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Registered Member #396
Joined: Wed Apr 19 2006, 12:55AM
Location: Pittsburgh, PA
Posts: 176
Now that I've obtained a reliable source of copper sulfate (Root killer for drains). I'd like to synthesize some copper (II) oxide (and later copper (II) chloride but that can be done fairly easily with HCl), mainly for flame coloring. From what I understand these are both superior to CuSO4 in this regard.
From what I understand I have two options:
1) Heat the (anhydrous) CuSO4 to 650C, which will release sulfur trioxide (would this decompose to dioxide at all?) leaving CuO. I have this exact kiln:
My concerns are the fairly large amounts of SO3 produced. For every mole of CuSO4, 1 mole of SO3 will need to be driven off. If I do this in 200g batches, I will need to disperse 100g, or more than 30 liters at room temperature and pressure. Obviously this would be done outside, and the kiln door cracked open, but my concerns are that the highly corrosive/reactive SO3 (or the H2SO4 from water vapor in the air) will essentially destroy my kiln or more specifically its glowing-hot heating elements.
2) Add solid NaOH to a concentrated solution of CuSO4 (carefully of course), then boil the resulting CuOH solution to form CuO and Na2SO4, which is water soluble so can be filtered out. This whole method consume NaOH, require boiling a caustic solution, and then filtering and drying the product, although this method still seems simpler/safer.
Any opinions or insight? Or even other project ideas for this practically free *score* kiln (just need to clean it up and replace one heating element)?
Registered Member #193
Joined: Fri Feb 17 2006, 07:04AM
Location: sheffield
Posts: 1022
SO3 may well kill the lin which would be a pity. If you don't want to use NaOH you could use Na2CO3. That would precipitate CuCO3. You could then heat this to turn it into the oxide but you could also, after washing it to remove sulphate, just dissolve it in HCl. (it will foam like anything). Heating the carbonate to give the oxide might help because the oxide will probably be more crystaline and will filter more easily. That makes it easier to wash free of, for example, Na.
In my experinece CuCl2 is as hygroscopic as anything, which might be a problem for pyrotechnics.
Registered Member #1497
Joined: Thu May 22 2008, 05:24AM
Location: Toronto, Ontario, Canada
Posts: 801
After having used the NaOH process to turn CuCl2 into CuO after drying and baking, I would recommend the NaOH method. CuO is a thick black paste which is hard to filter, however if you can do vacuum filtration, or use a large enough container of water to exchange and wash out the sodium salts, it should work out just fine. Only one batch of my CuO had NaCl remaining in it and even then it wasn't all too appreciable.
Keep in mind that you will get clumpy CuO and it stains surfaces easily.
Registered Member #396
Joined: Wed Apr 19 2006, 12:55AM
Location: Pittsburgh, PA
Posts: 176
Bored Chemist wrote ...
SO3 may well kill the lin which would be a pity. If you don't want to use NaOH you could use Na2CO3. That would precipitate CuCO3. Heating the carbonate to give the oxide might help because the oxide will probably be more crystaline and will filter more easily. That makes it easier to wash free of, for example, Na.
In my experinece CuCl2 is as hygroscopic as anything, which might be a problem for pyrotechnics.
Thanks for the info - today I tried the Na2CO3 method on a small scale - I obtained a suspension of CuCO3, then boiled it. From what I understand this could be Cu2CO3(OH)2? It turned a grey color, and after all of the water had evaporated, it was black, but a flame test only revelealed orange/yellow from the NaSO4 I assume. This probably had something to do with the fact that I only diluted and decanted the solution a few times instead of filtering it (I'd like to find the guy that decided it was a good idea to put a seam in the middle of the coffee filters I have . . .).
My real question is at what temperature does Cu2CO3 decompose? I can't seem to find it anywhere - is boiling enough or does it need kiln temps?
I will also try the NaOH reaction when I find some time.
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Production of Copper Oxide
