Iron oxide

“ The mechanism of the production of these globules is rendered very evident by their abundance in certain industrial residues, especially in the iron oxide produced by hammering, and in the product of the combustion of iron in oxygen. Evidently the melted oxide spread into laminas by mechanical projection goes through the same capillary action as gives their form to soap-bubbles. We can study all the details of the phenomenon with greater facility if we have recourse to substances much easier to melt than oxide of iron. ”

“ By far the most important property of the oxide, from the technical point of view, is the ease with which it resists high temperatures. The natural oxide can be freed, to a very large extent, from the iron oxide which it encloses, by the prolonged action of hydrochloric acid; experiments were carried out on the material so obtained by Simonis, [604] who showed that by prolonged heating at a high temperature, the remaining impurities, chiefly ferric oxide and silica, could be volatilised, leaving the zirconia unchanged. ”

“ The black oxide, which is formed by the combustion of iron, and by other processes, contains 56 iron + 16 oxygen. The common rust of iron is the peroxide of this metal, combined with carbonic acid. It may be formed by exposing the protosulphate of iron, or green vitriol, in solution, to the atmosphere, and then adding an alkali. This oxide contains more oxygen than the preceding; it consisting of 56 iron + 24 oxygen.
The tempering of cutting instruments, an operation which requires great delicacy and exactness, after that of hardening, is intended to obtain a fine and durable edge ”

“ As the iron oxide is stirred into the molten metal laboriously by the workman or “puddler” with his hook or “rabble,” it oxidizes the silicon to silica and the phosphorus to phosphoric acid, and unites with both these products, forming with them a basic iron silicate rich in phosphorus, called “puddling” or “tap cinder.” It oxidizes the carbon also, which escapes in purple jets of burning carbonic oxide. ”

“ In reality however the action is more complex than this in its chemical relations; for instance, metallic iron will under certain circumstances act conversely on carbonic acid, and rob it of half its oxygen. The net result of the reactions between carbon, iron, iron oxide, and these gases depends mainly upon the temperature and pressure and upon the relative quantities of each substance present. In the gases escaping from the blast furnace there is always a large quantity (nearly one-third) of carbonic oxide. ”

“ This oxide requires, at most, one or two proportions of flux, either saline or metallic, to enter into complete fusion; but a much smaller dose is commonly taken, and a little oxide of iron is introduced. To four pounds of frit, for instance, two ounces of oxide of copper and 48 grains of red oxide of iron are used; and the ordinary measures are pursued for making very homogeneous enamel.
The green produced by the oxide of chrome is much more solid; it is not affected by a powerful fire, but it is not always of a fine shade. ”

“ In the upper part of the furnace the carbonic oxide deoxidizes the iron oxide of the ore by such reactions as xCO + FeOx = Fe + xCO2. Part of the resultant carbonic acid is again deoxidized to carbonic oxide by the surrounding fuel, CO2 + C = 2CO, and the carbonic oxide thus formed deoxidizes more iron oxide, &c. As indicated in fig. 7, before the iron ore has descended very far it has given up nearly the whole of its oxygen, and thus lost its power of oxidizing the rising carbonic oxide, so that from here down the atmosphere of the furnace consists essentially of carbonic oxide and nitrogen. ”

“ During the melting of the charge the heat is kept as high as possible and the molten iron is “puddled,” i. e., stirred, by the “puddler” or his helper with a “rabbler” or iron bar. In order to take out the phosphorus and sulphur, which for best results should be removed before the carbon is eliminated, the heat of the furnace is lowered somewhat as soon as all of the pig has melted, and some iron oxide is mixed into the “bath” of molten iron and cinder. Most of the phosphorus and sulphur are chemically acted upon and pass into the cinder which covers the iron. ”

“ How is it when combined with linseed oil in the form of paint? In the economy of nature, iron oxide is a great disinfectant. When in contact with organic matter and moisture, even at a low temperature, under favourable conditions, it readily gives up oxygen, destroying more or less the organic matter, and being itself reduced to a lower oxide. ”

“ Iron ore is usually found in the form of iron oxide, because when this great earth was nothing but a swirling ball of burning gases, probably as hot as the sun, gradually cooling and forming a great cauldron of molten matter, boiling and bubbling more fiercely than the hottest cauldron of molten metal in any steel mill, much of the matter that later became iron ore was burned or oxidized. ”

“ By rapidly stirring molten iron oxide into molten pig iron in a furnace shaped like a saucer, slightly inclined and turning around its axis, at a temperature but little above the melting-point of the metal itself, the phosphorus and silicon are removed rapidly, without removing much of the carbon, and by this means an extremely pure cast iron is made. ”

“ Iron contains in its ores many impurities of different natures, according to circumstances, and is in its preparation exposed to several others; by these its quality is frequently much affected. Its valuable ores all contain the iron in the state of oxide. The oxygen, it is generally believed, is not wholly separated even in the best malleable iron, but enough still remains to impair in some degree its good qualities. In its manufacture it is exposed to the action of carbon, with which it is capable of combining. ”

“ Descending underground waters charged with oxygen have decomposed the iron carbonate and deposited the iron, in the form of iron oxide, in troughs of the strata where their downward progress was arrested by impervious floors.
The pre-Cambrian rocks of the eastern United States also are rich in iron. In certain districts, as in the Highlands of New Jersey, the black oxide of iron (magnetite) is so abundant in beds and disseminated grains that the ordinary surveyor's compass is useless. ”

“ There the carbon of the cast iron and the oxygen of the oxide form carbonic oxide, and the carbon therefore burns out, and thus cast steel is obtained from cast iron, providing, naturally, that there is a requisite proportion and corresponding degree of heat. The advantage of this process is that not only do the carbon, silicon, and manganese, but also a great part of the sulphur and phosphorus of the cast iron burn out at the expense of the oxygen of the iron oxides. ”

“ One of the most common methods by which iron ore is accumulated is when water carrying ferrous carbonate in solution forms swamps and lakes, and in many instances as the water is exposed to the air and aided by evaporation it parts with a portion of its carbon dioxide, and the hydrated sesquioxide of iron or limonite results. When, under similar conditions, an excess of organic matter is present, beds of ferrous carbonate are formed. In other instances iron oxide is precipitated in swamps and lakes through the action of low forms of plant life. ”

“ Furthermore, these oxides are not dissolved by carbonate of soda in the oxidation flame, but they produce colored beads with borax and microcosmic salt.
(a.) Iron.—It occurs in great abundance in nature. It is found in several places in America in the metallic state, and it likewise occurs in the same state in meteors. It occurs chiefly as the oxide (red hematite, brown hematite, magnetic oxide, etc.) , and frequently in combination with sulphur. Iron also forms a constituent of the blood.
Metallic iron is of a grey color, and presents the metallic lustre vividly when polished. ”

“ With mercury iron refuses to combine directly, the iron amalgam that has been used for electrical machines being made by a somewhat complicated process with the aid of the amalgam of sodium. When immersed in fuming nitric acid, iron becomes coated with insoluble oxide, and as it then refuses to dissolve in acids (unless the coating be removed) , it is said to be in a passive state. Dry air or oxygen gas has no effect on iron. The ‘rusting’ of iron in ordinary atmospheric air is due to the presence of moisture ”

“ As ferrous oxide, FeO, is isomorphous with magnesia, and ferric oxide, Fe2O3, with alumina, isomorphous substitution is possible here, and hence minerals are not unfrequently found in which the quantity of iron varies considerably; such, for instance, are pyroxene, amphibole, certain varieties of mica, &c. Although much iron oxide is deleterious to the growth of vegetation, still plants do not flourish without iron; it enters as an indispensable component into the composition of all higher organisms; in the ash of plants we always find more or less of its compounds. ”

“ The potassium-cyanide process may be used with all small iron objects. For larger ones molten potassium rhodanide is recommended. This converts the iron oxide into iron sulphide that is easily washed off and leaves the surface of a fine black color.
Old coins may be cleansed by first immersing them in strong nitric acid and then washing them in clean water. Wipe them dry before putting away.
To Clean Old Medals.—Immerse in lemon juice until the coating of oxide has completely disappeared; 24 hours is generally sufficient, but a longer time is not harmful. ”

“ Those in which the metallic oxide is mixed with much earthy matter, do not answer well; but those composed of the pure black oxide, red oxide, and carbonate, succeed much better. To extract the metal from such ores, it is sufficient to expose them to a high temperature, in contact either with charcoal, or with carbonaceous gases; the metallic oxide is speedily reduced. But when several earths are present, these tend continually, during the vitrification which they suffer, to retain in their vitreous mass the unreduced oxide of iron. ”

“ The reduction of the ores of iron into metallic iron is in principle very simple, because when the oxides of iron are strongly heated with charcoal, hydrogen, carbonic oxide, and other reducing agents, [5] they easily give metallic iron. But the matter is rendered more [322] difficult by the fact that the iron does not melt at the heat developed by the combustion of the charcoal, and therefore it does not separate from those mechanically mixed impurities which are found in the iron ore. ”

“ Similar alloys of iron with the other elements mentioned are made in an electric furnace by reducing the mixed oxides with carbon.
Pure iron. Perfectly pure iron is rarely prepared and is not adapted to commercial uses. It can be made by reducing pure oxide of iron in a current of hydrogen at a [Pg 349] high temperature. Prepared in this way it forms a black powder; when melted it forms a tin-white metal which is less fusible and more malleable than wrought iron. It is easily acted upon by moist air.
Compounds of iron. ”

“ There are many deposits of magnetic oxide or iron in nature which are almost chemically pure. By applying the thermit process to this, it may be as little as a pound or two mixed with powdered aluminum in a crucible and starting the ignition, the metal oxide will be reduced and made liquid, so that it can be cast in a mold, and you can have a piece of almost chemically pure iron, so soft, because of its purity, that, as the metallurgist says, it can be cut with a knife—but if you will believe the writer, it cannot be cut to any considerable depth. ”

“ The green oxide of iron contains 27/100 oxygene; the red 48/100. But the whole quantity of oxygene supplied from the water and nitrous gas is 0,8 + 0,85 = 1,65; and calculating on the difference of the composition of the red and green oxide of iron, 5,7 grains of red oxide must have been deposited, and consequently these would saturate as much acid as,79 grains of ammoniac, or 4,1 grains of green oxide of iron. ”

“ Iron thus combines with oxygen in three proportions: RO, R2O3, [345] and RO3. It might have been expected that there would be intermediate stages RO2 (corresponding to pyrites FeS2) and R2O5, but for iron these are unknown. [26 bis] The lower oxide has a distinctly basic character, the higher is feebly acid. The only one which is stable in the free state is ferric oxide, Fe2O3; the suboxide, FeO, absorbs oxygen, and ferric anhydride, FeO3, evolves it. It is also the same for other elements; the character of each is determined by the relative degree of stability of the known oxides. ”

“ When the iron is present as bicarbonate, it acts on soap solutions like the analogous lime and magnesia compounds, producing even worse results. In wool scouring, cotton bleaching, and other processes requiring the use of alkaline carbonates, ferric oxide is precipitated on the fibre. A yellowish tinge is communicated to bleached fabrics, and to dye bright and light colours is rendered almost out of the question. You may always suspect iron to be present in water flowing from or obtained directly out of old coal pits, iron mines, or from places abounding in iron and aluminous shales. ”

“ Pure water, free from air or carbonic acid, does not tarnish the surface of polished iron, but the combined action of air and moisture, especially when a little acid vapour is present, causes its surface to be soon covered with rust, which is hydrated sesquioxide of iron (ferric hydrate) . Nearly all acids attack iron; dilute sulphuric and hydrochloric acid do so with considerable energy and the evolution of hydrogen gas. At a red heat iron decomposes water rapidly, hydrogen being evolved, and the black oxide of iron formed. ”