Sciencemadness Discussion Board

Ways to isolate lead from its alloy state?

Darth-Vang - 4-8-2022 at 19:14

I'm wanting to make lead nitrate, but the thing is that it's an alloy, I'm wanting to purify the lead chemically if possible. Can anyone point me into the right direction into a synthesis of isolating the lead from it's alloy and then to lead nitrate? I have alot of lead in the garage and wanting to make some lead nitrate.

j_sum1 - 4-8-2022 at 21:16

Do you have any idea what it is alloyed with?

Two refining processes come to mind. Both I would consider messy.

1. Smelt -- melt the lead and then refine by oxidation. Most alloyed impurities will oxidise preferentially to lead. You would need an oxidising environment. You would need to bubble a gas through the melt to carry the impurities to the surface to be collected in a slag. Bubbling heated air would probably work. Furnace, porous plug, heater for air, effective gas extraction and scrubbing. A lot depends on how good your workshop is.

2. Precipitate an insoluble lead salt. Begin by dissolving everything with nitric acid. Then form a precipitate using a suitable solution: sulfate, chloride, iodide spring to mind. You want your lead salt to be insoluble but the other metal salts to be soluble. Check the solubilities of the salts of the alloyed impurities and see what is likely to work. Then convert your lead chloride or whatever back to lead nitrate. That is likely to involve reducing back to elemental lead and redissolving in nitric acid. My thoughts are that this will use a lot of precious nitric acid.

What scale do you think you need to work with?

Lead chemistry is an ancient art. There exist large scale low tech routes to lead oxides which were important historically for paint pigments. You might research those and consider how effective they are at isolating impurities. PbO to Pb(NO3)2 should not be a difficult process if you have acquired reasonably pure oxide.

This all said, do be careful with toxicity issues. I would not be making any more lead nitrate than I could reasonably use. Soluble lead salts deserve to be treated with caution and your best defence is to keep quantities small. As tempting as it might be to create bulk salts, it is probably safer to keep your lead in elemental form.

teodor - 4-8-2022 at 23:20

Darth-Vang, I had much success with this route:

1. Dissolve the alloy in DILUTED nitric acid.
2. Concentrate to get crude Pb(NO3)2.
3. Recrystallize Pb(NO3)2 from water.
4. Add HCl to water solution of Pb(NO3) to precipitate lead as PbCl2 (other cations will stay in the solution. Well, except Hg+ and Ag+ but who really cares about Ag).
5. The solution after step 4 will have HNO3 again which you can use to dissolve more lead.

Most of PbCl2 I used to produce PbO2 (reaction with NaOH and NaClO or Ca(ClO)2, washing with HNO3). I think at this stage Pb cations had the highest purity because they where precipitated not only as insoluble chloride but also as insoluble peroxide washed in HNO3.
Of course knowledge which cations you want to eliminate and to which extend can help to chose the right process.
Today I have much more experiments which I want to do comparing with the time I have for that. So I mostly stopped purification of chemicals and buy them instead. Buying chemical pure lead acetate or lead nitrate will save a lot of time, but if the goal is just educative you can try my process or its variations.

If you have lead from a battery in form of a sponge you can try to use it to reduce nitrate to nitrite in water solution which is also quite interesting experiment.

To dispose solutions containing lead I mix them with NaOH solution in which S is dissolved. Until you keep it alkaline it cause precipitation of lead in form of very insoluble sulfide which you keep and the rest you can dispose.


[Edited on 5-8-2022 by teodor]

Darth-Vang - 5-8-2022 at 00:29

Quote: Originally posted by j_sum1  
Do you have any idea what it is alloyed with?

Two refining processes come to mind. Both I would consider messy.

1. Smelt -- melt the lead and then refine by oxidation. Most alloyed impurities will oxidise preferentially to lead. You would need an oxidising environment. You would need to bubble a gas through the melt to carry the impurities to the surface to be collected in a slag. Bubbling heated air would probably work. Furnace, porous plug, heater for air, effective gas extraction and scrubbing. A lot depends on how good your workshop is.

2. Precipitate an insoluble lead salt. Begin by dissolving everything with nitric acid. Then form a precipitate using a suitable solution: sulfate, chloride, iodide spring to mind. You want your lead salt to be insoluble but the other metal salts to be soluble. Check the solubilities of the salts of the alloyed impurities and see what is likely to work. Then convert your lead chloride or whatever back to lead nitrate. That is likely to involve reducing back to elemental lead and redissolving in nitric acid. My thoughts are that this will use a lot of precious nitric acid.

What scale do you think you need to work with?

Lead chemistry is an ancient art. There exist large scale low tech routes to lead oxides which were important historically for paint pigments. You might research those and consider how effective they are at isolating impurities. PbO to Pb(NO3)2 should not be a difficult process if you have acquired reasonably pure oxide.

This all said, do be careful with toxicity issues. I would not be making any more lead nitrate than I could reasonably use. Soluble lead salts deserve to be treated with caution and your best defence is to keep quantities small. As tempting as it might be to create bulk salts, it is probably safer to keep your lead in elemental form.
Probably on a small scale, since I haven’t carry out any “lab style” synthesis yet(besides mixing baking soda and vinegar to unclog a drain XD). Yes I understand lead is a toxic metal that has poison alot of people since the roman times. I cast lead bullets for fun and plinking. Also the reason I am wanting to make lead nitrate is a needed ingredient for a primer compound, of course it must be as pure as possible to eliminate any and all variables from the primer making steps.

Tsjerk - 5-8-2022 at 01:58

If you don't know what it is alloyed with, then at least tell us where you got it from.

Darth-Vang - 5-8-2022 at 02:02

Quote: Originally posted by teodor  
Darth-Vang, I had much success with this route:

1. Dissolve the alloy in DILUTED nitric acid.
2. Concentrate to get crude Pb(NO3)2.
3. Recrystallize Pb(NO3)2 from water.
4. Add HCl to water solution of Pb(NO3) to precipitate lead as PbCl2 (other cations will stay in the solution. Well, except Hg+ and Ag+ but who really cares about Ag).
5. The solution after step 4 will have HNO3 again which you can use to dissolve more lead.

Most of PbCl2 I used to produce PbO2 (reaction with NaOH and NaClO or Ca(ClO)2, washing with HNO3). I think at this stage Pb cations had the highest purity because they where precipitated not only as insoluble chloride but also as insoluble peroxide washed in HNO3.
Of course knowledge which cations you want to eliminate and to which extend can help to chose the right process.
Today I have much more experiments which I want to do comparing with the time I have for that. So I mostly stopped purification of chemicals and buy them instead. Buying chemical pure lead acetate or lead nitrate will save a lot of time, but if the goal is just educative you can try my process or its variations.

If you have lead from a battery in form of a sponge you can try to use it to reduce nitrate to nitrite in water solution which is also quite interesting experiment.

To dispose solutions containing lead I mix them with NaOH solution in which S is dissolved. Until you keep it alkaline it cause precipitation of lead in form of very insoluble sulfide which you keep and the rest you can dispose.


[Edited on 5-8-2022 by teodor]
I’ll look into it. I bought some common household chemicals already a week ago. And I did have Muriatic acid(HCl) as one of them. I’ve yet to make my own nitric acid. Been looking at youtube of how to make nitric acid. Simple but deadly. So when synthesizing chemicals, one needs one “mole” of chemical to make one “mole” of compounds? So mole is “6.02X10 by the 23rd” or Avogadro’s number? I’m a total noob but did watch alot of youtube showing and explaining the formulas and stuff, of course I’m not going to learn things overnight. What manual do y’all recommend I should have in hand for a home chemists to use as references? I do plan to make some experiment in the future.

Darth-Vang - 5-8-2022 at 02:19

Quote: Originally posted by Tsjerk  
If you don't know what it is alloyed with, then at least tell us where you got it from.
The lead I have are supposedly close to pure lead. My Lee Lead Hardness tester has shown that it is fairly soft well below the Brinell hardness of 8. I can also attest that I have swage bullets with the same lead and have found no difficulty swaging the lead into usable bullets.(dies only work with pure or close to pure lead only) The lead should be for bullets, and in it I’m going to assume it is alloy with either antimony or tin. By how much I don’t know. I’m looking to make as pure lead nitrate that I can possibly make it to be by taking the advantage of the fact that I can isolate lead by chemical means to attain my desired product.(which I still think it’s cool that I don’t have to take the dangerous hot smelting route) I’m so going to enjoy this and give me reasons to setup my apparatuses! :D :D :D

j_sum1 - 5-8-2022 at 02:59

If it is already pure, then there is probably little point refining. Simply react with nitric acid and crystallise.

Nitric acid manfacture is a rite of passage imo. A variety of methods depending on the starting nitrate and the desired concentration. I recommend watching a good yt clip and scaling the quantities of reagents to your need. Doug's Lab is a good one, but you would want to make less than he does: at least until you get experience.

You don't need to know stoichiometry to copy a procedure. But this is a good skill to learn if you intend to pursue chemistry any further.

There is a very large difference between the toxicity of lead and the toxicity of lead nitrate. You could swallow a chumk of lead and it would go through you with little effect. The same quantity of lead nitrate would be 100% bioavailable and could kill you.

Do think about cleanup and environmental toxicity as well. My standard procedure when working with soluble lead is to have a bucket and a spray bottle of sodium carbonate solution. Any glasswsre or equipment that comes in contact with lead solutions goes in the bucket. At the end of it all I spray the area with the solution. It is amazing how much you spill even when careful. You see a white precipitate everywhere even if you think you have spilled nothing. (This should give you pause for thought.) I wipe my bench with paper towels and rinse them into the bucket with fresh water. I then let it settle and collect the sediment from the bottom of the bucket for disposal or recycling. Lead solutions do not go down the drain.

Tsjerk - 5-8-2022 at 07:36

The purification of lead from tin is easy if you have nitric acid. You just dissolve the lead, and filter of SnO2 (this will form a white precipitate). Tin nitrate is unstable in water.
How to get rid of the antimony I don't know.

Darth-Vang - 5-8-2022 at 12:14

Quote: Originally posted by j_sum1  
If it is already pure, then there is probably little point refining. Simply react with nitric acid and crystallise.

Nitric acid manfacture is a rite of passage imo. A variety of methods depending on the starting nitrate and the desired concentration. I recommend watching a good yt clip and scaling the quantities of reagents to your need. Doug's Lab is a good one, but you would want to make less than he does: at least until you get experience.

You don't need to know stoichiometry to copy a procedure. But this is a good skill to learn if you intend to pursue chemistry any further.

There is a very large difference between the toxicity of lead and the toxicity of lead nitrate. You could swallow a chumk of lead and it would go through you with little effect. The same quantity of lead nitrate would be 100% bioavailable and could kill you.

Do think about cleanup and environmental toxicity as well. My standard procedure when working with soluble lead is to have a bucket and a spray bottle of sodium carbonate solution. Any glasswsre or equipment that comes in contact with lead solutions goes in the bucket. At the end of it all I spray the area with the solution. It is amazing how much you spill even when careful. You see a white precipitate everywhere even if you think you have spilled nothing. (This should give you pause for thought.) I wipe my bench with paper towels and rinse them into the bucket with fresh water. I then let it settle and collect the sediment from the bottom of the bucket for disposal or recycling. Lead solutions do not go down the drain.
Thanks for the heads up. I’ll do it in small amounts and away from everybody else and away from the house. I’ll do it outside on a good and not too extreme weathers. I should definitely get a lab coat too so as not to contaminate my attirements…

Darth-Vang - 5-8-2022 at 12:15

Quote: Originally posted by Tsjerk  
The purification of lead from tin is easy if you have nitric acid. You just dissolve the lead, and filter of SnO2 (this will form a white precipitate). Tin nitrate is unstable in water.
How to get rid of the antimony I don't know.
I’ll give that a shot since it requires only nitric acid and elemental lead.

Tsjerk - 6-8-2022 at 00:08

If you use an excess of lead and run the reaction for a long enough time, maybe a day or so, you will use most nitric acid. Maybe filtering is not even necessary as the liquid can easily be decanted off. The lead and SnO2 both are heavy and will sediment easily. The clear liquid can then be boiled down (use a paper towel over the beaker against aerosols and work outside).

After boiling to a smaller volume you can crystallize the lead nitrate by cooling. The remaining liquid still contains a lot of lead, but you can add it to a next crystallization in the future.

If you are keen on

Darth-Vang - 10-8-2022 at 15:26

Quote: Originally posted by Tsjerk  
If you use an excess of lead and run the reaction for a long enough time, maybe a day or so, you will use most nitric acid. Maybe filtering is not even necessary as the liquid can easily be decanted off. The lead and SnO2 both are heavy and will sediment easily. The clear liquid can then be boiled down (use a paper towel over the beaker against aerosols and work outside).

After boiling to a smaller volume you can crystallize the lead nitrate by cooling. The remaining liquid still contains a lot of lead, but you can add it to a next crystallization in the future.

If you are keen on
I'll give that a shot too. Sounds fairly easy.