Calorimetry: Principles, devices and utilization

Calorimetry, which by definition measures heat, is all the more central to the study of physical, chemical or biological phenomena as they almost always involve measurable heat exchange. Yet calorimetric techniques often arouse a certain reserve among experimenters. There are many reasons for this: mixed memories of using Berthelot's old-fashioned calorimeter as a student, a feeling of discomfort with thermodynamics that seem both remote from the real world (apart from the steam engine!) and full of pitfalls, the multiplicity of calorimeters and their presentations, and finally, the need to submit to the demands of the laws of thermics, which generally require longer and more delicate experiments than, for example, measurements using current spectroscopic techniques. And yet, over the past two centuries, many researchers have developed a great deal of imagination to enable the measurement of heat, so ready to "escape" and so difficult to measure in its entirety. More recently, their efforts have focused on obtaining truly significant measurements: not just a heat measurement, but the measurement of the variation of a quantity such as enthalpy or internal energy, truly characteristic of the transformation undergone by the sample and truly independent of the calorimetric technique used. Last but not least, calorimetry has benefited from technological developments in scientific instrumentation, so that today's devices are easy to use, although they still require a great deal of care and rigor. As we shall see, their field of application extends to a wide variety of fields, many of which are accessible thanks to heat flowmeter calorimetry (also known as "Tian-Calvet" calorimetry), which will be the focus of our attention.

After presenting calorimetry in as orderly a fashion as possible, we describe its main applications in physics and physical chemistry.