Atomistry » Sulphur » Compounds » Pyrosulphates
Atomistry »
  Sulphur »
    Compounds »
      Pyrosulphates »

Pyrosulphates

The pyrosulphates of the alkali metals are obtained most easily by heating the corresponding acid sulphates to 300°-350° C:

2KHSO4 = K2S2O7 + H2O.

This dehydration, however, does not proceed to completion even under reduced pressure, and in order to obtain the pure salts it is preferable to allow the finely divided anhydrous normal sulphate to interact with sulphur trioxide. This latter process stands in fairly close relationship with the methods based on the treatment of a normal sulphate with chlorosulphonic acid, with the aid of heat, and on the crystallisation of the solution produced by dissolving a normal sulphate in warm "fuming sulphuric acid":

K2SO4 + SO3 = K2S2O7;
BaSO4 + Cl.SO2.OH = BaS2O7 + HCl;
K2SO4 + H2S2O7 = K2S2O7 + H2SO4.

When heated strongly, for instance above 450° C., the pyrosulphates undergo decomposition into sulphur trioxide and the corresponding normal sulphate. The sodium salt, which melts at 400.9° C., exhibits appreciable dissociation at about 460° C. In contact with moist air or water the pyrosulphates become converted into the corresponding acid sulphates:

K2S2O7 + H2O = 2KHSO4.

Last articles

Zn in 7NA9
Zn in 7LZP
Zn in 7M1H
Zn in 7L6V
Zn in 7CM0
V in 7P8R
Ni in 7L19
Na in 7T88
Na in 7MJ5
Na in 7L00
© Copyright 2008-2020 by atomistry.com
Home   |    Site Map   |    Copyright   |    Contact us   |    Privacy