Catalytic Mullitization of Kaolinite by Metallic Oxide*

A bstract The effect of the addition of various oxides on the mullitization of kaolinite was studied by chemical, microscopic, and X‐ray methods. A comparative study of the chemical and the X‐ray methods of mullite determination has shown that the chemical method (use of hydrofluoric acid) can yield only relative values. The use of X rays appears to give absolute results. The oxides of zinc, lithium, magnesium, iron, manganese, and molybdenum were found to be good mullite builders; sodium, potassium, titanium, and stannic oxides were poor; and boric oxide and calcium oxide were fair accelerators.