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The Volatile Chemist
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Copper Carbonate production Problem
I made a whole lot of Copper carbonate from 65g of CuSO4 a few days ago. I ended having to do the reaction twice and divide the CuSO4 up, so it would
fit in my largest vessels. The first half went great, and made a wonderfully large cake of CuCO3 in my brand new vac. filtration set. The second run
appeared to go well too, but I had to add reagents to the vessel after filtering a first time, to get more CuCO3 to precipitate. Upon dumping the
second 'cake' into a container I was going to use to let them dry in, the second one broke apart into a slightly soupy mess. But, there was a strange
green compound, much deeper, not teal, than the copper carbonate, left on the very bottom of the cake, where the filter paper was. I assume it was
some hydroxide. I left it last night to dry the whole mass. When I came back from work at noon today, it was all soupy, the first cake now soppy, and
the entire thing had that weird green color. I salvaged the soupy mess into a beaker, and let it sit. There's probably ~50mL water in there, along
with the green compound. There's only tiny traces of teal colored CuCO3 left. What the heck happened?
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aga
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Eeeek !
You didn't say 'Basic Copper Carbonate'
Blogfast25 is gonna bite you.
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blogfast25
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Nah. Let fools who believe in "CuCO3" be. I is so tired of this stupidity.
Zzzzzzzz....
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Bot0nist
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Cu<sub>2</sub>(OH)<sub>2</sub>CO<sub>3</sub>, rather?
"CuCO<sub>3</sub> is not known to occur..."
Holleman, A. F.; Wiberg, E. (2001),Inorganic Chemistry, San Diego: Academic Press, p. 1263, ISBN 0-12-352651-5
[Edited on 17-7-2015 by Bot0nist]
U.T.F.S.E. and learn the joys of autodidacticism!
Don't judge each day only by the harvest you reap, but also by the seeds you sow.
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careysub
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I am not sure about what you observed, but I was working with basic copper carbonate right now and do have a bit of advice - do not heat it up at all
to dry it. I read that it decomposes to CuO at 200 C, and thought it would be safe to dry it at 170 F (77 C). Nope - quite a lot of very black CuO
formed.
In addition to the teal malachite form of copper carbonate, I did find some portions of my cake turned the beautiful deep blue of azurite.
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blogfast25
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Quote: Originally posted by careysub  | I am not sure about what you observed, but I was working with basic copper carbonate right now and do have a bit of advice - do not heat it up at all
to dry it. I read that it decomposes to CuO at 200 C, and thought it would be safe to dry it at 170 F (77 C). Nope - quite a lot of very black CuO
formed.
In addition to the teal malachite form of copper carbonate, I did find some portions of my cake turned the beautiful deep blue of azurite.
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Tell me what quantities you used.
I've made basic copper carbonate several times and there's no reason for free Cu(OH)2 to form (that's what you're CuO comes from).
Basic copper carbonate indeed resists 200 C easily. Personal experience, that. It's easy to dry and can be bought as a dry powder easily.
[Edited on 17-7-2015 by blogfast25]
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Amos
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If anyone cares to know, I may have found the best way to make basic copper carbonate (I just call it copper carbonate, since there's no such thing as
CuCO3) quickly and easily. Just pour dilute sodium carbonate solution into an excess of BOILING copper(II) sulfate solution with magnetic stirring.
The effervescence subsides almost immediately, without any difficult foaming and a uniformly-colored pale green precipitate with large particles
forms. It settles almost immediately, and is a breeze to wash and dry.
TVC, give us some pictures of your weird green precipitate, please.
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aga
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That sounds like a very do-able reaction Amos.
Thanks.
Edit :
Maybe it's CuCO3.HHO
(runs for shelter ...)
[Edited on 17-7-2015 by aga]
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blogfast25
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Which merely adds to the confusion already surrounding copper basic carbonate.
Whatever.
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aga
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(phew ! this shelter is working really well)
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Amos
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Sorry, bloggy.
But, do you always say copper(II) sulfate pentahydrate? Or refer to chrome alum as potassium chromium(III) sulfate dodecahydrate? Some things are
almost immediately recognizable from simple names because there's not much else they could be referring to. Besides, anyone that has bothered to
google the compound before making/using it should know of the formula.
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blogfast25
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Amos:
The problem here is that copper basic carbonate and copper carbonate are two entirely separate things, with the latter something that cannot be
synthesised in watery conditions.
Your argument is one FOR scientific inaccuracy. Decent papers will indeed specify compounds used completely or use 'henceforth referred to as ...' to
simplify reading.
CuSO4 and CuSO4.5H2O are separate compounds, whether you like it or not. They are best referred to as such, to be unequivocal.
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careysub
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| Quote: Originally posted by blogfast25 | | Quote: Originally posted by careysub | I am not sure about what you observed, but I was working with basic copper carbonate right now and do have a bit of advice - do not heat it up at all
to dry it. I read that it decomposes to CuO at 200 C, and thought it would be safe to dry it at 170 F (77 C). Nope - quite a lot of very black CuO
formed.
In addition to the teal malachite form of copper carbonate, I did find some portions of my cake turned the beautiful deep blue of azurite.
|
Tell me what quantities you used.
I've made basic copper carbonate several times and there's no reason for free Cu(OH)2 to form (that's what you're CuO comes from).
Basic copper carbonate indeed resists 200 C easily. Personal experience, that. It's easy to dry and can be bought as a dry powder easily.
[Edited on 17-7-2015 by blogfast25] |
Thanks for the information - now I understand better what is going on.
I don't know the exact proportions as this was an off-the-cuff attempt to reuse potassium carbonate that had been used to dehydrate ethanol.
Rather than discard the watery carbonate (I does not seem to ever dry) I had the thought of trying to use it to make something and guesstimated the
amount of copper sulfate to add since I could not weigh the K2CO3. I guess that I used an excess of copper sulfate.
I'll have another go at this with fresh clean reagents and known ratios.
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blogfast25
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careysub:
Try and keep the concentrations of reagents quite low (about 1 M) and stir intensely when mixing.
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IrC
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"The compound Copper(II) carbonate CuCO3 is not known to occur naturally. There is a report in 1973 of the production of CuCO3 from CuO or
Cu3(CO3)2(OH)2 in the presence of carbon dioxide at 500 °C and 20 kb (2 GPa) pressure. What is often called copper(II) carbonate or cupric carbonate
is actually basic copper carbonate."
Seidel, H.; Ehrhardt, H.; Viswanathan, K.; Johannes, W. (1974). "Darstellung, Struktur und Eigenschaften von Kupfer(II)-Carbonat". Zeitschrift fur
anorganische und allgemeine Chemie 410 (2): 138–148. doi:10.1002/zaac.19744100207. ISSN 0044-2313.
https://www.worldcat.org/issn/0044-2313
https://en.wikipedia.org/wiki/Basic_copper_carbonate
"Science is the belief in the ignorance of the experts" Richard Feynman
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blogfast25
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| Quote: Originally posted by IrC | There is a report in 1973 of the production of CuCO3 from CuO or Cu3(CO3)2(OH)2 in the presence of carbon dioxide at 500 °C and 20 kb (2 GPa)
pressure. What is often called copper(II) carbonate or cupric carbonate is actually basic copper carbonate."
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Cu<sub>3</sub>(CO<sub>3</sub> <sub>2</sub>(OH)<sub>2</sub> is the other basic copper carbonate, the rare mineral Azurite, which is metastable and over
time pseudomorphs into Malachite.
https://en.wikipedia.org/wiki/Azurite
[Edited on 19-7-2015 by blogfast25]
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IrC
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Yes I know. But they made CuCO3 from it so the point remains the same that evidence exists that CuCO3 has existed, if only in the laboratory during
their experiments.
"Science is the belief in the ignorance of the experts" Richard Feynman
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aga
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Pseudomorphs ?
What's that mean ?
It changes, but not really ?
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blogfast25
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aga:
https://en.wikipedia.org/wiki/Pseudomorph
In the case of Azurite it loses CO2 and converts (slowly) to Malachite. Azurite is said to be 'metastable'.
3 3CuCO3.Cu(OH)2 + 2 H2O === > 4 2CuCO3.Cu(OH)2 + CO2
Azurite ====== weathering =====> Malachite
See pseudomorphing in (slow!) action here, the samples that contain both blue (Azurite) and green (Malachite):
https://www.google.co.uk/search?q=azurite&rls=com.micros...
IrC: I'd still like to have proof of that CuCO3 synthesis, all we have is a reference really. I'm not claiming it's impossible, though.
[Edited on 20-7-2015 by blogfast25]
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IrC
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So would I but that was all I could find. I saw it by accident on that page linked earlier and decided to search further. No luck. I have learned over
time that many things not thought to exist have been created with the common factor being incredible pressures. While geology isn't my strongest area
it seems that 2 Gpa or higher with the right other chemicals in proximity has likely occurred inside the earth at some time in the past so maybe it is
possible that somewhere CuCO3 has existed (maybe unstable - decomposing at lower pressures?). With only the one reference one would wonder was it not
reproducible, or just a lack of interest by others prevented further study? One thing I have learned however is few spend the time and resources
trying to create something they already believe is not possible. The number of things found (usually by accident) which convention says cannot be,
should indicate a paradigm shift is in order. Think of all the impossible things we would already have if preconceived prejudice had not prevented
experimentation along those lines. Examples abound through history. Imagine how many would have discovered the new world sooner had they not been in
terror of falling off the earth.
http://physics.aps.org/browse/
I like reading articles on sites such as this since over time there have been many articles on new discoveries previously thought not possible. Seems
a common block in science, which started advancing rapidly in the Victorian era compared with say the 1500's. I believe much was discovered in little
time by people doing things no one had told them is impossible. The more they started believing in the impossibility of things the slower science
advances became. In the 60's warp drive was not taken seriously by mainstream science ( the it's not possible mindset), thus no experimentation was
done along those lines. Along comes a brilliant mind from Mexico showing them it can be possible and you have NASA suddenly doing all kinds of
research on it.
"Science is the belief in the ignorance of the experts" Richard Feynman
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blogfast25
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There is no a priori reason why a 'straight' CuCO3 could not exist. What we know is that in aqueous synthesis the double salt
(carbonate.hydroxide, i.e. Malachite) precipitates out. In the absence of water, direct union of CuO and CO2 could be possible, pressure being
obviously the potential driving force.
[Edited on 20-7-2015 by blogfast25]
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The Volatile Chemist
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Wow, what an explosion.... sorry, I'd just never been educated on 'basic copper carbonate'. I assume the 'green stuff' was copper(II) hydroxide,
though I have no clue how it 'pseudomorphed' so quickly, if that's what it is. picture at
ptp.x10.mx/PTDC0349.JPG
Anyways, I guess it'll work for my purposes. I just made it to make lots of Cu(OAc)2 and CuCl2
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aga
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*If* it were do-able, how would one know that CuCO3 were in fact extant in a product ?
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blogfast25
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Measuring CO2 content (easy to do) would distinguish it from a basic carbonate.
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aga
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Easy for some maybe.
I find that molecule counting requires my extra-thick-lens glasses, and they are quite heavy.
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