Fe 3+ ion solution was added to an unknown acid solution and it turned purple, what does this tell you?

Question

I have tried looking everywhere, but I can't find anything. I added Fe 3+ ion solution to my unknown acid solution and it immediately turned purple. What does this tell me? Also when I burned the solid unknown acid a slightly green flame was observed. Again what does this tell me?

Potentially the unknown acid has a molar mass of around 142 g/mol and a melting point of 143 C. If someone could direct me of where to look for this information. I have the CRC handbook of chem and physics but theres over 500 pages of data which isn't organized by molar mass or melting point. So is there somewhere I can easily identify my acid with this information?

This is in school...haha. It's a safe, weak acid. I was told this.

Where in your CRC handbook is it organized by melting point?

Answer 1

Iron (III) complexes of oxalic acid are often purple.

My CRC handbook does have a table of Organic compounds by melting points. You might try a Lange's handbook as well.

Oxalic acid also has a dihydrate which might alter the MW and melting point.

Answer 2

I'd get the **** out of the room lol