During the past few years Dr. C. M. Johnson has succeeded in manufacturing laboratory ware made from zirconium minerals mixed with other refractories. Filtering crucibles, muffles, combustion tubes and boats, pyrometer protection tubes, and Kipp generators are now on the market, competing in price with German porcelain and fused silica. Zirconia crucibles are made from the fused material ground in a suitable mill. The powder is pressed or molded into shape with an organic binder, such as starch, or perhaps, better still, with a plastic cement made by grinding the fused material to 20 mesh, when it becomes colloidal in the presence of water. After drying, the articles are burned at a very high temperature (2300 to 2400°C.) until contraction ceases. Fused zirconia has a high thermal endurance; is not affected when heated to redness and plunged into cold water, its coefficient of expansion being as low as 0.00000084; and its resistance to crushing is many times that of quartz glass. Its hardness is between that of corundum and quartz; its specific gravity 5.89, and porosity below 1 per cent. Its melting point is 2950°C, but 0.5 per cent. impurity reduces that by 100°C. Platinum, with a melting point of about 1750°C., can be melted to a mobile liquid in zirconia crucibles, and it is claimed that the boiling point of pure iron has been determined in similar crucibles. Chemically, zirconia is very inert, being highly resistant to acids, fused alkalies, fused quartz, or molten glass. Possibly no other material known to chemists possesses such a combination of desirable refractory properties. Its one undesirable characteristic is its tendency under certain conditions at high temperatures, in the presence of nitrogen or carbon, to become converted into nitride or carbide. An instructive paper entitled “Zirconia as a Refractory,” by E. H. Rodd, was published in the Journal of the Society of Chemical Industry, June 15, 1918.