monitored by NMR. spectroscopy. The. solution calorimetric protocol has been described elsewhere." The enthalpy values were determined by anaerobic solution calorimetry in THF at 30 C by reacting 4 equivalents of each carbene with one equivalent of tetramer. The results of this study are presented in Table I. 

Low melting metals (Sn and also Bi, In, Pb, and Cd) are extensively used as solvents in calorimetric studies of metallic phases [35]. Transition metals do not, however, dissolve readily in tin [43] and other solvents such as Cu and A1 have been used. An experimental probe for high-temperature solution calorimetry is shown in Figure 10.8. 

Figure 8.2 Scheme of a typical calibration circuit used in isoperibol reaction-solution calorimetry. P power supply S switch R- electrical resistance inside the calorimetric vessel (F in figure 8.1) R2 standard resistance. 

CALORIMETRIC MEASOREMEMTS Solution calorimetry was performed at 298.2 0.1 K by using a C-80 differential flux calorimeter manufactured by Setaram. The energy equivalent of the calorimetric signal was determined by electric calibration. The reliability of the equipment was checked by the dissolution of tris-(hydroxymethyl) aminomethane (THAM). Agreement within 0.4% with the published value of +17.75 kJ. mol-1 ( 21) was obtained. 

Solution calorimetry of the molecular probes pyrrole, A-methylpyrrole, benzene, and toluene in 35 solvents has been used by Catalan el al. to determine a solvent HBA basicity scale, ranging from the gas phase to HMPT [31a]. Analogously, a solvent HBD acidity scale was derived calorimetrically using A-methylimidazole and A-methylpyrrole as probe molecules in 3 6 solvents, ranging from the gas phase to 2,2,2-trifluoroethanol [31b]. 

Solution calorimetry (2) gave A H = 1.125 0.016 kcal mol for BeF2(low quartz) BeF2(vitreous) at 298.15 K. Confirmation of ths result came from transposed temperature-drop calorimetry (p and calorimetric conversion (8). These gave... 

We dismiss two calorimetric values due to probable bias. These include AjH (t) -112 kcal mol from oxygen-bomb calorimetry (2) and A.H (g) -117.4 1.7 kcal raol from solution calorimetry (4) in dilute aqueous NaOH. Revised auxiliary 1 —1 data (1, 5) change these values to A H (g) -115 (,3) and -124 kcal mol . Wagman et al. (5) adopted -122.6 kcal mol, ... 

Calorimetric studies of surface and nanoparticle energetics fall into several classes enthalpies of wetting and hydration/dehydration, heat capacity measurements, thermal analysis of coarsening and phase transition, and enthalpy differences by solution calorimetry. These methods measure different quantities, suffer from different potential difficulties, and are generally regarded as complementary. 

Solution calorimetry has proven very useful for studying nanoparticle energetics. In its simplest form, the calorimetric experiment uses the following thermochemical cycle. 

Fewer data, particularily calorimetric, are available for evaluating the influence of temperature on metal cation adsorption. The enthalpy of Cd(II) adsorption onto rutile was determined using isoperibol solution calorimetry and a value of +10 kJ/mole was found (6). A recent variable temperature study (25) allows enthalpies for Cd(II), Zn(II), and Ni(II) adsorption onto hematite (synthesized in the presence of 0.86% Si) to be calculated using equation (8). These data are summarized in Table IV. 

The sample was the same as that used by Flotow et al. [1971FLO/OSB] for heat capacity measurements. More analytical details on the sample were given in this solution calorimetry study. It had a S/Th ratio of (1.043 +0.005) and was reported to contain 3.77 mass% Th2S3, 1.47 mass% ThOS, 88 ppm C, and 15 ppm N. The S/Th ratio of the monosulphide phase in the sample was calculated to be (1.029 + 0.019) and the reported calorimetric results are given for ThSi 029(cr). We therefore assume that these results refer to a measured value which has been adjusted for the presence of the impurities, although no mention is made in the paper as to the value assumed for Af/7° (ThOS, cr, 298.15 K), which is not known experimentally. 

The dark blue complex (P(C6Hu)3)2W(CO)3 binds a selective "menu of ligands and calorimetric data has been reported for a range of donors ( . Typical reactions studied by solution calorimetry are the reactions with pyridine shown in eqns.(2) and (3) below ... 

Researchers at the U.S. Bureau of Mines carried out combustion and solution calorimetry experiments to determine some AfH°(R203, cr) values (e.g. [16]) and also many adiabatic and drop calorimetric measurements to derive heat capacities up to about 1800 K (Pankratz, Kelley and coworkers). 

In order to determine the energies of dissociation of the metal-ligand bond, the following methods are commonly utilized calorimetric combustion, solution calorimetry, ion cyclotron resonance, mass spectrometry, ion beam technique, equilibrium constant measurements, kinetic methods, and photochemical determination of the threshold wavelength of the photolytic dissociation of the metal-ligand bond. ... 

While calorimetric methods, direct reaction calorimetry or solution calorimetry using tin or aluminum as solvent have been performed in rare earth based alloys, this has not been the case in actinide-based alloys, where acid solution calorimetry has sometimes... 

Some experimental results have been obtained using calorimetric methods. Unfortunately there are also discrepancies in the enthalpies of formation obtained by different authors in the Gd-Ni and Gd-Co systems where the enthalpies of formation have been obtained by Schott and Sommer (1986) using tin solution calorimetry and by Colinet et al. (1986, 1987c) using aluminum solution calorimetry. In both cases the values obtained by Schott and Sommer (1986) arc less negative than the values obtained by Colinet et al. (1986, 1987c). 

The calorimeter will perform with high precision to about 900 C. It is possible to measure heat effects as small as calorie in magnitude with a precision of 2 to 5. Heat effects of 5 200 calories can be obtained to within a standard deviation of 1%. This gives the necessary precision and sensitivity for solution calorimetry in oxide melts, where heats of solution of 0-30 kcal/mole are measured on samples of 50-100 m.y. (O.1-1.0 mmoles). Calorimetric solvents used, molten oxide mixtures suitable for dissolving solid silicate samples, will be described below. 

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