Sciencemadness Discussion Board - Reducing metal oxides with wood gas

Be careful, breathing lead fumes is not something you want to do!

Can you tell me at what temp lead fumes at? I'm interested in this b/c it's BP is like 3300F IIRC and any of the salts or oxides decompose to lead upon boiling, so I have a hard time figuring out where these fumes come from.

Take a look at high temp soldering for things like plumbing, I don't think that fumes and especially electrical soldering which uses much lower temps, there are no lead fumes that I know of. If you see fumes it is the flux burning off or some plastic part that has gotten too hot.

Where exactly am I going to have to worry about lead fumes b/c from what I can see, it is something that is said online that in reality has no basis in fact, just like "melting lead acid batteries" is so easy to get piles of lead.

I'm not being purposefully snarky or anything, I'm genuinely curious if I'm missing something when it comes to the fumes or if it is one of those industry/internet worry wart issues, b/c if you look at any other metals, you never hear anything about their fumes when they have high MP and especially high BP's.

morganbw - 13-5-2020 at 12:09

You should be okay. There are tons of people who melt lead to cast bullets.
I have melted it to make electrodes. Do it outside and use common sense.

RogueRose - 13-5-2020 at 12:12

Bend a borosilicate glass tube into an "L" with a propane torch, and mount it at a shallow horizontal angle with the short end of the "L" facing up. Put a small amount of alcohol into the tube, such that an inert gas (nitrogen,etc) bubbles slowly through the alcohol sitting at the bend in the tube.

Cut off a small amount of your metal sample and place it into the mouth of the other end of the tube. If the tube is mounted at a shallow enough angle then the sample will sit in the mouth of the tube without sliding in.

Gently heat the region of the tube that contains the sample with a propane torch. If it is a metal oxide that can be reduced with hydrogen to a low melting point metal, then you should slowly see it change colors and coalesce into a shiny ball.

You can use this same setup for reducing a wide variety of metal oxides, even ones with metals that don't melt at low temperatures (copper oxide/metal for example).

If this small experiment doesn't work, then there is no point to trying this on a larger scale.

Thanks for the suggestion, I'll try this, though I'm a little worried that the glass won't support the level of heat. I do have some quartz tube about 61/2" long by 3/4" diameter that is from 1500w halogen heating elements. I also have 10mm diam boro glass tube that fits inside the quartz nice and tight.

As far as the alcohol, will any kind work? I have 91% iso and can probably get 99%. I also have pure methanol and I have some 90-95% ethanol.

As a side note, I borrowed a nice acetylene torch to try to melt both the positive and negative plates (seperately). I also used 2 propane torches at the same time to supply heat to the outside of the crucible, so there was a lot of heat. I got all of them to melt, both turned into bright orange puddles and ended up being PbO at the end (a reduction of the PbO2 plate and an oxidation of the Pb plate....) I ended up with about 10% by weight of actual lead from the lead plate that didn't oxidize and it melted at normal temps and was the first to melt, pooling in the bottom. I really thought the acetylene would have been hot enough to melt the lead plate and not oxidize it when melting.

WGTR - 13-5-2020 at 14:40

Lead melts a bit over 300C, and boro should work fine for that. The reduction should occur at comparable temperatures.

With all this Covid stuff going on I can only be in the lab on certain days, and today is not one of those days. However, I'll be in town tomorrow, and can try to locate the piece of tubing that I last used for this experiment, just to show you what it looks like and how it's set up.

As far as the alcohol, will any kind work? I have 91% iso and can probably get 99%. I also have pure methanol and I have some 90-95% ethanol.

I routinely use 100% ethanol for this, but I imagine that 90-95% ethanol will be fine. If trying this experiment with iron oxide the extra water may cause a problem, but with lead oxide this should be OK. The other alcohols that you mentioned would probably also work, methanol being the best choice.

As a side note, I borrowed a nice acetylene torch to try to melt both the positive and negative plates (seperately). I also used 2 propane torches at the same time to supply heat to the outside of the crucible, so there was a lot of heat. I got all of them to melt, both turned into bright orange puddles and ended up being PbO at the end (a reduction of the PbO2 plate and an oxidation of the Pb plate....) I ended up with about 10% by weight of actual lead from the lead plate that didn't oxidize and it melted at normal temps and was the first to melt, pooling in the bottom. I really thought the acetylene would have been hot enough to melt the lead plate and not oxidize it when melting.

If you truly have lead oxide, I think you will be surprised at how easily it will melt into lead beads under gentle heating, when using a reducing atmosphere like this. If it's lead sulfate or something, then I'm not sure what will happen.

A friend of mine tried melting bismuth powder in open air, and was unable to melt it even heating it to the point of it glowing bright red. I took the same sample and heated it in a tube with flowing alcohol vapors, and it magically darkened and coalesced into shiny beads with patient, but minimal heating. He couldn't believe it.

I used nitrogen as the inert carrier gas (because we have probably 100+ gallons of LN2 sitting around at any given time). However, I can look at trying this with air. I'll have to give this a few minutes thought. Maybe I'll stuff a wad of copper wiring down the tube as a flame arrester. So long as there is excess alcohol left over, then the reduction should occur.

RogueRose - 13-5-2020 at 15:39

As far as the alcohol, will any kind work? I have 91% iso and can probably get 99%. I also have pure methanol and I have some 90-95% ethanol.

Thanks for the reply! I have tons of methanol, so that is good! I also have SS and copper tubing I could use, in lots of sizes.

As for the lead, I'll make some video's b/c it seems people just don't beleive how hard it is to melt these plates and it causes a huge mess to cut these batteries a part, so I'll record what it looks like trying to melt the different plates.

I know the pure lead in both plates will melt out at normal temps, but both are talking A LOT of heat to get to melt, and wiki states 1630 for the MP of PbO which is about what I suspect was the point for both the Pb and PbO2 plates I was working with. So what I'm thinking is that the Pb plate is oxidizing as soon as any heat gets on it and the only thing that melts out is the wire grid/mesh which is a small % of weight. Both end up as a yellow/orange powder on top where it melted and all are crumbly. The Pb plate leaves a silvery bead (under the yellow surface) that crumbles and I know it was melted as well.

I've dissolved these in hot vinegar before and the Pb plate dissolves much faster than the PbO2 plates, but both will dissolve. I can easily do the Pb plate with vinegar and H2O2 w/o heat. I was thinking of trying to test the acetate and see if there is anything else in it but I can't find out if it decomposes to Pb or PbO as I've found both listed.

Also, do you know of any swab tests to identify lead? I'd like to cover a cloth with some solution and draw air through it as I heat the lead and see if lead is coming off as fumes.

Metacelsus - 13-5-2020 at 19:10

Be careful, breathing lead fumes is not something you want to do!

You're right, it's not lead *vapor* as the boiling point of lead is much higher than the temperatures you would reach. But lead aerosols may still be generated. And even small amounts of lead can cause toxic effects, and cumulatively (biological half life ~10 years)

Sodium rhodizonate can be used to make lead test swabs (you can also buy said swabs online). I have a few that I used for paint testing.

[Edited on 2020-5-14 by Metacelsus]

RogueRose - 13-5-2020 at 21:34

Be careful, breathing lead fumes is not something you want to do!

Thank you for the reply and info!
I think this would be a really good test to see how dangerous it is to work with lead at different temps and for how long. I'm thinking of doing some soldering with standard 60/40 solder and also some piping solder. Then maybe melting some normal lead like wheel weights, sinkers, etc both electrically and with a torch. Finally I'll heat to high temp - 1700F+, both Pb & PbO/PbO2 with torch and electric and see what comes of it.

Any suggestions on other tests or how long to pull air in to see the effect?

Lead Metal Oxidation

WGTR - 14-5-2020 at 19:40

I quickly made some videos in the lab today. If you don't mind my poor camera skills, I will post some of them showing a basic setup for the oxidation and reduction of lead.

I have a big block of lead metal, but didn't have the oxide to demonstrate reduction. For this reason I shaved off some pieces of lead and first oxidized them in the tube using flowing air. Here is the setup for oxidation:

Attachment: oxidation_setup.mp4 (3.7MB)
This file has been downloaded 316 times

Actual oxidation in progress, using air flowing through the tube and gentle heating with an air/propane torch:

Attachment: lead_oxidation.mp4 (2.4MB)
This file has been downloaded 363 times

Lead Oxide Reduction

WGTR - 14-5-2020 at 19:52

In these videos I show the reduction of lead oxide to lead metal.

I used 100% methanol for this reduction (and only about 1-2ml at that) because this is something that both of us have. I used nitrogen as a carrier gas. I wanted to try to find a way to use air for this, but I honestly didn't have the time to think this through carefully enough. I didn't want to risk an explosion in a glass tube.

This video shows the setup for reduction:

Attachment: reduction_setup.mp4 (3.3MB)
This file has been downloaded 316 times

See how the borosilicate tube is bent and tilted slightly so that the methanol sits in the bend? See how slowly nitrogen is bubbled through it. This process doesn't take much carrier gas. I purposely let nitrogen bubble through the methanol for a few minutes before applying heat to the tube, to allow air to be purged from the tube.

This next video shows the reduction:

Attachment: lead_oxide_reduction.mp4 (7MB)
This file has been downloaded 326 times

I don't overheat the tube, but rather apply gradual heating over time to slowly reduce the metal oxide. Metallic lead gradually coalesces into shiny beads as the reduction progresses.

As an aside, does anyone know if lead is supposed to wet glass? I tried popping the small lead beads off the glass, and they took thin chunks of glass with them. Weird. Maybe it was the lead oxide that bonded to the glass, and then reduction caused adhesion of metallic lead. Interesting.

fusso - 14-5-2020 at 20:21

As an aside, does anyone know if lead is supposed to wet glass? I tried popping the small lead beads off the glass, and they took thin chunks of glass with them. Weird. Maybe it was the lead oxide that bonded to the glass, and then reduction caused adhesion of metallic lead. Interesting.

Wax can help remove the oxide coating and coalescence the beads, but only in higher temps where this reduction can happen.

B(a)P - 14-5-2020 at 20:38

So simple and effective! Thanks very much for sharing. Interesting observation with regard to the lead adhesion to the glass.
I don't have a full copy of Electrochemistry: Proceedings of the First Australian Conference on Held in Sydney, 13—15th February and Hobart, 18—20th February 1963, but from reading pages 601 and 602. It seems the molten lead does not wet glass. Seems likely it is the oxide causing this.

RogueRose - 16-5-2020 at 07:25

In these videos I show the reduction of lead oxide to lead metal.

I used 100% methanol for this reduction (and only about 1-2ml at that) because this is something that both of us have. I used nitrogen as a carrier gas. I wanted to try to find a way to use air for this, but I honestly didn't have the time to think this through carefully enough. I didn't want to risk an explosion in a glass tube.

This video shows the setup for reduction:

See how the borosilicate tube is bent and tilted slightly so that the methanol sits in the bend? See how slowly nitrogen is bubbled through it. This process doesn't take much carrier gas. I purposely let nitrogen bubble through the methanol for a few minutes before applying heat to the tube, to allow air to be purged from the tube.

This next video shows the reduction:

I don't overheat the tube, but rather apply gradual heating over time to slowly reduce the metal oxide. Metallic lead gradually coalesces into shiny beads as the reduction progresses.

As an aside, does anyone know if lead is supposed to wet glass? I tried popping the small lead beads off the glass, and they took thin chunks of glass with them. Weird. Maybe it was the lead oxide that bonded to the glass, and then reduction caused adhesion of metallic lead. Interesting.

thanks for the videos! I think I can do this setup pretty easily and might try to use the quartz tube to hold the lead as I can use the boro glass to bend, then the tube can be connected to the quartz tube & sealed (RTV silicone good for 500-600F?). the quartz is about 6" long. The only question I have is can air be used instead of N2? I don't have any N2 tanks.

WGTR - 17-5-2020 at 09:14

You may need the input from someone smarter than me for that. If air is bubbled through methanol that is kept at 0°C, then it looks like the resulting fuel/air mixture is below the lower flammability rating for methanol. This can be passed over a wad of fine copper wire that is kept heated with a torch (the torch might not even be necessary so long as the airflow is consistent, as the reaction is exothermic). The resulting gasses could, say, be bubbled through sodium hydroxide solution that is kept cold. This would remove water moisture, organic acids, and formaldehyde from the leftover gasses.

There would still be oxygen left over. The gas would have to be passed a second time through the same type of setup again to hopefully remove the last bit of oxygen, leaving mostly nitrogen left over.

Maybe carbon dioxide would work as a carrier gas instead. I'm not sure on that.

[Edited on 20-05-17 by WGTR]

RogueRose - 17-5-2020 at 09:23

You may need the input from someone smarter than me for that. If air is bubbled through methanol that is kept at 0°C, then it looks like the resulting fuel/air mixture is below the lower flammability rating for methanol. This can be passed over a wad of fine copper wire that is kept heated with a torch (the torch might not even be necessary so long as the airflow is consistent, as the reaction is exothermic). The resulting gasses could, say, be bubbled through sodium hydroxide solution that is kept cold. This would remove water moisture, organic acids, and formaldehyde from the leftover gasses.

There would still be oxygen left over. The gas would have to be passed a second time through the same type of setup again to hopefully remove the last bit of oxygen, and leave over a little methanol vapor to perform the reduction.

Maybe carbon dioxide would work as a carrier gas instead. I'm not sure on that.

[Edited on 20-05-17 by WGTR]

When I was studying the decomp of methanol I found that it turns into 2H2 + CO when it comes into contact with a Pt/Pd on carbon catalyst or Pt/Pd on alumina. I also saw that nickel (sponge or rainey maybe?) can do the same. I wonder what the difference is between what you did and what is being done here.

I'd like to try to do some Pt/Pd catalyst and I'm wondering if I can use the heater on my little torch that ignites butane or if i can use some honeycomb from a catalytic converter? I'd buy a cheap aftermarket cat and see if it works.

WGTR - 17-5-2020 at 09:40

It's a matter of temperature, oxygen concentration, and catalyst preparation. Maintaining copper metal at red heat will pretty much obliterate methanol, and any oxygen present will react with whatever reducing species that may be present. At much lower temperatures, copper metal (pipe even) can be used to dehydrogenate methanol in the absence of air to formaldehyde and hydrogen. Paul Sabatier's book in the Sciencemadness library contains a lot of information. Most of what I learned about gas-phase catalysis came from this book.

If you want hydrogen and nitrogen, then try passing ammonia vapor over a very hot iron wool catalyst. You should get almost 100% conversion.

Ubya - 17-5-2020 at 23:23

WGTR thanks a lot really.
i've been trying to convert lead oxides to lead metal from batteries for years (mostly because i try once every few months lol). The first time, i tried mixing charcoal, lead/lead dioxide powder in a steel can, lightning it up and feeding air from the bottom, it kinda worked but the amount of lead smoke it made was something i couldn't accept.
Then i tried again but lowering the amount of feed air, so with cooler temperatures the fumes would be less, but now lead dioxide would decompose to lead oxide and partially melt, at higher temperatures it would flow easily, but at colder temperatures it was dense as cold honey, slowly covering the charcoal and stopping combustion.

this is the 4Kg block of charcoal/lead/lead oxide block it formed, i still need to make it into smaller pieces (flying lead oxide dust how nice)

i tried a few other setups, one was a 1m steel tube made out of coffee cans to make a temperature gradient and have lead dioxide decomposition at the top and reduction of the yellow oxide from the top to the bottom, the bottom would be the hottest and i was hoping that the lead oxide vapours would condense on the colder charcoal at the top of the tube. too much air resistance it didn't work

i knew that hydrogen was used to reduce copper oxide as a lab demonstration, so i checked if it could be used for lead oxide also. there aren't any videos showing it but it is possible and even at a quite low temperature. the issue was to produce enough hydrogen to reduce 20kg of lead oxides without blowing me up.
a few weeks ago i tried another approach, putting a mix of lead oxides powder and charcoal powder in a small can, and heating it externally to red hot for a few minutes (until i finished my butane canister)

the metallic shine was awsome, it worked, and the initial decomposition of lead dioxide to oxide even made the heating process faster as the oxygen formed ignited the charcoal powder around each grain heating the mixture from the inside, the ony issue i had was that i needed a furnace to hold a crucible with the mix and not being able to go outside i couldn't buy the stuff i needed.

but now you showed me i could use alcohol vapour as a reducer.

instead of bubbling an inert gas through the alcohol and then heating the vapour mixture near the oxide, couldn't we just boil some alcohol and direct the vapours on the heated oxide? this way we remove the use of an inert gas or the added complications of using air and trying to not make the apparatus explode

unionised - 17-5-2020 at 23:58

How did the Romans smelt lead?

RogueRose - 18-5-2020 at 01:20

WGTR thanks a lot really.
i've been trying to convert lead oxides to lead metal from batteries for years (mostly because i try once every few months lol). The first time, i tried mixing charcoal, lead/lead dioxide powder in a steel can, lightning it up and feeding air from the bottom, it kinda worked but the amount of lead smoke it made was something i couldn't accept.
Then i tried again but lowering the amount of feed air, so with cooler temperatures the fumes would be less, but now lead dioxide would decompose to lead oxide and partially melt, at higher temperatures it would flow easily, but at colder temperatures it was dense as cold honey, slowly covering the charcoal and stopping combustion.

this is the 4Kg block of charcoal/lead/lead oxide block it formed, i still need to make it into smaller pieces (flying lead oxide dust how nice)

i tried a few other setups, one was a 1m steel tube made out of coffee cans to make a temperature gradient and have lead dioxide decomposition at the top and reduction of the yellow oxide from the top to the bottom, the bottom would be the hottest and i was hoping that the lead oxide vapours would condense on the colder charcoal at the top of the tube. too much air resistance it didn't work

i knew that hydrogen was used to reduce copper oxide as a lab demonstration, so i checked if it could be used for lead oxide also. there aren't any videos showing it but it is possible and even at a quite low temperature. the issue was to produce enough hydrogen to reduce 20kg of lead oxides without blowing me up.
a few weeks ago i tried another approach, putting a mix of lead oxides powder and charcoal powder in a small can, and heating it externally to red hot for a few minutes (until i finished my butane canister)

the metallic shine was awsome, it worked, and the initial decomposition of lead dioxide to oxide even made the heating process faster as the oxygen formed ignited the charcoal powder around each grain heating the mixture from the inside, the ony issue i had was that i needed a furnace to hold a crucible with the mix and not being able to go outside i couldn't buy the stuff i needed.

but now you showed me i could use alcohol vapour as a reducer.

instead of bubbling an inert gas through the alcohol and then heating the vapour mixture near the oxide, couldn't we just boil some alcohol and direct the vapours on the heated oxide? this way we remove the use of an inert gas or the added complications of using air and trying to not make the apparatus explode

well, TBH, I'm glad I'm not the only one who has had problems with turning lead acid batteries into useable lead. I can't count the number of web sites that tell people that its easy to get mountains of lead by just melting lead acid batteries and it's like "super easy". Well, I've NEVER found this to be true, have you? It seemed like this was one of those internet myths we hear of. I've tried heating the plates about 10x and have basically had failures each time.

When you are trying the reduction are you doing just the PbO2 plates, both or the Pb plates? Have you found any of them to melt with just a torch or are you finding that even the "pure lead" plates will not melt with a torch. I found that people wouldn't believe me that the lead wouldn't melt even with an acetylene torch.

I'm still planning on working on a wood gas setup or even a syn/water gas setup to make use of the charcoal left over after making the wood gas. The water gas produces H2 + CO IIRC, where the woodgas is more CO, and the water gas is made by passing steam over hot charcoal (I think charcoal works, I've seen coke is often used).

fusso - 18-5-2020 at 01:34

Have you found any of them to melt with just a torch or are you finding that even the "pure lead" plates will not melt with a torch. I found that people wouldn't believe me that the lead wouldn't melt even with an acetylene torch.

So the lead is in the form of sponge/foam/compressed powder? Such forms of lead would oxidise without melting cuz there's too much surface area to be oxidised.

Ubya - 18-5-2020 at 02:00

Quote: Originally posted by fusso

So the lead is in the form of sponge/foam/compressed powder? Such forms of lead would oxidise without melting cuz there's too much surface area to be oxidised.

to test this i tried melting pure lead plates in a semi closed container flushed with argon, it still didn't work.

i've never tried melting a new/working lead acid battery, in total i have lead/lead oxides from 3 batteries, all compleately dead, like, electrodes crumbling "dead", Grant Thompson made a video melting lead from a car battery, but he used a working one, or at least not a totally dead one, and got some lead out of it, i also managed to melt some lead from the thicker pieces like the connectors and the thick parts of a plate, but most of the battery is lead sponge and thin wires that got oxidized pretty deeply.
another thing, if the amount of oxides is far greather than the metal, even if you are able to melt it, it remains in the grain structure without flowing out and eventually making a puddle on the bottom of the crucible.

i also tried to heat a piece of lead plate with a torch ignoring the temperature, as you can see 90% of it is/turns into lead oxide, only a really small part is lead metal (that tiny bead), and heating 10kg of plates to red hot, for many hours, nust to get in the end a solid 9kg block of lead oxide that needs to be reduced anyway and 1kg of lead on the bottom of the crucible mhh, not really a good idea.

to answer about the question if i try to reduce just the PbO2 plates, nah i put them all together, as i said before even my Pb plates are mostly oxidized.

if you manage to get it work with syn gas, tell us about it, hydrogen is the one that is going to reduce the lead oxide at a lower temperature.
oh another thing, PbO2 decomposes to PbO and O2, be careful as you could get an explosive mixture of hydrogen/CO and oxygen even if the apparatus is airtight

WGTR - 18-5-2020 at 05:37

Your welcome. No problem...

I knew that hydrogen was used to reduce copper oxide as a lab demonstration, so i checked if it could be used for lead oxide also. there aren't any videos showing it but it is possible and even at a quite low temperature. the issue was to produce enough hydrogen to reduce 20kg of lead oxides without blowing me up.
a few weeks ago i tried another approach, putting a mix of lead oxides powder and charcoal powder in a small can, and heating it externally to red hot for a few minutes (until i finished my butane canister)

Yes, I think that external heating is they key thing here. A self-heating reaction is going to be a headache even on the best of days.