Tian-Calvet Calorimeter Research Articles

Quelques reflexions a propos de la mesure calorimetrique de l'enthalpie de sublimation ou vaporisation

In order to determine the enthalpy of sublimation or vaporization of a compound with a vapour pressure between 10 −5 and some tens of Torr by calorimetry in the range 298–498 K, an experimental set-up associated with a Tian-Calvet calorimeter is described. With regard to a previously described apparatus, this set-up is of differential type and presents many advantages, especially in the practical field. The reproducibility and accuracy of the first results obtained are satisfying. A careful study of the influence of the conditions on the evaluation of enthalpy of sublimation or vaporization is also done. The results obtained with some classical compounds illustrated the influence of vaporization rate on the value of Δ b or vap H(T).

Determination of Lφ and L2 from calorimetric differential enthalpies of solution of NaCl in water at 298.15 K

A Tian-Calvet calorimeter type was adapted to measure differential enthalpies of solution. To test the calorimetric system and the experimental procedure, the differential enthalpies of solution of NaCl in water at 298.15 K in the molality range from 0.1 to 4.0 mol · kg −1 were measured. The results were compared with values computed using the enthalpy of solution at infinite dilution and the relative apparent molar enthalpy as a function of molality tabulated by Parker. The literature data have been analysed jointly with the results reported in this work to obtain the values of the relative partial molar enthalpy L 2( m) and the relative apparent molar enthalpy L φ ( m).

High-density amorphous ice. III. Thermal properties

The thermal properties of high-density amorphous ice, which is made by ‘‘melting’’ ice I at 77 K by applying a pressure of ∼10 kbar, have been measured in an automated Tian–Calvet calorimeter. The samples were heated from 78 to 270 K at a rate of 10 K h−1 and heat amounting to 544, 1425, and 35.5 J mol−1 was evolved in one run at the sharp transitions from high-density to low-density amorphous ice, from the low-density amorph to ice Ic, and from ice Ic to Ih, respectively. In addition, heat was spontaneously evolved by the high-density amorph before the transition, and by the sample over a range of ∼50 K around the temperature of the transition from ice Ic to Ih.

Thermodynamique de substances soufrees. IV. Etude thermochimique de la thiouree, de la thiosemicarbazide et de la thiocarbohydrazide

The thermochemistry of thiourea, thiosemicarbazide and thiocarbohydrazide has been studied by combustion and sublimation calorimetry, using a rotative bomb isoperibol calorimeter in the first case, and a Tian—Calvet calorimeter equipped with a Knudsen effusion cell in the second. These investigations enabled the determination of the corresponding enthalpies. Substance − △ H ° c( c, 298.15 K) (kJ mole −1) △ H ° sub( c, 298.15 K) (kJ mole −1) Thiourea 1478.03±0.45 112.0±1.5 Thiosemicarbazide 1712.43±0.54 125.8±1.5 Thiocarbohydrazide 1961.05±0.28 152.1±3.0 The experimental values of the conjugation of these molecules are also given, and a comparison with the theoretical values is discussed. The CS bond energy was calculated from the experimental enthalpy of atomization of thiourea. The use of these value to determine △ H ° a,calc (298.15 K) for the thioamides studied resulted in excellent agreement with △ H ° a,exp (298.15 K).

Thermodynamique de Substances Soufrees. III. Etude thermochimique de la thioacetamide et de la thiobenzamide

The thermochemistry of thioacetamide and thiobenzamide has been studied by combustion and sublimination calorimetry, using a rotative bomb isoperibol calorimeter in the first case, and a Tian—Calvet calorimeter equipped with a Knudsen effusion cell in the second. These investigations enabled us to determine the corresponding enthalpies. ▪ The planar molecule of thioacetamide is conjugated. From its theoretical energy of conjugation, we could propose a value for the contribution of the CS bond (598.8 kJ mole −1) in Klages' scheme. The use of this value in the case of thiobenzamide gave E conj.exp (298.15 K)= E conj.theor (298.15 K), so one might assume that this molecule is planar. The enthalpy of formation of thioacetamide in the gaseous state enabled us to determine its experimental enthalpy of atomization and a value of E (CS)=537.9 kJ mole −1. The use of this value in the case of thiobenzamide resulted in an excellent agreement between the calculated and experimental enthalpies of atomization.

High temperature reaction calorimetry: Potentialities, limitations and application of results

Various calorimeters devised by the author and his associates during the last forty years are briefly surveyed. The type of calorimeter to be developed depends on the type of reaction to be studied. A rough distinction is between spontaneous and slow reactions, the latter requiring high-temperature or solution methods, or both. Critical remarks on the performance of the various calorimeters are made and the restrictions on their application to high temperatures are outlined. The potentialities of the Tian-Calvet calorimeter are noted. In the second part of the paper, examples for the practical applications of thermochemical data are given. These pertain to aluminothermic types of reaction, “chill factors”, thermal production of magnesium, deoxidation of iron and the calculation of phase boundaries in binary and ternary systems (Cu-Ni, Fe-Ni-Co, FeNiCr, FeNiCu and FeCoCr).

Significance of thermal effects associated with solid-gas reactions in the Tian-Calvet calorimeter

The Tian-Calvet calorimeter has proved to be an extremely useful tool in determinations of the partial molar enthalpies of the gas in metal + oxygen and metal + hydrogen systems. Under the usual operating conditions, the thermal effects measured in the calorimeter proper do not represent all the thermal effects which occur in the entire gaseous volume. It is demonstrated that the observed thermal effects associated with such solid + gas reactions (carried out under conditions of constant total volume) represent changes in enthalpy, rather than in internal energy. This fact has important implications with respect to recent calorimetric studies of metal + hydrogen systems.

Development of a Thermometric Assay for Cancer Differentiation Based on Aldolase Isozyme Patterns

Abstract A microcalorimetric assay for aldolase isoenzymes in serum, using a Tian-Calvet conduction calorimeter, has been investigated for measurement of activities of serum aldolase toward fructose-1, 6-diphosphate (FDP) and fructose-1-monophosphate (FMP), and of the ratios between these activities as a function of disease state, specifically cancer. Chart deflection measures were found to be proportional to total heat involved and to bear a linear relationship to the amount of aldolase activity toward either substrate in the sample. Differentiation of a cancerous from a noncancerous population was distinct and unambiguous. The ratios of activity toward FDP and FMP were 3. 73 ± 0. 22 and 13. 20 ± 0. 80 in noncancerous and cancerous sera, respectively. The ease and rapidity of assay suggests considerable potential utility as a routine screening method for certain forms of cancer.