Sciencemadness Discussion Board - Pyrophoric copper: How?

Pyrophoric copper: How?

mayko - 10-4-2013 at 18:12

I have been trying to make pyrophoric copper; it seems like the green color of burning copper particles would be visually striking, especially if used to ignite a mixture of boric acid and methanol.

Unfortunately, I haven't had any success with the route most obvious to me, the decomposition of copper oxalate in an inert atmosphere. I have prepared pyrophoric manganese, iron, and cobalt this way, so it seems reasonable to expect copper to behave similarly. However, although this procedure does seem to produce copper, it isn't pyrophoric.

Has anyone made pyrophoric copper? A search of the forums revealed this blurb in the short questions thread; the opinion seems to be that this approach is plausible, and mentions creating pyrophoric copper by decomposing copper acetate, but I can't find the thread it references.

The copper oxalate was prepared by reacting copper sulfate with oxalic acid in solution, and washing the resulting precipitate with fresh water and decanting until the pH was neutral (an early attempt was unwashed; this wound up being very clumpy). The resulting paste was warmed on a hot plate to evaporate off water; once dry, it was ground into a fine robin's egg blue powder.

A scoopful of the oxalate was put in a test tube. CO2 was generated by mixing vinegar and baking soda in a beaker and pouring the gas into the test tube. The tube was heated with a propane torch, guiding condensed water up and out as it was released from the oxalate. Once no more gas was observed coming from the powder, the tube was turned over and the powder poured out. No pyrophoricity was observed.

Mixell - 10-4-2013 at 18:56

As I've said in the above mentioned thread, he used copper acetate.
The effect may not visible in an illuminated environment, so try to see if your freshly prepared copper is visibly burning in the dark. Also, the temperature may affect particle size, so you can try lowering or increasing it (not sure what is necessary in this case).

Morgan - 10-4-2013 at 20:01

Maybe experiment 268 would work for you.
http://books.google.com/books?id=dQpDAAAAIAAJ&pg=PA236&a...

I've only done the iron oxalate and some 1% Pt on alumina powder sprinkled into a flask containing methanol. I was watching the tiniest bit of dust fall through the alcohol vapor making these red flecks of light in the liter flask and even though I was expecting it, the sudden whoosh from the Erlenmeyer flask up close startled me so much I "dropped" the flask on my back porch breaking it.
Very thin copper wire that is coiled and heated will sustain a dull red glow with methanol vapor and air.
Here's that Pt powder I used. I used to fire boric acid laced methanol out of a intubated steel canister, the tube/pipe just off the bottom of the canister. With a tablespoon of methanol in the bottom and ignition of the vapor from the top of the tube/flush with the lid, it would aspirate/launch a green fire ring or torus that grew to 6 feet or more 10 feet above you and made a beautiful short-lived swirl of green light. Several friends really liked it. The flame front travels down the tube, igniting the vapor in the canister and all the hot gases and methanol shoot out the top creating the expanding torus.
What I tried to do which didn't work was to put some of the Pt dust in with the methanol, boric acid and form a flammable vapor ring, which when the particles swirled and dried in the air, ignition of the vortex would have occurred/that was the plan at a respectable distance from the launcher, somehow seemingly out of nowhere. Even when just methanol and boric acid was launched from my fire ring shooter, the green flame or any light would not become apparent until the ring grew to three feet or so. You had to do it at night, but it looked very pretty, and all from a pint-sized vessel.
My Pt on alumina at room temperature igniting methanol
http://www.youtube.com/watch?v=h3lS3TBuntw

As an aside the way I discovered the fire ring effect was when I was toying with Reynst jam jars trying to see how they would run with a tube partly inside the jar. On evening in the garage I did just that with the tube almost all the way to the bottom. When I lit it, it fired a ringed vortex of burning alcohol and the next thing I knew my ceiling was on fire for a brief few tense seconds before it burned out.

Pok - 11-4-2013 at 04:08

Try copper citrate (see image below)

How did you make pyrophoric manganese? Also oxalate? It isn't mentioned in this table. But iron oxalate isn't mentioned as well, which indeed is pyrophoric.

BTW: pyrophoric lead can be made from the tartrate (own expierience based on some literature).

mayko - 11-4-2013 at 20:21

Quote: Originally posted by Pok

How did you make pyrophoric manganese? Also oxalate? It isn't mentioned in this table. But iron oxalate isn't mentioned as well, which indeed is pyrophoric.

BTW: pyrophoric lead can be made from the tartrate (own expierience based on some literature).

The manganese was indeed made from the oxalate.

Pyrophoric lead sounds cool, but also a bit toxic. I had the same reservations about nickel >.>

Can citrates and tartrates be prepared from a similar replacement reaction as with the oxalate?

Pok - 12-4-2013 at 01:04

With copper citrate it should work. It is almost insoluble in water as far as I know. I'm not sure about other heavy metal citrates, but expect that these are insoluble. The same for the tartrates.

Pyrophoric lead indeed is problematic. While burning it emits dense fumes of lead oxides (really toxic if inhalated). How to make it: here.

[Edited on 12-4-2013 by Pok]

kristofvagyok - 12-4-2013 at 14:07

Long ago I made some ultra fine copper powder from copper(II)-oxide and hydrogen at 400 Celsius. The produced shiny copper powder rapidly oxidized back at even lower temperatures (100-200 Celsius) with a iridescent oxide layer. It looked like this:

If I would like to make pyrophoric copper, than I would choose this method, it produces much more smaller particles of elemental copper and there is no oxide forming due side reactions (like from oxalates).

mayko - 12-4-2013 at 18:19

I've always sort of had this idea that there is an ordering to acid replacements, that a strong acid always replaces a weaker acid. For example, sulfuric acid and sodium acetate yields acetic acid and sodium acetate, not the other way around. The replacement of sulfate by relatively weak acid like citric acid seems to challenge this intuition.

Of course the reaction is actually in equilibrium, so a small amount of both salts would be expected. The insoluble salt quickly precipitates; this I would expect to drive the equilibrium towards the products. Is my thinking right?

Quote: Originally posted by Morgan

As an aside the way I discovered the fire ring effect was when I was toying with Reynst jam jars trying to see how they would run with a tube partly inside the jar. On evening in the garage I did just that with the tube almost all the way to the bottom. When I lit it, it fired a ringed vortex of burning alcohol and the next thing I knew my ceiling was on fire for a brief few tense seconds before it burned out.

I love vortex rings :3 Various projects on my to-do list include making automated vortex ring launchers, a giant launcher from a trash can, and modelling puffballs ejections as vortex rings.

AndersHoveland - 13-4-2013 at 01:26

Copper is not a very reactive metal. Is pyrophoric copper even possible?

I do not think copper can burn in pure O2, but this does not necessarily mean that finely particlized copper would not be able to burn. Finely particlized Al can burn in nitrogen, whereas bulk Al cannot.

[Edited on 13-4-2013 by AndersHoveland]

Pok - 13-4-2013 at 02:13

Quote: Originally posted by AndersHoveland

Copper is not a very reactive metal. Is pyrophoric copper even possible?

According to the table I posted it is possible.

Copper is highly reactive with oxygen if its fine enough. I made "nano" copper powder by digesting Cu2O with sulfuric acid (copper sulfate + elemental copper is produced). After washing the copper powder and pressing it almost dry, it became very warm (about 50°C) only due to contact with the air! It oxidized back to Cu2O partially. And this copper powder was still a bit wet so that there was only a small surface area of the "lump". I can imagine that pyrophoric copper (with a much higher surface area and no water content) is possible.

AJKOER - 14-4-2013 at 17:17

Copper oxalate is an interesting salt as upon heating it in an inert atmosphere liberates Cu, but in air stream for some 2 hours, produces a very fine CuO with a high surface area (useful for catalytic purposes). See: "Copper Oxalate synthesis and decomposition" at http://info.tuwien.ac.at/struchem/files/poster_cuox.pdf

Another chemical reductive preparation (see abstract at http://iopscience.iop.org/0957-4484/19/41/415604 ), to quote:

"In this study, copper nanoparticles were synthesized through a relatively large-scale (5 l), high-throughput (0.2 M) process. This facile method occurs through the chemical reduction of copper sulfate with sodium hypophosphite in ethylene glycol within the presence of a polymer surfactant (PVP), which was included to prevent aggregation and give dispersion stability to the resulting colloidal nanoparticles. Reaction yields were determined to be quantitative while particle dispersion yields were between 68 and 73%. The size of the copper nanoparticles could be controlled between 30 and 65 nm by varying the reaction time, reaction temperature, and relative ratio of copper sulfate to the surfactant"

One source (see http://www.google.com/url?sa=t&rct=j&q=copper%20nano... ) notes, to quote:

"We are working on a simple and rapid approach
to pure copper nanoparticle preparation via a natural
antioxidant—ascorbic acid, with no gas protection. Ascorbic
acid is essential to avoid the oxidation of copper nanoparticles
during the synthesis process and in storage. The antioxidant
properties of ascorbic acid come from its ability to
scavenge free radicals and reactive oxygen molecules [11],
accompanying the donation of electrons to give the
semi-dehydroascorbate radical and dehydroascorbic acid."

mayko - 1-5-2013 at 21:56

I just tried heating some copper acetate under a CO2 atmosphere. There was a crackling sound and a bit of smoke produced, white to yellow-brown, and smelling of acetic acid. This smoke colored the blow torch flame copper blue-green, and often behaved like a flammable gas. This suggested that it was a fine suspension of copper particles which could support combustion.

However, I could never get the solid to self-ignite. If anything, it seemed like the dust created was too fine, that it drifted lazily out of the tube rather than falling at a sufficient velocity to ignite the metal. Like I said, I couldn't find any trace of the original thread claiming success from copper acetate, only second hand mention, so there might be something I'm missing. If anyone has a link I'd like to read it

I'll try the citrate and tartrate next, as soon as I get the chemicals together...

Mailinmypocket - 2-5-2013 at 07:08

Check out this thread, within it the member Peach has a post with lots of pictures of the dry distillation of copper acetate. The last photos show that the copper remnants are pyrophoric:

https://www.sciencemadness.org/whisper/viewthread.php?tid=10...

chemcam - 3-5-2013 at 13:38

I made copper citrate today in hopes of decomposing it to pyrophoric copper but I have not had success yet. I will keep trying and let this thread know what happens. I have been using an argon atmosphere. Anybody have anything specific I should try?

I got it, copper citrate decomposed into pyrophoric copper easily not sure why it didn't work earlier.

cool effect!

[Edited on 5-4-2013 by chemcam]

Morgan - 3-5-2013 at 17:49

I wonder if it could light methanol vapor in air if it didn't want to ignite by itself?

mayko - 7-5-2013 at 08:45

Omitting the CO2 atmosphere causes the suspended copper dust to be much more flammable. I was able to get a self-sustaining blue-green flame by continuously heating the acetate in the bottom of the tube while lighting the mouth of the tube with a lighter. It's not what I started out looking for, but could be a cool demonstration in its own right.

I still haven't achieved auto-ignition, but pouring the reduced copper into a torch flame colors the flame green while producing dribbly yellow meteors of burning metal. Also quite nice

Finnnicus - 7-5-2013 at 15:24

Ok. What about CuSO4 + Fe -> FeSO4 + Cu, or am I missing something here?

chemcam - 7-5-2013 at 16:24

Quote: Originally posted by Finnnicus

Ok. What about CuSO4 + Fe -> FeSO4 + Cu, or am I missing something here?

For them to react they would need to be in solution which doesn't work for pyrophoric metal. Copper can also be precipitated by aluminum in a copper nitrate solution. Again though, not pyrophoric.

Finnnicus - 7-5-2013 at 16:28

I think it could work on contact between iron and the crystal. I'll try it, but you will probably get copper coated iron.

Morgan - 7-5-2013 at 20:34

It might be interesting to sprinkle the copper particles in a flask of pure oxygen, to see what happens.

mayko - 11-6-2013 at 04:12

Quote: Originally posted by Morgan

I wonder if it could light methanol vapor in air if it didn't want to ignite by itself?

Quote: Originally posted by Morgan

It might be interesting to sprinkle the copper particles in a flask of pure oxygen, to see what happens.

I tried both of these; nothing noteworthy occurred. Too bad!

subsecret - 6-8-2013 at 19:48

Quote: Originally posted by Finnnicus

Ok. What about CuSO4 + Fe -> FeSO4 + Cu, or am I missing something here?

I believe that this reaction would work to form pyrophoric copper. I designed a little procedure, though it lacks stoichiometric values...

1) React a solution of copper (II) sulfate with iron, probably in the form of steel wool. As described in the quote, iron (II) sulfate and copper would be produced. I assume that the copper would form a suspension of nanoparticles. Keep the copper sulfate in excess.
2) Filter the solution to acquire the copper particles. If you happened to add too much iron, HCl could be added to form iron (II) chloride, which is a soluble material.
3) Wash and dry your copper particles. The copper may form into a cake, but that's nothing that a mortar and pestle can't fix.

I'm going to try this experiment when I get home from vacation (tomorrow). I'll post the results in "chemistry in general."

Pok - 6-8-2013 at 21:28

You can't make pyrophoric or nano copper this way. The copper will form huge crystals ("huge" compared to nano copper). Also, washing and drying the copper powder would require total absence of oxygen.

I already mentioned how to make nano copper in my last post in this thread. But I don't know whether you can make pyrophoric copper this way (if dried in absence of O2) or not.

Copper citrate is easy to make and works for the production of pyrophoric copper as chemcam found out.

Finnnicus - 7-8-2013 at 03:08

Sorry guys. I was naive (still am!) unless the reduction to copper metal can take place in the solid state (highly doubtful) what I was talking about couldn't be performed.

Sorry.

subsecret - 7-8-2013 at 14:49

While we're still somewhat on topic, how does CO₂ work as in inert gas?

hyfalcon - 7-8-2013 at 16:49

By displacing the oxygen and acting as a shield gas.

subsecret - 7-8-2013 at 17:11

Should've rephrased my question...I was wondering how CO₂ compares to other inert gases. Don't bother to answer, I've received an answer elsewhere.