Uber die Azotierreaktion von kornigem Calciumcarbid, III : Azotierung mit Zuschlagen

Abstract

The reaction at different temperatures T between nitrogen at atmospheric pressure and calcium carbide mixed with various amounts x of calcium chloride or fluoride has been studied. It was found that the reaction is generally accelerated. Assuming that the powder particles are all spheres of the same radius a, the experimental results were arranged in the form of l-t curves, where l=(a-r)/a, r being the radius of the still remaining carbide core at the time t. The curves have an irregular initial period followed by a straight part with an inclination S/a, the meaning of which was examined. Simple mathematical expressions for S as a function of x and T have been obtained. The rate of passage of nitrogen through the melted calcium chloride was experimentally found to be very large in comparison with that through the solid layer of the reaction product. This rapid passage is assumed also is the liquid mixtures of the reaction product and calcium chloride or fluoride. The relation between x and the volume of nitrogen absorbed until the end of the straight part has been connected with the liquidus of the CaCN_2+C-CaF_2 system and the accelerating action of calcium chloride or fluoride has been ascribed to its dissolving action on the solid reaction product layer. A tentative elucidation of the constancy of the dissolution rate S has been proposed.