Neutral refractories are chemically stable to both acids and bases and are used in areas where slag and atmosphere are either acidic or basic. They are used in areas where slags and atmosphere are either acidic or basic. The common substances of neutral refractories are Carbon, Chromites (Cr2O3) and Alumina (Al2O3).
Basic refractories are those which are attacked by acid slags but stable to alkaline slags. These are used on areas where slags and atmosphere are basic. Since they do not react with alkaline slags, these refractories are of considerable importance for furnace linings where the environment is alkaline; for example non-ferrous metallurgical operations. The common substances of basic refractories includes magnesia (MgO), dolomite and chrome-magnesia.
Acid refractories are those which are not attacked or affected by acidic materials, but easily attacked by alkalis (basic slags). These are used in areas where slag and atmosphere are acidic. Acid refractories include substances such as zirconia (ZrO2), alumina (Al2O3), silica (SiO2) and fire clay brick refractories.