certain circumstances, sometimes to a remarkable QUESTIONS. 1. Define the terms "atom," "element," "compound," "metal," and "non-metal." 2. What do you understand by the atomic weight of an element? 3. How is an element and a compound usually represented? 4. Upon what principles is the naming of chemical compounds based? Write the names for FeO, Al2O3, and MnO2. 5. What do you understand by a chemical equation? What advantage is gained by its use? 6. What is the general result of chemical action? 7. Define the terms oxidation and reduction, and give examples of each. 8. What is an oxide? Give examples. 9. Clearly explain the difference between an acid- and a basic-substance. 10. Describe the properties of the gases hydrogen and nitrogen. 11. What is the difference in character and properties between silicon and silica? What is a silicate? 12. Describe the different forms of carbon. general effects of carbon on iron? What are the 13. What is the chief difference between carbonic acid and carbonic oxide from a metallurgical point of view? 14. What is the difference between phosphorus and phosphoric acid? What is a phosphate ? CHAPTER IV. ORES OF IRON, COMPOUNDS, ETC. Native iron.-Iron in the metallic state is of very rare occurrence, which may be accounted for by its great affinity for oxygen and other non-metals. Large masses of iron, known as meteorites, are occasionally found in different parts of the world; they are easily distinguished from the masses of terrestrial origin, as they invariably contain nickel (which very rarely occurs in ordinary iron. ores) and the metal is usually found in a mass containing crystals. The mass is nearly always covered on the surface with a thin coating of oxide, which protects the metal from oxidation. Berzelius gives the analysis of a mass from Siberia weighing 1600 lbs., and of one from Bohemia weighing 103 lbs. Stromeyer analysed an enormous mass found near Treves which weighed 3300 lbs. Iron occurs in a great variety of minerals, but the oxides and carbonates are almost the only forms utilised by the smelter. Magnetite or magnetic iron ore. When pure it contains 72.41 per cent. of iron, and is represented by the formula FeO. It is sometimes crystalline, but more generally massive. It is black or dark brown in colour, brittle, magnetic, and leaves a black streak when drawn across a plate of unglazed porcelain; it has a specific gravity of about 5.2. It occurs in granite, gneiss, clayslate, hornblende, chlorite, and occasionally in limestone. Nearly all the Swedish iron is obtained from this ore, which also occurs in great abundance in the island of Elba and in the United States of America. Franklinite. This ore is similar in colour to magnetite, but less magnetic, occurring in crystals and massive. It gives a dark reddish brown streak, and has a specific gravity of about 5.1. It consists of ferrous and ferric oxides, manganous and manganic oxides, and oxide of zinc. It is chiefly found in New Jersey, and is used as a source of zinc, and spiegel-eisen. Hæmatite. Composition Fe,O,, containing 70 per cent. of iron when pure. It exists in crystals, in fibrous, columnar, kidney-shaped, granular, and compact forms. Its colour varies from dark iron-grey in the crystallised, to deep red in the compact varieties. Its specific gravity is as high as 5.3 when in crystals, and as low as 4.2 in earthy varieties. Special names are given to different forms, thus :-Specular ore, as in the brilliant crystalline species of Elba and Brazil. Micaceous ore, as in the scaly varieties of South Devon. Kidney ore, as that from Cumberland. Red ochre is a compact earthy variety, often containing clay. Puddlers' ore is a compact, unctuous form from Cleveland, and used for lining puddling furnaces. Spanish or Bilbao ore is a siliceous. hæmatite containing manganese, and noted for its purity, hence its use in the open-hearth steel process. Ilmenite or titaniferous iron ore. This is a dead black mineral, generally found massive, consisting of ferrous and ferric oxides, titanic oxide and magnesia. It gives a brownish streak, and its specific gravity varies from 4.5 to 5. It may be typically represented by the formula FeO.TiO2 + MgO. TiO2. Turgite. This is an ore resembling hæmatite in colour and streak, but is hydrated, consisting of 94.7 per cent. ferric oxide, and 5.3 per cent. water. Formula 2Fe2O3, H2O. It occurs both compact and fibrous. Its specific gravity varies from 4.2 to 4.7. Brown hæmatite.---This class, which contains several varieties, is distinguished by its brown or yellowishbrown colour, its brown streak, and a considerable proportion of water. It is chemically a hydrated ferric oxide. The different forms are :-Göthite, Fe,O,, H2O; brown iron ore or limonite, pea ore, yellow ochre, and bog ore, 2Fe2O3, 3H,O. Its specific gravity varies from 3.6 to 4.4. Ŏolitic deposits, like those of Northamptonshire, frequently contain phosphorus from the fossil remains of organic matter. Siderite or spathic iron ore. This is a carbonate of iron FeCO. The purer varieties occur in crystalline forms, the more impure and most abundant occur in beds of considerable thickness, or in detached nodules in the clay and shales of the coal measures. This class is the chief source of British iron. Manganese is often present in spathic ore, in some cases to the extent of 50 per cent. The pig-iron obtained from rich manganese ores is termed spiegel-eisen. Siderite contains 48.27 per cent. of iron, the crystals have a pearly lustre of a yellowishbrown or grey colour, owing to a surface coating of hydrated oxide. The streak is white, representing the true colour of the mineral. Clay-ironstone is a compact earthy variety containing clay, and of a brown colour. Black-band is a carbonate, mixed with carbonaceous matter, frequently in laminæ, amounting in some varieties to 20 and even 30 per cent. These ores are often very impure, containing carbonates of lime, magnesia, and manganese; clay, potash, phosphoric and sulphuric acids, iron and copper pyrites, along with water and organic matter. Iron pyrites.-This mineral is very abundant in nature, and is only used as a source of iron after the sulphur has been removed in the manufacture of sulphuric acid, when the resulting oxide is known as "blue billy." The chemical formula is FeS2. Some varieties are bronzeyellow in appearance, others are nearly white, with a metallic lustre; the streak is brownish black, and the specific gravity varies from 4.8 to 5.1. British ores.-The chief ores of Britain are spathic |