263. Compounds.--The compounds of zinc are abundant. Its chief ores are zincite, ZnO, sphalerite or blende, ZnS, Smithsonite, ZnCO3. For their reduction these ores are first roasted, i.e. heated in presence of air. With ZnS this reaction takes place: ZnS + 3 O = Zn0 + S02. The oxide is reduced with C, and then Zn is distilled. State the reaction. Zinc is sublimed-in the form of zinc dust-like flowers of S. Granulated Zn is made by pouring a stream of the molten metal into water. Experiment 121.--Burn a strip of Zn foil, and note the color of the flame and of the product. State the reaction. The red color of zincite is supposed to be imparted by Mn present in the compound. 264. Uses.--Name any use of Zn in the chemical laboratory. It is employed for coating wire and sheet iron --galvanized iron. This is done by plunging the wire or the sheets of iron into melted Zn. Describe the use of Zn as an alloy. See page 136. ZnO forms the basis of a white paint called zinc white. White vitriol, ZnSO4 + 7 H2O, is employed in medicine. Name two other vitriols. CHAPTER XLVIII. IRON AND ITS COMPOUNDS. Examine magnetite, hematite, limonite, siderite, pig-iron, wrought-iron, steel. 265. Ores and Irons.--As Fe occurs native only in meteorites and in small quantities of terrestrial origin, it is obtained from its ores. There are four of these ores--magnetite (Fe3O4), hematite (Fe2O3), limonite (2 Fe2O3 + 3 H2O), and siderite (FeCO3). Which is richest in Fe? Compute the proportion. FeCO3 occurs mostly in Europe. The reduction of these ores, as well as of other metallic oxides, consists in removing O by C at a high tempera- ture. As ordinarily classified there are three kinds of iron,--pig- or cast-iron, steel, and wrought-iron. Study this table, noting the purity, the fusing-point, and the per cent of C in each case. Per Cent Fe Fusibility. Per Cent (general). C. Pig......... 90 1200 degrees 2-6 Steel........ 99 1400 degrees 0.5-2 Wrought....... 99.7 1500 degrees Fraction. Pure iron melts at about 1800 degrees. Pig-iron is obtained from the ore by smelting, and from this are made steel and wrought- iron. 266. Pig-Iron.--The ore is reduced in a blast furnace (Fig. 47), in some cases eighty or one hundred feet high, and having a capacity of about 12,000 cubic feet. The reducing agent is either charcoal, anthracite coal, or coke,bituminous coal being too impure. Charcoal is the best agent, and is used in preparing Swedish iron; but it is too expensive for general use. Fig. 47. Blast furnace. F, entrance of tuyeres, or blast-pipes. E, F, hottest part. C, conductor for gases, which are subsequently used to heat the air going into the tuyeres. G, upper portion, slag, lower portion, melted iron. Were ores absolutely pure, only C would be needed to reduce them. Complete: Fe3O4 + 4 C =? Fe3O4 + 2C=?