# Silver Contacts



## Goldfinger4

Hello!

I have no experiences with silver contacts but from time to time some are sold on ebay.
Can someone tell me how much silver you would expact on contacts like these : http://i.ebayimg.com/00/$%28KGrHqIOKi!E2+o!WjUSBN384%29Qw5w~~_3.JPG (1 kg at all)?

Are the contacts made of pure silver or an alloy? Cadmium could be a serious problem right?

Thanks!


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## Claudie

On the contacts pictured, it looks like there is a significant amount of other metals present. Most of what you would be buying is brass. There are posts here about silver contacts but I don't recall where I read about them. Maybe try a search for "Silver Contacts".

EDIT: Try this thread, it should help you. http://goldrefiningforum.com/phpBB3/viewtopic.php?f=50&t=10613&p=103014&hilit=silver+contacts#p103014


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## goldsilverpro

The contact points are silver soldered onto large, bulky pieces of silver plated (usually) pure copper bussing, which makes up most of the weight. As pictured, I would guess that the silver content would be between 2% to 5% of the total weight but, as I said, that is a total guess. The contacts, themselves, are usually 90% silver with the remainder copper or a mix of copper and other metals such as cadmium. Although I don't see any, if any of the points are of the tungsten/silver variety, the silver content of these will be much lower, typically between 25-40%. The silver solder is likely to contain cadmium.

The points are generally removed from the copper bussing by holding them with long pliers (using heavy welding gloves) and heating only the copper behind the point with a torch, until the solder just melts, and then sliding the point off with a small steel rod (I used a heavy stainless dinner knife) into a can. This must be done with good exhaust or outside (upwind) because of the possible cadmium fumes. The sweated points will generally run about 80-82% silver, since they now contain lower silver content silver solder and they have picked up some of the copper from the bussing.

It is not safe to now melt the points due to the very possible cadmium content. They are usually dissolved in 50/50 nitric acid and the silver is then cemented out of the solution with copper. If all this goes well, the resulting silver can be about 99% pure.

The silver plating on the copper bussing is quite thin and doesn't contribute much to the total silver value.


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## goldsilverpro

RosyWilliams said:


> Btw, what's wrong with this metal? My ears always suffer after I wear silver earrings. Do I have a bad silver or just my ears are bad? LOL


And what does that have to do with silver contact points?


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## Goldfinger4

Thanks, the processing would have been my next question. Do you think it is possible to remove the silver points with hammer and chisel without heating?
I really don't want to come in contact with cadmium and would send the silver points to a refinary..

@ Rosy: Do you mean cadmium? It settles down in your kidneys and disturbs your calcium metabolism for years.


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## kurt

Hi goldfinger4

I just bought 600 lb of contactors & just getting down to the last of the processing. That was 600 lb of the complete contactors meaning the plastic housing & all.

Anyway – looks to me like most (if not all) the points pictured came out of magnetic disconnects 

Without something of known size (a dime or penny) in the pic its hard to say what there actual size is but my best guess would be that they are about the same size as the ITE disconnects I just did which would put each de-soldered point at about ½ a gram each of about 90% Ag

If you look at the one with a point on each end of the buss bar you are probably looking at “about” 7 or 8 grams total weight & about 1 gram Ag in the 2 point - so you can kinda use that to judge silver to copper/bass on the others.

However – when it comes to points – you run it ALL KINDS of different things. --- Some are actually copper capped with Ag. In this case the Ag cap is only about 1/3 of the point. There are some that have an Ag top cap with a magnetic base metal for that bottom 2/3 of the point. Some are an Ag/tungsten alloy (about 30% Ag &70% tungsten) in that case you need to boil them in nitric for several hours to leach out the silver --- & that’s just the tip of the ice berg.

As far as removing the point from the bus bar – NO – you wont be able to do it with hammer & chisel. They are not soldered on with a soft solder but rather brazed on with a Ag barring braze or hard solder (this is often were the cadmium is) so you ether have to cut the buss bar as close to the point as you can with wire nippers - & dissolve lots of copper with the silver – or de-solder them. 

If you de-solder it takes “a lot” of time & “a lot” of mapp gas – in some cases I have had to use oxy/acetylene. If you nip them – its faster – but it takes “a lot” more acid as it take 4 time more acid to dissolve a gram of Cu then a gram of Ag & when you nip them you have 3 or 4 times more Cu to dissolve then Ag.

If the points are rived on instead of soldered on you have to ether nip them (cut bus bar close to point) or drill out from back side. --- I nip them if the buss bar is not to heavy & drill out or de-solder if buss bar is heavy.

Hope that helps
Kurt


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## goldsilverpro

kurt said:


> Without something of known size (a dime or penny) in the pic its hard to say what there actual size is but my best guess would be that they are about the same size as the ITE disconnects I just did which would put each de-soldered point at about ½ a gram each of about 90% Ag


I think you're right. They're a lot smaller than I first thought they were. When silver was $6, these weren't hardly worth messing with.


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## Goldfinger4

So if it is so much manual labour to recover the silver, what estimated hourly income did you receive?

Dealing with silver scrap I sometimes feel like a Nigerian slum inhabitant who burns our e-scrap for metal recovery and wastes his health for a few dollars^^








But silver looks so nice


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## kurt

About as much as a Nigerian slum inhabitant & because silver looks so nice --- Its an addiction 

All kidding aside – I am not quite done yet, but it looks like on this batch about $10 an hour. However this batch was about learning & I can see several things to improve the process.

Right out the gate – on this batch I ran each type of contactor (magnetic disconnects, breakers, relays, timers, etc) as there own batch to see what recovery was per type of contactor. Next time I will just brake them all down & run the point as one batch. That should cut time by 1/3 to ½

Maybe a stamp mill or hammer mill for busting up the plastic on some types. And besides the silver you do get some return on the copper & brass. The bigger the better on the Cu & brass. I had one 1600 amp disconnect that was 150 lb & 38 of that was copper.

Kurt


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## Barren Realms 007

kurt said:


> About as much as a Nigerian slum inhabitant & because silver looks so nice --- Its an addiction
> 
> All kidding aside – I am not quite done yet, but it looks like on this batch about $10 an hour. However this batch was about learning & I can see several things to improve the process.
> 
> Right out the gate – on this batch I ran each type of contactor (magnetic disconnects, breakers, relays, timers, etc) as there own batch to see what recovery was per type of contactor. Next time I will just brake them all down & run the point as one batch. That should cut time by 1/3 to ½
> Maybe a stamp mill or hammer mill for busting up the plastic on some types. And besides the silver you do get some return on the copper & brass. The bigger the better on the Cu & brass. I had one 1600 amp disconnect that was 150 lb & 38 of that was copper.
> 
> Kurt



You might want to rethink the highlighted section till you know more about how the different contact's break down while being dissolved.


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## Harold_V

Barren Realms 007 said:


> You might want to rethink the highlighted section till you know more about how the different contact's break down while being dissolved.


That's not an issue. I used to run mixed contacts routinely. Those that have no tungsten dissolve and are long gone, not interfering in the least with the operation. The only real disadvantage is that you can't determine percentages. 

Harold


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## depperl001

RosyWilliams said:


> Btw, what's wrong with this metal? My ears always suffer after I wear silver earrings. Do I have a bad silver or just my ears are bad? LOL




Hi Rosy,

Your Earrings are made from Silver containing Nickel. You get what is known as Red Ears,
a allergic reaction. I don't know where you get your earrings but Topako Mercantile make silver settings that are Nickel free.

Regards,

Josef Vavryn


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## kurt

Thanks for answering that Harold – I thought I had just explained how I just got done running numerous small batch’s separated by type (& I did that mainly to find out yield per type)

I should mention that I do run a magnet over them before putting in acid & anything magnetic I run separate from non-magnetic & that’s done only to keep magnetic base metals & non-magnetic base metal solutions separate. 

So its really – in the future I will run everything in 2 batch’s – magnet & non magnetic – which should cut my time by 1/3 or ½ --- maybe even more then ½ - considering I just ran about 12 batch’s separated by type.

I now know how much to offer electrical contractors in my area for contactors based on yield per type of contactor.

Kurt


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## Oz

kurt said:


> I now know how much to offer electrical contractors in my area for contactors based on yield per type of contactor.


A wise investment of your time.


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## kurt

Thanke as Oz

I should maybe mention that prior to running this 600 lb lot (thats 600lb of contactors still in there plastic housing) I had run numerous even smaller batch's by type to see if there was any concerns about proccessing types of points on the chem proccess end - which is why I will continue to run magnetic & non-magnetic in there own batch's. 

Concerning tundsten/Ag alloyed points - you can (to start with) run them along with the non-magnetic points & when everything except the tungsten points are dissolved - pull your solution off to cement or precip with HCL (which ever you prefer) & then add some more nitric & boil for several hour to leach the Ag out of the tungsten (tungsten remains un-dissolved) Use a dilute nitric here due to evaporation

Kurt


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## Harold_V

kurt said:


> Thanks for answering that Harold – I thought I had just explained how I just got done running numerous small batch’s separated by type (& I did that mainly to find out yield per type)


Yep, I understood your post, Kurt, and endorse it heartily. Having an understanding of content is quite important if you're buying materials. 

Having read more of your posts in this thread, it's clear you understand extraction procedures, in particular with tungsten contacts. 

Harold


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## kurt

Well I can’t take all the credit for doing a good job &/or sounding like I know what I’m doing. In fact – most of the credit needs to go to “all you guys” on this forum that have taken the time to provide it, moderate it & share your vast knowledge & experience in refining PMs.

I have spent countless hours reading the advice posted by you pro’s on this forum (as well as Hoke’s) for the last few months. I only wish I had found this site a little over a year & a half ago when I first started playing around with this. Only God knows how much I have lost (its been a lot) to the HUGE amount of bad advice floating around out there on the net. --- I was really beginning to get discouraged with it all

Now I look forward to each day & what my days efforts are going to produce. --- So the credit really goes to the bunch of you all – you’re an AWESOME BUNCH OF GUYS --- & I only hope I can give back some in time to come.

Kurt


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## oldgoldman

I've read for about 4 hours on the Silver Removal issues and still need important advice.

I am evaluating the contacts here from a large industrial breaker.

I want to prepare for most reliable outsourced refining .. and tight yields.

How should I cut out the Cu with light industrial tools ??

Don't want any Cadmium Risk .. just close to $$ spot value as possible .. maybe 90% Ag / 10% Cu + Solder ??

Thank you in advance ..


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## glondor

I think the proscribed way is to heat the back side of the copper and melt the solder. Slide the contact off with a tool. Cheap and easy. ( As per Gold silverpro)

Cutting will be slower and messier I believe. I believe a map torch would do the trick. Just don't get things too hot and all should be well.


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## jimdoc

Good luck finding a refinery to take them. 
Most won't because of the chance of cadmium content.

Jim


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## oldgoldman

Maybe I won't be going Silver hunting..


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## jimdoc

Don't stop saving them. You just have to find the right person to process them.
When silver prices keep rising, they should pass the point where cadmium is not
a money losing problem. I don't know what that price would be, but I am curious.

Jim


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## old thompson

I had about 7 or 8 lbs. of silver alloy three phase motor starter contacts processed for me by an anonymous refiner a few months ago. To get a ballpark figure of the yeild I measured the volume of the contact points in milimeters, multiplied by a pecentage of what I thought the silver content might be (betweeen 90% for coin contacts and 50% for tungsten), and then multiplied by silver's mass of 10.49 grams per a cubic centimeter. 

My high estimate was with a 90% silver content and the processed contacts came out to within 50 grams of what I estimated. I guess my contact points were pretty close to 90% silver. Also my refiner was an honest man.

I got a few more pounds of contacts still on the buss but I am waiting till winter to maybe try refining them myself.


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## Sodbuster

oldgoldman :

" How should I cut out the Cu with light industrial tools "

I think I would have to try and just crack them off. To me, in the picture it looks like the point itself is a tad bit wider than the buss. 

If I cold clamp the point in a vise leaving the copper hanging out I could just grab it (the buss portion) with pliers, and with a slight wobbling side to side it should fatigue at the solder. 

Some may snap off clean wile others may have small bits of buss come off with it.
The key to doing it this way would be weather or not you could clamp the point only into the vise being as small as they are. 

Just a thought 

Ray


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## kurt

I am on the tail end of tearing down about 300 lbs of contactors I just picked up this week. I should be done processing them by monday or tuesday & will post the details when I am done.

I think you will find that the points in the picture are going to be of the tungsten silver alloy type which only run about 30 % silver (maybe a little more) & you will need to "boil" them in nitric for several hours to leach the silver out of them. Dilute the nitric to allow for evaporation. they get real brittle once the silver is leached out which is how you tell if all the silver is leached out. After they have boiled for awhile brake a couple of them in half, if they are brittle & consistent in color all the way to the center they are done

If the bus bar they are soldered to is to heavy you wont get it hot enough with mapp gas because the solder is a hard solder (brazzing) not a soft solder so you may need oxy acetalene


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## kurt

contact points are attached to the bus bar with a hard solder (brazzing) in order to with stand the momentary heat from the arc when they make contact - not soft solder. So "high" heat is the only way you are going to remove them from the bus bar. Mapp gas only works if the buss bar is not to heavy & even then it takes a lot of mapp. If the buss bar is heavy - get out the oxy acetalene

chiseling them off or trying to brake them off in a vise wont work - been there - tried that - good luck

the other option - if the bus bar is not to heavy - is to cut the bus bar close to the point with a nippers - but then you have a lot of copper to dissolve & it takes 4 time as much nitric to dissolve a gram copper then a gram of silver

Kurt


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## Sodbuster

I agree with Kurt.

" I think you will find that the points in the picture are going to be of the tungsten silver alloy type "

I find that any time they are brazed on, or irregular shaped, they are very likely to be tungsten silver alloy. But their are exceptions. 

I also find tungsten silver in most, if not all of the breakers I have ever dealt with. 

Ray


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## oldgoldman

thank you for the information .. i'm getting them all next week and will be collecting in the meantime

i'm going to use 30% recovery for the business case estimate just to be safe..

the buss bar Cu is annealed I believe and it would take an act of God to remove the contact by chisel, saw etc. I tried the biggest of bolt cutters and barely got through anything.

i'll try the cubic mm calculation to project net Ag value per contact.


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## rusty

oldgoldman said:


> I've read for about 4 hours on the Silver Removal issues and still need important advice.
> 
> I am evaluating the contacts here from a large industrial breaker.
> 
> I want to prepare for most reliable outsourced refining .. and tight yields.
> 
> How should I cut out the Cu with light industrial tools ??
> 
> Don't want any Cadmium Risk .. just close to $$ spot value as possible .. maybe 90% Ag / 10% Cu + Solder ??
> 
> Thank you in advance ..



I rigged up an old bench grinder with a water injector trickling onto the wheel, for the water pump used an aquarium air pump to transport the water onto the grinding wheel. The aquarium pump will do a good job with water as long as you can keep the ground up silver particles from entering the pump.

Everything except the pump sits inside a wooden box with enough water to feed the pump, your silver will collect in the box where you can collect it later for further refining.

Regards
Rusty


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## oldgoldman

it does appear the contacts are alloyed .. when one broke, it looked pretty grainy on the inside.

the bed however where the contacts make contact is different. it was so soft I shaved it away with my small swiss army knife.

this may be where the money is ..


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## Goldfinger4

jimdoc said:


> Good luck finding a refinery to take them.
> Most won't because of the chance of cadmium content.
> 
> Jim



I sent 3 kg of 60% silver, containing 180g cadmium, to a refinary. They wanted 140 USD for refining and 70 USD extra for the cadmium pollution.


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## snail

When I process contacts like the ones pictured in oldgoldmans post, I clamp the copper in a vise with the silver just above the jaws. Then I use a 12in adjustable wrench to twist the contact off. This works like a shear. I also use a pair of Vise-Grips and a wrench in a similar manner to remove small relay points. I find it cuts the base metal much easier than bolt cutters or snips, Dale


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## RESET

I just collected a single 300 amp contact switch. After taking it apart I found that the contact pads were silver. The metal of the pad is dead soft, I can slice some off with an x-acto knife. Half of them look like they are soldered onto copper bars with some kind of ferrous metal attached. The other half are soldered into a copper bar. The copper and ferrous bar seems to be plated with some kind of soft grey metal. I am hoping it is also silver but have no clue. The buss bars from the switch are also copper plated with the grey metal. 





Any suggestions on processing or opinions on what the plating may be?


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## Geo

looks like tin.


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## RESET

Thanks, now I have an idea what I am dealing with. Time to do some research. Copper is my bread and butter so I hope to keep that intact. This will be my first venture into anything dealing with precious metals. Can anyone give me a quick hint how to remove the tin without harming the values or the copper?


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## Geo

you can leave the tin in place and still sell the copper for #2 prices, of coarse if you heat to remove the silver it will still be #2. use a respirator that is rated for smoke pollutants (cut dust mask in large enough pieces to cover inlets on respirator and use a rubber band to hold them in place) and wear gloves that can be disposed of. heat the heavy copper and not the silver, when you see the solder melt (it will be easy to see) push the contact point off the copper base with a tool. after all the points are off gather the points and solder drops in one container, place copper in another container to be recycled. clean torch tip and clean area of any solder. remove and discard gloves, remove respirator and remove and discard dust mask covers and clean respirator with warm water and mild detergent. take a shower and wash clothes seperately from other clothes. now you have your silver contacts safely and ready to be processed.


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## RESET

That is awesome. Thanks for the info. 

I think I may leave the tin. I will have to see what the cost difference is between Lye treatment to remove it or leaving it and getting a lower price for the copper. 

Some of the other scrap I have collected has gold plated pin connectors. I will be reading up on that while I collect more. I am very glad I found this forum.


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## Goldfinger4

In which electronical parts are such silver contacts to be found? For breakers, is there a correlation between capacity and amount of silver?
Some pictures of parts and the estimated amount of silver would be helpful. As silver recycling becomes more popular one has to find new sources


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## Geo

ive found that most breaker switches do not contain silver contacts but tungsten. the most average contact points you will find in general scrap will be the switches in large heating/cooling units but smaller contacts can be found in a large variety of places even microwave ovens. a way to determine if a contact is silver or tungsten is the most dangerous and that is to heat it up with a small torch, if the contact turns white its silver and if it turns black its tungsten, also if your not sure from the appearance the silver contact will be smooth on the back and the tungsten will have a waffle pattern (i assume to dissipate the heat). large switches for electric engine start (especially 3 phase) and lighting assemblies for large buildings will have the largest contact points. be care with all of these as there will be the presence of the heavy metal cadmium which is toxic to handle or breath the smoke or vapors from sweating them off the base metal.


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## RESET

Since heating releases the cadmium vapors, would I be able to cut the copper close to the solder/braze then dissolve the points in nitric? Could I then cement out the silver or drop it out with salt/HCL and bypass any interaction with the cadmium? Hoke's doesn't get into the heavy metal, that I saw, and that is all I have read so far. Would it cement out with the silver? Would the salt/HCL drop the cadmium with the silver?


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## butcher

http://en.wikipedia.org/wiki/Cadmium_chloride
http://en.wikipedia.org/wiki/Reactivity_series
http://www.ausetute.com.au/solrules.html

From these we see silver is insoluble as chloride, but cadmium is soluble.
silver and cadmium are soluble in nitric acid or as nitrates.

Silver is lower in series than copper, cadmium is high in the series of metal, and would not cement from nitrate solution using copper buss bar

Copper buss bar would be my choice for cementing silver from the nitrate solution it can be washed and melted, silver chloride if formed would need conversion before melting.


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## Geo

one gallon of nitric acid will dissolve 8 pounds of silver but a gallon of nitric acid will only dissolve 2 pounds of copper. cutting contact points close but leaving copper on the point will seriously inhibit the amount of silver you can process with a certain amout of nitric acid. it would be more cost effective to remove as much of the copper before processing as possible.


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## RESET

Excellent Info. Thanks guys. I knew someone was going to mention the reactivity series in a reply to that and was going to look it up today. Thanks for the link. Would I be correct in thinking that if I dissolved both in Nitric then precipitated using salt/HCL I would create both cadmium chloride as well as silver chloride? Would I then be able to remove the cadmium chloride with liberal amounts of hot water rinses? Leaving the silver chloride clean to convert to silver metal, resulting in higher purity than the cementing process?

Geo, I appreciate the input on the cost effectiveness. I have no where near 8 lbs of silver in these contacts. I am guessing closer to 1.5 to 2 ozt. The amount of copper that would remain attached would probably be minimal since I want to save as much as I can for the recycler. I can not sell them anything that they can not identify so I can't even cement out the copper and melt it later. It will be lost in the dissolution process. I can get Nitric rather easily thru work and not have to pay shipping charges, maybe the hazmat but I am not sure. I calculate the 2 ozt to need 65.25 mL by your dissolution ratio. What concentration is that at? I assume the volume goes up at the amount of water goes up. Is that at 70% nitric or do I need to account for the volume of water as well? I can start with 65 mL and slowly add more until all is dissolved. I can get 1 L of 70% nitric for roughly $45 and have plenty left over for other processes. MAP gas and all the other gear needed just to sweat the contacts off of the copper would cost me more than that. (Yes, I sell scrap metal and do not own a cutting torch or MAP gas. I usually deal in copper and aluminum and just sell it whole without cutting.)

Is my reasoning sound?


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## Geo

actually that ratio is for tech grade nitric acid (70%) just remember that in some instances dilute nitric acid works better than concentrated, like for silver for example. the volume increase lets more copper go into solution as well as silver. the reaction of concentrated nitric acid on silver is very slow to start. i believe the concentrated acid creates a layer of oxidized metal on the surface that inhibits the acid from further attacking the metal underneath.


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## RESET

After reading the silver section in Hoke's book, last night, I thought I had it clear in my head how to deal with the AgCl. Now, after reading some posts about dealing with the AgCl, maybe I will just cement out the silver and sell it as less pure silver. At $3/Lb copper is cheaper than HCL and it will be far easier to deal with the metal than the AgCl. Just when you think you have things figured out...


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## goldsilverpro

RESET said:


> After reading the silver section in Hoke's book, last night, I thought I had it clear in my head how to deal with the AgCl. Now, after reading some posts about dealing with the AgCl, maybe I will just cement out the silver and sell it as less pure silver. At $3/Lb copper is cheaper than HCL and it will be far easier to deal with the metal than the AgCl. Just when you think you have things figured out...



I certainly agree. If done right, with no free nitric in the silver nitrate solution, a pound of pure copper will cement almost 50 oz of silver. Cu buss bar is the best; Cu tubing is OK; Cu wire is the worst because the cemented silver particles get trapped among the wires. Don't produce silver chloride intentionally unless absolutely necessary (I could give a couple of examples when this is necessary, but they are rare). Working with silver chloride is difficult and, if you don't do it right, the final silver purity can be less than well-rinsed cement silver. Also, it's not easy to get 100% conversion of the silver chloride, in many cases, and anything unconverted will likely be lost in the melt. Think cementation and then think silver cell, if you want pure silver and a simpler life.


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## RESET

I was just coming back here to say that I am considering using a silver cell with cemented silver. This sounds simpler. I have experience with electrolysis cells, just have to do some reading about a silver cell. I see that there area several people using the cells but have not yet found anything showing the ins and outs. I suppose I could buy Steve's video. I just hope that processing this silver pays for the video, nitric and everything else that I am going to have to use.


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## Geo

some times its cheaper to make the nitric acid than to buy it. it depends on your experience with making it of course and the price of components. the price of me buying by the 5 gallon container is comparable to the price i pay to make the same amount. it would be much simpler to buy it but i have a storage issue.


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## RESET

I have done a little research into making my own nitric. I think at this point I would rather have a known concentration and pay for it than possibly trying to use water to dissolve silver. :lol:

Tell me if I am on the correct track here. First I dissolve the silver, copper and whatever else is in the points in Nitric acid. I only use enough nitric to dissolve the solids that I have. Then I just dangle a buss bar in the solution and the silver will cement out, being replaced in the solution by copper. Now this is where I am fuzzy. Do I now wash the silver and dry it and then dissolve it in Nitric again to create my silver nitrate solution that is used in the silver cell? Where do the bars of silver for the cell come from?

EDIT: OK so I could keep half of the cemented silver and melt and cast into a bar for the cell then dissolve the other half in nitric for the electrolyte. I assume that the solution is saturated. If I had silver of unknown purity could use that for the bar instead?Does the purity of the bar effect the purity of the silver that precipitates from the cell? I have some solid silver parts that I took out of a cellular signal booster. Could I melt these or should I dissolve them and cement them first?


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## Geo

ok. the electrolyte needs to have a little copper contamination in it or the crystals will adhere to the cathode tightly. the silver cemented with copper should contain enough copper to serve this purpose so digest the silver you cement for the electrolyte. the electrolyte will balance itself out with the correct amount of silver the first time you use it. your anode can be any metal of high silver content, even large contact points. you will use a basket with a cloth filter to catch the "slimes" which will contain all the impurities from your silver. just dont use points that have a big chunk of copper on it. you cant run silver plate in the thumb cell. the silver cell is the final step in refining your silver, if done correctly the crystals you make will be relatively pure. after cementing, melt the silver into one larger piece and then solder (use silver solder) a silver hook onto your anode to suspend it into your solution with. i would suggest using a phone charger with less than 5v at around 350 milliamps for good crystal formation. on a side note, dont toss your copper nitrate into your stock pot right away because it can be used in a copper cell other forum members are working on that can be used to plate out copper and leave the PM's behind in the anode slimes which would be most useful.


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## Goldfinger4

I hope you read the security instructions on wikipedia for cadmium.. and especially for cadmium chloride.
Cadmium and zinc in the solder will dissolve under production of hydrogen. The hydrogen bubbles will soar up to the surface and cause an aerosol containing all the stuff like cadmium and you will inhale it or at least release it to the environment. And there is always some vapour, even at room temperature.
The washing water will be extremely toxic and as you won't be able to wash out all cadmium you will vaporize the rest when melting the silver.

Maybe I'm too careful, cadmium solder is used for many years.. but I would not try to refine it for myself. You could ask a refinery.


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## Geo

there are simple precautions you can do to protect your self and others from contamination. and if the truth be known there are many heavy metals that are dealt with while refining and cadmium is just one, there are a host of toxic metals and minerals we deal with. if done properly you should be able to process this with no more danger than working with lead or mercury which we deal with almost on a daily basis. if you miss a button battery from an old computer you have put more mercury into your process than you have cadmium from a few contact points. make sure to use the proper PPE's, make sure they are in good working order, clean work area thoroughly and wipe down all exposed surface with mild detergent and warm water after each work session, wash and/or clean PPE's after each work session with mild detergent and warm water, make sure to dispose of all cloth or paper cleaning products after you clean up in proper waste disposal manner, never pour wash water onto the ground or storm drain, reduce air pollutants by keeping your work covered, wash hands often during breaks and never put fingers in your mouth or rub your eyes, always shower immediately after working with heavy metals and wash cloths separately from household laundry, use disposable gloves that can be discarded after each work session or break time. with proper work and cleaning habits you should be able to work with these metals safely.


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## RESET

Goldfinger4 said:


> I hope you read the security instructions on wikipedia for cadmium.. and especially for cadmium chloride.
> Cadmium and zinc in the solder will dissolve under production of hydrogen. The hydrogen bubbles will soar up to the surface and cause an aerosol containing all the stuff like cadmium and you will inhale it or at least release it to the environment. And there is always some vapour, even at room temperature.
> The washing water will be extremely toxic and as you won't be able to wash out all cadmium you will vaporize the rest when melting the silver.
> 
> Maybe I'm too careful, cadmium solder is used for many years.. but I would not try to refine it for myself. You could ask a refinery.



I am no longer planning on precipitating with salt/HCL so no chlorides will be formed. I have an old HHO cell that I could dissolve the points in and run the gasses thru a bubbler full of activated carbon and water. I could then bring the activated carbon in to work and have them dispose of it properly with the acid gas fume hood filters that I change every month.

EDIT: I just thought of a side note. Could I put the tin covered bars in the resulting copper nitrate solution, after cementing out the silver, and remove the tin, dropping some copper from the solution? I could also do this with the trimmed ends to make sure that all lead, tin and cadmium has been removed from the bars as well, correct? It has been a while since high school chemistry so I am trying to get this all back in my head. When looking at the reactivity series. Am I correct to assume that it could also be read as an order in which the metals are dissolved when Nitric acid is introduced? Lesser metals being dissolved first and greater metals only being dissolved when there is "room" for them in the solution. For instance, if I only added enough acid to dissolve the copper that is present, 2 lbs per gallon, would it not effect the silver if these two metals were the only thing in the experiment?


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## butcher

"When looking at the reactivity series. Am I correct to assume that it could also be read as an order in which the metals are dissolved when Nitric acid is introduced? Lesser metals being dissolved first and greater metals only being dissolved when there is "room" for them in the solution. For instance, if I only added enough acid to dissolve the copper that is present, 2 lbs per gallon, would it not effect the silver if these two metals were the only thing in the experiment?"

Well yes to a very limited extent it would be true, but in reality most all metals would turn to nitrates of that metal, the higher in series are much more reactive and would dissolve vigorously, the metals lower in series would dissolve slowly (unless a passivation was involved with that metal), now if all metals did not dissolve and some metal was left in solution, any of the metals lower in series would cement out of solution as powders


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## seawolf

Is there a test procedure to see if cadmium is present? I have seen cadmium test kits for sale on Ebay but they are expensive and only for one shot. Does anyone know the chemicals used in the test kits?
If the silver contacts could be sorted out then I feel they could be dealt with more safely.
If this has been covered before please post links.
Mark


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## butcher

Here are some web search results,
I did not look very long.
They also make test kits for water.
hhttp://boomeria.org/chemlectures/qual/qualnotes.pdfttp://in.answers.yahoo.com/question/index?qid=20110105222133AAbILL4
http://pubs.acs.org/doi/abs/10.1021/ed017p532
http://pubs.acs.org/doi/abs/10.1021/ed018p525


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## seawolf

I went to the links provided above, the first one will not work on my computer, the other two give the first page and for a small fee the rest can be purchased.
This made some good reading but what I am trying to accomplish is some type of test where a small amount of the metals in question could be digested in nitric acid then neutralize the nitric and add a drop of X solution to get a color change or other reaction. This could/would be done before removing the contacts and possibly exposing me or others to cadmium fumes. Also it would make removal/reporting the cadmium in waste solutions possible.
Mark


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## Geo

i may be wrong about this , but i have never found anything that says that there are cadmium fumes released during dissolution. where the cadmium get into the atmosphere is when the bubbles of hydrogen are released and come to the surface and pops, it forms an aerosol mist that contains the metal thats in the solution. a simple way to avoid this is to cover your container before the reaction starts and to keep it covered until the reaction stops. unless cadmiun can mix with NOx i dont think fumes would be and issue.


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## butcher

Where I would be more concerned about cadmium would be in fumes of melting, and in waste solutions.

a search of qualitative analysis test for metal Ions in solution, will help you see some testing procedures, usually these are done as a series’ of steps to remove metals that may interfere with the test of a particular metal, and the steps must be followed in sequence, you may be able to find some test strips at a pharmacy to test for heavy metals in drinking water.


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## RESET

Geo said:


> unless cadmium can mix with NOx i dont think fumes would be and issue.



I have been doing a little reading and have a question on this. I have read that the addition of peroxide to the nitric acid can reduce the production of NOX fumes, the peroxide reacts with the NOX and forms new Nitric acid (or something like that). Would this help to keep any cadmium in the solution and out of the air? I have access to the acid gas filters used in the fume hood I use at work. We change them out every month regardless of the hours on them. Could I cover my reaction with one of these to absorb and NOX fumes that come out of the reaction?


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## Geo

RESET said:


> Geo said:
> 
> 
> 
> unless cadmium can mix with NOx i dont think fumes would be and issue.
> 
> 
> 
> 
> I have been doing a little reading and have a question on this. I have read that the addition of peroxide to the nitric acid can reduce the production of NOX fumes, the peroxide reacts with the NOX and forms new Nitric acid (or something like that). Would this help to keep any cadmium in the solution and out of the air? I have access to the acid gas filters used in the fume hood I use at work. We change them out every month regardless of the hours on them. Could I cover my reaction with one of these to absorb and NOX fumes that come out of the reaction?
Click to expand...

there are several ways to keep NOx from escaping, but i feel the best way is to use a reflux on your reaction chamber. it can be some thing as simple as a piece of glass tubing sealed in the top of the flask on a cool day. there are reflux devices you can buy that distill the vapors back to your flask. this will actually save on chemicals because the fluid returned is nitric acid. with a reflux device attached you shouldnt have anything coming from your reaction but water.


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## RESET

Thanks Geo, I will look into a reflux device.


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## Goldfinger4

Silver dissolution: 3 Ag + 4 HNO3 -> 3 Ag(NO3)2 + 2 H2O + NO
The NO produces the fume - it reacts with oxygen from the air to brown NO2 which can react with water in your lungs to new nitric acid.
With H2O2 in your solution: H2O2 + NO -> NO2 which reacts to HNO3.
In theory this could save some acid because new acid is permanently produced.
BUT: Hydrogen peroxide is much more expensive than nitric acid and it decomposes in contact with metals (2 H2O2 -> 2 H2O + O2), especially with copper.
This reaction will dilute your nitric acid and make it less reactive and it causes much more bubbles than the original reaction which would spread out a corrosive aerosol of the whole solution, including cadmium ions (if there are some).

I would not recommend the use of hydrogen peroxide.


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## RESET

Well, I finally got some Nitric. 70% and it cost me $80 for 2.5L, ouch. I only have a couple Pyrex dishes for now but I put 150ml nitric/water in one of the smaller ones to dissolve some smaller contacts that I had. They were the plated type, nothing with the big pads on them like the ones discussed here. I also added a couple solid silver connection type pieces that i had. There are still some large pieces left and some silver started cementing out but this was at room temp and I did not weigh my samples first so I need to heat and possibly add more nitric/water mix.


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## Geo

yes. heating will excite the acids atoms causing more reaction making your acid go farther. be sure you dilute your acid 50/50 with water. add acid till all metals are dissolved.


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## RESET

How would I go about adding acid/water while heating? I don't want to break my dish. I would like to heat the solution first to save acid. If I add my 50/50 slowly, do you think it will be OK? the depth of the solution is only about an inch or so and I will be heating on a potpourri heater. I see lots of posts saying to heat and more saying NOT to boil. is there a target temperature I should shoot for?


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## goldsilverpro

DON'T direct heat Pyrex kitchen dishes - ever! They are made for oven use only and they will break on a hotplate - guaranteed! Besides labware, about the only common Pyrex vessels that will take direct heat, at all, are Pyrex coffee pots. Even then, you have to be careful. Ideally, you would place the coffee pot in a Pyroceram Corning Ware dish, just in case it did break.


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## RESET

Thanks GSP, did not know that. I have had the dish on the potpourri heater once, for something else, but never again. I have the dish in a Corning dish during the reaction but my heater probably would not fit in there anyway. Looks like I am back to waiting until I can get some lab ware. That or I just waste acid until I get some. 

Just out of curiosity, when you heat acid to increase the amount of metal that it dissolves, does the metal fall out when it cools?


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## goldsilverpro

RESET said:


> Thanks GSP, did not know that. I have had the dish on the potpourri heater once, for something else, but never again. I have the dish in a Corning dish during the reaction but my heater probably would not fit in there anyway. Looks like I am back to waiting until I can get some lab ware. That or I just waste acid until I get some.



What kind of Corning Ware dish do you have? If it's not made of Pyroceram, it will break on a hotplate, sooner or later - guaranteed (don't ask me how I know this to be true). I've covered this several times in these posts.
http://www.goldrefiningforum.com/phpBB3/search.php?keywords=pyroceram&terms=all&author=goldsilverpro&sv=0&sc=1&sf=all&sk=t&sd=d&sr=posts&st=0&ch=300&t=0&submit=Search

The coffee pot or beaker is placed in the Pyroceram dish and the dish is placed on the hotplate. You can also place the coffee pot on top of about 1" - 2" of dry sand in a skillet and put the skillet on the hotplate. These has also been discussed a few times.
http://www.goldrefiningforum.com/phpBB3/search.php?keywords=sand+bath+beaker+&terms=all&author=&sv=0&sc=1&sf=all&sk=t&sd=d&sr=posts&st=0&ch=300&t=0&submit=Search



> Just out of curiosity, when you heat acid to increase the amount of metal that it dissolves, does the metal fall out when it cools?


When dissolving about any metal in nitric, with heat, as long as you have enough water, the metals will remain in solution when cooled. If you don't have enough water and, if you saturate the solution, when hot, with dissolved metal, clear silver nitrate crystals and/or blue copper nitrate crystals can crystallize out when the solution cools. If this ever happens, both types of crystals will dissolve by adding some hot distilled water to the solution. For most situations, the ideal mix is 50% nitric and 50% water, by volume. Also, when dissolving silver, always use distilled water. Why? Because tap water usually contains chlorine/chlorides and this will combine with some of the dissolved silver and produce an undesirable white precipitate of silver chloride. 

To keep the nitric usage at a minimum, it is always a good idea to first estimate how much nitric it will take for a particular batch of material, especially for the novice. Not counting the water you will be using in the mix, it will take about 1.22 ml of nitric to dissolve 1 gram of silver and about 4.1 ml to dissolve 1 gram of copper (or, most other base metals that are likely to be present). If you have an unknown mix of silver and base metals, this will be difficult to predict, but will be in between these extremes.

Please note that any combination of nitric and water will dissolve these metals. The 50/50 combination is usually chosen because it works the fastest and because it provides enough water to keep the metals in solution when cooled. 

To me, this is a simple, controllable way to do it, on a small scale, with heat. Put the metal in the beaker or coffee pot. Just cover the metal with distilled water and heat (on about medium-low) until a little steam is seen. Add a small amount of full strength nitric - if you use too much at one time, it could foam over. You should notice a fairly immediate reaction (bubbles, brown fumes, etc.). When the reaction dies down, give it a gentle stir, and add a little more nitric. Repeat until a small addition of nitric produces no reaction. At this point, all the metal should be dissolved. Although the solution should never boil, it is best to increase the heat a little towards the end. When all is dissolved, make sure you have at least 50% water in the mix (add more if needed - it doesn't hurt to have more than 50% - I prefer a little extra), turn off the hot plate, and let it cool. Filter the solution (if the small silver points were gold plated, the gold will be in the filter) and cement the silver with pure copper (buss bar is best; copper tubing is next best; copper wire is the worst unless it is quite large).

Note: When dissolving the points, the solution will sometimes get more than about 2" deep and the reaction will slow down. This can happen if you started with too much metal in the beaker or coffee pot. The reaction slows down mainly because the free acid is more diluted and little of it is coming in immediate contact with the parts. When this happens, I usually pour the acid off into another container and start over with fresh hot water.

2nd note: When the metal dissolves, it generates heat and this may be enough to maintain the reaction without applying extra heat. I have probably dissolved several tons of the large silver contact points in my life, without heat or waste of acid. These were all sweated off of copper buss and the silver percentage most always ran about 82-83%, with the remainder as base metals. Therefore, I could calculate the amount of nitric and water I would need fairly accurately. I placed exactly 2# of points in a bucket, under a fume hood, and covered them with exactly enough distilled water to produce a 50/50 solution with the amount of nitric I would eventually add. I then measured out the nitric I needed and added about 1/4 of it to the bucket. When the reaction subsided, I stirred it and added another 1/4 of the nitric. I repeated this until all the acid was in. I then put a lid on the bucket (loosely) and let it work overnight. By the next morning, most everything was dissolved. I usually had about an oz of silver left over (I was using 67% nitric). I poured off the solution, put the remaining silver in a beaker, dissolved it in a little 50/50 nitric and added it to the main solution.


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## RESET

I added another 100ml of 50/50 mix. The cement dissolved straight away. The last large bit of connector started to react as well. I will leave this to react over night. I think it is starting to get too diluted like you were saying. Once this is done, I think I will cement it out and then store it, next batch in fresh acid. I have a few mylars that I want to try as well as some ribbon cable. But that is for a different thread. I will try to get this thread back on topic.


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## Geo

on a side note the copper nitrate can be used in a copper cell following NoIdea's thread. im gathering material to build my first one. i have over 50 pounds of metal dust that has been cemented out of my AP and hcl/cl solutions. i melted a 5 OZ sample and took it to my local scrap yard and had it tested with a hand held gas spectrometer. the results looked like a grocery list with some symbols ive never seen but the biggest % of metal is copper with nickle a close second. they offered to pay me cupernickle if i melted it. i said "no thanks". i want to use a copper cell to purify the copper and reclaim the other metal in order to get the PM's out.


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## MysticColby

goldsilverpro said:


> 2nd note: When the metal dissolves, it generates heat and this may be enough to maintain the reaction without applying extra heat.



Yeah, this is my usual experience (what little of it there is). I found that I tend to: Have silver in beaker, add water, add small amount of acid, wait a minute, reaction starts, generates it's own heat, and keeps going. When reaction starts to die down, add a bit more acid. reaction picks up again. Sometimes I get upwards of 70ºC. After I add the last bit of acid I calculated I needed, I wait for that reaction to slow down, then increase the temp via hot plate to 90ºC and wait a couple hours. I think that if the silver is more pure, it won't generate enough of it's own heat and will need to be on hot plate (maybe 50ºC is my ideal - I don't mind waiting a couple hours). The other side to that: if you unknowingly try to dissolve something that is plated, non-silver metal will react faster than silver will, generating too much heat, too much bubbles, and the solution will bubble over. Had that happen to one batch... it's a good idea to have a secondary container that your beaker is in to catch anything that overflows.


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## RESET

goldsilverpro said:


> What kind of Corning Ware dish do you have? If it's not made of Pyroceram, it will break on a hotplate, sooner or later - guaranteed (don't ask me how I know this to be true). I've covered this several times in these posts.
> http://www.goldrefiningforum.com/phpBB3/search.php?keywords=pyroceram&terms=all&author=goldsilverpro&sv=0&sc=1&sf=all&sk=t&sd=d&sr=posts&st=0&ch=300&t=0&submit=Search



My Corning dish says range and microwave on the bottom. I thought I read somewhere here that was what to look for. If it is Pyroceram, will it say it every time? 

Just to be clear, I don't have a hot plate. I have a potpourri heater. I don't know what temp it can reach but I doubt it would boil anything. I saw it at Good-Will while doing some "prospecting". My small Pyrex dish pits in it perfectly. Do you think I should just donate it back to GW or can I use it for now? I used it to evaporate water from some mystery solution a couple days ago and it didn't even create visible steam. It took about 4 hours to evaporate 2 cups of water.


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## Geo

it should work fine for heating solutions but you will need to boil solutions from time to time so a hotter heat source would come in handy.as in most things accidents happen at the worst times and it makes it even worse when your down a piece of equipment without a replacement handy. when ever possible try to double up on any thing you will use regularly.working blindly without thinking through the processes before starting can lead to alot of headaches.what equipment will you need? if an accident occurs,what can break?if it breaks,do you have another?easy questions that can save your day.


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## goldsilverpro

RESET,

None of the Pyroceram dishes I've seen are labeled as such. You just have to know what types are and what types aren't. I've made several posts with much detailed information on this subject. I'm not saying that the Pyroceram dishes are the only ones that will not break on direct heat. However, they're the only ones I've ever found that I totally trust, long term, besides the clear Corning Ware Vision dishes. Believe me, I've broken a big bunch of other types of dishes, some of which were expensive, in finding out this information.

Do you have a photo of the dish you have?


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## RESET

Doubling isn't a bad idea. For now I am just doing this in my spare time and in really small lots. If this dish broke right now I would be out about $10, including the value of the silver that I think I have in there. When I start running lots that would be costly to lose, I will have backup equipment and dishes just like you said.

GSP, I don't have a pic but i think it is the cornflower type that you mentioned in one post. It is opaque white with a blue flower on the side, 2 quart. I will snap a pic of my "lab" and post it later. Might be late, have to clean a 75 gallon fish tank first. My Green Sunfish and Bullhead catfish are messy.


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## goldsilverpro

All the ones I've seen with the Cornflower design are Pyroceram.


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## Palladium

:arrow:


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## Palladium

Interesting....

http://www.tower.com/complete-guide-corning-ware-visions-cookware-kyle-coroneos-paperback/wapi/100179562


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## Palladium

http://news.consumerreports.org/safety/2010/12/foia-requests-examine-glass-bakeware-that-shatters-.html

Note at 1:17 in the video. That looks like a Pyrocreme dish she is scooping sand out of. :mrgreen:


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## RESET

RE: Consumer reports video. Can anyone identify the Borosilicate dish that he mentions at the end that did not break when heated to 500 degrees? I can't understand him at that point.

RE: Complete guide to Corning. My dish is shaped like the one in the upper left corner picture on the cover of the book but has the blue flower like on the other two dishes.

Sorry, couldn't upload the picture last night. My internet was acting up and wouldn't let me open any web pages.


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## kurt

Ok – I see the concerns of cracking glass ware when heat is applied (&/or by the heat generated when dissolving metals with acids for that matter) has come up once again which is a good reason to use plastic buckets when dissolving metals instead of glass. However – plastic buckets don’t work if you want to or need to apply heat – so I have a question.

I buy my nitric acid in 15 gallon drums because I can get 68% tec grade nitric for about $8 a gallon ($125 for 15 gallons) --- These 15 gallon drums are made of stainless steel because the nitric doesn’t react on the stainless – so – is there any reason you couldn’t or shouldn’t use a stainless pot with nitric if & when you are going to “apply” heat including up to the point of boiling

Kurt


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## Geo

actually you can bring liquid to a boil in a plastic bucket.i have done it a few times. you need a metal wash tub and an adequate heat source, i don't recommend anyone do it especially with liquid containing acid due to the accident potential. i do it with caustic soda to remove solder mask from whole boards, i guess thats as bad as acid solutions but im very careful.


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## qst42know

> is there any reason you couldn’t or shouldn’t use a stainless pot with nitric if & when you are going to “apply” heat including up to the point of boiling



Palladium posted video a while back of a shop in India (I think) dissolving silver inquarted gold over a gas burner in several large stainless salad bowls. I don't know if it would cause any problems though.


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## RESET

I had an interesting thought today. Please let me know if I would harm my self doing this. 

My contacts are a copper bar with an iron spring and the silver pads are bonded to it with the silver/cadmium braze. There are four metals in the mix and I only want to keep two of them. I have been trying to think of a dissolution process that would keep me from dealing with the cadmium fumes generated by heating. My thought is HCl. Hydrochloric will dissolve iron and cadmium, not touch silver and, so long as I don't include an oxidizing agent, it won't dissolve the copper either. Could I place my contacts in HCl to dissolve the iron and cadmium or is there something that I am missing that would make this dangerous? If this worked, would the silver pads come off easily having lost most of the bond from the braze? Would the HCl even be able to get to the cadmium since it is alloyed with silver? I know I would have to incinerate to avoid getting silver chloride when I dissolve the pads in nitric.


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## Barren Realms 007

That's a waste of time chemicals and manpower. There should not be cadmium in the braze only in the contact pad. Get the pad off with heat and then process the pad's


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## RESET

Might be a waste of chemicals but I can't see the waste of time or manpower. Doesn't take much of either to toss something in a bucket and go do something else for a while. I thought the Cd was in the braze to keep the pads from sliding off due to the heat generated by making and breaking the contact with the high amp switches?


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## gold4mike

I remember seeing a thread some time ago where one of our members (maybe BarrenRealms) was using a turkey fryer full of water and a sheet of plywood with a round hole in it just big enough to let a bucket slide down into it up to the ridges at the top of the bucket.

This bucket is suspended lowered into the water, not allowing it to touch the sides. I believe he said he heats the water to boiling, turns off the heat, suspends the bucket partially submerged.

It generates enough heat for long enough to get a reaction moving along.

I bought a used turkey fryer for $20 for this purpose but haven't tried it yet.


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## RESET

Just lost a nice long post so I will keep this one short. I tested a sample. The sample had an iron bar, a copper bar and the silver pad attached to the copper. The Copper and the Iron were plated in what I thought was Tin. Some time ago, I dissolved some of the "tin" from a section of the Iron bar. I put this piece in a small container and added just enough HCl to cover. The acid dissolved the rust on the exposed Iron but has stopped reacting. Shouldn't this dissolve the tin plating and the iron? Should this be a noticeable reaction, rigorous?

EDIT: I posted this picture earlier in this thread. The sample I tested was one like the one shown with the dime on it. The dime is sitting on the plated Iron bar.


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## Geo

depends on the thickness of the iron. hcl reacts to iron better when heated but even then its slow. it would eventually dissolve it until the acid was neutralized but it takes a lot of acid to digest a small amount of iron compared to other processes.


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## RESET

Thanks Geo. Any thoughts on the plating?


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## Geo

definitely an oxidation barrier. if you tested and no PM's showed up, i would focus on the recovery of the silver. its not uncommon for heavy copper parts to be coated with a thin coating of silver but its so little its not economical to recover it. im not saying thats what it is, just that if its not gold or a PGM, its not worth worrying about.


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## qst42know

I wouldn't expect a tin plate over a silver contact.

Silver plate over all would make more sense in keeping with the function of a contact.

Schwerter's solution should reveal any silver in the plating.


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## RESET

Thanks guys. I will remove the piece and test the coating for silver. I wonder if the HCl is still reacting with the cadmium to any extent.


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## qst42know

Cadmium is soluble in HCL, nitric, and sulfuric.

http://en.wikipedia.org/wiki/Cadmium


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## qst42know

Barren Realms 007 said:


> There should not be cadmium in the braze only in the contact pad.



That can't be assumed. Cadmium braze alloys always have had desirable properties, such as lower melt temperature and enhanced flow-ability. If these were from an automated brazing operation a cadmium alloy may have been deliberately chosen for the task.


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## Geo

as long as you practice good safety, cadmium in solution is very controllable. its when you melt it and it becomes airborne you have a problem because it tends to stick to whatever it touches.

wear safety gear - avoid spills - use a catch basin - dispose of solution responsibly. once a month, the county here does a chemical collection day. it gives the homeowner a chance to dispose of unwanted chemicals no questions asked.each household is allowed a certain amount for free. if you process metals that are known to be toxic and you are aware of how to deal with and dispose of them properly, cadmium is no more dangerous or deadly than lead or any of the other heavy metals we deal with.


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## RESET

qst42know said:


> Cadmium is soluble in HCL, nitric, and sulfuric.
> 
> http://en.wikipedia.org/wiki/Cadmium



This is why I chose to use HCl. It was supposed to dissolve the Cadmium, if present, the Iron and the Tin on the ones that had the covering though it now looks like the covering is not Tin. I was trying to dissolve all but the Copper and the Silver. I am going to leave the piece in the HCL for a while and see what it does. I may do a test on the other type of bar, no plating, to see how long it takes to dissolve the Iron spring.


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## goldsilverpro

If I had those, I would have sweated off the points a long time ago.


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## RESET

If I had the proper torch and PPE I probably would have too.


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## Golddigger Greg

I've collected a few different relays and have separated them into the two types I've encountered so far; Ag/Ni and Ag/CdO. I'd like to get a feel for how much silver is in both types but haven't been able to find any composition information on the Ag/CdO alloy. I want to sweat a small quantity of the contacts off to get some yield data to work from. I want to do this safely, of course, but I'm lost as to the type of respirator I need. Is the P100 (magenta) cartridge that the salesman at Canadian Tire was 'thinking it'll work' what I'm after to deal with the cadmium oxide fumes?


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## Geo

any respirator thats rated for smoke particles will work. Cadmium doesnt form a gas but rather it oxidizes just like zinc or tin when it gets hot enough and turns into smoke. if you see a white stringy wisp of smoke when you heat a contact point, thats cadmium burning off. keep in mind that it sticks to whatever it touches. after it has been converted to an oxide, it is still just as toxic and even more so because now it can be absorbed through your skin. after working with contact points, wash your gloves before taking them off, remove your respirator with your gloves on, do not blow yourself off with an air hose (this will send particles airborne), wash your hands and face immediately, shower or bath as soon as possible, wash work clothes separately from household laundry. and as always, keep your fingers out of your mouth,nose and ears.


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## Golddigger Greg

Thanks Geo!


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