Non-Chemical Melting and what it means

[Macleight]

Hi!

Not super new to the boards, have read some posts here, read through Hoke about 1.5x, work in a chemistry lab, study mechanical engineering. I searched a few times for a related topic, and didn't get far. Hope this question doesn't violate the rules.

So I was playing around with some electronic boards and some nitric acid. I dissolved some scrap I had mechanically separated in lab grade 68% HNO3. The separated scrap was the little gold fingers that come from motherboard connectors and some gold plated video cable wire. After the initial reaction, my curiosity was not sated. I was out of HNO3 but had unlimited time, so taking a page from Hoke, I watered it down a little bit to increase the efficiency. I was a careless chemist though, and just used Austin, TX tapwater instead of distilled water. Tapwater is full of chlorine, chlorides, bromides, and not a small amount of dissolved minerals (all our water comes from a limestone aquifer). This didn't matter much at first, but later on, I decided to just toss a small but fully populated PCB and a CPU in, instead of mechanically breaking it down first.

So now I have a fully populated board, a CPU from a laptop, a few other pieces of scrap, and a mixture of HNO3 and tapwater. The end result is that I have a lot of white gunk that settles rapidly onto the remaining full pieces of scrap inside an aquamarine solution of dissolved copper. More exactly, here is what I think I have, combining my knowledge from work and Hoke.

Copper Chloride, Maybe some Copper II Chloride (Not sure how the reaction preferentially occurs, but lots of copper is in solution)
Lead Nitrate and Lead Chloride (From solder)
Tin Nitrate and Tin Chloride (from solder)
Antimony, again from solder. Not sure if it has a nitrate or chloride form, but probably.
Silver Nitrate and Silver Chloride
Whatever the ceramic was that made up some monolithic capacitors (Zinc, Magnesium, Barium)
Tiny, miniscule amounts of Palladium, Platinum, Gold

Not all of the lead or tin has been dissolved, neither has the silver. Pretty sure all the copper is gone, except one little coil from a hard drive that I can see floating. It has yet to change at all - it is well insulated in a clear polymer.

So, obviously, incineration of these parts would have been the best starting place, long before dunking them in HNO3, but I just wanted to play around. Right now, the solution is on my back porch, slowly evaporating. Really slowly, it is December, after all. I have no time limits and am just having fun, so I'm not worried or bummed out. Here is the crux of my question now.

I am about to purchase a small, benchtop melting pot (maybe like http://www.mcmaster.com/#3429k41/=uzdkb2). Can I just separate the solids, and melt them back down? Eventually, whether it is lead, tin, silver chloride, whatever, at a high enough temp, won't the chloride gas out, and only molten metal will remain? I don't really care about losing values or recovering things, again, I'm just sort of playing around. I know the linked unit only goes to 900F and the melting point of the more valuable items is twice that or more, but won't they just be left as powders? With enough heat, I should be left with some little alloy balls or bars of lead, tin and antimony, with some unmelted copper, silver, etc inside of it? Which I could then treat again with HNO3, separate via the process Hoke talks about, and continue to refine down?

Or not? One reason for this question is I was bored at work one day and I got some Lead II Oxide that we have (we research batteries) and put it in a crucible and fired up a propane torch. I heated it for probably 10 minutes, and it never seemed to melt? The melting point of lead is around 600F, and the tip of a propane flame is 2000+. Shouldn't it have melted? Did I not wait long enough? Somewhere between 400 and 1200 F, the oxygen attached to the lead should have been liberated, and just molten lead left in the crucible, right?

Thanks for reading my long post! If you can teach me about the actual melting of metals, I would like that! I know I haven't included all the info here, so if anything is unclear, just ask!

Pic related, it's the solution I made, still agitated. You can see a corner of the CPU on the left. When all the white stuff settles out, it is a very pretty, clear, aquamarine solution of dissolved copper.

*edit* Putting a drop of the solution on some soda ash still causes a very small reaction, so the solution is still acidic. From experience, I would say the pH is between 1 and 2. I don't have any pH paper yet, so I can't test it for sure. But the reaction is ongoing. I agitate the solution about once a day for the last month and some bubbles regularly come out from under the PCB and CPU.

*edit 2 grammar*

 

[Barren Realms 007]

The only thing that furnace is good for is melting lead.

 

[butcher]

Macleight,
It sounds like you are good at making a mess :lol:

Most of the products will eventually be chlorides, as the oxidizer is consumed, some metal chlorides will be insoluble.

The battery lead may have been lead sulfate, (Just a guess here, if this was from a lead acid battery), lead sulfate will not melt like pure lead or lead oxide will.

About the only thing I can see you doing here with these experiments is creating some toxic messes to deal with. I sure hope you read the dealing with waste in our safety section...

Now that your learned how not to do things, I suggest spending your time learning how it is done properly.

 

[Macleight]

I know the furnace is not good for much. I was hoping it would be good for what I am talking about. In my head, once I wash and dry all these parts, I can put them in the furnace and the lead will melt, and I can drain it off. I can also use it for incinerating small parts in a controlled manner. I was also thinking it might be strong enough to use an acetylene torch on top and melt higher melting temp metals? Am I wrong? Could you maybe suggest a better idea?

Macleight,
It sounds like you are good at making a mess :lol:

Butcher, I am good at making messes. I'm also very good at cleaning them up. I know many of these things are toxic. I'm not going to dump them on the ground.

Most of the products will eventually be chlorides, as the oxidizer is consumed, some metal chlorides will be insoluble.

I know. I am thinking most of the chloride is used up right now. I could test it with some HCl or some table salt, and see if more white powder precipitates out. I will, but I just finished finals. Not tonight.

The battery lead may have been lead sulfate, (Just a guess here, if this was from a lead acid battery), lead sulfate will not melt like pure lead or lead oxide will.

No. It is lab grade lead oxide. I believe it should all be Lead II Oxide, but I'm still a little unclear on Lead Oxide versus Lead II, Lead III, etc. I know it has to do with the D subshell, but I'm still learning that part.

About the only thing I can see you doing here with these experiments is creating some toxic messes to deal with. I sure hope you read the dealing with waste in our safety section...

Again, I deal with hazardous waste on a daily basis. You can see, this is less than 500cc of total solution. I know how to neutralize it and even have a place to completely discard, if I like. I'm not really worried about that part. More to the point, I want to know what will happen if I filter off all the liquid and heat all the solids. The PCB will burn off, and I will be left with the ceramic materials (won't melt until very high temp) and some metals. Mostly solder metals. Which melt at manageable temps and can be drawn off.

Now that your learned how not to do things, I suggest spending your time learning how it is done properly.

Thanks for the advice. It's not really advice, it's snarky commenting, and not really helpful at all, but thanks for taking the time anyways. I am still learning and reading.

So I will repose the question. If I heat all this up, what happens? I know I can solubilize the lead chloride in the aqueous copper solution if I boil it, but upon cooling it will precipitate back out.

Here is what I thought about doing:

1: Agitate heavily.
2: Decant the soultion.
3: Wash all the solid parts to neutrality.
4: Boil the liquid to solubilize some of the other chlorides.
5: Filter again, hot.
6: The filtrate should be copper and lead in an aqueous form. Hoke doesn't seem to say, does boiling solubilize other solder components? She wouldn't, electronics of this grade didn't exist back then. That's why I am asking you! And searching the forums!
7: The filtrate can be dealt with later, but I would like to separate the lead and copper too. I just think it would be neat to refine each part down to it's elemental form. Worthless as lead and antimony may be, I want to make little ingots of them.
8: The remaining solids could then be placed in a crucible or furnace and melted into an alloy button, for processing at a later time with more parts.

Thanks again for reading and commenting!

 

[Macleight]

Broadly, to be even more clear:

Why do some things melt and others not? No matter the composition of my solution, shouldn't I be able to heat it and get molten metal back? If we were to take it to the extreme, say I had a furnace capable of 5000C. Most things on earth evolve into plasma above 5000C. I don't, but if I had a PID controller and a thermocouple made of unobtanium, couldn't I heat slowly to the melting point of each metal possible and then draw it off? Assuming a furnace capable of this heating with a little drain? Why or why not? Tin at 200C, Antimony at 500C, lead at 600C, silver at 1200C, gold at 1400C? Elemental metals would follow this criteria, but not once they are oxides or nitrides or chlorides, right? Does the addition of nitrogen species simply raise or lower the melting temp? It does, from my understanding of metals and chemistry. But these are small and weak at best.

I'm not worried about 'saving' my solution. As mentioned above, I just think it would be neat to find ways to refine each one of these metals down to elemental form. Right now they are all a mix. From what I know, I should be able, at any time, to heat them all into a single alloy button, then dissolve them again with different acids. Then melt them down again. And repeat. With careful reagent and temperature control, I should be able to get each element out at a time, yes? Now, eliminating my Mass Effect space furnace capable of melting all things and coming back to equipment I can get as a hobbyist, what would block me from doing this?

EX: As mentioned, I found a post where someone said (sorry, closed tab) "heat alone will not reduce silver chloride to elemental silver." Why not? Won't it though? Eventually? The chloride bond will break and gaseous chloride will evolve long before silver turns into a gas, right?

*edit, spelling*

 

[butcher]

Macleight,

I think you misunderstand me, I am not sure what snarky means, but I am sure I do not make snarky comments.
My comments are intended to help you, and to help you in a direction where you will gain the most from it.

I just see so many problems with your ideas, and how you think things work, thinking that will lead to many problems, and roadblocks for you learning to recover and refine metals.

I was just trying to point you in a more successful direction. it is not my intention to offend you, but to help.

"It's snarky commenting, and not really helpful at all, but thanks for taking the time anyways."
Macleight, I am sorry you thought this.

I see many details your wrong about on how it will work, I also see that you are not aware of many of the dangers involved with these metals and their salts, which can put you in danger with some of the ideas you propose.

I just hope you do more study before trying some of these dangerous ideas. Ideas that are likely to put gold in the fumes along with the fumes of other toxic metals, and deadly gases...

 

[butcher]

Your covering a wide range of questions, most of your assumptions are wrong or would not work that well and there are easier ways to get to your goal.

If you take one question at a time it will be easier to discuss.

Can you drive off chloride from the silver chloride with heat before melting.

Yes you could in theory with a very controlled heating, but the fact remains the silver chloride is volatile, and controlling the temperature is not easy to do to where you drive off chloride and not your silver in the fumes, NaCl also becomes a problem (at these temperatures) in the silver, its melting point make driving off chloride and keeping your silver in the crucible a real juggling act, and virtually impossible, even if you could control the temperatures well.

Basically you will loose silver, it is better to convert the silver chloride to metal first before melting, or do so with a flux melt with controlled heat and sodium carbonate...

 

[Macleight]

I have not yet read about the volatility of silver chloride. I will check closer. Thank you for the starting point.

 

[butcher]

Metals and alloys (combinations of metals) can have very different melting points.

Separation of metals from a mix of metals by heat or temperature will not work.

Although silver and lead can some what be separated with a dross method.

Most metals when combined form an alloy, which will have a different melting point than the metals alone would by themselves...

Gold will dissolve into tin (or solder) at a very low melting point, and form an alloy of a lower melting point than gold alone...

The more metals in solution the more problems you will encounter separating metals out chemically, some metals can also make separation difficult if not impossible by normal chemical precipitation or metal replacement reactions. Take tin and gold in solution together for example, the gold can form a colloidal solution, where the stannous reduces the gold in solution that will not settle, and is constantly held in motion by the repelling forces of the charge on the colloidal gold particles, and the gold cannot be precipitated normally, the gold cannot be tested for with stannous chloride...

 

[Macleight]

I see now how I will lose silver if I heat, among other metals.

It would work in theory, but is not a good idea in practice. Probably why I didn't find search results for it, because it is a bad idea.

Thanks to both.

 

[Macleight]

Gold will dissolve into tin (or solder) at a very low melting point, and form an alloy of a lower melting point than gold alone...

Probably why it is used in all these electronics, right? As I said, I am still doing much learning.

But still, why didn't my lead oxide melt?

 

[NobleMetalWorks]

Every time you melt metal, there is some loss. It's best to only use metallurgical processes only when required, and melt your metals that have values as few times as possible to prevent loss.

If you spend any time reading posts on this forum, you will soon realize, specially with people who are just being introduced to the world of metal refining, that many believe they will quickly discover and/or invent some new novel process that will allow them to process the values from material more effectively, efficiently or just plain more novel. Simply stated, most of the processes we currently used have been used for 100s of years. The reason for this is that they also happen to be the best processes/practices.

You would serve yourself far better following in the footsteps of those processes that have been proven to work for the type of refining you are doing. In doing so you ensure you can follow correct processes, standards, procedures, etc, without creating more problems and work for yourself, and risk loosing some or all values.

Scott

 

[butcher]

My guess is the oxygen from your torch is oxidizing the lead, you can try using a reducing flame, or just add a carbon source (charcoal, sugar, sawdust, flour) or some other source of carbon.

Caution do not breath those deadly lead fumes.

 

[Macleight]

Separation of metals from a mix of metals by heat or temperature will not work.

Also, why not? Doesn't it though? We get elemental metals from ores, which we heat until the molten metal flows out. I know I have more reading, because part of the answer is above, that they evaporate as well. We would need some way to capture and condense the flue gasses if we wanted to collect that. Which is absurd.

So what do you think would happen if I agitated that solution and then put it in a little 250 mL distillation unit I have? Here is what I think:

Unused acid would begin to quickly react with the remaining base metals. This would release hydrogen gas, a salt, and water. If fully isothermic at 100C, only water and hydrogen gas will come from the small flask. If the acid has fully eaten all the metal it can some will remain and will begin to evaporate when the concentration is 68% (azeotrope for HNO3). If never heated above 150C, all that will be left are salts.

As I said, I know how to deal with hazards. I have a respirator and lab coats and P100 masks and latex gloves and ventilation and all kinds of stuff. I haven't read about any of these things being volatile if I am very slow and careful, I may be wrong. I just might not have seen it yet.

 

[Macleight]

Every time you melt metal, there is some loss. It's best to only use metallurgical processes only when required, and melt your metals that have values as few times as possible to prevent loss.

Ok. That makes sense.

If you spend any time reading posts on this forum, you will soon realize, specially with people who are just being introduced to the world of metal refining, that many believe they will quickly discover and/or invent some new novel process that will allow them to process the values from material more effectively, efficiently or just plain more novel. Simply stated, most of the processes we currently used have been used for 100s of years. The reason for this is that they also happen to be the best processes/practices.

I have read a lot and I have seen this. I understand. I'm not trying to come up with something new. I know this is old science.

You know how you get a Rubiks cube and you mix it up? That's what I did. Now I get to have fun figuring it out. I'm just looking for ideas. Maybe 'help' was the wrong word.

You would serve yourself far better following in the footsteps of those processes that have been proven to work for the type of refining you are doing. In doing so you ensure you can follow correct processes, standards, procedures, etc, without creating more problems and work for yourself, and risk loosing some or all values.

I would argue I am. This is just an acquaintance test. But I get so excited! I just want to play!

 

[Macleight]

My guess is the oxygen from your torch is oxidizing the lead, you can try using a reducing flame, or just add a carbon source (charcoal, sugar, sawdust, flour) or some other source of carbon.

Caution do not breath those deadly lead fumes.

The oxygen in the propane is working as a shielding gas? Of course it is!

I know not to breathe the gas. Thank you.

 

[NobleMetalWorks]

Also, why not? Doesn't it though? We get elemental metals from ores, which we heat until the molten metal flows out. I know I have more reading, because part of the answer is above, that they evaporate as well. We would need some way to capture and condense the flue gasses if we wanted to collect that. Which is absurd.

If you are correctly processing your material, you should not have to concern yourself with capturing and condensing the flue gasses.

As I said, I know how to deal with hazards. I have a respirator and lab coats and P100 masks and latex gloves and ventilation and all kinds of stuff. I haven't read about any of these things being volatile if I am very slow and careful, I may be wrong. I just might not have seen it yet.

First, I would read up on NOx gases, and then read the specs or talk with a rep at the company that produces your "respirator" and ask about it's ability to filter NOx gas. I think you will find that your respirator is utterly useless under the conditions and/or processes we use to recover and refine metals. The only thing your "P100" masks are really good for is to look at. They provide no protection against gases we create during these processes, they tend to be mostly used for particulates in air.

I hope you read this for the content and do not feel the need to respond emotionally. Slow and careful is good, but it is no protection against actual gases. Knowledge is the shield against the hazards of recovering and processing metals. When you state "I know how to deal with hazards" and then continue by stating you are using equipment that does not provide protection against gases we generate, you are contradicting yourself. Imagine all of us that already understand these things, reading your post, what we might think of everything that comes after. It is obvious you do not understand the hazards as you need in order to keep yourself safe, and should spend far more time reading posts on this forum, Hoke and other books related to the subject, and humble yourself in regards to the knowledge and experience that people like Butcher have acquired over a long period of time recovering and processing these metals. Many new members make the mistake of reacting to critical criticism in a defensive way, and end up either leaving, frustrated, or being removed from the forum for bad behavior in their responses. You might also want to consider that you are posting on a professional forum, made up of members that have 100s of years of accumulated experience, who have processed hundreds of thousands if not millions of dollars worth of material and know what they are talking about. They are freely giving their time in answering your questions without any benefit implied or monetary. In other words, these people do not know you, and yet are still willing to give up their valuable time reading your posts and attempting to respond in a way that will help you most.

The reason I bring this up is that your posts sound as if you are taking criticism as an attack, and responding emotionally to good solid information based on scientific fact, experience and knowledge that was years in the making and hard won. Imagine if you would that this forum did not exist, how would you then acquire this knowledge, without harming yourself or others around you?

You also stated:

I would argue I am. This is just an acquaintance test. But I get so excited! I just want to play!

I would not argue anything unless you are able to back it up with scientific proof, empirical data, or accumulated experience/knowledge. Acquaintance tests are done by the book, in a lab, under supervision usually, and using known materials, known processes with known results. They are done, so that the person doing them learns what the reactions or processes actually are. What you are referring to as an acquaintance test is really experimenting, and doing so with dangerous acids and harmful/deadly gases. If you want to "play", do so with a ball and bat, or a video game, or monopoly, but please, not with chemistry. It's far too dangerous, and the life that is harmed might not only be your own, but those whom you love that are around you at the time.

My guess is the oxygen from your torch is oxidizing the lead, you can try using a reducing flame, or just add a carbon source (charcoal, sugar, sawdust, flour) or some other source of carbon.

Caution do not breath those deadly lead fumes.

The oxygen in the propane is working as a shielding gas? Of course it is!

I know not to breathe the gas. Thank you.

You may know not to breath the gas, but you are using the wrong equipment, and believing it seems that it provides you with a level of protection which it honestly does not. Also, consider that you are not the only person reading these responses. If you spend any time reading posts, you will notice that senior members such as Butcher, almost always if not always, attempt to word things in such a way so that those that come after, who have not posted and read these posts, realize the precautions and safety measures they must employ to keep themselves safe from harm. It's not only you he is posting this information for, but for all others just starting to learn about these processes.

Finally, I would suggest not taking what is said here personally, but as knowledge hard won and freely shared without expectation of any benefit from you. You happen to be very fortunate that this forum exists and that people such as butcher are willing to answer questions that have been answered many times before.

I hope you do well in your endeavors, and I hope that you take what I have stated in the spirit I meant it, and not as a personal attack on you.

Scott

 

[Macleight]

Thanks everyone for their comments!

 

[butcher]

Scott ( NobleMetalWorks),
Thank you for that informative and helpful post, you seem to be able to put things into words which I struggle with.

Macleight, I wish I had time and the ability to help you understand better the many complexities of the chemistry behind this subject, truth is it would take many discussions that could last for possibly years, and it most likely would not be the best way.

The best way to learn is with study, the forum is a great resource, it holds a vast library of information, when you follow your interest, you can learn to process refine and recover precious metals, and be able to do so relatively safely, learning the chemistry and the physics involved, it does take time to learn, and non of us will live long enough to learn all there is about this vast science, but it is also what make this field so interesting, you can always learn more about it.

Right now you are new to this science, and seem to have many of the wrong assumptions most of us do when we are beginning, things do not work the way we think they do, they work the way they do, and we just need to learn how that is.

Welcome to the forum, a great place to learn how these things work, follow your interest on a particular subject, if you think something will work a certain way, research it to see if it really works that way or not, if you find a question keep it in mind, you will find the answer in the forum, or through your research, it seems one question leads to an answer and more questions, that is the beauty, this keeps this field of study interesting and a continued learning experience.

With all of this we should never assume we know enough about the safety, we work with such a complicated science and chemistry, we always need to understand more, and our goal should be to always strive to learn more in this area, and improve our technique, skills and knowledge in this area, that can be more important than gold.

 

[goldsilverpro]

PbO melts at 1630F.