The Volatile Chemist - 16-12-2015 at 18:31
It's not often I have a compound that a good deal of users don't. I realized I had some KHP, potassium hydrogen phthalate, often used as a
primary standard in titration (I had it for this in a micro-chem kit, about 5g).
This compound is pretty soluble in water, and I added copper sulfate solution to some which had partially dissolved in water, and after ~2 hours
I got a crystalline precipitate, slightly more blue than typical copper(II) sulfate. Given the fact that a Google of copper phthalate gives results
(eg. http://www.ncbi.nlm.nih.gov/pubmed/19382760), it seems copper(II) phthalate compound exists. My first assumption was that (using P for phthalate)
CuP, K2SO4, and H2P were produced, and possibly some potassium double salt of the copper compound.
I plan on doing the same thing in a more controlled environment tomorrow.
Does this product seem reasonable? Should I neutralize the Phthalate acid-salt first in my attempt tomorrow? Or should I use basic copper(II)
carbonate instead of a soluble salt?
Just trying to get a collectable, known-composition phthalate-copper compound. Any help/suggestions much appreciated.
[Edited on 12-17-2015 by The Volatile Chemist]
DraconicAcid - 16-12-2015 at 21:16
I'd stick with the KHP instead of trying to make K2P to add. If your solution is too basic, you'll get a basic copper(II) salt precipitating. You
could buffer your solution with acetic acid/acetate, but you want to rely on the insolubility of the product to drive the reaction.
The Volatile Chemist - 30-12-2015 at 14:28
Thanks for the suggestion. I performed the procedure with 1.0g KHP and 0.7g copper(II) sulfate, though I totally forgot to check the solubility of
phthalic acid (one of the expected products) and got a colorless crystalline solid before the 'CuP' crystallized as blue needles. Another member made
note that his copper phthalate was very light blue, which didn't exactly match my observations.