Iron sulfide

“ Where beds of common iron pyrites occur, the iron sulphide is converted into sulphate by exposure to the oxidising influence of the air. The result is an acid sulphate of iron, which is leached out and neutralised by addition of more iron in the form of scrap. The neutral sulphate is crystallised out of the liquor, and calcined in a muffle furnace, the shade of the ultimate product being governed by the degree or duration of the roasting. ”

“ In the arts, as sulphate of iron (copperas) , it is extensively used in dyeing, and for various other purposes. The dried sulphate (ferri sulphus exsiccatum) is chiefly used to make pills.
Crude sulphate of iron is frequently contaminated with the sulphates of copper, zinc, manganese, aluminium, magnesium, and calcium, which, with the exception of the first, are removed with difficulty. It also contains variable proportions of the neutral and basic ferric sulphates. The preparation obtained by direct solution of iron in dilute sulphuric acid should, therefore, be alone used in medicine. ”

“ This device not only makes the cast iron much more uniform, but also removes much of its sulphur by a curious slow reaction. Many metals have the power of dissolving their own oxides and sulphides, but not those of other metals. Thus iron, at least highly carburetted, i.e. cast iron, dissolves its own sulphide freely, but not that of either calcium or manganese. Consequently, when we deoxidize calcium in the iron blast-furnace, it greedily absorbs the sulphur which has been dissolved in the iron as iron sulphide, and the sulphide of calcium thus formed separates from the iron. ”

“ Metallic sulphides when fused with an excess of nitre are completely oxidised. If the ore is rich in sulphur, some inert body (such as sodium chloride, or, better, sodium carbonate) is added to dilute the action. With pure sulphur, the action is so energetic as to cause an explosion, so that care should be taken. With burnt ores (incompletely calcined pyrites) , there is sufficient oxide of iron present to prevent too rapid action. ”

“ The iron in water from old coal pits and shale deposits is usually present as sulphate due to the oxidation of pyrites, a sulphuret or sulphide of iron. Water from heaths and moorlands is often acid from certain vegetable acids termed "peaty acids." This acidity places the water in the condition of a direct solvent for iron, and that dissolved iron may cause great injury. If such water cannot be dispensed with, the best way is to carefully neutralise it with carbonate of soda ”

“ The explanation is, that the waste pyrites 'contained not only sulphide of iron and earthy constituents, but also sulphide of zinc, and that by the influence of the oxygen of the atmosphere and the presence of water, these sulphides were gradually converted into the corresponding sulphates;' and these, continually extracted by the{751} rain-water, soaked into the soil, contaminated the wells, and produced other injurious effects.
The want of really efficient names to distinguish various kinds of manufactured iron has long been felt in the iron trade. ”

“ The sulphate of iron is the starting point in preparing all the compounds of iron which are used in medicine, and it is important therefore, to know how to separate easily the impurities which are contingent to this extremely cheap article of commerce. ”

“ The result is a bluish colored mixture, soon changing to olive green. If the sulphate of iron be not properly selected, or if it be rubbed in the mortar, as inferred from the formula, the mixture is more or less brown and proportionably deteriorated. Of course, we should not “take sulphate of iron in powder.” {44}
In giving directions for making a compound, something, certainly, is to be expected from the knowledge and skill of the manipulator. ”

“ For this purpose long iron conductors were used, which were kept cool by the circulation of the air. As far as our knowledge went at that time, these iron conductors could occasion no untoward influence upon the contact-process; for when dry pyrites are used in the burners, the sulfuric acid in the gases has a concentration of at least ninety per cent. Should this act on the iron at all, it would result in the formation of sulfur dioxid, and this could of course do no damage in the process. ”

“ The effects of oxidation may be seen in the alteration of many kinds of rocks and in red and yellow colors of soils and subsoils.
Pyrite is a very hard mineral of a pale brass color, found in scattered crystals in many rocks, and is composed of iron and sulphur (iron sulphide) . Under the attack of the weather it takes up oxygen, forming iron sulphate (green vitriol) , a soluble compound, and insoluble hydrated iron oxide, which as a mineral is known as limonite. Several large masses of iron sulphide were placed some years ago on the lawn in front of the National Museum at Washington. ”

“ It is largely used in the laboratory as a source of sulphuretted hydrogen. The hydrated sulphide is a black, insoluble substance, rapidly decomposed by exposure to the air. Proposed by Mialhe as an antidote to the salts of arsenic, antimony, bismuth, lead, mercury, silver, and tin, and to arsenious acid; more especially to white arsenic and corrosive sublimate. A gargle containing a little hydrated sulphide of iron will instantly remove the metallic taste caused by putting a little corrosive sublimate into the mouth. ”

“ The residuary impure black oxide is mixed with as much sulphuric acid (concentrated) as will make it into a paste, which is exposed at first to a moderate heat, then to a cherry-red ignition for an hour. The sulphate thus obtained is reduced to powder, and dissolved in water. To the solution, carbonate of potash is gradually added, in order to separate the remaining portion of oxide of iron; the quantity of which depends upon the previous degree of calcination. If it be not enough oxidized, the iron is difficult to be got rid of. ”

“ A solution of the sulphate of iron in ordinary water may be preserved for a long time in the dark without undergoing any change; expose it to the sunshine, and a precipitation of oxide of iron is very rapidly produced. The mineral chameleon, the manganesiate of potash in solution, is almost instantly decomposed in daylight; but it is a long time before it undergoes any change in darkness. The same thing occurs with a combination of platinum and lime: indeed, it appears that precipitation is at all times, and under all circumstances, accelerated by the solar rays. ”

“ The presence of certain neutral salts, especially sodium chloride (common salt) , has a very marked influence on the destruction of iron [17] .
When iron filings are exposed to air and moisture, oxidation takes place; the action is, however, according to Krefting, far more intense in the presence of an alkaline chloride. A mixture of iron filings and sodium chloride exposed to moisture is converted in a few days into a black powder which has the following composition:—11·4% FeO, 80·0% Fe2O3, 8·6% H2O, thus resembling the “iron-black” of Lemery ”

“ Sulphur is now generally regarded as emanating from the stage of intermittent lethargy of a volcano, and the sulphides of iron, copper, arsenic, zinc, selenium, etc., fall in the same category as sulphur; they are secondary, not primary, formations. In the stage further off we have the host of sulphates produced by the oxidation of the sulphur into sulphuric acid, and its subsequent reaction on the metals and earths with which it becomes associated. ”

“ Many methods are employed. Sometimes the lead sulphide is decomposed by heating it with cast iron. The iron takes up the sulphur from the lead and forms [135] easily-fusible iron sulphide, which does not mix with the heavier reduced lead. But another process is more frequently used: the lead ore (it must be clean; that is, free from earthy matter, which may be easily removed by washing) is heated in a reverberatory furnace to a moderate temperature with a free access of air. During this operation part of the lead sulphide oxidises and forms lead sulphate, PbSO4, and lead oxide. ”

“ When strongly heated iron inflames in oxygen and in sulphur vapour; it also combines directly with the halogens. It dissolves in most dilute acids with liberation of hydrogen; the reaction between sulphuric acid and iron turnings being used for the commercial manufacture of this gas. It dissolves in dilute cold nitric acid with the formation of ferrous and ammonium nitrates, no gases being liberated; when heated or with stronger acid ferric nitrate is formed with evolution of nitrogen oxides. ”

“ If exposed to a sudden, though gentle heat, by holding it, for instance, in a hand when that is warm, it will sometimes break in pieces with a crackling noise.
145It is a remarkable circumstance, that, if a bar of iron be heated to perfect whiteness, and then touched with a roll of sulphur, the two bodies combine, and drop down together, in a fluid state, forming what is called sulphuret of iron, a compound of the same nature as iron pyrites (236) . ”

“ That's a good idea, Dave. I might use a sulphide—nearly all sulphides are colored, and form very easily and rapidly. Or I might use liquid ozone. That will tarnish almost anything to an oxide, which is also apt to be colored. I could certainly heat the ship that way, but I wonder—I'm afraid that the oxide or sulphide would break down too easily. There is only one metal that they might use on which that would work, namely steel. Iron sulphide is black, stable, and will not decompose readily. ”

“ This popular remedy as a lotion for Aphthæ and other similar diseases, I am well satisfied possesses considerable efficacy. It may, perhaps, be necessary to state that Forge-water is that in which the Blacksmith has plunged his hot iron, for the purpose of refrigeration. It is to be taken early in the morning, when, all the mechanical impurities having had time to subside, it is beautifully limpid. Upon examining some of this water I found it to contain sulphate of iron. The sulphuric acid was probably derived from the sulphur of the coals. ”

“ The fuel has, in addition to its duties of deoxidizing and carburizing the iron and yielding the heat needed for melting both the iron and slag, the further task of desulphurizing the iron, probably by the reaction FeS + CaO + C = Fe + CaS + CO.
The desulphurizing effect of this transfer of the sulphur from union with iron to union with calcium is due to the fact that, whereas iron sulphide dissolves readily in the molten metallic iron, calcium sulphide, in the presence of a slag rich in lime, does not, but by preference enters the slag, which may thus absorb even as much as 3% of sulphur. ”

“ But if sufficient quantities of iron are taken internally, the alkaline sulphides are decomposed and the organic iron of the food becomes available. The amounts of iron required depend of course upon the amount of alkaline sulphides in the intestines, and this is why it may be found necessary to administer as much as 18 grains a day to an anæmic woman whose body, in a normal state, contains altogether about 30 grains. ”

“ Copper sulphate is nearly as active, and is followed by zinc sulphate and cadmium sulphate. Lead acetate and nitrate, in a one-percent solution, only delay decay, while it is prevented by the same strength of iron sulphide. ”

“ Precipitation with sulphur dioxide and sulphuretted hydrogen proceeds much more rapidly, and has been adopted at many works. Sulphur dioxide, generated by burning sulphur, is forced into the solution under pressure, where it interacts with any free chlorine present to form hydrochloric and sulphuric acids. Sulphuretted hydrogen, obtained by treating iron sulphide or a coarse matte with dilute sulphuric acid, is forced in similarly. The gold is precipitated as the sulphide, together with any arsenic, antimony, copper, silver and lead which may be present. ”

“ Iron is magnetic up to a dull-red heat, at which point it loses all traces of that property. It melts at about 3300° Fahr. With oxygen, chlorine, iodine, the acids, &c., it forms numerous important compounds. As a remedial agent, when properly exhibited, iron acts as a genial stimulant and tonic, and generally proves beneficial in cases of chronic debility, unaccompanied with organic congestion or inflammation. The carbonate (ferrous carbonate) , as it exists in mineral waters, held in solution by carbonic acid in excess, appears to be the form most congenial to the human body ”

“ Persoz: 32.5 grammes of green sulphate of iron in crystals are to be mixed in a porcelain capsule with 5 grammes of sulphuric acid, 30 grammes of water, and as much nitro-muriatic acid as will suffice to effect the oxidation of the protoxide of iron. The above mixture is to be evaporated to dryness in order to get rid of the free acid, and then treated with water to the amount of one litre. From 107 to 110 grammes of crystallized pyrophosphate of soda are to be dissolved likewise in a litre of water, of course in a separate vessel. ”

“ The next day, the 8th of May, the engineer began his manipulations. These shistose pyrites being composed principally of coal, flint, alumina, and sulphuret of iron—the latter in excess—it was necessary to separate the sulphuret of iron, and transform it into sulphate as rapidly as possible. The sulphate obtained, the sulphuric acid could then be extracted.
This was the object to be attained. Sulphuric acid is one of the agents the most frequently employed, and the manufacturing importance of a nation can be measured by the consumption which is made of it. ”