Kinetic parameters from derivatograms on ligand dissociation reaction of mixed chelate complexes of dioxouranium(VI) with cupferron
About: This article is published in Journal of Inorganic and Nuclear Chemistry.The article was published on 1981-01-01. It has received 1 citations till now. The article focuses on the topics: Cupferron & Ligand.
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TL;DR: In this article, a thermocouple is used to measure the sample temperature in a Stanton HT-D thermobalance, the bead of which is positioned in or near the sample, depending on crucible design.
Abstract: THE use of thermogravimetric data to evaluate kinetic parameters of solid-state reactions involving weight loss (or gain) has been investigated by a number of workers1–4. Freeman and Carroll2 have stated some of the advantages of this method over conventional isothermal studies. To these reasons may be added the advantage of using one single sample for investigation. However, the importance of procedural details, such as crucible geometry, heating rate, pre-history of sample, and particle size, on the parameters has yet to be fully investigated. It is also necessary to ensure accurate temperature measurement, both for precision and also to detect any departure from a linear heating rate due to endo- or exo-thermic reactions. (The effect of these may be largely eliminated by the use of small samples.) In our present work (using a Stanton HT–D thermobalance) the sample temperature is measured directly by means of a thermocouple the bead of which is positioned in or near the sample, depending on crucible design, the wires of which run down a twin-bore rise rod. The connexion between the end of the thermocouple wires on the balance arm and the terminal block is made by 0.001 in. platinum and platinum/rhodium wires5. It has been shown that these wires do not affect the performance of the balance but act merely as a subsidiary damping. From the terminal block compensated cable leads to the cold junction and a potentiometric arrangement for direct measurement of the thermocouple output.
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TL;DR: In this article, the activation energy of a chemical reaction is calculated from the angle between the straight line and the abscissa of the chemical reaction, and the results are then plotted as ln b/Tm2 against 1/tm, where Tm is the peak temperature in ° K, and b is the rate of heating.
Abstract: A NUMBER of articles have been published dealing with the differential thermal analysis (DTA) of chemical reaction kinetics1–5. Only one of these, however, gives a direct method for determining the activation energy (E) of the chemical reaction4. In this method, DTA curves are recorded at several different rates of heating. The results are then plotted as ln b/Tm2 against 1/Tm, where Tm is the peak temperature in ° K (the temperature of point B, Fig. 1), and b is the rate of heating. The magnitude of E is calculated from the angle between this straight line and the abscissa. This procedure has two principal shortcomings: (1) it is necessary to record several DTA curves with various rates of heating; and (2) it is necessary to use a special programming device to control the temperature. This device must be capable of providing linear heating at a number of rates of heating. The latter condition imposes serious technical difficulties, because all the DTA apparatuses at present available are adjusted for only one rate of heating.
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