Calorimetric methods differential Scanning Calorimetry

Calorimetric Methods.—Differential Scanning Calorimetry (d.s.c.). The use of commercially available d.s.c. apparatusto study phase separation in polymer and copolymer solutions is described. In this context perhaps the main advantage of the method is to distinguish between liquid-liquid phase separation, where the enthalpy change is usually small, and crystallization of polymer (see Chapter 12). The method is much used to study the glass transition in polymer mixtures (see p. 320). 

J. H. Flynn. Thermodynamic Properties from Differential Scanning Calorimetry by Calorimetric Methods. Thermochim. Acta 1974, 8, 69-81. 

For the determination of reaction parameters, as well as for the assessment of thermal safety, several thermokinetic methods have been developed such as differential scanning calorimetry (DSC), differential thermal analysis (DTA), accelerating rate calorimetry (ARC) and reaction calorimetry. Here, the discussion will be restricted to reaction calorimeters which resemble the later production-scale reactors of the corresponding industrial processes (batch or semi-batch reactors). We shall not discuss thermal analysis devices such as DSC or other micro-calorimetric devices which differ significantly from the production-scale reactor. 

Differential Scanning Calorimetry (DSC) was used for a long time in the field of process safety [21-23], This is essentially due to its versatility for screening purposes. The small amount of sample required (micro-calorimetric technique) and the fact that quantitative data are obtained, confer on this technique a number of advantages. The sample is contained in a crucible placed into a temperature controlled oven. Since it is a differential method, a second crucible is used as a reference. This may be empty or contain an inert substance. 

Differential scanning calorimetry (DSC) is a calorimetric method that finds widespread use in many fields, including protein dynamics, polymers, pharmaceuticals, and inorganic materials. DSC measures energy (heat) flow into a sample and a reference substance as a function of controlled increase or decrease of temperature. In a typical power-compensated DSC (Fig. 3.2), the sample and reference are placed on metal pans in identical furnaces each containing a platinum resistance thermometer (thermocouple) and heater. During a thermal transition (e.g., when a physical change in the sample occurs),... 

A study of the relaxational transitions and related heat capacity anomalies for galactose and fructose has been described which employs calorimetric methods. The kinetics of solution oxidation of L-ascorbic acid have been studied using an isothermal microcalorimeter. Differential scanning calorimetry (DSC) has been used to measure solid state co-crystallization of sugar alcohols (xylitol, o-sorbitol and D-mannitol), and the thermal behaviour of anticoagulant heparins. Thermal measurements indicate a role for the structural transition from hydrated P-CD to dehydrated P-CD. Calorimetry was used to establish thermodynamic parameters for (1 1) complexation equilibrium of citric acid and P-CD in water. Several thermal techniques were used to study the decomposition of p-CD inclusion complexes of ferrocene and derivatives. DSC and derivative thermogravimetric measurements have been reported for crystalline cytidine and deoxycytidine. Heats of formation have been determined for a-D-glucose esters and compared with semiempirical quantum mechanical calculations. ... 

Calorimetric methods have been used to obtain qualitative data or parameters that could correlate with the CCD [55-57]. It should be clear, however, that differential scanning calorimetry (DSC), although very powerful in other areas, does not provide the ideal environment for crystallization, does not result in... 

The heat of reaction and the rate of heat production in a reaction mixture as a function of temperature are important quantities for the design of reactors in chemical industry. Presently, several methods for the determination of these quantities are available, such as Differential Scanning Calorimetry, Differential Thermal Analysis, Bench Scale Calorimetry / / and adiabatic calorimetric methods. 

The term calorimetry denotes a variety of measurement methods which involve a measurement of the heat of physical or chemical changes in a sample. One of the most commonly used calorimetric methods is differential scanning calorimetry in which the difference in the heat flow rate to a primary sample and a reference sample is measured, when both are subjected to the similarly alternating temperature. Usually this is done in a specified, controlled atmosphere. In isothermal calorimetty the measurement temperature is kept as constant as possible, and, instead of temperature alternation, the other environmental parameters such as gas atmosphere, relative humidity, light exposure, etc., are alternated. 

Hancock BC, Dalton CR (1999) The effect of temperature on water vapor sorption by some amorphous pharmaceutical sugars. Pharma Dev Technol 4 125-131 Hancock BC, Shamblin SL (2001) Molecular mobility of amorphous pharmaceuticals determined using differential scanning calorimetry. Thermochim Acta 380 95-107 Hancock B, Dalton C, Pikal M, Shamblin S (1998) A pragmatic test of a simple calorimetric method for determining the fragility of some amorphous pharmaceutical materials. Pharm Res 15 762-767... 

The specific T] can be measured by different techniques, such as turbidity analysis or calorimetric methods (Fig. 2). The first method is characterized by a turbidity profile showing a sharp step, with T, taken to be the temperature that shows a 50% change in the relative turbidity shape. In contrast, differential scanning calorimetry (DSC) measurements are always characterized by a broad peak covering 20 °C or more. In this case, T, can be considered as either the onset or the peak temperature. The T, values obtained by these methods usually differ because of the influence of several factors [26]. 

In the direct calorimetric determination, (- AH =f nn)T), the amount adsorbed ( ta) is calculated either from the variations of the gas pressure in a known volume (volumetric determination) or from variations of the weight of the catalyst sample in a static or continuous-flow apparatus (gravimetric determination). In a static adsorption system, the gas is brought into contact with the catalyst sample in successive doses, whereas the catalyst is swept by a continuous flow in a dynamic apparatus. Comparative calorimetric studies of the acidity of zeolites by static (calorimetry linked to volumetry) and temperature-programmed (differential scanning calorimetry linked to thermogravimetry) methods of ammonia adsorption and desorption have been performed [23]. 

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