First Example Reaction Calorimeter

The idea of calorimetry is based on the chemical reaction characteristic of molecules. The calorimetry method does not allow absolute measurements, as is the case, for example, with volumetric methods. The results given by unknown compounds must be compared with the calibration curve prepared from known amounts of pure standard compounds under the same conditions. In practical laboratory work there are very different applications of this method, because there is no general rule for reporting results of calorimetric determinations. A conventional spectrophotometry is used with a calorimeter. The limitations of many calometric procedures lie in the chemical reactions upon which these procedures are based rather than upon the instruments available . This method was first adapted for quinolizidine alkaloid analysis in 1940 by Prudhomme, and subsequently used and developed by many authors. In particular, a calorimetric microdetermination of lupine and sparteine was developed in 1957. The micromethod depends upon the reaction between the alkaloid bases and methyl range in chloroform. 

Wadso (11) has noted that for a reaction with an enthalpy change of 500 kJ mol1, the smallest detectable reaction would be 0.02% degradation per year. This is calculated on the basis that the molecular mass is 100 (any increase in the molecular mass would result in the detection limit decreasing by the same factor because of the lowering of the number of moles available to react), that 3 g of sample is used and that all of the material is available to react, that the detection limit for the calorimeter is 0.1 pW, and that the process is first order. These assumptions are reasonable as, for example, oxidation reactions can often have high enthalpy changes. It is clear that on this basis the isothermal microcalorimeter would easily be able to detect reactions, and should be able to predict the shelf life parameters for a product. 

Various thermometric assessments have been in the center of retailored techniques used to detect a wide variety of heat effects and properties. The traditional operation aims to measure, for example, heat capacities, total enthalpy changes, transitions and phase change heats, heats of adsorption, solution, mixing, and chemical reactions. The measured data can be used in a variety of clever ways to determine other quantities. Special role was executed by methods associated with enough adequate temperature measurements, which reveals an extensive history coming back to the first use of the word calorimeter introduced by the work Wilcke and later used by Laplace, Lavoisier as already discussed in the previous Chapter 4. 

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