Collection of copper compounds.

Hi, I have been lurking this forum for a while, but I finally decided to post my collection of copper compounds.



https://imgur.com/a/nPxHC



From left to right


CuSO4 (White)
Mostly dry copper sulfate can be prepared simply by heating the pentahydrate and quickly storing the product before it absorbs muistutetaan from the air.

CuO (Black)
Easy to prepare by adding solution of sodium carbonate or bicarbonate to a solution of CuSO4 and filtering out the basic copper carbonate. The basic carbonate is then heated until it becomes copper oxide.

CuCl2 (Brown)
Prepared by adding HCl-solution to the basic copper carbonate or the oxide and removing the water by heating.

Cu2O (Red)
https://en.wikipedia.org/wiki/Benedict's_reagent

173g of sodium citrate, 17.3g of copper sulfate pentahydrate and 100g of sodium carbonate are mixed into a solution.
Then about 40g of glucose is dissolved into other solution, and the solutions are mixed. Cu2O is precipitated, and can be filttered off.

The filttering must be done quickly, because wet Cu2O reacts to form CuO, and is diifficult because the precipitate is very fine.

This reaction generally has an pretty horrible wield.

Cu3(SO3)2 (Orange)
http://www.sciencemadness.org/smwiki/index.php/Chevreul's_salt

Chevreuls salt is prepared by mixing solutions of sodium metabisulfite and copper sulfate. The precipitate must be ground into finner powder to get orange colour, the coarser powder is dark red.

Cs2CuCl4 (Yellow)
http://woelen.homescience.net/science/chem/exps/CsCuCl3/inde...

Small amount CuCl2 is dissolved in concentrated hcl, solution of CsCl2 is added The concentration of copper must be low to avoid the formation of the red trichloro complex.
The precipitate that forms is then filtered of and dried.

Other than hydrated Cu2O this is the only yellow compound of copper I have been able to find information about, an compound that doesn't require the valuable CsCl2 would be preferable


Cu2(OH)3Cl (green)
https://en.wikipedia.org/wiki/Dicopper_chloride_trihydroxide

"Copper oxychloride" doesn't always have an precise stoichiometry, but I believe the preparation method I used should give something close to one.
A solution of CuCl2 and NaCl in water is exposed to air, and an copper metal object is submerged in the solution. After a few days the formed green precipitate is filtered and washed.

CuCl2 + Cu + 2 NaCl → 2 NaCuCl2
6 NaCuCl2 + 3/2 O2 + H2O → 2 Cu2(OH)3Cl + 2 CuCl2 + 6 NaCl

I would prefer an compound easily prepared to precise stoichiometry, but pure green copper compounds are surprisingly rare.


Cu2(CH3COO)4(H2O)2 (Cyan)

Copper acetate can be prepared by either adding acetic acid (found in vinegar)
to basic copper carbonate or copper oxide, or simply keeping copper objects submerged in a solution of acetic acid exposed to air for several weeks.

After evaporating the water, dark green crystals are left behind, which can be ground into blue-green powder.

CaCu(CH3COO)4(H2O)6 (Blue)
http://dmishin.blogspot.fi/2014/03/crystal-growing-acetates-...

About 4 mass units of calcium acetate and 1 unit of copper acetate are dissolved in water. On partial evaporation, blue crystals are produced, these are used to make a blue powder.

While blue compounds of copper are common, most of them become very faintly colored when ground into powder. Calsium-Copper acetate retains most of its colour

Cu(C6H8NO2)2(H2O)2 (Violet)

Zinc picolinate and copper sulfate are dissolved in hot water, on cooling copper picolinate precipitates. I sadly forgot to record the amounts of Zinc picolinate and copper sulphate to use, but they were pretty easy to find by experimentation.

Other option for violet would be to use copper ammine complexes, but they are hard to get in pure form.


For all of these colours, the only "real" reagent needed is the CsCl, all the other things can be bought from normal stores.

The tiny bottles were sold as "parfyme testers"



I'm currently working on a similar set of compounds for iron, which has proven to be more difficult for some of the colours.




[Edited on 14-1-2017 by CaCl2]

Quote: Originally posted by j_sum1

That's a lovely little rainbow. Beautifully-presented samples and a nice little write-up. I am looking forward to seeing the iron. In my experience, iron is a bit more fickle. There are more oxides and hydroxides to work around and keeping control of the oxidation state is harder. Red, blue, orange, yellow, light green, black and brown seem to have obvious candidates but I m not sure what you might choose for the violet. A deep green might require some thought also.

Quote: Originally posted by Ozone

Ferrous sulfate is a nice (albeit light) green.