Aneroid calorimeter

Using a "home made" aneroid calorimeter, we have measured rates of production of heat and thence rates of oxidation of Athabasca bitumen under nearly isothermal conditions in the temperature range 155-320°C. Results of these kinetic measurements, supported by chemical analyses, mass balances, and fuel-energy relationships, indicate that there are two principal classes of oxidation reactions in the specified temperature region. At temperatures much lc er than 285°C, the principal reactions of oxygen with Athabasca bitumen lead to deposition of "fuel" or coke. At temperatures much higher than 285°C, the principal oxidation reactions lead to formation of carbon oxides and water. We have fitted an overall mathematical model (related to the factorial design of the experiments) to the kinetic results, and have also developed a "two reaction chemical model". 

The focus of our investigations of the kinetics of oxidation of Athabasca bitumen has been on the use of an aneroid calorimeter ( 1 ) for measuring rates of heat production under nearly isothermal (AT < 1.2°C in each experiment) conditions. Initial attention was given to just two of the variables that affect the kinetics of oxidation (i) temperature and (ii) pressure of oxygen. 

The calorimetry lexicon also includes other frequently used designations of calorimeters. When the calorimeter proper contains a stirred liquid, the calorimeter is called stirred-liquid. When the calorimeter proper is a solid block (usually made of metal, such as copper), the calorimeter is said to be aneroid. For example, both instruments represented in figure 6.1 are stirred-liquid isoperibol calorimeters. The term scanning calorimeter is used to designate an instrument where the temperatures of the calorimeter proper and/or the jacket vary at a programmed rate. 

The corrections due to the bomb rotation can also be eliminated by using a dynamic calorimeter, in which the whole calorimeter is rotated and the rotation mechanism is outside the calorimeter proper. An example of such instrument is the aneroid calorimeter developed by Adams, Carson, and Laye [77], shown in figure 7.9. 

Figure 7.8 Scheme of a micro rotating-bomb aneroid combustion calorimeter [75,76]. 

Figure 7.9 Scheme of the aneroid dynamic combustion calorimeter designed by Adams, Carson, and Laye [77], A jacket B jacket lid C motor that drives the rotation of calorimetric system D rotation system E bomb (which is also the calorimeter proper) F channels to accommodate the temperature sensor, which is a copper wire resistance wound around the bomb G crucible H electrode I gas valve. Adapted from [77]. 

G. P. Adams, A. S. Carson, P. G. Laye. Heats of Combustion of Organo-metallic Compounds using a Vacuum-Jacketed, Rotating, Aneroid Calorimeter. Trans. Faraday Soc. 1969, 65, 113-120. 

Thermochemical data were required for the estimation of ground state strain. Heats of formation ( 0.5 kcal mol-1) were obtained by the experimental determination of heats of combustion 25 -27) using either a stirred liquid calorimeter 25) or an aneroid microcalorimeter 26) heats of fusion and heat capacities were measured by differential scanning calorimetry (DSC), heats of vaporization 21, 25, 27) by several transport methods, or they were calculated from increments 28). For the definition of the strain enthalpies Schleyer s single conformation increments 29) were used and complemented by increments for other groups containing phenyl30) and cyano substituents. 

Values for the enthalpies of fusion of alkali-metal cryolites may be obtained, using an aneroid, inverse-drop calorimeter with adiabatic shields.475... 

For many readers, the term "construction principle may mean much more than a twinning the calorimeter can also be built liquid or aneroid, closed or open, in a Dewar, with a liquid thermostat or a furnace, with thermopiles or thermistors, with a batch or liquid flow mixing system, with a steady flame or a bomb combustion device, with a sample drop facility and with a multi-sampler). 

Figure 4.29 represents an isoperibol drop calorimeter [7]. The surroundings are at almost constant temperature and are linked to the sample via a heat leak. The recipient is a solid block of metal making it an aneroid calorimeter (Fr. androide, not using a liquid, derived from the Gk.). The solid block eliminates losses due to... 

In both the aneroid and liquid calorimeters, a compromise in the block and pail construction has to be taken. The metal or liquid must be sufficient to surround the unknown, but it must not be too much, so that its temperature-rise permits sufficient accuracy in AT measurement. The calibration of isothermal calorimeters is best done with an electric heater in place of the sample, matching the measured effect as closely as possible. To improve the simple calculation of the output of the aneroid and liquid calorimeters, a loss calculation must be carried out as described in the next section. 

Isothermal calorimeters have also been used in polymer studies and primarily in investigations of heats and rates of polymerization reactions 28—37). Shielding and controls in reaction calorimeters are not as critical as in nonisothermal calorimeters used in spedfic heat measurement since most polymerization reactions are accompanied by relatively large enthalpy changes. On the other hand special attention must be jaid in the selection of the calorimeter material for a particular combination of monomers, solvents, catalysts, etc, to ensure inertness of the reactor wall to reaction components. Frisch and Mackle describe an aneroid high precision, semi-micro reaction calorimeter (Fig. 2) usable for a wide range of reaction systems including those in which one component is a gas. 

The calorimeter substance used for this purpose does not have to be water. Other liquid and even solid substances are also suitable. If the calorimeter substance is a solid (usually a metal), the calorimeter is referred to as aneroid (nonliquid). 

Nernst, Koref, and Lindematm (1910) described an aneroid drop calorimeter for the measurement of specific heat capacities. Figure 7.14 shows the design of this instrument. The entire system is located in isothermal surroundings such as melting ice. Of particular interest is the measurement of the temperature change of the calorimeter substance by means of 10 iron-constantan thermocouples mounted between the calorimeter substance and the isothermal Ud. 

An aneroid static-bomb combustion calorimeter has been employed to determine the standard enthalpy of formation of a small sample (ca. 20 mg) of bicyclo[3,3,3]nonane (— 36-4g + 0-42 kcal mol ), and a temperature-scanning technique makes use of a commercial gas chromatograph in the measurement of the vapour pressures of several adamantane and diamantane derivatives. Results were converted into heats of sublimation by employing the Clausius-Clapeyron equation doubt is cast on the accuracy of a previously recorded value for diamantane. 

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