Ferric sulphide

Hydrated ferric sulphide,10 Fe2S3.Aq., is readily produced by... 

A precipitate of ferric sulphide is also obtained when ammonium sulphide is added to a solution of a ferric salt, the alkali remaining in excess.4 If, however, the ferric salt is present in excess, the precipitate appears to consist of a mixture of ferrous sulphide and free sulphur. As obtained by either of the foregoing methods, the sulphide is hydrated and unstable in air. Dilute hydrochloric acid decomposes it completely into ferrous chloride, with evolution of hydrogen sulphide and a simultaneous deposition of sulphur. When boiled with water it yields ferric hydroxide and hydrogen sulphide. 

In the moist condition in the absence of air, or in the presence of excess hydrogen sulphide, ferric sulphide is transformed into a mixture of disulphide and ferrous sulphide 3... 

This transformation, which takes a week at the ordinary temperature, may be effected in a few hours at 60° C. Upon exposure to air in the presence of alkaline substances, ferric sulphide becomes light yellow m colour, and sulphur is deposited. 

Anhydrous ferric sulphide is produced in massive form by gently heating iron and sulphur together. As obtained in this way it is a yellow, non-magnetic mass, soluble in dilute mineral acids, density 4 4. 

Sodium ferric sulphide, Na2S.Fe2S3, may be obtained in a similar... 

When heated, sodium ferric sulphide is converted into oxide. With concentrated hydrochloric acid it yields hydrogen sulphide, free sulphur being deposited. It is insoluble in water but, when boiled with an aqueous solution of potassium cyanide, it yields potassium ferrocyanide. 

Sodium ferric sulphide occurs in the c< black ash 55 liquors formed in the Leblanc Soda Process,2 and a convenient wet method of producing it in the laboratory consists in adding a solution of a ferric salt to excess of sodium sulphide solution. It also results when excess of sodium polysulphide acts on a solution of a ferrous salt.3... 

Cuprous ferric sulphide, Cu2S.FeaS3, occurs in nature as copper pyrites, cholcopyrite, or towcmite, and is one of the commonest ores of copper (see p. 23). It is tetragonal, possessed of a brass-yellow colour, and exhibits a conchoidal fracture. It is decomposed by nitric acid, and tarnishes upon exposure to air, frequently yielding beautiful iridescent surfaces, a blue colour predominating. Masses of such tarnished ore are found in Cornwall, and arc known as peacock ore. The blue colour is probably due to the formation of a surface layer of cupric sulphide or covellite, CuS. 

Copper pyrites may be obtained in the laboratory in the wet way by shaking a weakly ammoniacal solution of cuprous chloride with potassium ferric sulphide until the solution no longer contains copper —6... 

Iron and Sulphur—Subsulphides of Iron—Ferrous Sulphide—Ferric Sulphide-Double Sulphides—Iron Pyrites—Marcasite—Magnetic Pyrites—Ferrous Sulphite—Ferri-sulphites—Ferrous Sulphate—Double Sulphates—Fern-sulphates—Alums—Anndo-sulphonates, Thiosulphate, Disulphate, and Thionates of Iron. 

At temperatures above 300°C Holinski found that molybdenum disulphide produced embrittlement of stainless steel. He suggested that free sulphur released at these temperatures reacted with nickel in austenitic alloys to deposit nickel sulphide preferentially at grain boundaries, thus leading to a form of stress corrosion. Knappwost similarly reported that molybdenum disulphide reacted with iron at 700°C to produce ferric sulphide and free molybdenum, and Tsuya et al showed that it reacted more rapidly with iron and nickel than with silver or copper in a vacuum of 10 Torr above 500°C. The reaction with copper was in fact slow above 500°C but very rapid about 700 C. 

Hydrogen sulphide was prepared from ferric sulphide and sulphuric acid and also by the action of water on an intimate mixture of calcium sulphide and phosphorous pentoxide. It was dried over CaCl, and PaOg and fractionally distilled in vacuo. At pressures of 40 mm. of HjS one flash produced a partial pressure of 9 mm. Hj, sulphur being deposited on the wall, and there was no overall pressure change. Spectra were taken of the products on a Littrow (Hilger E.I.) spectrograph at increasing time intervals, after the flash. Immediately after the flash the absorption spectrum showed, in addition to the continuum of HjS and the — U system of Sg, the o—o band of SH at A identical with that described... 

The mercury distils over, and the ferric sulphide remains in the retort. 

A determination of dimethyl sulphoxide by Dizdar and Idjakovic" is based on the fact that it can cause changes in the visible absorption spectra of some metal compounds, especially transition metals, in aqueous solution. In these solutions water and sulphoxide evidently compete for places in the coordination sphere of the metal ions. The authors found the effect to be largest with ammonium ferric sulphate, (NH4)2S04 Fe2(S04)3T2H20, in dilute acid and related the observed increase in absorption at 410 nm with the concentration of dimethyl sulphoxide. Neither sulphide nor sulphone interfered. Toma and coworkers described a method, which may bear a relation to this group displacement in a sphere of coordination. They reacted sulphoxides (also cyanides and carbon monoxide) with excess sodium aquapentacyanoferrate" (the corresponding amminopentacyanoferrate complex was used) with which a 1 1 complex is formed. In the sulphoxide determination they then titrated spectrophotometrically with methylpyrazinium iodide, the cation of which reacts with the unused ferrate" complex to give a deep blue ion combination product (absorption maximum at 658 nm). 

Novak, M. Zadrazil, M. (1991) Oxidation of hydrogen sulphide over ferric oxide/alumina catalyst. Collection Czech. Chem. Comm. 56 1893-1899... 

Similarly, the MgO content of the ashes is largely derived from thermal decomposition of magnesian carbonates. This process also expels water from hydrated minerals present in the oil shale. The Fe-sulphide content of the original shales is oxidized to ferric oxides and sulphates in the ash (expressed as S03 in Table 4). 

Lead sulphide (galena - PbS) is another likely candidate for hydrometallurgical processing particularly in the United States where, apart from the problems of the sulphur dioxide emissions, the lead toxicity problem is making it very difficult for the lead smelters to operate their conventional pyrometallurgical process and comply with EPA and OSHA standards. The total amount of lead mined in the United States is about 600,000 tons per year which, if fully converted, would yield about 100,000 tons per year of by-product sulphur. The Bureau of Mines in Reno, Nevada, have an active pilot plant study to produce lead via a hydrometal-lurigal process (2). In this process the common lead mineral galena is dissolved in an acid brine solution of ferric chloride. 

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