Fluorine flame calorimetry

Fluorine flame calorimetry is a logical extension of oxygen flame calorimetry in which a gas is burned in excess of gaseous oxidant (214). The decision does not reach that of the oxygen flame calorimeter in which, for example, Affj(H20) was determined with a standard deviation of 0.01%. Combustions of H2, NH3 (8), and fluorinated hydrocarbons are typical applications, but the uncertain nonideality corrections of HF(g) prevent full realization of the inherent accuracy. 

The first reported attempt to use fluorine in calorimetric measurements is probably Berthelot and Moissan s study of the reaction between K.2SC>3(aq) and F2(g), in 1891 [ 19,120]. Modem fluorine bomb calorimetry, however, was started in the 1960s by Hubbard and co-workers [110,111,121], while in the same period Jessup and Armstrong and their colleagues [ 109,115-117] developed the method of fluorine flame calorimetry to a high degree of accuracy and precision. 

Much of the discussion of oxygen flame calorimetry presented in section 7.3 is directly applicable to fluorine flame calorimetry. As in the case of bomb calorimetry, however, the special properties of fluorine combustion systems and problems associated with handling fluorine require a somewhat different experimental method [109,115,116]. Thus, for example, a metal burner should be used. Also, the fact that the mixing of many gases with F2 may lead to spontaneous ignition hinders the use of a premixed flame. Fluorine combustion calorimetry has been used to study the thermochemistry of important reactions, such as... 

G. T. Armstrong, R. C. King. Fluorine Flame Calorimetry. In Experimental Chemical Thermodynamics, vol. 1 Combustion Calorimetry S. Sunner, M. Mansson, Eds. IUPAC-Pergamon Press Oxford, 1979 chapter 15. 

As illustrated in this section, the problems associated with using fluorine in combustion calorimetry seem to have been largely overcome. The fluorine bomb and flame calorimetry methods have been perfected to such an extent that, provided the chemistry of the process under study is well characterized, results of very good accuracy and precision can be obtained routinely. 

R. C. King, G. T. Armstrong. Constant Pressure Flame Calorimetry with Fluorine II. The Heat of Formation of Oxygen Difluoride. J. Res. Nat. Bur. Stand. 1968, 72A, 113-131. 

Although there have been various early attempts to use fluorine as the oxidant in flame calorimetry, the problem of corrosion restricted these efforts to the use of fluorine as a minor component of the reaction mixture. More recent work at the National Bureau of Standards has overcome many of the difficulties and Armstrong and Jessup have described a calorimeter in which volatile substances can be burnt in excess fluorine. Because the... 

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