Sciencemadness Discussion Board

I burnt my copper tartrate

Arcaeca - 31-8-2019 at 19:28

So in my ongoing quest to make pigments from scratch, copper(II) tartrate was suggested as a blue pigment in a now deleted thread; the path I've been using goes something like:

Cu(s) --> CuCH3COO --> Cu(OH)2 --> CuC4H4O6

using copper metal, hydrogen peroxide, vinegar, NaOH and potassium hydrogen tartate (cream of tartar) as the full list of reactants. Then I poured the deep blue solution into a pan to evaporate and crystallize.

Well, I got tired of waiting for the water to evaporate, and Walmart made the terrible mistake of selling me a propane torch, so I decanted the solution into a different pan and started a big ol' fire to bubble the water away. Then since it seemed to be going slowly I wandered away for a while, and when I came back... well...

Anyway, I mostly just wanted to share the picture because I think they're cool (not what I was trying to make, but interesting nonetheless) and there's a nice color striation: blue (probably copper tartrate) on top of yellow (copper(I) oxide?) on top of red (also copper(I) oxide?) on top of black (copper(II) oxide?).

But I suppose it's worth asking - since copper tartate is fairly soluble and doesn't precipitate out easily, what's a faster way to crystallize it than just waiting it out, but doesn't... uh... make it stop being copper tartrate?

IMG_4577.JPG - 2.2MB

Sulaiman - 31-8-2019 at 20:46

other than boiling, every method that I have tried needs an air pump,
and atmospheric air has all kinds of 'dust' (at least where I live/work)
so the air needs to be filtered.

I rely mostly on patience ...
e.g. 100ml of solution in a 250ml beaker covered with a filter paper,
taped down around the beaker wall for a dustproof seal,
left on a shelf the water will slowly evaporate.
One benefit is that the slow evaporation causes slow crystalisation,
which gives larger crystals,
that are easier to wash AND carry/contain less contaminants.

In winter I have put such beakers on my central heating radiators for quicker results.

Deathunter88 - 31-8-2019 at 22:29

Use something other than a direct flame for boiling down the solution. A temp controllable hotplate is best.

unionised - 1-9-2019 at 01:35

Some salts can be crystalised by adding alcohol to an aqueous solution.
I have no idea if it will work in this case.

On an unrelated note, if copper nitrate is overtime pay for policemen, what is copper tartrate?

[Edited on 1-9-19 by unionised]

mayko - 1-9-2019 at 05:55

Copper tartrate decomposes to copper metal, iirc, and probably dehydrates before that. A drop of copper tartrate solution dry and decompose on a ceramic dish is nice to watch.

Organic copper salts are often a pain to crystallize and this was my experience with the tartrate. Keeping it in a desiccator might speed things up. Another trick I've used is to add dry alcohol once the salt solution gets syrupy, and change the alcohol every now and then to suck out the water. It's solvent-hungry, though.

Tsjerk - 1-9-2019 at 07:17

Use CaCl2 as dessicator and add methanol or ethanol if needed. CaCl2 will absorb both alcohols and water. I just put stuff to dry in cupboard with some CaCl2.

draculic acid69 - 1-9-2019 at 07:39

Quote: Originally posted by unionised  
Some salts can be crystalised by adding alcohol to an aqueous solution.
I have no idea if it will work in this case.

On an unrelated note, if copper nitrate is overtime pay for policemen, what is copper tartrate?

[Edited on 1-9-19 by unionised]


That's the rate you pay a police officer for being a tart.

Arcaeca - 1-9-2019 at 17:03

Okay, so, proving that I learned nothing from the copper tartrate, I vigorously boiled several jarfuls of copper(II) acetate solution in a big pan in an attempt to at least make it more concentrated (by reducing the volume of the solvent), if not necessarily crystallize it. You'll be shocked to know that the results were much the same as with the tartrate - a little bit of greenish residue (what I was actually aiming for) crystallized on the top edges of the pan, but the bottom was caked in red/yellow/black layers of copper oxide.

So yeah. Not much luck crystallizing organic copper salts. You all are saying I should build a makeshift desiccator with CaCl2? (Can be made from calcium carbonate + HCl? I have both of those on hand) And will isopropanol work instead of methanol or ethanol? Isopropanol is easier to aquire.

In the meantime, I'm dissolving the copper oxide waste in HCl to reclaim as much of the copper as possible (and because I don't really have anything else to do with the oxide - it's brownish, neither yellow nor red) to get at least some blue copper(II) solution back - this time ostensibly CuCl2 instead of acetate.

[Edited on 9-2-2019 by Arcaeca]

Bedlasky - 2-9-2019 at 04:19

If you want dark blue pigment, try prussian blue. It's easily made by mixing solutions of ferric salt and potassium ferrocyanide (or ferrous salt and potassium ferricyanide) and filtered off.

mayko - 2-9-2019 at 07:48

Quote: Originally posted by Arcaeca  
Okay, so, proving that I learned nothing from the copper tartrate, I vigorously boiled several jarfuls of copper(II) acetate solution in a big pan in an attempt to at least make it more concentrated (by reducing the volume of the solvent), if not necessarily crystallize it. You'll be shocked to know that the results were much the same as with the tartrate - a little bit of greenish residue (what I was actually aiming for) crystallized on the top edges of the pan, but the bottom was caked in red/yellow/black layers of copper oxide.


Copper acetate can decompose to basic copper acetate if you boil it too aggressively and evaporate off the excess acetic acid, iirc. Copper acetate will give very nice crystals with slow evaporation!


Arcaeca - 2-9-2019 at 09:42

Well, I don't really care about the crystals - I'm going to be grinding them up into powder anyway. I just need my copper salts to be solid, but I'm impatient. The problem is since the goal is to use them for pigment - i.e., it's being used specifically for its color - anything that results in significant discoloration amounts to ruining it.

AJKOER - 2-9-2019 at 13:18

Per a source 'Synthesis of Cu and Co metal oxide nanoparticles from thermal decomposition of tartrate complexes', link: https://www.sciencedirect.com/science/article/pii/S002016931... to quote:

"Highlights
► Metal tartrates were used as precursors for the preparation of nanostructured metal oxides. ► Co3O4 and CuO nanoparticles were obtained in high yield by thermal decomposition of metal complexes. "

Apparently, the thermal decomposition of tartrate complexes could be a source of a metal oxide (and not the metal) in the form of nanoparticles (which I would advise to keep out of ones lungs).

[Edited on 2-9-2019 by AJKOER]