# AG/moly contacts



## glondor (Jan 27, 2012)

Hey all, looking for some advice on some electrical contacts. Is there an economical method for doing 25% silver 75% molybdenum. I have 50 pounds available if I can find a sensible way to do them. Any help appreciated.


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## metatp (Jan 27, 2012)

I used 50/50 nitric acid and let them sit in there for a couple of days. It appeared to work, but after cementing with copper there was some contaminates dragged down as well. I ended up refining the silver cement again to clean it up. 

Tom


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## glondor (Jan 27, 2012)

Thanks Tom. I will try a sample batch in 50/50 nitric and see how it goes. I was not even sure if Nitric would effect the Moly. Do you remember how much Nitric per gram it used? Thanks.


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## metatp (Jan 27, 2012)

Do you have a picture of the contacts? The nitric will dissolve the silver and leave the Mo behind. You should definitely try a sample first. If I remember correctly, it took a while and left a colorful powder behind. The contacts I had may also included some tungsten. I think it filtered ok, but can't remember. Now that I think about it, I may have used a diluted nitric acid (25/75?). I don't recall the amount of nitric acid I used per gram of contact. I don't know if Mo readily dissolves in nitric acid. I would start with about 1.2g of nitric acid per expected silver content and then adjust from there.

Tom


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## glondor (Jan 28, 2012)

Photo.


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## kurt (Jan 29, 2012)

Here is how you test for moly --- “react” to completion with 1 or2 drops of 50/50 nitric acid. Remove reaction products with paper towel. React again with 1 drop 205 sulfuric acid & immerse a piece of filter paper saturated with a 10% solution of potassium ethyl xanthogenate – a red color identifies moly

So yes nitric reacts with moly. --- I had some points awhile back that I believe were a moly/ag alloy ( don’t know this for a fact – just that it took more acid to dissolve them then your average higher Ag alloy points) 

The moly is a base metal & like most base metals it takes more nitric to dissolve then nitric needed to dissolve Ag – probably around 3 - 4 times more. (per base metal content) I can’t say for sure but when I processed mine I had to keep adding nitric to get them completely dissolved. Also dilute your nitric a bit more the 50/50 (to allow for evaporation) & apply heat.

As a test – I would start with about 3 times the nitric needed to dissolve Ag – dilute about 40/60 (or a little more) – apply heat. If they completely dissolve – cementing with copper will tell you if you have excess nitric & you can adjust – or add more nitric if not completely dissolved.

If the moly prevents them from dissolving – try “boiling” in nitric to leach the Ag – like tungsten points.

Kurt


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