07-25-03 10:02
No 449737
Practical Organic Chemistry
A. Vogel, 3rd Ed., pg. 192 :
Copper Powder
100g of recrystallized CuSO4 are dissolved in 350ml hot water in a 1l beaker; a mechanical stirrer is provided. After cooling to room temperature, the stirrer is set in motion and 35g (or more if necessary) of high grade Zn powder are gradually added until the solution is decolourized.
The precipitated Cu is washed by decantation with water. Dilute HCl (5%) is added to the precipitate in order to remove excess Zn, and stirring is continued until the evolution of H2 ceases.
The Cu powder is filtered, washed with water, and kept in a moist condition (as a paste) in a stoppered bottle.
Mountain Boy
(Hive Addict)
07-25-03 10:19
No 449740
Al foil would do the same thing, wouldn't it?
It is seductive, way too seductive. -Eleusis
(Hive Bee)
07-25-03 10:21
No 449743
The above prep of Cu powder requires good quality Zn powder. Now Zn powder may not seem particularly expensive or hard to get, but the last time I ordered some I had to fill in an end use declaration form, requiring information I was not happy to part with.
So rather than subject myself to further scrutiny I'm thinking of making Cu powder electochemically (i.e. a non-Zn method):
With a battery, using copper wire as electrodes in a CuSO4/H2SO4 soln, the anode should corrode away and Cu powder should be formed at the cathode. I suspect that this process would actually make a purer Cu than the Zn method, but I'm not sure.
Mountain Boy
(Daddy)
07-25-03 12:41
No 449751
intended to do what, with your pure Cu powder? LT/
WISDOMwillWIN
(Hive Bee)
07-25-03 14:14
No 449759
El_Zorro:
If I understand electrochem properely then you are right :
Cu(2+) + 2e- __> Cu E° = 0.34 V
Zn __> Zn(2+) + 2e- E° = 0.76 V
Al __> Al(3+) + 3e- E° = 1.66 V
I guess the Al would have to be washed with something like H2SO4 first, to remove the oxide layer.
LT:
I need it for hydoxyvanillin from bromovanillin synthesis.
( ../rhodium /mmda.me
I have tried once with CuSO4 with no success and although I don't really think this was the reason, next time I would like to deviate as little as possible from the procedure described.
Mountain Boy
(Hive Addict)
07-25-03 14:27
No 449760
in my neck of the woods, painters need Cu-powder.
(no idea about purity though)
(Hive Bee)
07-25-03 14:50
No 449763
mg> i think you need to amalgate you'r Al to get it to work. Simply washing it with dilute acid won't work. It'll form the oxide layer in zero time again.
Size doesn't matter, it's the sound you make when hitting the ground after smoking it, that matters!
(Hive Addict)
07-25-03 18:59
No 449790
I know that adding Al foil without any kind of cleanup to a solution of copper made with aqua regia will precipitate the copper as a powder, I've done it myself.
It is seductive, way too seductive. -Eleusis
(Hive Bee)
07-26-03 00:39
No 449832
There is a technique called "electroforming" which is based upon electroplating and uses the same equipment.
For example, let's say one wanted to recreate the beauty of a Sassafras leaf in 24 karat gold. One need only acquire a beautiful specimen of such a leaf and coat it in a pure copper/lacquer coating made by combining as much ultra pure copper power (as fine as can be)in the minimum amout of lacquer which allows smooth paintability and total conductivity.
Once the lacquer/copper coating is dry and an electrode has been affixed (cathode if memory serves), the resulting "armature" is slowly electroplated with the desired metal until a thick coating of metal has been deposited, essentially reproducing the underlying object in your metal of choice.
There may have been better than usual specs on the plating power supply to prevent a surface covered with random nodules of metal. Those are inevitable to some degree and may need to be polished out.
But anyway, that's one absolute need for very pure powdered copper. It's a fun way to make things too, and you would probably have enough left over for any other hobbies you might wish to persue.
Very pure powdered zinc would behave similarly but I have no such experience.
(Hive Bee)
07-26-03 16:07
No 449959
You can use plain iron as powder or wool to precipiate the copper as metal from a CuSO4 solution.
But if zinc or iron is used you always have to face the so called cementation of the copper - no fine metal powder but a kind of sintered stuff results from this. (if not a substrate is added to precipiate the copper onto). For copper metal powder it is much more conveniant to precipiate Cu(OH) with KOH from the CuSO4 to dehydrate this to CuO by drying and heating and reduce the copper with hydrogen or ammonia to the metalpowder:
Copper(II) hydroxide --> Copper(II) oxide + water
Cu(OH)2 --> CuO + H2O
followed by reduction
(Hive Bee)
07-28-03 14:36
No 450368
The cent seems to depend largely on when,
http://www.usmint.gov/about_the_mint/fun
(Official Hive Translator)
07-28-03 16:38
No 450390
Hey, people, c'mon!
Noone wants that Cu powder in Br-vanillin hydrolysis, cause CuO (made in situ from CuSO4) will work none worse (actually, better). This comes from both Uemura's experience and that Japanese patent (in TFSE).
And of course, Al foil will work to make Cu powder just fine, without any prior acid washes - just make sure you add a coupla tablespoons of tablesalt into the rxn ((CuCl4)2-, y'know)
Antoncho
(Hive Bee)
07-29-03 10:50
No 450529
1
I must apologize
, this has been discussed before Post 437037 (Organikum: "precipating of copper", Chemicals & Equipment). Dunno how I didn't find it when I originally used TFSE.
2
Added a steel dishwashing scrubbing pad to CuSO4 soln. It warmed up and copper was pptd almost immediately. Useful to know.
Thanks Ragnaroekk.
3
Antoncho: "Noone wants that Cu powder in Br-vanillin hydrolysis, cause CuO (made in situ from CuSO4) will work none worse (actually, better). This comes from both Uemura's experience and that Japanese patent (in TFSE)."
* As I said before, I doubt if my failure was related to the catalyst, but I thought that next time maybe I should work strictly according to Patent US3855306 so that if it still doesn't work it's easier to guess why.
* In ../rhodium /iodovan
'Example 3 was also repeated using from 5 to 10 mole % of cuprous oxide, cuprous chloride, cuprous iodide and copper dust, as the catalyst for conversion of the iodovanillin to hydroxyvanillin. Recovery of 5-hydroxyvanillin was 80-85% (remainder vanillin) with copper dust, from 70-80% with the copper oxide or salts.'
This suggests that the Cu powder may be a little more effective ?
* For some reason I can't find the Jap patent you're referring to, but then we've already established that I need to improve my FSE skills (not to mention chemistry).
4
Antoncho: "Gos`h!", "Hey, people, c'mon!", "And of course"
This is why you are moderator,
and I, a mere participator.
Mountain Boy
(Hive Adickt)
07-29-03 11:29
No 450531
'Example 3 was also repeated using from 5 to 10 mole % of cuprous oxide, cuprous chloride, cuprous iodide and copper dust, as the catalyst for conversion of the iodovanillin to hydroxyvanillin. Recovery of 5-hydroxyvanillin was 80-85% (remainder vanillin) with copper dust, from 70-80% with the copper oxide or salts.'
This suggests that the Cu powder may be a little more effective ?
Hi Mountain_Girl, good to see you'r still working :-)
I don't think that Cu powder is more reactive than Cu(I)Cl (or bromide or iodide). There is a nice synt on Cu(I)Br in vogel. Usual you get diff. yeald from time to time with the same eksperiment.
xxx
Hest
(Active Asperger Archivist)
07-30-03 19:13
No 450724
The effectiveness has to take into account yields and mole % used for catalyst. (or simply the ratio between the two as compared with the same from another reaction).
You are correct though. But why go the extra step in catalyst preparation for such a small change in yield when everything is so cheap to obtain?
Act quickly or not at all.
(Hive Bee)
07-31-03 12:17
No 450858
Hest:
Never really stopped working
In recent times my productivity dropped drastically due to the distraction of my S.O.
I actually have CuBr which I may one day use for the synth of syringaldehyde if I can get my hands on some DMF.
Aurelius:
I agree, which is why I'll probably just stick to CuSO4.
Mountain Boy