Zinc Oxide: Zinc Sulphate Heated with Carbon, 2 Hours at 650 °C

A route to zinc oxide without burning the metal, from Thorpe's Dictionary (1913, after English Patent 3906 and German patent 93315): heat zinc sulphate with carbon for about 2 hours at about 650 °C. Zinc oxide is a white powder that turns lemon-yellow while hot and white again on cooling. The sulphate gives off sulphur dioxide: furnace with a flue, fume hood. The picture: our diagram.