# Potassium Metavanadate Synthesis

I am looking to synthesize potassium metavanadate. Possible precursors that I have are $\ce{V2O5}$ and $\ce{NH4VO3}$.

I have considered the following procedure: Combine $\ce{V2O5}$ and $\ce{KOH}$ then adjust pH and precipitate out with $\ce{CH3OH}$. The problem is multiple species exist at various pH values, so I am looking for a method to obtain $\ce{KVO3}$. I read a while ago a source for synthesis of different alkali metal vanadates, but I cannot find it again.

• I found a synthesis from Inorganic Syntheses vol 15 using potassium carbonate and vanadium oxide. I will try it this week, but if anyone else has any other references, please let me know! Aug 16 '16 at 18:47

## 1 Answer

Potassium Vanadate can be prepared by any of the three process:

1. Potassium Metavanadate, $\ce{KVO3}$, is obtained as white or colourless crystals by dissolving vanadium pentoxide in hot, strong caustic potash solution. By varying the concentrations several hydrates have also been prepared: $\ce{2KVO3.3H2O}$; $\ce{KVO3.2H2O}$; $\ce{2KVO3.5H2O}$; $\ce{KVO3.3H2O}$. On being heated, all these hydrates lose their water and leave a white, nacreous mass of the anhydrous salt, which melts at 495° C. Two other hydrates were prepared by Rammelsberg: $\ce{KVO3.H2O}$ and $\ce{KVO3.7H2O}$. (source)

2. [...] the reaction of vanadium(V) oxide from waste catalyst with potassium chloride in the presence of steam. $$\ce{2KCl + V2O5 + H2O(g) → 2KVO3 + 2HCl↑}$$ (source)

3. Ammonium metavanadate react with potassium carbonate to produce potassium metavanadate, ammonia, carbon dioxide and water. Potassium carbonate - concentrated solution. The reaction takes place in a boiling solution.

$$\ce{2NH4VO3 + K2CO3 → 2KVO3 + 2NH3 + CO2 + H2O}$$ (source)

• Thanks, I know the reaction schemes, but the problem is that due to vanadium speciation in water, the pH and concentrations need to be precisely controlled. If you look at the Inorganic Syntheses link I sent, you can see the care taken to control these variables. Therefore I was asking for a detailed procedure with analytical results of the product obtained. Oct 23 '16 at 17:44
• For example, see this speciation figure: Oct 23 '16 at 17:47
• researchgate.net/profile/Li_Zeng6/publication/257130795/figure/… Oct 23 '16 at 17:48
• And that chart is only valid for a certain range of concentrations and doesnt include other possible ions such as K+, NH3, (CO3)2-, etc. The balanced equations are trivial to obtain and general methods are easy to find, but a detailed synthesis with analytically pure product, is what I was looking for (lab scale) and the Inorganic Syntheses was the only one I found. Oct 23 '16 at 17:51