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Abstract
Initial plant scale trials of the nitrosation of an amino acid revealed a number of issues: _ Much lower yield compared to laboratory scale _ Considerable loss of mass balance _ Large excess of nitrosating agent required for complete reaction _ Highly reactive off-gases produced causing fires in the carbon absorber _ Reaction sensitive to agitation speed _ The by-product produces an impurity in the next process stage which has high human toxicity A kinetic and mechanistic study of the nitrosation reaction, using isothermal power compensation calorimetry and GC/mass spectrometry, has been undertaken in order to understand the above observations and to produce an improved manufacturing process - more robust, higher yielding, reduced effluent volumes and toxicity.
A thermodynamic analysis of the uniaxial stretching of polyurethanes of various compositions and mechanical histories was carried out by using deformation calorimetry. The initial small strain deformations were found to result from the volume elasticity of the hard phase. The intramolecular energy contributions of the soft blocks were estimated. The hard block contributions were shown to depend on their content and on the degree of sample stretching. The predominant role of the soft component is proved to be manifested only in softened samples with a hard block content not exceeding 30%. The thermodynamics of the softening and hysteresis phenomena were studied. The dependence of the deformation mechanism on the hard block content and mechanical history is discussed.
Abstract
Several DTA experiments followed by calorimetric works are reviewed here to emphasise the importance of complementary role of both techniques. The thermal analysis is advantageous in the sense that it gives quickly the overall view of thermal behaviour of a material under various conditions. Calorimetric work provides accurate heat capacity data which enable to derive thermodynamic functions including the enthalpy and entropy. The latter quantity is especially important in judging whether the material obeys the third law of thermodynamics. However, calorimetric work leads occasionally to an erroneous conclusion if the work is not preceded by thermal analysis performed under various conditions. Sometimes, quality of information obtained by DTA exceeds that obtained by laborious calorimetry.
crystallinity have made them too brittle for many applications. Differential scanning calorimetry (DSC) is an important technique to study melting and crystallisation behaviour of polymers. The interpretation of DSC results is difficult due to various
methods to monitor in MM patients in any stages. Differential scanning calorimetry (DSC) is unsurpassed for understanding the stability of biological systems. DSC directly measures the stability and unfolding of a protein, lipid, or nucleic acid
, the ethanolic solution of sodium dipyrone or sodium diclofenac was incrementally added using a microsyringe, coupled to the calorimetry. For each increment, the thermal effect (Δ Q tit ) was recorded, as indicated by a constant thermal effect at the
extensively reviewed in the literature [ 8 – 12 ]. One of the most widely used thermal analysis techniques for the investigation of polymorphism is differential scanning calorimetry (DSC). The technique basically involves the application of a heating
High temperature calorimetric methods used in metallurgy are discussed. Two types of isoperibolic mixing calorimeters are presented. They allow to determine directly the enthalpy of mixing of liquid alloys as a function of concentration and temperature and to measure the derivative as a function of concentration for temperatures up to 1300 K and 2000 K, respectively. A high temperature solution calorimeter in which a liquid metal or alloy is used as the bath (maximum temperature 1800 K) can be used to determine the heat of formation of solid alloys and to measure the partial enthalpy of mixing at infinite dilution. With a drop calorimeter it is possible to measure the thermodynamic properties of highly reactive alloy systems. Thermodynamic measurements of high melting refractory metals and alloys for temperatures up to 4000 K can be achieved with levitation calorimetry.
vanillin by isothermal calorimetry . J Colloid Interface Sci. 2006 ; 298 : 74 – 8 http://dx.doi.org/10.1016/j.jcis.2005.12.021 . 30. Okuno Y
calorimetry Springer Verlag Berlin . 12. Yakubov , TS 1990 About heat capacity of solids having fractal character . Doklady Akad Nauk SSSR 310 : 145 – 149
