Iron pyrites FeS

Sulfur is widely distributed as sulfide ores, which include galena, PbS cinnabar, HgS iron pyrite, FeS, and sphalerite, ZnS (Fig. 15.11). Because these ores are so common, sulfur is a by-product of the extraction of a number of metals, especially copper. Sulfur is also found as deposits of the native element (called brimstone), which are formed by bacterial action on H,S. The low melting point of sulfur (115°C) is utilized in the Frasch process, in which superheated water is used to melt solid sulfur underground and compressed air pushes the resulting slurry to the surface. Sulfur is also commonly found in petroleum, and extracting it chemically has been made inexpensive and safe by the use of heterogeneous catalysts, particularly zeolites (see Section 13.14). One method used to remove sulfur in the form of H2S from petroleum and natural gas is the Claus process, in which some of the H2S is first oxidized to sulfur dioxide ... 

Another phenomenon which proved to be of operational concern was the deposition of iron pyrite, FeS , which I will discuss later. 

Much of this early work was strictly pragmatic without any theory as we would understand it. It was necessary to be able to identify the best and richest ores, to be able to distinguish between superficial resemblances. The ramiliar properties of foots gold, iron pyrites, FeS-, as compared with the dement gold is a well-known example. 

You can produce your own vitriol though it takes some time. Collect together ten to twenty pounds (at least) of iron pyrite (FeS) and grind it to powder. Spread the powder out onto a large flat iron tray then alternately roast it gently and spray with rainwater to moisten, then dry. 

Iron pyrite, Fe 2, looks something like gold. It fooled many gullible people and got the name fooTs gold as a result. The composition of pyrite is 46.5 percent iron and 53.5 percent sulfur by mass. These proportions are the same for every sample of pyrite. They are independent of the origin or amount of the substance. 

A FIGURE 22.19 Iron pyrite (FeS, on the righq with gold for comparison. 

Pyrite (FeS ) is more commonly known as fool s gold. It is used as an iron ore and in the production of sulfur chemicals such as sulfuric acid. 

Applications of the core shielding factors in X-ray studies of pyrite, Fe(Il) phthalocyanine, and bis(pyridine)(meso-tetraphenylporphinato)iron(II) generally improve agreement with spectroscopic values (Su and Coppens 1996). 

The apparent exceptions to this hypothesis disappear on investigation thus iron, which is a dyad in ferrous compounds (as FeCl,), a tetrad in cubical pyrites (FeS,"), and a hexad in ferric acid (FeO,Ho,), is apparently a triad in ferric chloride (FeCl,) but the vapour-density of ferric chloride shows that its formula must be doubled—that, in ct, the two atoms of the hypothetical molecule of iron (FeJ have not been com-... 

The pyrite sulfur is generally considered to be sulfur associated with iron pyrite, FeS2 In most cases only the second sulfur of the pyrite molecule can be considered to be in this class. This sulfur can be expelled from iron pyrite with moderate heating (approximately 500°C) to form iron sulfide, FeS, and elemental sulfur condensate in the cooler vapor space above the sample. 

A set of values of tetrahedral covalent radii 7 for use in crystals of these types is given in Table 7-13 and represented graphically in Figure 7-7. These values were obtained from the observed interatomic distances in crystals of these tetrahedral types and of other types in which the atom of interest forms four covalent bonds with neighboring atoms which surround it tetrahedraliy. For example, in pyrite, FeS. each sulfur atom is surrounded tetrahedraliy by three iron atoms and one sulfur atom, with all of which it forms essentially covalent bonds (Fig. 7-8) the substance is a derivative of hydrogen disulfide, H2S2. That the Fe—S bonds are essentially covalent is shown by the magnetic eri-... 

Fig. 7-8.—The arrangement of iron atoms (small circles) and sulfur atoms (large circles) in the cubic crystal pyrite, FeS. Each iron atom is surrounded octahedrally by six sulfur atoms, and each sulfur atom is surrounded tetrahedrally by one sulfur atom and three iron atoms.

The pyrrhotite or magnetic pyrites is essentially iron sulphide, Fe,Sg or 4FeS.Fe3S4 chalcopyrite or copper pyrites, Cu2S.Fe.jS3, contains some 35 per cent of copper, whilst the pentlandite contains the nickel as sulphide associated with iron sulphide, thus, NiS.2FeS, and contains approximately 22 per cent, of nickel. 

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