Page:Encyclopædia Britannica, Ninth Edition, v. 13.djvu/354

338 IRON a consumption of not more than 25 cwts. of coal, and a ton of cast steel made with about 40 cwts. of coal ; whilst even though the ore and fuel may contain considerable amounts of sulphur and phosphorus, the "precipitated " iron is almost chemically pure. The temperature requisite in this process being excessive, the bricks of which the furnace is con- FIG. 57. Siemens Rotator Longitudinal Section. structed must be of the most infusible material possible ; a particular kind of silica brick consisting of crushed quartz and about 2 per cent, of lime mixed together and moulded into bricks answers better than alumina (bauxite) bricks. FIG. 58. Siemens Rotator Sectional Plan. ( hi comparing the actual consumption of fuel in this process with that used in the smelting of iron by the blast furnace and its puri fication by puddling, it is at once evident that a much less amount of heat is lost by radiation, conduction, and escape of hot gases and of only partially oxidized carbon (in the state of carbon oxide) in the regenerative direct process than in the blast and puddling furnaces