THERMODYNAMICS OF LIQUID BLAST-FURNACE-TYPE SLAGS I.EVALUATION OF ACTIVITIES OF CaO AND SiO_2

This is the first of a series of papers with a view to evaluation activities inliquid blast-furnace-type slags.The purpose of this paper is to present new results of calculation for activities of CaO and SiO_2 in liquid CaO-SiO_2,CaO-SiO_2-Al_2O_3 and CaO-MgO-SiO_2-Al_2O_3 systems from existing chemical and electrochemi-caldata with certain assumptions The activities of CaO in the above-mentionedsystems with reference to solid CaO as the standard state are plotted against(%CaO)/(%SiO_2).From a comparison of these ~αCaO-(%CaO)/(%SiO_2)curves,a new expression for basicity has been proposed instead of the simple(%CaO)/(%SiO_2)ratio.The activities of CaO in the various systems concerned becomeapproximately equal at the same basicity when the latter is calculated accordingto the new formula.Alumina shows amphoteric behaviour in the new basicityformula in agreement with the general pattern of slag constitution.