Petit microcalorimeter

Fig. 5. The Petit microcalorimeter (31) vertical axles (A and A2) mobile arms (Bi-B3) flux-meter holders (C1-C3) cell guide (D) thermoelectric element (E) cell-positioning block (F) top and bottom flanges (Gi and G2) portholes (Jj and J2) and springs (R). 

The Petit microcalorimeter which is presented in Fig. 5 appears to be particularly suitable for chemisorption studies. 

In this microcalorimeter, the heat sink is not a massive metal block but is divided into several parts which are mobile with respect to each other. Each thermoelectric element (E) and a cell guide (D) are affixed to a fluxmeter holder (C). The holder (C) is mobile with respect to a massive arm (B) which, in turn, rotates around a vertical axle (A). All parts of the heat sink are made of brass. Surfaces in contact are lubricated by silicone grease. Four thermoelectric elements (E) are mounted in this fashion. They enclose two parallelepipedic calorimetric cells, which can be made of glass (cells for the spectrography of liquids are particularly convenient) or of metal (in this case, the electrical insulation is provided by a very thin sheet of mica). The thermoelectric elements surrounding both cells are connected differentially, the Petit microcalorimeter being thus a twin differential calorimeter. 

The purpose of the particular arrangement of the heat sink in the Petit microcalorimeter is to ensure an excellent and reproducible contact, at any temperature, between the surface of the thermoelectric elements and the outside walls of the calorimetric cells (31) and, moreover, to avoid... 

It is clear that in this microcalorimeter, only a fraction of the outside wrall of the inner vessel is covered by thermoelectric elements. Consequently, only a part of the total heat flux emitted by the cell is detected. This may be the cause of a systematic error which, however, can be avoided if the heat transfer via the thermoelectric elements constitutes a constant fraction of the total, irrespective of the process taking place in the calorimeter cell. The present version of the Petit microcalorimeter can be used only at moderate temperatures (<100°C), mainly because some components of the thermoelectric elements wrould be damaged at higher temperatures. 

PES, see X-ray photoelectron spectroscopy Petit-Eyraud microcalorimeter, 22 203-205 Petrochemicals oxidation of, 2S-.21d Petroleum products... 

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