Heat of solution measuring

Table 8 Heats of Solution Measured for Auranofin Polymorphs in Different Solvent Systems at Ambient Temperature...

The heat of formation of BtF, obtained from adiabatic calorimetry on Br2/F2 gas mixtures implies an exothermic heat of solution of 18.4 kJ for the Br2 in the BrF3/Br2 mixture and is consistent with the non-equilibrated heats of solution measured (218). 

Salvetti, G. Tognoni, E. Tombari, E. Johari, G.P. Excess energy of polymorphic states or glass over the crystal state by heat of solution measurement. Thermochim. Acta 1996,... 

Efimov, Kislova, and Medvedev (2) measured the heat of solution of AlBrg(cr) in an aqueous HCl solution containing KCl(cr) and the heat of solution of AlClg(cr) in an aqueous HCl solution containing KBr(cr). From these heats of solution measurements and using the heats of formation of AlClg(cr)(3), KCl(cr)(4, 5) and KBr(cr)(4, 6) as auxiliary data, they obtained A H (AlBrg, cr, 298.15 K) -122.510.5 kcal mol". ... 

Stuart ( ) have re-examined the data of Klemm and Tanke (1 ) and have calculated A H (AlBrg, cr, 298.15 K)- -122.4 kcal mol This latter value was based on the heat of solution measurements (13), AjH (AlClg, cr, 298.15 K) = -168.65 kcal mol", and on the enthalpies of formation difference of chloride and bromide ions at the proper concentration. 

The heat of the reaction AlgO Ccr, o) + SiOgCquartz) Al2Si0g(andalusite) has been determined at 968 K by Holm and Kleppa (i, ) to be -1.99 0.17 kcal mol . This value was obtained from heat of solution measurements in a high temperature oxide melt calorimeter. Using the JANAP functions, this reduces to (298,15 K) = -1.42 kcal mol which is used to calculate the adopted value for the enthalpy of formation. 

Hetherington and Robinson ( ) quoted A H = 26 kcal mol" (presumably it has a minus sign) for NOgF(g) which was derived from the heat of solution measured by Nichols and Robinson (4). 

They also obtained good agreement between heat of solution and thermal activity measured in an isothermal microcalorimeter over the range 0 to 100% crystallinity. Salvetti et al. (36) have demonstrated that different physical forms of carbohydrates can be differentiated by measuring heats of solution. Pikal et al. (1978) used heat of solution measurements to correlate the extent of crystallinity with the chemical stability of antibiotics. 

Ahyd// was measured in glacial acetic acid and corrected by a separate heat of solution measurement. The value given is for the liquid - liquid reaction. Experimental uncertainty is large for alkynes and ene-ynes because experimental error increases linearly with Ahyd77. The ene-yne conjugation stabilization relative to propyne and 2-butene is small, —96.0 —(—97.3) = 1.3 kcal mol 1 = 5.4 kJ mol"1, that is, Ahy(JH is smaller in magnitude by this amount than it would be for a hypothetical molecule with no conjugation interaction. 

AhydH was measured in glacial acetic acid and corrected by a separate heat of solution measurement experiment for n-hexane. The value given is for a liquid —> liquid reaction. 

Based on the NBA TDB auxiliary value for Af//° (H2O, 1, 298.15 K), and the selected enthalpy of formation of NiCl2(cr) (-(304.90 0.11) kJ-mol ), Thomsen s values would lead to an enthalpy of hydration of - (2104.9+ 1.8) kJ-mor , where the uncertainty (estimated here) is slightly lower than if the two heat of solution measurements were independent, because it is probable there were compensating errors. 

Crut [24CRU2] reported the heat of solution of anhydrous and hydrated NiBr2 as - 19.9 kcal mol (- 83.26 kJ-mol" ) and 0 kcal moE, respectively. The paper also reports a somewhat different derived value for the heat of hydration of the anhydrous salt as - 19 kcal moP (- 79.50 kJ-moP ). This value is consistent with the heats of solution of anhydrous and hydrated NiBt2, - 18.9 kcal moE (- 79.08 kJ moE ) and 0 kcal moE, probably from the same experiments, reported in an earlier paper by the same author [24CRU]. The extent of hydration of the hydrated salt is not reported, nor is the salt purity, the final solution concentrations nor the measurement temperature. Because nickel bromide prepared at high temperatures dissolved slowly in water at room temperature, a sample of anhydrous NiBr2(cr) was prepared in a manner to enhance its rate of dissolution in water. The dissolution rate difference may reflect a structural difference that could have been affected the value determined in the heat of solution measurements. 

For each of the three salts [72AUF/CAR], [72AUF/CAR2], the values for the five lowest concentrations were averaged to estimate a value at the third-lowest concentration with a solvent salt ratio of 8000 1. The difference between each experimental heat of solution measurement and the measurement (for the same hydrate) resulting in a solution with a solvent salt ratio of 8000 1 (0.00694 m) was calculated. Only values from the measurements with final solution concentrations below 0.056 m were used. Different values from 650 J mol to 200 J-mol were assumed for the heat of dilution to zero molality of the solution with a solvent salt ratio of 8000 1 (0.00694 m). Chukurov et al. [73CHU/DRA] provided an equation for heat of solution of the tetrahydrate in the concentration range 0.007 m to 0.03 m, and difference values based on that equation... 

Degrees of crystallinity can also be evaluated from heat of solution measurements that compare the sample to be characterized with known crystalline and amorphous standards [1]. The heat of solution technique is particularly useful for materials that decompose upon melting. The method sensitivity depends upon the difference in heat of solution between crystalline and amorphous phases, and it can be better than 1%, allowing detection of small differences in highly crystalline samples [1]. 

The second example concerning heat of solution measurements was chosen to stress a crucial problem in non-aqueous electrochemistry. This is the proper extrapolation to infinite dilution when association of the electrolyte occurs . Figure 4 shows that the validity range of the limiting law is attained only at very low concentrations (here <10 M), generally inaccessible to measurements. Hence, extrapolation from measured values (>5 10 M) yields erroneous data. Reliable... 

The binary sodium chloride-water system has been the object of many studies. As a result there is a wealth of published data for a wide range of temperatures. This data includes solubility, density, vapor pressure lowering and heat of solution measurements. Because of this availability of data and the straightforward strong electrolyte behavior of the system, sodium chloride has almost always been included as an example when illustrating activity coefficient modeling techniques. For this application, Meissner s method of activity coefficient calculation will be used. 

LAN Lanzavecchia, L. and Pedemonte, E., Evaluation of the interaction parameter for polystyrene-poly(a-methylstyrene) mixtures from heat of solution measurements, Thermochim. Acta, 137, 123, 1988. 

These limited quantities of californium metal place restrictions on the amount of analytical data that can be obtained for the products normally, analyses for hydrogen, nitrogen, and oxygen contents are not performed. The quality of the metal products has been determined by spark-source mass spectrometry, x-ray diffraction analysis, physical properties, appearance, and behavior in an experiment (such as the rate and extent of dissolution for heat-of-solution measurements). 

Solubility and heat of solution measurements These were carried out as described elsewhere [25]. 

The Heat of Solution of Neptunium Metal and the Heats of Formation of Some Neptunium Chlorides. A Microcalorimeter for Heat of Solution Measurements, E.F. Westram Jr. and L. Eyring, J. Amer. Chem. Soc., 74,2045-2047 (1952). 

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