G.A. Gamlen

Mass spectrometric evolved gas analysis: an overview

Abstract The uses of mass spectrometric evolved gas analysis systems have been described and discussed in relation to solid state reactions giving rise to gaseous products. Emphasis has been placed on the use of such systems for kinetic studies. The theoretical considerations necessary to ensure quantitative and linear results have been described.

Aspects of the chemistry of poly(ethylene terephthalate): 5. Polymerization of bis(hydroxyethyl)terephthalate by various metallic catalysts

Abstract Bis(hydroxyethyl)terephthalate (BHET) was polymerized to poly(ethylene terephthalate) (PET) in the presence of various metallic catalysts. The influence of the nature and concentration of these catalysts on the rate of polymerization has been investigated. The effect of the reaction temperature has also been studied. The order of decreasing catalytic influence of various metal ions, on the polymerization of BHET was found to be: Ti>Sn>Mn>Zn>Pb>No.

The mass spectrometric and thermogravimetric determination of rising temperature kinetic parameters for the solid state decomposition of nickel nitrate hexahydrate

Abstract Rising temperature kinetic parameters have been obtained for the solid state decomposition of nickel nitrate hexahydrate in vacuo. The decomposition was followed by normal thermogravimetric analysis (TG), an evolved gas analysis (EGA) system, and by differential thermal analysis (DTA). The EGA system used is a development of a mass spectrometric system employing a large expansion bulb to reduce pressure rises and minimal gas removal. An integral method of calculating the kinetic parameters was used. The decomposition of nickel nitrate hexahydrate was found to begin at 315 K, the only product of any significance being water up to 400 K; thereafter water and nitric oxide/dioxide were evolved. The rate controlling steps, considering both kinetic and theoretical thermodynamic data, are diffusion controlled for the main nitrate decomposition. Evolution of nitric oxide/dioxide occurred in three rate determined stages. The first occurred over the range α=0.0–0.073 and was thought to correspond to hydrolysis of the nitrate. The remaining two stages had Arrhenius kinetic parameters of E=160.3 kJ mole−1, A=2.50×1011 s−1 and E=53.5 kJ mol−1. A=5.90×101 s−1 for the ranges α=0.073–0.425 and α=0.425–0.993, respectively, where E is the activation energy and A is a pre-exponential term.

Deaquation and denitration studies on copper nitrate trihydrate

Abstract Previous studies on the thermal degradation of copper nitrate trihydrate have been reviewed. These indicate that the conditions used strongly influence the processes involved. The degradation has been studied here using slow heating rates and in vacuum, so reducing these effects. Possible mechanisms using these conditions have been discussed, using data for the degradation of the ammine complex to supplement the study.

Estimation of calcium hydroxide in OPC, OPC/PFA and OPC/PFA/polymer modified systems

Abstract Formation of calcium hydroxide in a hydrating ordinary Portland cement (OPC) not only determines the process of cement hydration but also influences the ultimate mechanical properties. Calcium hydroxide is a well crystallized material and possesses a typical morphology which can change upon the incorporation of any additives and admixtures capable of altering the hydration mechanisms in a given cement paste, thus resulting into varying degrees of calcium hydroxide formations. The additives used in the present work are the pulverized fuel ash (PFA) and a Versicol W13 polymer. Thermogravimetric (TG) and differential thermal analysis (DTA) techniques have been used to estimate the quantity of calcium hydroxide present in the hydrating OPC, OPC/PFA and OPC/PFA polymer systems. The results have shown that by incorporating PFA and W13 polymer into OPC the quantity of calcium hydroxide formed is reduced apparently due to a secondary reaction taking place between calcium hydroxide and silica present in PFA.

The effect of a pre-exponential function A = AnTn on rising temperature kinetic parameter calculations

Abstract In this study the effect of a pre-exponential function A = A n T n on rising temperature kinetic parameter calculations has been shown. The integral methods have been derived using this function and an improvement has been proposed. This eliminates the error induced by introducting more complex temperature integrals and removes the need to recalculate the integral for new values of n .

Degradation studies on nickel nitrate hexahydrate: Part 2. evolved gas analysis

Abstract The work from Part 1 of this study has been extended by the use of evolved gas analysis. Deaquation and denitration processes have thus been examined in detail and possible mechanisms postulated. Three factors are involved, namely, the coordination chemistry of nickel, the rate of removal of water from the sample, and the ability of water vapour to hydrolyse the intermediate nickel nitrate dihydrate.

Degradation studies on nickel nitrate hexahydrate. Part 1. Effect of experimental conditions

Abstract Previous studies of the effect of heat on nickel nitrate hexahydrate have been reviewed. Many reports are conflicting in their description of observed intermediates. This study has resolved these differences in terms of variations in experimental conditions. The deaquation of nickel nitrate hexahydrate can be seen to be greatly influenced by factors such as sample size, heating rate and atmosphere.

Particle-cluster formation and associated liquid in the sedimentation of ballotini in aqueous glycerol

Abstract The sedimentation rates of small clusters of glass ballotini in aqueous glycerol have been interpreted in terms of liquid being carried down in association with the clusters.

Aspects of the Chemistry of Poly(ethylene Terephthalate). III. Transesterification of Dimethyl Terephthalate with Ethylene Glycol in the Presence of Various Catalytic Systems

Abstract The transesterification of dimethyl terephthalate has been studied by measuring the amount of methanol formed as a function of time. The influence of various catalytic systems was investigated with regard to the nature and concentration of the metal ion and temperature. The order of decreasing activity was found to be Pb, Zn, Mn, Sn, Sb, Ti, and mixtures of Zn plus Pb and Zn plus Sb were found to be synergistic. The postulate that there is a correlation between the metal oxygen bond and the activity of the catalyst is discussed.