The decomposition of single sintered calcium carbonate pellets of different porosities and the decomposition of packed beds of pellets has been investigated. A. thermobalance, modified to allow the ...simultaneous measurement of the temperature and weight of a decomposing sample was used for the single pellets investigation. It has been shown that the mechanism governing the decomposition reaction is independent of the pellet's porosity up to porosities of 70 %. According to this mechanism the rate of the reaction is controlled by heat and mass transfer. Thus the thermal conductivity of the porous lime and the effective CO2 diffusion coefficients through it are important parameters in the reaction model, and their values were measured in independent experiments, and compared with the values calculated from the decomposition experiments. The excellent agreement between the two sets of results, and the accuracy with which the model predicts measured reaction rates, confirmed the validity of the proposed reaction mechanism.
In a Late Bronze Age hoard at Kanalski Vrh in Slovenia, bronze pendants were found among numerous other artifacts. Among them a group of nine pendants of very similar compositions contained higher ...amounts of antimony, arsenic, nickel, cobalt, and iron, which suggested that speiss was added to bronze. Furthermore, most pendants had a silvery grey surface that differed from the common color of tin bronze, with about 13% Sn. One of the pendants was analysed by light optical and electron microscopy, Auger electron spectroscopy (AES), X-ray diffraction (XRD), and differential thermal analysis (DTA). Analyses revealed that the surface of the pendant was corroded, the copper alpha phase was eaten away, and the remaining eutectoid phase exhibited that silvery grey color. Comparison of chemical composition of the pendant and of compositions of speiss ingots found in the same hoard indicated that speisses could be used as alloying additions in making melts for casting pendants.
