A high-precision moving bomb combustion calorimeter is described. The system is entirely fluidless ; the bomb, which was machined from a copper billet, acting as its own calorimeter. It has a mass of 10 kg, and its temperature rise is measured by the resistance change of a fine copper wire element wound in circular grooves cut into the external surface. The usual thermometer " lag " is thereby almost completely eliminated. Heat equilibration throughout the system is quite rapid, the main period in a combustion experiment occupying not more than 10 min. Heat-loss correction terms are correspondingly small.The bomb is completely surrounded by a thick solid copper jacket of mass 70 kg. For the duration of an experiment, periodic temperature-fluctuations in this jacket are vanishingly small (< 04005 deg.). This degree of control has been accomplished by immersing it in a suitably regulated air-bath. The bomb can be rotated round its cylindrical axis by a bearing-mounted motor-driven tufnol shaft. The entire bombjacket system is mounted in a cradle which can be rocked through an angle of 90' or more.The fluidless technique makes possible considerable simplification in the design and operation of a moving-bomb system. Furthermore, apart from the diminution of heat-los3 correction terms, errors arising from evaporation and non-uniform stirring are eliminated,The system has been calibrated using British Drug Houses thermochemical standard benzoic acid, and also a sample supplied by the N.B.S., Washington. The heats of combustion of succinic acid and thianthrene have been measured. The results obtained support the currently accepted values.The experimental techniques of calorimetry in general have reached a high degree ofprecision during the past twenty-five years.1 This is especially true of bomb calorimetry where very great accuracy is now attainable. Noteworthy among the more recently designed bomb systems are those of Rossini,2 Magnus and Becker,3 Meetham et al. 4 and Coops et al.5 All of these are highly successful in the production of accurate combustion heat data for C, H, 0 and C, H, 0, N compounds. On the other hand, for a variety of reasons they cannot give reliable results for sulphur or halogen containing molecules. Indeed, it is only in very recent times that a systematic thermochemistry of these latter types of compound has begun to develop, due to the pioneering work of Sunner 6 and Bjellerup 7 at Lund, Sweden, and the Bureau of Mines Group8 led by Waddington at Bartlesville, U.S.A. Of the problems enumerated by these workers only one directly affects the actual calorimetric design. This is the problem of achieving experimentally a thermodynamically definable end-state in the bomb liquid. In the past, several attempts 99 10 to solve this problem have been made using the conventional static bomb technique. These, however, are subject to a number of criticisms 8.11 and it is now generally accepted that a moving bomb system provides the best starting point for reliable combustion calorimetry of halogen and s...
