Dissolve 3 mL of sulfuric acid and 2 g of potassium dichromate in 50 mL of 60°C water, then put the impure white phosphorus to it and mechanically stir few times and leave the mixture to stand for 2 days in a dark room with occasional stirring. Discard the solution and wash the WP with water. Then add 50 mL of 30% nitric acid and stir the mixture in 60°C for 6h, then remove magnetic stir bar and cool down to room temperature, wash with water few times and store underwater in dark.
The impure product
Chromic acid solution
After washing of the chromic acid
Then purification with nitric acid
Very pure White phosphorus