circuit breaker contacts

[azgard]

anyone know what the contact points are on Circuit breakers. i have smashed a bunch open and they got round silver things welded to copper bar where it makes the contact for on and off for the breaker. i got a few diffrent types. some are very soft and i can easily slide off a piece with razor others are a little harder but are all a shiny silver color once i scratch on them.

 

[patnor1011]

This will be some silver alloy.
http://en.wikipedia.org/wiki/Circuit_breaker

 

[azgard]

anyone know what the percentages of silver would be on the alloys. i am trying to figure out if its worth my time to cut them off. whats the best way to test for silver content.

 

[patnor1011]

Try to use search function on forum. There is plenty of threads covering silver in contact points.

 

[adam_mizer]

Here is an interesting find and explains alot about the make-up alloys of contacts.
It seems to me in my opinion that a small contact in low current electrical may have to 95% silver in general.
From unsoldering contacts recently from make/break contactors like squareD from aproximately size0 to maybe size5 15amps thru 300amps devices and seeing a slight goldy color tint at the solder points may possibly be the cadmium-oxide types and will range at the worst from 83% to 90%.
My guess is 90% for lower amperage devices and 83% for heavy amperage devices now question would be to find out these amperage ranges to zone in on the actual percentages of silver to expect, in relation to contact size.
So again my opinion would be a large contact will be most likely to contain 83%ag and the smaller the higher the %ag available.

Anyways here is an excellent link for reference to the type of alloy used in contact points.

http://www.cmwinc.com/silver-contacts.php

Picture is roughly 22-23 ounces, large contacts to expect 83% and smaller at best probably 90%ag.

 

[goldsilverpro]

The thicker non-tungsten ones are generally made from coin silver, which is 90% silver. When you sweat them off, much of the the lower grade braze and some copper from the buss sticks to them. This lowers the percentage of silver. Based on the many 100s of pounds of these I ran about 15-20 years ago, from all sorts of sources, they will average from about 81% to 83% silver, when all is said and done. There is most always cadmium involved, which makes them quite hazardous to melt. Wear a particle mask when sweating them off and do this upwind out side. I used to heat the back of the buss, behind the point, with a torch and then slid the points off of the buss on the edge of a large coffee can, which had been secured to prevent it from moving around. I dissolved the points in 50/50 nitric, cemented the silver on copper, and ran it through a silver cell.

 

[Harold_V]

So again my opinion would be a large contact will be most likely to contain 83%ag and the smaller the higher the %ag available.

GSP has pretty well summed up the percentages, although he didn't discuss sintered tungsten contacts, which you will find used regularly. The backs have a waffle pattern, so they're easily sorted form other types. Tungsten, being very heavy, lowers the yield considerably.

I ran such contacts routinely. The yield is just under 50%, and they require a prolonged boil in dilute nitric in order to extract all of the silver. Keep the vessel covered with a watch glass. You can gauge the progress of silver extraction by removing a contact from the lot, rinsing well. It is then given a thumb break test. If all silver has been extracted, it will break easily. If silver remains, it may not break, and if it does, there will be a well defined line in the center of the contact, which is the area that has yet to have silver eliminated. Extraction can take hours---you must be patient.

You are best served to pour off the spent solution and allow it to settle. Filtering is a slow process and not necessary. You would likely benefit by filtering the remaining solids, after rinsing well to remove traces of silver.

Harold

 

[Barren Realms 007]

So again my opinion would be a large contact will be most likely to contain 83%ag and the smaller the higher the %ag available.

GSP has pretty well summed up the percentages, although he didn't discuss sintered tungsten contacts, which you will find used regularly. The backs have a waffle pattern, so they're easily sorted form other types. Tungsten, being very heavy, lowers the yield considerably.

I ran such contacts routinely. The yield is just under 50%, and they require a prolonged boil in dilute nitric in order to extract all of the silver. Keep the vessel covered with a watch glass. You can gauge the progress of silver extraction by removing a contact from the lot, rinsing well. It is then given a thumb break test. If all silver has been extracted, it will break easily. If silver remains, it may not break, and if it does, there will be a well defined line in the center of the contact, which is the area that has yet to have silver eliminated. Extraction can take hours---you must be patient.

You are best served to pour off the spent solution and allow it to settle. Filtering is a slow process and not necessary. You would likely benefit by filtering the remaining solids, after rinsing well to remove traces of silver.

Harold

Harold,

Did you have these contacts develope a layer of silver chloride on the surface and cause problems with the reaction? Or anything else that caused problems with contacts like these?

 

[goldsilverpro]

So again my opinion would be a large contact will be most likely to contain 83%ag and the smaller the higher the %ag available.

GSP has pretty well summed up the percentages, although he didn't discuss sintered tungsten contacts, which you will find used regularly. The backs have a waffle pattern, so they're easily sorted form other types. Tungsten, being very heavy, lowers the yield considerably.

I ran such contacts routinely. The yield is just under 50%, and they require a prolonged boil in dilute nitric in order to extract all of the silver. Keep the vessel covered with a watch glass. You can gauge the progress of silver extraction by removing a contact from the lot, rinsing well. It is then given a thumb break test. If all silver has been extracted, it will break easily. If silver remains, it may not break, and if it does, there will be a well defined line in the center of the contact, which is the area that has yet to have silver eliminated. Extraction can take hours---you must be patient.

You are best served to pour off the spent solution and allow it to settle. Filtering is a slow process and not necessary. You would likely benefit by filtering the remaining solids, after rinsing well to remove traces of silver.

Harold

Harold,

Did you have these contacts develope a layer of silver chloride on the surface and cause problems with the reaction? Or anything else that caused problems with contacts like these?

And, Barren, where does this chloride come from?

 

[Barren Realms 007]

So again my opinion would be a large contact will be most likely to contain 83%ag and the smaller the higher the %ag available.

GSP has pretty well summed up the percentages, although he didn't discuss sintered tungsten contacts, which you will find used regularly. The backs have a waffle pattern, so they're easily sorted form other types. Tungsten, being very heavy, lowers the yield considerably.

I ran such contacts routinely. The yield is just under 50%, and they require a prolonged boil in dilute nitric in order to extract all of the silver. Keep the vessel covered with a watch glass. You can gauge the progress of silver extraction by removing a contact from the lot, rinsing well. It is then given a thumb break test. If all silver has been extracted, it will break easily. If silver remains, it may not break, and if it does, there will be a well defined line in the center of the contact, which is the area that has yet to have silver eliminated. Extraction can take hours---you must be patient.

You are best served to pour off the spent solution and allow it to settle. Filtering is a slow process and not necessary. You would likely benefit by filtering the remaining solids, after rinsing well to remove traces of silver.

Harold

Harold,

Did you have these contacts develope a layer of silver chloride on the surface and cause problems with the reaction? Or anything else that caused problems with contacts like these?

And, Barren, where does this chloride come from?

That is a good question and not even sure it was chloride. It is a large set of contact that I was running that have given me fit's. I am using home made nitric that was made with distilled water and let set in an ice bath over night in 30 degree weather and then filtered.

I ran them in nitric the 1st time and removed the copper that had stuck to them from sweating them off of thier supports. What appeared to be silver chloride seemed to develope on them when the solution turned cloudy. This stayed in the solution. I washed them in distilled water to remove the residue and then ran them in some ammona to remove the silver chloride and some more of the copper residue, the deposit seemed to stay on the contacts. I heated them up and sweated some of the silver out and then put them back in nitric and the same cloudy substance showed up again. I even went as far as making a new batch of nitric up and the same thing happens with them. After I had sweated some of the silver out of the contacts and put them back in nitric the same clowdy substance appears but dissloves to an extent when the solution is heated. But the silver developes a frosty appearence and dosen't seem to get much of a reaction even tho I still get a small amount of brown fumes from the nitric reaction. It's the batch I had asked you about a while back and you had suggested they might be tungsten and to look for a post by Harold on processing them. I found this post by him and thought I would ask him about them and see if he would be kind enough to give me a suggestion on them rather than me just chasing my tail. I don't usually have problems like this but these things have beat the hell out of me.

 

[goldsilverpro]

http://www.goldrefiningforum.com/phpBB3/viewtopic.php?f=49&t=7532&p=68740&hilit=tungsten+contacts+nitric#p68740

Harold. How weak was the nitric?

 

[Harold_V]

http://www.goldrefiningforum.com/phpBB3/viewtopic.php?f=49&t=7532&p=68740&hilit=tungsten+contacts+nitric#p68740

Harold. How weak was the nitric?

I was never scientific about the process, just poured, roughly, 50% water (tap water in this case) to 50% tech grade nitric (68%?). As in all cases except for making electrolyte for my parting cell, I was never concerned about forming traces of silver chloride, for it all ended up in my waste material, where I hoped to have the recovered silver serve as a collector for greater values. I was rewarded with an excellent recovery, so I'm confident I made a sound decision in that regard, and there were no negative consequences from using tap water that I ever identified.

Back to the contacts, I don't recall ever having what I'd call a clear solution. None of the contacts are pure silver---they all have some alloying agent, some of which manifests itself as a cream colored material upon dissolution of the contacts. I talked about that in the post you referenced. In order for it to not accumulate in the digestion vessel, I always got it well in suspension so it would pour off with the silver nitrate. It was then allowed to settle well (didn't take long--a few minutes), then the relatively clear pale blue silver nitrate solution was siphoned off. I think that's what Barren is experiencing. It's not silver chloride, but is a fact of life when processing contacts. I suggest it be poured off as I did, then after siphoning the bulk of solution, rinsed a few times to recover traces of silver. After the final wash siphon, one would then filter the solids to recover the last traces of silver. Unless there is a recovery operation (by furnace), I would expect that the material would then just be discarded. No action is required to deal with the residue I speak of aside from continuing to pour it off with the solution. Otherwise it builds up so deeply that it tends to help isolate the contacts from acid. Best results in dissolving the contacts is achieved by heating the solution to a boil, keeping the vessel covered with a watch glass. I used to do this process in a 4,000 ml beaker.

I have no idea what the material is that forms the cream colored residue. Batches that were devoid of tungsten contacts formed the material. That is not to imply that tungsten doesn't liberate a residue----it does--but it's relatively low in volume as compared to the other types of contacts, what ever they may be.

Harold

 

[Harold_V]

I ran them in nitric the 1st time and removed the copper that had stuck to them from sweating them off of thier supports. What appeared to be silver chloride seemed to develope on them when the solution turned cloudy. This stayed in the solution. I washed them in distilled water to remove the residue and then ran them in some ammona to remove the silver chloride and some more of the copper residue, the deposit seemed to stay on the contacts.

Don't screw with them. Place them in a beaker that can be heated, add dilute nitric and heat to a boil, and maintain boiling, so the resulting deposit is kept in suspension. Insure that it is poured off when you pour off the pregnant solution. I do not recommend you allow contacts such as this to sit in cold acid.

Do understand, they are slow to dissolve, although faster than the tungsten contacts. Expect them to be in solution for an hour or more for complete dissolution, and that's when you keep the fluid at a low boil. Cover with a watch glass to avoid the loss of nitric and value.

Harold

 

[goldsilverpro]

Harold, when I ran them in nitric, I always thought the creamy colored material was a tungsten compound.

 

[Barren Realms 007]

I ran them in nitric the 1st time and removed the copper that had stuck to them from sweating them off of thier supports. What appeared to be silver chloride seemed to develope on them when the solution turned cloudy. This stayed in the solution. I washed them in distilled water to remove the residue and then ran them in some ammona to remove the silver chloride and some more of the copper residue, the deposit seemed to stay on the contacts.

Don't screw with them. Place them in a beaker that can be heated, add dilute nitric and heat to a boil, and maintain boiling, so the resulting deposit is kept in suspension. Insure that it is poured off when you pour off the pregnant solution. I do not recommend you allow contacts such as this to sit in cold acid.

Do understand, they are slow to dissolve, although faster than the tungsten contacts. Expect them to be in solution for an hour or more for complete dissolution, and that's when you keep the fluid at a low boil. Cover with a watch glass to avoid the loss of nitric and value.

Harold

Thank you Harold I will keep after them down that pathway.

 

[Harold_V]

Harold, when I ran them in nitric, I always thought the creamy colored material was a tungsten compound.

It may well be, for it somewhat resembles exactly what came from sintered tungsten contacts, although much greater in volume. Not knowing if tungsten was used aside from being sintered, could it be that a percentage of tungsten powder was used in silver, perhaps with the idea of increasing it's resiliency? Perhaps to better control arcing erosion? I was never concerned enough to do any research, which would have been, at best, difficult back then without having the internet at my disposal.

Maybe some of these guys can do some research and draw some conclusions. Contacts are a pretty good source of silver, so with the higher price now, they can be very well worthwhile for those that have a source for reasonably priced nitric.

One thing I recall with certainty. Silver that was recovered from tungsten bearing contacts yielded an inky blue solution when washed with HCl. That indicates to me that if Barren were to remove a little of the residue and add a drop of HCl, if it's tungsten, I would expect an inky blue reaction. How about it, Barren?

Harold

 

[Barren Realms 007]

Harold, when I ran them in nitric, I always thought the creamy colored material was a tungsten compound.

It may well be, for it somewhat resembles exactly what came from sintered tungsten contacts, although much greater in volume. Not knowing if tungsten was used aside from being sintered, could it be that a percentage of tungsten powder was used in silver, perhaps with the idea of increasing it's resiliency? Perhaps to better control arcing erosion? I was never concerned enough to do any research, which would have been, at best, difficult back then without having the internet at my disposal.

Maybe some of these guys can do some research and draw some conclusions. Contacts are a pretty good source of silver, so with the higher price now, they can be very well worthwhile for those that have a source for reasonably priced nitric.

One thing I recall with certainty. Silver that was recovered from tungsten bearing contacts yielded an inky blue solution when washed with HCl. That indicates to me that if Barren were to remove a little of the residue and add a drop of HCl, if it's tungsten, I would expect an inky blue reaction. How about it, Barren?

Harold

I will try that tomorrow and see what happens and let you know. Thanks for the heads up Harold.

 

[dtectr]

Harold, when I ran them in nitric, I always thought the creamy colored material was a tungsten compound.

I just processed 200g of new, plated-before-insertion pins from edge connectors in 50/50 nitric - 68%, made with phosphor-bronze, nickel-plated (30-100 microinches) & Au plated, min. 10 microinches, acc. to datasheet. I was plagued with Hoke's "gelatinous tin paste", metastannic acid, mixed in with beautiful foils.
I removed small samples of the paste to test & found it to be insoluble in ammonia, Nitric & later after several rinses, HCl, but since there was no solder to be accounted for, it must have come from the bronze alloy (3.5-10% tin), because I had to treat it as such. I gave the solution a boil in a mild steel pan, got a mild reaction, & a powder began to settle, tan in color, which I assume was tin, as (hopefully) all the Cu was dissolved in the nitric. In solution it was quite puffy

Could the tan powder be tin from the solder or alloy?

 

[Harold_V]

Could the tan powder be tin from the solder or alloy?

Judging from the specs you provided, tin is a component of the base material. You should see acceptable results by prolonged heating the foils along with the tan powder in HCl, assuming you incinerate the material prior to the process. That insures you don't lose any of the values to dissolution, the result of remaining nitric. I've talked about that method of processing many times previously. You won't eliminate all of the tan powder, but it will be altered to the point where it filters well.

I'm concerned about your comment of giving the material a boil in a steel pan. That's not a good idea. HCl readily dissolves steel. Do your boiling in lab glass (Griffin beaker works fine. Cover with a watch glass). Steel pans work fine for incineration, although they do oxidize rapidly. The Boy Scouts have a small stainless pan that is often found at second hand stores. They're perfect for incinerating small lots. Much slower to fail due to heating, so you get less contamination from the process.

Harold

 

[dtectr]

Could the tan powder be tin from the solder or alloy?

Judging from the specs you provided, tin is a component of the base material. You should see acceptable results by prolonged heating the foils along with the tan powder in HCl, assuming you incinerate the material prior to the process. That insures you don't lose any of the values to dissolution, the result of remaining nitric. I've talked about that method of processing many times previously. You won't eliminate all of the tan powder, but it will be altered to the point where it filters well.

i found this after trying to process this simply with nitric:
http://goldrefiningforum.com/phpBB3/viewtopic.php?f=37&t=8792&p=82825#p82825
Harold's usual admonition of roasting to red heat may be key in resolving metastannic acid problems?
"and at a red heat, into anhydrous stannic oxide."
[which is soluble in concentrated sulfuric acid.]
"According to Weber, nitric acid of specific gravity 1-2 converts tin, at ordinary temperatures, into stannous nitrate, stannic acid, and metastannic acid, which is coloured yellow by admixed stannous metastannate. With nitric acid of specific gravity 1-35, the products, if the liquid is well cooled, are metastannic acid [? stannic] and stannic nitrate; by dilution and heating, the stannic acid is converted into insoluble metastannic acid, which indeed is always produced under the influence of heat." both quotes A dictionary of chemistry and the allied branches of other sciences, Volume 5 By Henry Watts
http://books.google.com/books?id=cUcsAA ... 298&edge=0

I also wonder if stannic oxide is insoluble in HCl-Cl? Haven't tried that yet, though - any ideas?

I'm concerned about your comment of giving the material a boil in a steel pan. That's not a good idea. HCl readily dissolves steel.
Harold

With good reason! I did this before HCl but after nitric with several rinses. Once the "nitric" is expelled, am i left with simply HCl? And yes! SOMETHING began to dissolve the steel. :shock:

Though not great thinking, here was my reasoning at the time - I was trying to evaporate it down & thought the addition of the iron may precipitate the tin as a metal - It didn't & I was left with a grey/green cloudy mixture. But after letting it sit in Pyrex overnight, the grey/green liquid froze, & on careful thawing, I was able to easily pour the grey/green sludge off the yellowish powder & foils. I was then able to rinse out most of the yellow tin contaminate.

From this http://www.public.asu.edu/~jpbirk/qual/qualanal/tin.html could the yellow powder be a result of sulfide precipitation? just trying to get my head around this - most of the residue did dissolve readily in concentrated HCl.

any ideas welcome.
thanks