How can i get a copper carbonate precipitate instead of a blue gel?

[Charles97]

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[Kenneth_M]

I’m trying to precipitate copper carbonate from a solution of copper sulfate and sodium carbonate, but my product keeps coming out as this loose, fluffy blue gel instead of the solid powder I expected. I’m following the basic double displacement reaction, but something about the concentrations or the mixing order must be off.

[NicholasHG]

That blue gel is Cu(OH)2 or a basic copper carbonate, not a nice dry CuCO3 powder. In practice the moment you splash carbonate in you raise the pH and the precipitate forms as a fluffy gel. The fix is to control supersaturation: add carbonate slowly with stirring, keep the batch cold, and don’t let it sit and age. Then filter quickly, wash with cold water to remove sodium sulfate, and dry the solid gently at a low temperature. Sometimes you’ll still get a fluffy product, not a true powder.

[David_B]

I’ve seen the same thing. A quick dump of carbonate gave a blue slime. Filtering helped a bit, but the solid would crumble to a powdery film instead of a neat crystalline solid. It didn’t look like textbook copper carbonate.

[Justin_H]

From what I saw, copper carbonate isn’t stable in water anyway; you mostly end up with a basic carbonate or copper hydroxide. The “powder” you want may just be a metastable gel that hardens only after removing all the water slowly.

[Robert_H]

Do you observe CO2 bubbling or a rapid rise in pH as you add the carbonate?

[Violet_S]

I experimented by warming a bit and stirring a lot; the gel turned a bit more brittle when it cooled, but it still never turned into a clean powder. The temperature tweak changed the color a touch but not the fundamental form.

[Ryan19]

Another observation: washing the precipitate with deionized water helps remove the sodium and sulfate, but if you over-wash you disperse the material into a fine slurry again. Grinding it gently after filtration sometimes yields a coarser, more powdery feel, but you risk breaking up any basic carbonate into smaller particles.

[Anthony.T]

Sometimes the result is simply a basic copper carbonate rather than true copper carbonate; trying to 'crystalize' from this aqueous route is hard. If you want a stable solid, you might need to alter the chemistry (buffering, different reagents) or accept that you’re making a bluish powdery material that’s not the pure salt.