Thermal Stability Of Folic Acid in the solid-state

This study attempts to identify the degradative process which folic acid undergoes in the solid-state under thermal stress. In order to facilitate the process, the various pieces of the chemical structure, namely, p-amino benzoic acid, pterin and glutamic acid as both its d- and l-isomers were investigated as separate entities. These structured solid-state pieces were then compared to the composite solid state folic acid degradative curves in order to identify the peaks seen and provide direction for the interpolation of the degradative mechanism. It was observed that none of the structural pieces could be superimposed as assumed earlier and hence an attempt was made to identify the decomposition products using various analytical techniques such as infrared spectroscopy, mass spectroscopy and X-ray diffraction which suggested that the glutamic acid fragment is lost first as evidenced by acid loss and amide enhancement in the IR spectra. The vitamin was ultimately degrading to carbon fragments and that further identification was not necessary. This revised version was published online in August 2006 with corrections to the Cover Date.     

Characterization of some essential oils and their key components: Thermoanalytical techniques

The present study was aimed at determining the kinetics of evaporation and establishing vapor pressure curves for both single and multi-component systems by thermogravimetry (TG) and differential scanning calorimetry (DSC). Essential oils (e.g. lavender oil, orange oil, clove oil and eucalyptus oil, etc.) are typically multi-component systems consisting of various volatile pure components (e.g. linalyl acetate, limonene, cinnamaldehyde, etc.) which resemble single component systems. In this study linalyl acetate was taken as the calibration compound for TG. The vapor pressure curves for the pure substances were plotted using TG and vapor pressure plots for clove oil and eucalyptus oil were constructed using DSC. The thermodynamic and kinetic parameters of the pure compounds were compared to that of the multi-component systems to quantitatively and qualitatively measure the influence of different compounds on each other. The k-value from the vapor pressure data for linalyl acetate was calculated as 112006 Pa kg^0.5mol^0.5s^-1 m^-2 K^-0.5. The vapor pressure values were used to determine the Antoine constants using the SPSS 10.0 software.This revised version was published online in November 2005 with corrections to the Cover Date.     

Application of thermal analysis to carbon black-elastomer systems

In this study a relationship between the surface and textural properties of carbon blacks and the gasification process induced thermally in air is noted. A temperature jump method was used to follow the gasification in air and to establish the relevant Arrhenius parameters. This can be associated with the activity of ‘basal’ plane carbon atoms as well as ‘edge’ carbon atoms at the surface. This is based on a model of carbon black structure consisting of the irregular packing of small graphite carbon structures. The carbon black surface was measured using a single measurement of adsorption based essentially on the BET volumetric method. The carbon black surface had a rate of oxidation per unit are which clearly indicated that the lower area carbon blacks had a predominately active area of ‘edge’ atoms at the surface while the surface of the higher area carbon blacks had a predominate amount of ‘basal’ plane graphite carbon atoms.     

The thermal decomposition of metal formates. II. Solid state thermal decomposition studies on magnesium formate dihydrate

Magnesium formate dihydrate has been synthesized by the action of formic acid on anhydrous magnesium oxide. This product analysed as Mg(COOH)₂ · 2H₂O. Its mode of thermal decomposition has been studied by thermal methods of analysis including simultaneous DTA/mass spectrometry. Nitrogen adsorption surface area of the solid products at various stages of its decomposition have been obtained. X-Ray diffraction and scanning electron micrographs have also been used to interpret the results. The decomposition of magnesium formate took place in three stages, which includes a phase change, at 265°C. The endotherm at 430°C changed to an exotherm in the presence of air; it corresponded to the decomposition of a new anhydrous phase of magnesium formate. The effect of the sample holder and changing atmospheres on the DSC analysis has been investigated. A scheme is presented for the thermal decomposition.     

Thermal analytical investigation of ancient mortars from gothic churches

The use of thermal analysis in studying ancient mortars in English cathedrals is explained. Thermal analysis can be used to investigate both mortar and stone in dated structures. Analysis of ancient mortars show that though recarbonated, they remain soft, yielding to structural deformations. The use of hard (cement mortar) in modern renovation can result in micro-cracking in the stone and subsequent chemical attack from the atmosphere. Contrary to the literature, data developed in the present study suggests that most medieval mortars have reached a near total state of recarbonation.     

Characterisation of Porous Solids : Edited by S.J. Gregg,K.S.W. Sing and H.F. Stoeckli,Society of Chemical Industry,London, 1979, 392 pp., £ 21.

Techniques combining thermogravimetry (TG) and mass spectrometry (MS) are described whereby TG provides precise heating conditions and weight loss information and MS identifies volatiles evolved during the weight losss process. In the present work the DuPont 990 thermal analysis system, a DuPont 21-104 mass spectrometer, and a Hewlett-Packard 21-MX/Digital Equipment PDP-10 computer system are combined through simple, unique interfaces. The instrumentation features flexibility in thermal treatment of the sample and good atmospheric control. Tests with model substances and practical industrial problems have shown good enrichment and recovery of eluted components and no significant delay in TG operations.     

Ignition temperatures of carbon samples containing metal oxide catalysts by a DTA method

The variation of the ignition temperature of a carbon black impregnated with various amounts of manganese oxide and uranium oxide has been measured by a DTA method. The technique allows a rapid assessment to be made of sample reactivity and only small amounts (approximately 5 mg) are required. Correlation of sample reactivity by ignition temperature measurement and isothermal weight-loss data is shown.     

A handbook of decomposition methods in analytical chemistry : Rudolf Bock (translated and revised by Iain L. Marr), International Textbook Company,London, 1979, 444 pp., £19.75

The influence of anthralin (1,8-dihydroxy-9-anthron) and some of its derivatives on the energy metabolism of human skin fibroblasts in culture has been investigated by means of a batch calorimeter. In the absence of any drug, confluent monolayers produced a fairly constant heat output of 51 ± 5 pW per cell reflecting metabolism of maintenance. Addition of anthralin or a derivative resulted in different effects on the heat production.     

Coal and Modern Coal Processing: An Introduction : Edited by G.J. Pitt and G.R. Millward,Academic Press,London, 1979, 210 pp., £ 8.50

The reconstruction of a commercial heat-flow-calorimeter is described, to get a sensitive apparatus for measuring the heat of deformation of small samples during elongation. Some problems with this kind of calorimeters are discussed. The described solution allows the measurement of heat-flows in the range of 10^?6 W at room-temperature.