Chemical elements
    Amorphous Sulphur
    Colloidal Sulphur
    Physical Properties
    Chemical Properties
      Hydrogen Sulphide
      Metal Polysulphides
      Hydrogen Polysulphides
      Hydrogen Pentasulphide
      Hydrogen Trisulphide
      Hydrogen Disulphide
      Sulphur Monofluoride
      Sulphur Tetrafluoride
      Sulphur Hexafluoride
      Sulphur Monochloride
      Sulphur Dichloride
      Sulphur Tetrachloride
      Sulphur Monobromide
      Thionyl Fluoride
      Sulphuryl Fluoride
      Fluorosulphonic Acid
      Thionyl Chloride
      Sulphuryl Chloride
      Sulphur Oxytetrachloride
      Pyrosulphuryl Chloride
      Chlorosulphonic Acid
      Thionyl Bromide
      Sodium Sulphoxylate
      Sulphur Dioxide
      Sulphurous Acid
      Sulphur Trioxide
      Pyrosulphuric Acid
      Sulphuric Acid
      Persulphuric Anhydride
      Persulphuric Acid or Perdisulphuric Acid
      Permonosulphuric Acid
      Amidopermonosulphuric Acid
      Thiosulphuric Acid
      Polythionic Acids
      Dithionic Acid
      Trithionic Acid
      Tetrathionic Acid
      Pentathionic Acid
      Wackenroders Solution
      Hexathionic Acid
      Polythionic Acids
      Sulphur Sesquioxide
      Hydrosulphurous Acid
      Nitrogen Sulphide
      Nitrogen Persulphide
      Nitrogen Pentasulphide
      Nitrogen Chlorosulphide
      Trithiazyl Chloride
      Thiotrithiazyl Chloride
      Dithiotetrathiazyl Chloride
      Nitrogen Bromosulphide
      Thiotrithiazyl Bromide
      Thiotrithiazyl Iodide
      Thiotrithiazyl Nitrate
      Thiotrithiazyl Hydrogen Sulphate
      Thiotrithiazyl Thiocyanate
      Sulphonic Acids
      Amidosulphonic Acid
      Imidosulphonic Acid
      Nitrilosulphonic Acid
      Hydroxylamine-monosulphonic Acid
      Nitrososulphonic Acid
      Hydroxylamine-disulphonic Acid
      Hydroxylamine-isodisulphonic Acid
      Hydroxylamine-trisulphonic Acid
      Dihydroxylamidosulphonic Acid
      Sulphazinic Acid
      Sulphazotinic Acid
      Dehydrosulphazotinic Acid
      Nitrosulphonic Acid
      Nitrosulphonyl Chloride
      Nitrosulphonic Anhydride
      Nitrosulphuric Acid
      Nitrosodisulphonic Acid
      Sulphonitronic Acid
      Sulphates of Hydroxylamine
      Hydroxylamine Dithionate
      Hydrazine Dithionate
      Hydrazine Amidosulphonate
      Carbon Subsulphide
      Carbon Monosulphide
      Carbon Disulphide
      Thiocarbonic Acid
      Ammonium thiocarbonate
      Thiolcarbonic Acid
      Xanthic Acid
      Perthiocarbonic Acid
      Sodium perthiocarbonate
      Carbonyl Sulphide
      Thiocarbonyl Chloride
      Thiocarbonyl Tetrachloride or
      Carbon Hexachlorosulphide
      Trichloromethyl Disulphide
      Thiocarbonyl Sulphochloride
      Carbon Bromosulphide
      Amino-derivatives of Thiocarbonic Acid
      Dithiocarbamic Acid
      Azidodithiocarbonic Acid
      Cyanogen Monosulphide
      Cyanogen Trisulphide
      Sulphur Thiocyanate
      Disulphur Dithiocyanate
      Thiocyanic Acid
      Dithiocyanic Acid
      Trithiocyanuric Acid
      Perthiocyanic Acid

Compounds of Sulphur

Although sulphur in the compact form appears to be a comparatively inactive element, yet when in a fine state of division it reacts with many metals, and at elevated temperatures it combines directly with nearly all other elements (exceptions being nitrogen, iodine, beryllium, gold, platinum and iridium) to form stable binary compounds, the reactions often occurring with great vigour.

In its most stable compounds with hydrogen and the metals, sulphur in Compounds of Sulphur is usually bivalent, but it possesses the property of combining with these elements in proportions exceeding the valency requirements, forming series of polysulphides of the type R2Sx, where x may be as high as 6. The polysulphides of hydrogen are unstable oily liquids of uncertain freezing-points, and on heating undergo decomposition.

Towards the halogens, sulphur is electropositive. Combination with fluorine and chlorine takes place at ordinary temperatures, the product in the former case being the hexafluoride, SF6, whilst with chlorine, sulphur monochloride, S2Cl2, is first formed, then the dichloride, S2Cl2, and finally the tetrachloride, SCl4. A monofluoride and a mono- bromide are also known, but no compound of sulphur and iodine has been isolated.

Sulphur is also electropositive towards oxygen, and in the oxides and their derivatives the element usually exhibits a valency of 4 or 6. The two stable oxides, SO2 and SO3, are strongly acidic, giving rise to sulphurous and sulphuric acids, respectively, from which numerous other oxyacids are derived. An intermediate unstable sesquioxide, S2O3, is known, but it does not appear to be the anhydride of hydro-sulphurous acid, H2S2O4, as its formula would suggest, since this acid cannot be obtained from it. Products have also been described purporting to contain a higher oxide variously formulated as S2O7, SO4 and S3O11, from which the peracids are derived, but the identity of such an oxide has not yet been satisfactorily established.

The following is a list of the oxyacids of sulphur; those in brackets are only known in the form of their derivatives, whilst those marked

with an asterisk are known in solution, but have not been isolated:

(Sulphoxylic acid, H2SO2).
*Hydrosulphurous acid, H2S2O4.
*Sulphurous acid, H2SO3.
Sulphuric acid, H2SO4.
Pyrosulphuric acid, H2S2O7.
*Thiosulphuric acid, H2S2O3.
Permonosulphuric acid, H2SO5.
Perdisulphuric acid, H2S2O8.
*Dithionic acid, H2S2O6.
*Trithionic acid, H2S3O6.
*Tetrathionic acid, H2S4O6.
*Pentathionic acid, H2S5O6.
(Hexathionic acid, H2S6O6).

Arranged in order of increasing strength, the sulphur acids are as follows:

H2S, H2SO3, H2S2O4, H2S2O3, H2SO4, H2S2O6, H2S3O6.

Hydrogen sulphide is the weakest acid, di- and tri-thionic acids are approximately of equal strength, whilst sulphurous acid is the weakest oxyacid in the list.

On replacement of one hydroxyl group in sulphuric acid, SO2(OH)2, by such univalent radicals as -NH2, -NO2, -F or -Cl, a series of sulphonic acids may be obtained, from which a large number of derivatives, both inorganic and organic, have been prepared.

Sulphur and Hydrogen

The most important and the most stable compound of sulphur and hydrogen is the well-known hydrogen sulphide, but, in addition, at least three well-defined compounds, H2S2, H2S3 and H2S5, are known, and there is evidence that a hexasulphide, H2S6, also exists.
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