Calorimeter macro

This sequence was then repeated with a different titer composition as many times as necessary to cover the required range of amphiphile/water compositions. An MS-DOS desk-top computer with 640K of random-access memory (RAM) was used to control the calorimeter and to collect thermistor voltages at the fixed time intervals. Spread-sheet macros running on this same computer were used to make various plots, including thermistor voltage y . time and corrected heat ys time. 

Conventional combustion calorimeters operate on a macro scale, that is, they require samples of 0.5-1.0 g per experiment. Unfortunately, many interesting compounds are available only in much smaller amounts. In the case of oxygen combustion calorimetry, however, several combustion microcalori-meters that only demand 2-50 mg samples have been developed in recent years. The achievements and trends in this area through 1999 have been reviewed [7-10], and interested readers are directed to these publications. Since then, a few new apparatus have been reported [11-17], Nevertheless, it should be pointed out that the general principles and techniques used to study compounds at the micro scale are not greatly different from those used in macro combustion calorimetry. 

Figure 7.1 Scheme of a macro static-bomb isoperibol combustion calorimeter (see text). 

Figure 7.7 Scheme of an isoperibol macro rotating-bomb combustion calorimeter. A calorimeter proper B bomb C thermostatic bath D motors for rotation of the bomb E drive shaft F stirrer of the calorimeter proper G motor that drives the stirrer F H motor that drives the stirrer of the thermostatic bath I miter gear J gas outlet valve K gas inlet valve L crucible. 

This overview has attempted to show that calorimetry has found applications in all areas of the pharmaceutical industry from discovery through receptor site binding to characterisation, on through compatibility to formulation and stability. The nanocalorimeters should find their real application in HTS whilst the more macro (but still micro ) calorimeters will still be needed, because of their better long-term stability to define the physicochemical properties of the selected pharmaceutical systems. 

The major developments in the e q)erimental technique carried out in the last few years have been concerned widi the development of micro-scale combustion calorimeters [156-164], One of the main limitations of the macro-scale combustion calorimeter is the quantity of sample needed to determine the enthalpy of combustion of a compound of purity degree around 99.9 %. In each experiment samples of mass between 0.5 g to 1 g are used and at least five experiments are needed. 

Since the discovery by Kroto et al. [232] of the third molecular form of carbon, Ceoj named buckminsterfiillerene, and especially after the development of effective ways of production of these type of molecules, there has been great interest in the thermochemistry of these molecules. The enthalpy of formation of Cao is a key value in establishing its thermodynamic stability. Several micro- and macro-combustion calorimeters have been used for the experimental determination of the enthalpies of formation of Ceo in the crystalline state at 298.15 K [233]. A graphical representation of the available results collected in... 

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