Chemical elements
  Sulphur
    Isotopes
    Energy
    Extraction
    Refining
    Applications
    Allotropy
    Crystalline
    Amorphous Sulphur
    Colloidal Sulphur
    Physical Properties
    Chemical Properties
    Detection
    Estimation
    Compounds
      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
      Sulphites
      Sulphur Trioxide
      Pyrosulphuric Acid
      Pyrosulphates
      Sulphuric Acid
      Persulphuric Anhydride
      Persulphuric Acid or Perdisulphuric Acid
      Perdisulphates
      Permonosulphuric Acid
      Amidopermonosulphuric Acid
      Thiosulphuric Acid
      Thiosulphates
      Polythionic Acids
      Dithionic Acid
      Trithionic Acid
      Trithionates
      Tetrathionic Acid
      Tetrathionates
      Pentathionic Acid
      Pentathionates
      Wackenroders Solution
      Hexathionic Acid
      Polythionic Acids
      Sulphur Sesquioxide
      Hydrosulphurous Acid
      Hydrosulphites
      Nitrogen Sulphide
      Nitrogen Persulphide
      Nitrogen Pentasulphide
      Sulphammonium
      Hexasulphamide
      Nitrogen Chlorosulphide
      Trithiazyl Chloride
      Thiotrithiazyl Chloride
      Dithiotetrathiazyl Chloride
      Nitrogen Bromosulphide
      Thiotrithiazyl Bromide
      Thiotrithiazyl Iodide
      Thiotrithiazyl Nitrate
      Thiotrithiazyl Hydrogen Sulphate
      Thiotrithiazyl Thiocyanate
      Thionylamide
      Sulphamide
      Imidodisulphamide
      Sulphimide
      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
      Thioformaldehyde
      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
      Thiocarbamide
      Azidodithiocarbonic Acid
      Thiocyanogen
      Cyanogen Monosulphide
      Cyanogen Trisulphide
      Sulphur Thiocyanate
      Disulphur Dithiocyanate
      Thiocyanic Acid
      Thiocyanates
      Dithiocyanic Acid
      Trithiocyanuric Acid
      Perthiocyanic Acid
      Perthiocyanogen
      Sulphates

Hydrogen Disulphide, H2S2






Hydrogen Disulphide, H2S2, in addition to being obtained from the distillation of crude "hydrogen persulphide," is also formed when hydrogen trisulphide is distilled at 100° C. under a pressure of 20 mm.; approximately one-third of the trisulphide is converted into disulphide, whilst the remainder passes into hydrogen sulphide and sulphur. The disulphide, therefore, is the most stable of the hydrogen polysulphides towards heat, and can actually be distilled under atmospheric pressure at 71° to 75° C. with only partial decomposition.

It is a clear yellow liquid, of density 1.327 at 25° C.; its vapour is much more pungent than that of the trisulphide and more severely attacks the eyes and mucous membranes. The melting-point is -89.6° C., and the boiling-point 70.7° C. It is soluble in the same solvents as the trisulphide.

Towards alkalis the disulphide is much less stable than the trisulphide and decomposes almost explosively in an untreated glass flask. Distilled water induces rapid decomposition, whilst contact with alkali causes explosive formation of hydrogen sulphide. When placed on paper or on the skin, rapid decomposition occurs, in the latter case with formation of a white fleck, resembling the effect of hydrogen peroxide. The disulphide resembles the trisulphide in its behaviour with sulphuric acid and with silver oxide; it is more readily inflamed than the trisulphide.


Constitution of Hydrogen Disulphide

From the composition of hydrogen disulphide and its chemical behaviour, it is natural to regard it as the analogue of hydrogen peroxide, and as having therefore the structure HSSH. It is probable that the higher polysulphides are of a similar " chain " type, that is, of constitutions HSSSH, HSSSSSH, and the missing member of this series, H2S4, may be present, in addition to hydrogen pentasulphide, in crude hydrogen persulphide.

On the other hand, the suggestion has been made that the poly-sulphides are analogous in structure to the periodides and are to be represented as additive compounds of hydrogen sulphide with sulphur of the general formula H2S.Sn. In such a case, the additional sulphur atoms would presumably be attached in the manner , etc. This view possesses an advantage in giving a possible reason why hydrogen disulphide should be more stable than the higher poly- sulphides towards rise in temperature, because, of the polysulphides, it alone would be free from a quadrivalent sulphur atom with its four valencies entirely satisfied by other sulphur atoms. Indeed, the change in colour of hydrogen trisulphide with alteration of temperature, as well as the low stability of the trisulphide relative to the disulphide at higher temperatures, have been tentatively referred to the existence of dynamic isomerism between the two structures HSSSH.

The evidence, however, is very slight, and this suggestion, together with that of a structure for hydrogen pentasulphide, making the latter structurally analogous to sulphuric acid, must be regarded as requiring experimental confirmation before serious consideration can be claimed.

An alternative method of representing the formulae of the polysulphides has been proposed, namely



and this shares with the earlier H2S.Sn formulae the advantage of indicating a possible reason for the relatively greater stability of hydrogen disulphide at higher temperatures. This type of constitution is favoured also by the behaviour of the polysulphides of sodium and potassium when heated in hydrogen. Sulphur is readily removed from the higher sulphides, but the disulphides of both metals are very stable compounds from which sulphur can only be removed with difficulty at 700° to 800° C. The evidence supplied by the organic polysulphides corresponding with hydrogen disulphide, trisulphide, etc., appears, however, to be strongly in favour of the " chain " structure mentioned at the commencement of this discussion. Hydrogen disulphide and trisulphide form additive compounds with aromatic aldehydes such as benzaldehyde, e.g. (C6H5CHO)2.H2S2, (C6H5CHO)2.H2S3, and the behaviour of these products indicates that the sulphur atoms are present in a continuous chain.1 In the light of our present knowledge, therefore, the most satisfactory method of representing the constitution of the hydrogen polysulphides is by means of the "sulphur chain" formulae.
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