Note 20 bis — Chapter XXIV · COPPER, SILVER, AND GOLD

According to Müller, ferric oxide is reduced by hydrogen (see Chapter XXII., Note 5) at 295° (into what ?), cupric oxide at 140°, Ni2O3 at 150°; nickelous oxide, NiO, is reduced to the suboxide, Ni2O, at 195°, and to nickel at 270°; zinc oxide requires so high a temperature for its reduction that the glass tube in which Müller conducted the experiment did not stand the heat; antimony oxide requires a temperature of 215° for its reduction; yellow mercuric oxide is reduced at 130° and the red oxide at 230°; silver oxide at 85°, and platinum oxide even at the ordinary temperature.