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
Authors:Marek Gawlicki, Wiesława Nocuń-Wczelik, and Łukasz Bąk
Calorimetry was applied to an investigation of the early hydration of Portland cement (PC)–calcium aluminate cement (CAC)
pastes. The heat evolution measurements were related to the strength tests on small cylindrical samples and standard mortar
bars. Different heat-evolution profiles were observed, depending on the calcium aluminate cement/Portland cement ratio. The
significant modification of Portland cement heat evolution profile within a few hours after mixing with water was observed
generally in pastes containing up to 25% CAC. On the other hand the CAC hydration acceleration effect was also obtained with
the 10% and 20% addition of Portland cement. As one could expect the compressive and flexural strength development was more
or less changed—reduced in the presence of larger amount of the second component in the mixture, presumably because of the
internal cracks generated by expansive calcium sulfoaluminate formation.
Alumina-boria catalysts were prepared by impregnation of porous and non porous aluminas with various amounts of boron oxide. A calorimetric investigation of their acidity was performed by gaseous ammonia adsorption. The differential heat evolved decreases when the amount of boria on alumina increases while the corresponding number of acid sites, as determined by volumetry, increases with the amount of boron oxide. The thermal behaviour and the stability of the catalysts, when dehydration occurs, were studied by differential scanning calorimetry linked to thermogravimetry.
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.
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
Authors:Tamás Fekecs, István Zapf, Andrea Ferencz, and Dénes Lőrinczy
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
A number of studies of micellar aggregation in aqueous solutions of ethylene oxide-propylene oxide block copolymers — using high sensitivity differential scanning calorimetry (HSDSC) — are reviewed. The review attempts to show how the calorimetric output can be analysed, using a model fitting procedure, to obtain estimates for various thermodynamic parameters, which characterise the micellization event, as observed by HSDSC. These important parameters include:
T1/2 the temperature at which half the surfactant has been incorporated into micelles;
Hcal — the calorimetric enthalpy for the process which is measured by integration of the calorimetric output;
HvH — the van't Hoff enthalpy — which characterises the functional dependence of the equilibrium composition of the system upon temperature and which is derived from the application of the van't Hoff isochore to the data analysis procedure;
Cp — the heat capacity change between the initial and final states;and n the aggregation number.Using this data it is possible to examine how extent of aggregation functionally varies with temperature. Subsequent interpolation of these thermal aggregation plots permits an examination of how the extent of aggregation is affected by changes in solution composition under isothermal conditions. A large body of data is presented which shows how co-solvents, co-solutes and pH affect the aggregation process in aqueous solution.
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.
Authors:Mohd Abu Bakar, Zoltan Nagy, and Christopher Rielly
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
Authors:Zheng Fang, Shaofen Wang, and Zhenghua Zhang
standard electrode reaction, the standard potential of which is the one corresponding to a reversible electrode reaction.
In the electrochemical–calorimetry experiments, it is necessary to measure EPH. Vetter has shown in his book [ 25 ], EPH, as