Calorimeter discontinuous, isothermal

Fig. 2.35 Compact calorimeter and reflux condenser for discontinuous, isothermal reaction...

The common method of determining the gross calorific value of coal is with either an adiabatic calorimeter (ASTM D-2015 this test method was discontinued without replacement in 2000 but is still in use in many laboratories) or an isothermal bomb calorimeter (ASTM D-3286). In these methods, a weighed sample is burned in an oxygen bomb covered with water in a container surrounded by a jacket. 

The results can be presented in the form of a continuous curve of differential enthalpies of adsorption A versus na, as shown in Figure 3.16b, with a resolution which is much higher than that obtained by the discontinuous procedure (Figure 3.16a). If the adsorption calorimeter cannot be easily connected to a well-calibrated and well-temperature-controlled adsorption sonic nozzle set-up, or when the adsorption isotherm is difficult to determine (e.g. if very small amounts are adsorbed), there remains the possibility of determining, separately, the adsorption isotherm by any of the discontinuous or continuous procedures described in Sections 3.3.1 or 3.3.2. A simple procedure can be applied which does not require the gas flow rate calibration ... 

An alternative is the isothermal dilution calorimeter. For an endothermic system, one component is slowly injected into the second component with the simultaneous addition of electrical energy sufficient to maintain the calorimeter isothermal. The addition is discontinued at any desired composition and the excess enthalpy determined from the initial amount of substance of component B in the vessel, the amount of substance of component A injected, and the electrical energy added to maintain isothermal conditions. The apparatus is normally designed so that the entire composition range can be covered in two experimental runs. For exothermic systems it is possible to add electrical energy... 

Fig. 2.1 Principle of accurate determination of thermal reaction power during an isothermal, discontinuous reaction [based on the same measuring principle of the calorimeter, this system of intermediate thermostat—controlled heater, base thermostat (controlled heat sink)—was replaced recently [54] by a new type of intermediate thermostat metal, bordering controlled Peltier elements, thermostat (controlled heat sink)]...

Chapter 2 presents calorimeters for measuring accurately the rate of heat release during discontinuous and continuous reactions versus time under isothermal and nonisothermal conditions. In addition, the chapter contains a description of an apparatus that can be used to record online the rate of heat release within a stirred tank reactor during a reaction. 

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