Sciencemadness Discussion Board - Copper oxide

Copper oxide

Dragonjack12 - 25-12-2018 at 19:21

Does anyone have a good synthesis of copper oxide besides heating up copper metal.

ninhydric1 - 25-12-2018 at 20:00

Copper(I) oxide or copper(II) oxide?

Copper(II) oxide is relatively simple. Get a soluble copper(II) salt, precipitate with hydroxide or carbonate ions, filter off the precipitate, then heat the precipitate to decomposition. There's residue is your CuO.

Copper(I) oxide is slightly more tricky. Get a soluble copper(II) salt and make it slightly alkaline with Rochelle salt (Na-K tartrate). Then add a reducing sugar such as glucose to the solution and heat it up. A reddish-oxide should precipitate. That's your Cu2O. This is the basis of the Fehling's test of aldehyde/ketone functional groups.

Dragonjack12 - 25-12-2018 at 20:04

Thank you. it was Cu(l) oxide but Cu(ll) oxide could be usefull as well...

Ubya - 26-12-2018 at 10:54

for the Cu (II) oxide you don't even need to filter firstif you precipitate the hydroxide (colloids are a PITA to filter), by just boiling the solution you'll get the oxide, filtration is now fast and easy

Fulmen - 26-12-2018 at 12:33

That has not been the case in my experiments. Gels tend to produce extremely fine particles, to the point that it become impossible to filter. I'm talking of batches in the 0,1-1kg here, not a single 1g synth. In any practical concentration it is also hard to boil, expect extreme bumping. I once broke a 2l beaker full with CuO this way, the bumping lifted the beaker almost a cm in the air. That was a mess like you wouldn't believe...

Starting from copper metal there is a very elegant route available. In addition to being cheap and simple it can also produce CuO free from metal impurities. It produces a much denser precipitate that filters like a dream. This is also beneficial for use in pyrotechnics where very fine powders can cause problems.

The copper is leached with a mixture of ammonia and ammonium carbonate, using atmospheric oxygen as the oxidizer. It's fairly slow, but it can be run unattended for days and even weeks except for refilling water. The copper will be present as an ammonia-carbonate complex, which breaks down with boiling to basic copper carbonate (malachite, Cu₂CO₃(OH)₂) and ammonia. Further heating will produce the oxide.

The liquid is recycled with more ammonia, if the released ammonia is recycled the reaction is in theory lossless, consuming only air and water.

Felab - 30-12-2018 at 04:18

Cu(I) oxide can also be prepared by adding ascorbic acid to copper hydroxide in the right amount. The Thought Empiorum has a great video on this synthesis: https://www.youtube.com/watch?v=cLy8iVLvoRk&t=18s

DraconicAcid - 3-1-2019 at 10:57

Quote: Originally posted by Fulmen

That has not been the case in my experiments. Gels tend to produce extremely fine particles, to the point that it become impossible to filter. I'm talking of batches in the 0,1-1kg here, not a single 1g synth. In any practical concentration it is also hard to boil, expect extreme bumping. I once broke a 2l beaker full with CuO this way, the bumping lifted the beaker almost a cm in the air. That was a mess like you wouldn't believe...

I can believe the mess. If you have a large excess of hydroxide in solution, you don't need to boil it- just get it hot.

lordcookies24 - 3-1-2019 at 11:02

fusso - 3-1-2019 at 11:34

Quote: Originally posted by lordcookies24

What's the source for this?

Fulmen - 3-1-2019 at 12:30

Draconic: You're right. Heating is enough to convert the hydroxide to oxide, at least with an excess NaOH. But it doesn't solve the problems with filtration. Any time you have an instant precipitation of insoluble matter it ends up clogging filters. Industrially I've seen this solved by using flocculants, large settling trays, revolving vacuum filters and a big-ass rotary kiln.
But for "large small-scale" it's very tedious work. It's fine for a one-off small synth, but if you're planning to produce it in larger quantities these things begin to matter.

DraconicAcid - 3-1-2019 at 13:15

True. I haven't done it in large quantities, but the supernatant is far easier to decant from the oxide than from the hydroxide. Perhaps washing and decanting a few times would clear off the other products enough that you could then add acetone and filter that? Acetone helps it turn from a goop to an actual solid.

TheDude - 31-1-2019 at 17:15

Quote: Originally posted by Fulmen

But for "large small-scale" it's very tedious work. It's fine for a one-off small synth, but if you're planning to produce it in larger quantities these things begin to matter.

I really wish I had thought about this before I went for 3 moles of it. Oh well, I learned a valuable lesson, problems of scale are definitely a thing.

Amos - 31-1-2019 at 19:31

If basic copper carbonate is reacted with citric acid in solution to generate first the tribasic, insoluble salt and then more citric acid to generate the soluble dihydrogen citrate complex (a stunning deep blue, by the way) and then boiled for a time, copper(I) oxide forms first as a yellow hydrated form and then upon further heating decomposes(or perhaps just forms larger particles) to give bright red particles of Cu2O that are easily filtered. The only sources I have are videos though.

https://www.youtube.com/watch?v=Mr9MjdTEIw0

Alternatively, copper(II) sulfate solution can be treated with excess ascorbic acid solution, heated, and copper metal powder will form. The yellow supernatant that remains can be treated with base to form an incredibly fine precipitate of hydrated cuprous oxide that slips right through filter papers. This, again, turns red and forms larger particles on boiling. I've never tried using already neutralized asorbic acid solution but I have a feeling the first step of generating the copper powder can be skipped. I think woelen's site has a demo that produces the yellow solution directly.

[Edited on 2-1-2019 by Amos]

RogueRose - 31-1-2019 at 22:09

I found a really easy way to make CuO. I used copper wire (more surface area) and added bleach (12.5% pool shock) this will make CuO but it is a little slow and if you add just a little bit of H2SO4 to act as a catalyst (I used about 5ml of 30% with 1/2 gallon of bleach). It will heat up with the acid, nothing major but it will bet hotter than "warm".

Now there seems to be a fine line between a blue-green precipitate (hydroxide) and a black precip and it seems like adding more acid tends to push towards the blue-green. The blue-green will decompose to black when I baked it in the oven and it also seems to turn to the oxide by adding bleach (after the acid/salt water is drained from the precipitate)

I think this will work with calcium hypochlorite. If you need inexpensive hypochlorite, I've found pool stores sell it by the gallon, 5 gal, 15 gal (drum), all for less than $2/gal of 12.5% (I've seen the gallons go for less than this). Also check feed & farm stores, they often have strong bleach for cleaning equipment.

j_sum1 - 31-1-2019 at 22:15

Thanks RR. I have tens of kilograms of copper wiring waiting for me to strip. I might merely shred and do some bucket chemistry via this procedure. Even if it takes a while I will end up with a useful reagent and a tidier shed.