Atomistry » Selenium » Chemical Properties » Selenophosphates and Oxyselenophosphates
Atomistry »
  Selenium »
    Chemical Properties »
      Selenophosphates and Oxyselenophosphates »

Selenophosphates and Oxyselenophosphates

By the action of phosphorus pentaselenide on aqueous solutions of the selenides of the respective metals, selenophosphates of the alkali and alkaline earth metals and of magnesium can be prepared. The reaction takes place according to the equation:

3M2Se + P2Se5 = 2M3PSe4.

The tetraselenophosphate is not obtained in the solid state, however, being decomposed by water, thus:

M3PSe4 + H2O = M3PSe3O + H2Se.

The decomposition may go still further, the compound M3PSe2O2 or even M3PSeO3 being formed. Intermediate compounds such as K3PSe2.5O1.5 are also formed, which may be isomorphous mixtures of various oxyselenophosphates.

The oxyselenophosphates may also be prepared by the action of phosphorus pentaselenide on the hydroxides of the metals. Normal salts are only obtained in the case of the alkali metals; the alkaline earth metals give monohydrogen salts. The following oxyselenophosphates have been prepared and described:

Sodium Trioxysele no phosphate, Na3PSeO3.20H2O, obtained by the action of phosphorus pentaselenide on either sodium hydroxide or sodium hydroselenide, crystallises in needles.

Ammonium Oxytriseleno phosphate, obtained from phosphorus pentaselenide and a saturated solution of hydrogen selenide in strong ammonia, crystallises from the warm mother-liquor in leaflets having the composition (NH4)3PSe3O.10H2O. The cold mother-liquor afterwards deposits octahedra and four-sided leaflets having the composition (NH4)5H(PSe3O)2.18H2O.

Potassium Oxyselenophosphate, K3PSe2.5.O1.5.H2O, is obtained as greenish-yellow octahedra by using potassium hydroselenide.

Barium Dioxydiseleno phosphate, BaHPSe2O2.14H2O, formed when phosphorus pentaselenide is treated either with a solution of barium hydroxide or with a saturated solution of hydrogen selenide in barium hydroxide, is a white, microcrystalline powder.

Strontium Oxyselenophosphate, obtained as a light yellow precipitate by the action of phosphorus pentasulphide on strontium hydroxide and treatment of the filtrate with alcohol, has the composition SrHPSe2/3O10/3.7H2O. Using a large excess of phosphorus pentaselenide the crystals obtained are colourless and have the composition SrHPSe4/3O8/3.8H2O, which may possibly be 2SrHPSeO3.SrHPSe2O2.24H2O.

Calcium Oxyselenophosphate has been obtained in the same way, using calcium hydroxide instead of strontium hydroxide. With the smaller proportion of phosphorus pentaselenide the crystals have the composition CaHPSeO11/3.5H2O, whilst with the larger proportion their composition is CaHPSeO3.8H2O.
© Copyright 2008-2020 by atomistry.com
Home   |    Site Map   |    Copyright   |    Contact us   |    Privacy