Method of Analysis of Vanadium Pentoxide
Weigh 0.1g of sample (accurate to 0.0001g) in a 300ml conical flask, add 5ml of 1:1 sulphuric acid, add a small amount of distilled water, heat to dissolve, take 15ml of 3:1:1 phosphorothioic acid, add 10% ferrous ammonium sulphate solution dropwise to emerald green colour, cool it down to room temperature in cold water, then oxidise it with 3% KMnO₄ until the red colour of the solution does not disappear , then add about 1 g of solid. Excess 1 ~ 3 drops, shake vigorously for 30 seconds, add 3 drops of V indicator for a few moments, titrate with standard solution of ammonium ferrous sulphate until the solution changes from purple to bright green, which is the end point.
Calculation V2O5% = vt/g× 100
Where:V - consumption of ammonium ferrous sulphate standard solution
Ammonium ferrous sulphate standard solution titrated to V2O5
g - weight of sample
Reagents required.
1. Sulphuric acid:1:1
2. Sulphur and phosphorus mixed acid: 3:1:1 (H2SO4: H3PO4: H2O)
3.Ammonium ferrous sulphate:10%Weigh 10g of ammonium ferrous sulphate and dissolve in 100ml 5% h2so 4 solution.
4.KMnO₄:3% when dissolved, must be boiled for a few minutes to avoid insoluble KMnO4 residue.
5.Urea:solid
6.Sodium nitrite:1% aqueous solution
7.Benzo-p-aminobenzoic acid indicator:0.2% Weigh 0.2g, dissolve in 100ml 0.2% sodium carbonate solution.
8.Ammonium ferrous sulphate standard solution-about 0.03N:Weigh 53g of ammonium ferrous sulphate [(NH4)2]. Fe(SO4)2-6h2o] and dissolve it in 10l of 5% sulphuric acid solution. (The standard solution should be stored for a long time on pure aluminium wire.) After a few days it can be calibrated.
