Chemical Forums
Specialty Chemistry Forums => Citizen Chemist => Topic started by: greenbreen on February 09, 2014, 09:38:54 AM
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I recently started taking both magnesium citrate and ascorbic acid as dietary supplements. If I dissolve magnesium citrate in a mug and drink it but don't wash out the residue before adding more water and then ascorbic acid, I notice that I start to get a brownish color. I came home today and noticed that there was a reddish residue at the bottom of the mug I had used. Does anyone know or have a reasonable guess as to what it might be? I'm not a chemistry student--I'm just curious.
I checked drugs.com, and it has a page for reactions between magnesium citrate and vitamin C, but it just says that it knows of no adverse reaction between the two. I thought maybe it would be magnesium ascorbate, but I found an MSDS that says that that is a light yellow color. Whatever it is, it seems to be slightly soluble in water because I get a pink tint to any water I add.
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My bet is that the color has nothing to do with neither magnesium citrate nor ascorbic acid, but either with impurities present in the the salt, or impurities present in water.
Note: these impurities can be safe, just giving unexpected color reactions.
Reddish/brownish sounds like iron(III), but it doesn't add with the presence of ascorbic acid. Ascorbic acid is a reducing agent, so I am not sure if iron wouldn't be reduced to Fe(II), which is not reddish. Checking redox potentials would give more info.
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Thanks for the reply. That's interesting. It's been a long time since I took chemistry. I'll have to review information about redox potentials when I get some spare time.
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You should look at the ingredient list.
Drugs list 2 types of ingredients : medical and non-medical.
The non-medical part often contain microcellulose and a bunch of other things.
It could be that there is something in your magnesium citrate pill that is effected by a pH change.