Sodium pyrovanadate

Sodium Orthovanadate, Na3V04.12H20, is the orthovanadate most frequently met with. It is readily obtained by adding excess of caustic soda to a solution of sodium pyrovanadate ... 

Pyrovanadates are more stable than orthovanadates, but, in consequence of the weakly add character of pyrovanadic add, they undergo easy conversion into the metavanadates. Sodium pyrovanadate in solution is thus converted by carbon dioxide into the metavanadate ... 

These reactions suggest that sodium pyrovanadate undergoes partial hydrolysis in solution ... 

Barium Pyrovanadate, BaaVaO is precipitated on addition of barium chloride to a solution of sodium pyrovanadate or of other vanadates in the presence of ammonia.3 It has more recently been prepared by the action of barium peroxide on vanadium pentoxide.4 It is a white, amorphous powder which melts above 868° C.5... 

Calcium Pyrovanadate, 2Ca2Va07.5Ha0, is formed by adding calcium chloride to a solution of sodium pyrovanadate and drying the precipitate at 100° C.6 The dihydrate, CaaVa07.2Ha0, has been obtained in transparent needles by adding calcium chloride to ammonium metavanadate solution and then excess of ammonium hydroxide.7... 

Silver Pyrovanadate, Ag4V207, is obtained as a dense yellow precipitate by the addition of neutral silver nitrate to sodium pyrovanadate solution. It has also been obtained as brilliant yellow, transparent plates.9 M.pt. 383° C.1 ... 

T120.5V20s or Tl2O.10TlVO3 is prepared by the action of thallium sulphate on sodium pyrovanadate, Na4V207, in the presence of excess of vanadium pentoxide.7 It dissolves in 9372 parts of water at 11° C. and in 83C6 parts of water at 100 0 C. 

Ammonium Orthothiovanadate, (NH4)3VS4, is obtained in rhombic crystals by the action of ammonium hydrosulphide on potassium metavanadate or sodium pyrovanadate solution. It also separates out slowly from an ice-cold saturated solution of ammonium metavanadate in concentrated ammonium hydroxide which has been previously treated with hydrogen sulphide. 

Sodium Orthoxytrithiovanadate, Na8VS30.5H20, is obtained in dark, reddish-brown, deliquescent crystals by the action of sodium hydrosulphide on sodium pyrovanadate. The anhydrous salt is formed when vanadium pentoxide, sulphur and sodium carbonate are fused together,4 or by the action of hydrogen sulphide on sodium orthovanadate at 500° to 700° C.5... 

Sodium Orthoxymonothiovanadate, Na3VSO3.10H2O, has been obtained in orange-yellow crystals by the action of sodium hydrosulphide on sodium pyrovanadate. 

The action of hydrogen sulphide at high temperatures on sodium pyrovanadate gives rise to sodium pentathiopyrovanadate, Na4V2Ss02, which is a hygroscopic substance very similar in its colour and lustre to potassium permanganate. 

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