# Are these silver?



## Tevlon (Nov 11, 2021)

Hello all. It's been a long time. I replaced a contactor in a welding unit recently. I have been reading about silver contacts lately and thought these might be silver. The new unit cost over $600 so a little silver wouldn't be out of the question. I tried a scratch test and got no colour change. I put a drop directly on the "silver" and again no change. My solutions are very old so I wouldn't be surprised if they are garbage. So, do any of you know if I have silver here? Image 1 is the old contactor top. 2 is the snipped copper with "silver" contact points. 3 is the one I put a drop on with tarnish removed. If it is in fact silver, what is a standard purity for this type of contact? I have access to a lot of this stuff right now so it could be very good for me. Thanks in advance to any of you that take the time to respond.


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## butcher (Nov 11, 2021)

Do some research tungsten/silver high current contacts


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## Lino1406 (Nov 12, 2021)

Silver check: 1. A drop of nitric acid will produce brown NO2 gas 2. To the solution formed add K2Cr2O7 - tomatoe red will show


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## kurtak (Nov 12, 2021)

butcher said:


> Do some research tungsten/silver high current contacts



Based on the first pic (contactor cover) those points are out of a magnetic disconnect so they wont be the tungsten/silver type points (which come out of hand thrown circuit breakers) 

The points used in magnetic disconnects will normally run 95 - 98 % silver - which is what he has there

Kurt


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## Tevlon (Nov 12, 2021)

Lino, the test solution I have is nitric and K2Cr2O7.

Well I though because I got no colour change from my solution, it must be the 20% silver tungsten contacts (thanks Butcher, I didn't know about that type). But if they are in fact 95-98%, my solutions must be bad. How long do they last for?

Now that I have two different opinions on the silver content, does anyone want to break the tie?


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## adam mizer (Nov 12, 2021)

With all do respect my point of view 90% plus at least. 
Those will show a good red with Schwerters reagent.


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## FrugalRefiner (Nov 12, 2021)

Tevlon, what color is your test solution? Is it an orange red, or is it dark and kind of greenish?

Tie breaker - they're slver.

Dave


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## Tevlon (Nov 12, 2021)

sweet. Thanks everyone.

Frugal, do you mean before or after? No change either way. The solution looks dark. I thought it was blue, but it could be a very dark green. I haven't used it in years and don't remember what it should look like.

But now that I think about it, potassium dichromate is reddish so it should be reddish orange right? Very dark green is probably expired.


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## FrugalRefiner (Nov 12, 2021)

Yes, the fresh crystals are bright orange. When the solution is freshly made it should also be a bright orange. As it ages, it gets darker. When it's dark greenish or bluish, it no longer of use. Then it's just very hazardous waste. Dispose of it accordingly.

Dave


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## Tevlon (Nov 12, 2021)

Don't worry. It will be dealt with properly.


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## kurtak (Nov 13, 2021)

Tevlon said:


> I have access to a lot of this stuff right now so it could be very good for me



Tevlon - for what its worth - back when I was making a living with recovery & refining PMs silver was my bread & butter (gold & PGMs was the gravy) in other words for every kilo of silver I refined I refined a couple ozt gold & 1/2 - 1 ozt PGMs --- & I refined MANY kilos of silver

one of my bigger sources of silver was the points from magnetic disconnects - disconnects can range in size from LARGE to small - I tore down literally thousands of disconnects to get the points out of them

Some of the "large" disconnects had points in them that weighed as much as 1 ozt per point & there are 12 points per disconnect (so 12 ozt per disconnect) on the other hand some of the smallest disconnects only have 1/4 - 1/3 ozt per disconnect (all 12 points)

The cost of processing points (or silver for that matter) depends on a couple things

First is the cost of nitric acid - if you have to pay a high price for your nitric (like $50 - $80 per liter) you will be lucky to see a profit (& it may actually cost you money) on the other hand I was able to buy may nitric (67%) in a 15 gallon keg for about $7 per gallon (so very cheap)

Keep in mind that it takes "about" 4 times more nitric to dissolve a pound of copper then to dissolve a pound of silver

So a gallon of 67% nitric will dissolve (about) 8 pounds of silver BUT only (about) 2 pounds of copper

So if you if you nip the points from the copper bus bar (as you pictured) & though you have reduced the amount of copper you still have silver plus copper to dissolve which will factor into your nitric consumption

So that brings me to the second thing - with larger points - if you can "de-solder" the points to remove them from the copper (or brass) buss bar you will use less nitric for the rest of the refining process 

I had a system for doing this that I posted about years ago - I will "try" to find that & post it again (no promise)

Bottom line - contact points are always worth going after because of there silver value

The question is - are they worth your while (profitable) processing them yourself (nitric cost)

If you have to pay a "high" price for your nitric they are still worth while going after but instead of processing them - just pull them from the disconnect & throw them in a 5 gallon bucket ( you don't need to nip them from the buss bar) when you have a 5 gallon bucket full (or two or three) send them to a refiner that will process them 

Kurt


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## Tevlon (Nov 14, 2021)

The reason I was interested in these is their size. They are about 1.5 by 1.5 cm and fairly thick. I would love to find some ounce sized contacts though. Never seen that before. And if you find your old post, please share, I’d love to check it out. 

I haven’t tried to separate the silver from the copper yet. If it doesn’t de solder easily, I figured I could just put the copper side to a belt sander. I do have some nitric but refining isn’t really necessary for me, just fun to do. I can just melt everything into an ingot. There’s a store near me that will just scan it and pay for the silver content. If it’s 95-98% and the residual copper brings it down a few percent, I will get an appropriate amount. I refine only because I love chemistry.


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## kurtak (Nov 14, 2021)

Ok I found the old thread where I posted about my de-soldering set up 

With the new forum structure I have not yet figured out how to link a post from one thread to another

However - if you go to the "Silver" forum - then go to page 19 - then look for thread title "Milling silver contacts off" (second thread on page 19) you will see my set up

Be aware the the braze used to braze the points to the buss bars is OFTEN a silver/cadmium alloy

Cadmium volatizes & fumes off at a relatively low temp so there is a concern for getting heavy metal fume poisoning when melting the points so really needs to be done ether in a fume hood or at the very least outside with the wind at your back

To clarify - though Cd in it's self volatizes at a low temp - when alloyed with other metals (copper &/or silver) it needs a higher temp to really volatize so at the de-soldering temp it's not a big problem so outside wind at your back will be fine

However at the silver melt temp the Cd will most definitely fume off --- in fact you can "burn off" a lot of the Cd by running it in a furnace for an "extended" melt time so melting should really be done in a fume hood

Kurt


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## FrugalRefiner (Nov 14, 2021)

Here's the link: Milling silver contacts off.

Kurt, take a look in my Tips thread at the Including Links post. It's a little tricky the first time or two, but it's how I linked all the posts in that thread.

Dave


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## kurtak (Nov 14, 2021)

Thanks Dave - I will look at your "tips" thread later --- right now I have to get to work canning up about 30 pounds of elk meat from last weeks hunting

Kurt


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## Tevlon (Nov 14, 2021)

I didn’t know about potential cadmium. I’ll be sure to keep that in mind when I decide how to process. Thanks a lot.


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