Sciencemadness Discussion Board

Chemically removing colored dyes

jamit - 2-4-2014 at 23:44

I just received some ammonium phosphate for crystal growing but it is colored with dye- my guess is that it's food coloring.

I want to remove the color dye and crystallize out the ammonium phosphate. I looked up on google and someone suggested using magnesium chloride but I don't know if it will work and I don't have this chemical.

I was thinking of using some cheap and readily available chemical that will absorb just the color dye but not reaction with the ammonium phosphate, such as, diatomaceous earth or maybe activated charcoal? Do you think this would work? Any suggestions?


Chemosynthesis - 3-4-2014 at 00:13

I would definitely try a little bit stirred with activated charcoal. What color dye?

jamit - 3-4-2014 at 00:37

I have three different colored ammonium phosphate crystal growing packages -- red, green, orange. I'd tried recrystallization but the dyes crystallizes out with the ammonium phosphate so there's no way to remove it by recrystallization.

Zyklon-A - 3-4-2014 at 05:56

Just make sure not to do anything to the whole batch. If you test any color removing procedures, try first on a few grams, if it works, then do the whole thing.

forgottenpassword - 3-4-2014 at 06:25

Yes, use decolourising carbon and filter whilst hot.

blogfast25 - 3-4-2014 at 08:31

Quote: Originally posted by jamit  
Any suggestions?



Try hydrogen peroxide. Organic dyes may be prone to oxidation.