Berthelot calorimeter

Adiabatic calorimeters the thermal conductance between the calorimetric vessel and the surrounding thermostat equals 0. These calorimeters integrate all heat effects. The heat measurement is based on the measurement of the sample temperature. The most perfect adiabatic calorimeters are those for which the temperature of the thermostat is brought to follow that of the internal vessel, like those proposed by Person (1849) and Richards (1905). In this group of adiabatic calorimeters, the authors also mention the Dewar vessel calorimeter (which they call quasi-adiabatic ) and the Berthelot calorimeter. 

It should be noted that, prior to Parr, other calorimeters existed which used oxygen under pressure for combustion in closed vessels, namely, those of Berthelot (1881) and its modifications and variations, Berthelot-Vieille, Moreau, Landrieu-Malsallez, and of the Commission des Substances Explosives . Later bombs were those of Mahler (1892), Attwater (1899) and Kast (constructed at Chemisch-Technische Reichsanstalt, New-Babelsberg, near Berlin, Ger)... 

The first closed bomb calorimeter using oxygen under pressure was developed in 1881 by Berthelot (Refs 1,15 16). It was improved by Mahler in 1892 and by Atwater in 1899. These bombs were made of steel with linings of Pt, Au,... 

Refs l)M.Berthelot, "Thermochimie , Gauthier - Villars, Paris (1897) 2)Marshall 2(1917), 440 - 4 3)W.P.White, "Modern Calorimeter ,... 

Na2S04 (c, II). The data on the heat of solution yield the following values for S4m- Thomsen,18 0.257 Tilden,2 0.25 Pickering,8 —0.09. Other data on the heat of solution, lacking in most cases necessary information as to temperatures and concentration, were reported by Graham,1 Favre and Valson,2 Berthelot,10 Berthelot and Ilosvay,1 and Varali-Thevenet.1 Mixter6 measured, in a bomb calorimeter, the heat... 

KCIO4 (c). Berthelot and Vielle4 determined the heat of decomposition of KCIO4 (c) into KC1 (c) and 02 (g), in a tomb calorimeter using potassium picrate and ammonium picrate as the auxiliary combustibles. Their data yield, for KC104 (c), Qf= 110.9 and 113.0, respectively. 

Any of the calorimeters described in Chapter II. is in principle capable of being used for the determination of heats of reaction. In any actual case it will, of course, be necessary to adapt the apparatus to the purpose which it is intended to serve. Jul. Thomsen, Berthelot, Favre and Silbermann, Stoh-mann, de Forcrand, Luginin, and of late years Th. W. Richards, AVrede, and W. A. Roth have been the chief workers in the development of thermo-chemistry. The more important of the apparatus devised and used by them are described in detail in many text-books. 

Andrews, Quart. J. Chem. Soc., 1849,1, 27 Favre and Silbermann, Ann. Chim., 1853, 37, 406 Berthelot, Compt. Rend., 1877,85, 646 Hartog and Harker, Manch. Mem., 1893-4,8, 37, Harker, ibid., 1895-6, 10, 38 (who found that the vapour must go superheated into the calorimeter to prevent liquid droplets being carried over). 

A simple but not very accurate apparatus for the determination of latent heats of evaporation is that of Berthelot.4 The liquid in a pear-shaped flask A (Fig. 2.VIII L) is heated by a ring gas-burner B covered by a metal disc. The vapour passes down a central tube into a glass worm-condenser in the calorimeter. The actual evaporation lasts only 2 to 4 mins., the correction for heat radiated from the burner (which is screened from the calorimeter by a sheet of wood covered with wire gauze) being determined by measuring the rise in temperature in the calorimeter before the liquid boils, and after evaporation is completed. The weight of liquid condensed is determined. 

Figure 4. Two historical calorimeters of the passive adiabatic group the Thomsen (left) and Berthelot (right) calorimeters...

Because the heat to be measured is usually brought to a vessel containing water, most calorimeters used in this method can be called water calorimeters . Examples James Watt (1786), Regnault (1840), Favre and Silbermann (1845), Berthelot (1875). Other liquids can be used Favre and Silbermann s mercury calorimeter. 

Between 1881 and 1905, Berthelot and co-workers developed the first combustion calorimeter, precursor of the modem calorimeters with static bomb [27-30]. 

Using such a calorimeter (from the Latin for heat-measure), Berthelot ran careful determinations of the quantity of heat evolved by hundreds of different chemical reactions. Independently, the Danish chemist Hans Peter Jorgen Julius Thomsen (1826-1909) did similar experiments. 

The bomb calorimeter, introduced in 1869 by Berthelot, has found a more widespread application than the flame calorimeter. In bomb calorimetry oxidation of the solid or liquid compound is carried out at constant volume, under a pressure of oxygen from 25 to 35 atmospheres. The bomb itself, of about 350 ml internal... 

Berthelot introduced the bomb calorimeter for combustions in oxygen. A... 

Further thermochemical measurements were made in the 1850s and 1860s by the Danish chemist Julius Thomsen (1826-1909) and the Frenchman Marcelin Berthelot, who had earlier made such important contributions to organic synthesis (Chapter 10). It was Berthelot who introduced the terms endothermic and exothermic and invented the bomb calorimeter for the accurate determination of heats of combustion. Berthelot suggested that all spontaneous reactions occur with the evolution of heat, and that the reaction which actually occurs in a given situation is the one which is accompanied by the greatest evolution of heat. These conclusions are erroneous, and it was not until the new discipline of thermodynamics was more fully developed that the criteria for spontaneous chemical change were properly understood. 

Figure 7.9 Classic mixing calorimeter" (from Meyers Crofies Conversationslexikon, 1905, according to Berthelot, 1879, p. 140).

The most important type of mixing calorimeter with a reaction vessel is the combustion calorimeter, whose sealed reaction vessel (the so-called Berthelot bomb or calorimetric bomb) serves for the combustion of solid or liquid samples by electric ignition in the presence of excess oxygen (Figure 7.12). 

Figure 7.12 Sealed reaction vessel of a combustion calorimeter ( Berthelot bomb" or calorimetric bomb )(from Meyers Grofies Conversationslexikon, 1905).

The main application of such a calorimeter, the burning of substances inside a sealed, pressure-tight reaction vessel, was developed by Berthelot (1827-1907) into a standard procedure. Berthelot was the first to fill the reaction vessel with pure oxygen to excess pressure in order to obtain a quick, thorough combustion into definite reaction products. Calorimeters of this type were soon given the name bomb calorimeter because of the bomb-like appearance of the reaction vessel. Berthelot s numerous thermochemical measurements owe their success to this experimental procedure. Even today, this instrument remains a valuable aid for the determination of the standard enthalpies of formation of chemical compounds, of the combustion heats of foodstuffs, and of the gross heating values of fuels (Rossini, 1956 Skinner, 1962). 

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