Sciencemadness Discussion Board

Separation of copper nitrate from mixture

CNMobile10086 - 24-1-2022 at 20:54

I had some dilute homemade copper nitrate solution, it has already crystallized quite a bit but i somehow poured it on a drying dish for somereason. It seems that the water has stopped evaporating but it is still all wet and acidic(pH2-3 probably due to excess nitricacid) . I tried drying a bit of it under sunlight but the copper nitrate decomposed unfortunately. Is there a possible way to somehow separate the Cu(NO3)2 from the mixture?

Rainwater - 25-1-2022 at 09:02

It will absorb water from the air. Using a desiccator bag will help.

If your original compount was pure, you can react your mixture with HNO3 to convert it all back to copper nitrate.
Then, heat the solution to 120c to remove the remaining nitric acid.
If you heat it under a vacuum, you can obtain a very dry sample,[edit. Next statement is incorrect] if not completely anhydrous
Be very careful with temperature control, or it will decompose again.

[Edited on 26-1-2022 by Rainwater]

woelen - 25-1-2022 at 13:45

You cannot make it anhydrous, not even in vacuum, at least not with decomposition and formation of basic compounds.

Anhydrous copper nitrate was not prepared before the 1960's. This was made by dissolving copper in a mix of nitrogen dioxide and ethyl acetate and then allowing the solvent and excess NO2 to evaporate, leaving copper nitrate with NO2 of crystallization behind, which on careful heating can be decomposed, to leave anhydrous Cu(NO3)2 behind.

Rainwater - 26-1-2022 at 17:56

Would pure(ish 95% or better) hno3 form an azeotropic mix with the bonded water and be able to remove it by distillation?
I need a break from watching electrodes plate. Might be worth trying

AJKOER - 2-2-2022 at 18:17

Here is a path but it really should be performed only in micro-amounts due to possible explosion hazard. Also note, even if successful a few times, this does not remove the issue of explosion for the next time.

Basically, follow prep path to tetra-amine copper nitrate. I will not cite prep further here as it is an energetic compound, especially upon using alcohol to isolate a non-hydrated form of the compound.

Like many amine salts, mild heating will liberate the NH3. The question here is this actually a successful path and further, is it even possible in a safe manner (as spread out over a flat open disk)?

In any event, I want to impress on you that contaminants presence (perhaps even unknown) associated with your attempts at drying to create Cu(NO3)2 may incidentally create other such related energetics (so, assume you may have an energetic).

As such, I recommend working with small amounts and install proper safety measures.

[Edited on 3-2-2022 by AJKOER]

B(a)P - 2-2-2022 at 18:36

I have previously prepared copper nitrate hexahydrate (not 100% sure it was hexahydrate, that was my guess).
Just looking back at my notes and it took over a month to dry. I left it in a desiccator bag with NaOH.