# Contact Points - Platinum alloy



## stoneware (Nov 8, 2021)

I processed a small batch of platinum iridium contacts the same way one would do silver, interesting observation once the iridium along with other non ferris goes into solution the platinum forms a puff ball.

I made the mistake of not removing everything magnetic and one or two contacts with an iron base made its way into the process, the ferris nitrate was floating on top of the leach.

A large platinum puff ball floated to the top and when it made contact with the ferris float it was instantly absorbed into the puff ball.

Next time I'll not forget to use the magnet.


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## 4metals (Nov 8, 2021)

Something fishy here. I wasn’t aware Platinum and Iridium were soluble in nitric.


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## stoneware (Nov 8, 2021)

Thanks 4metals, My mistake was thinking these contacts were made of a similar alloy used in the old engine magneto's.

A small amount of a precious metal did end up in solution which I'm cementing out with copper. Later I'll post an image of the undissolved material from the nitric leach caught in the filter paper, along with the weight.


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## stoneware (Nov 8, 2021)

Working outdoors with a snow forecast later in the week, it's time to set this project aside.


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## Yggdrasil (Nov 8, 2021)

stoneware said:


> Working outdoors with a snow forecast later in the week, it's time to set this project aside.
> 
> View attachment 47157
> 
> View attachment 47158


This picture makes me shudder.
What happens when your beaker breaks, not if, when.
All or most of your precious solution will be lost.
Use a catch basin of some kind, it will save you a lot of grief.


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## VK3NHL (Nov 8, 2021)

110% agree one day your glassware will break when on heat.
Corning ware (Pyroceram) catch dish will save you a lot of heartache.
Check out your local thrift shops for them…


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## Geo (Nov 9, 2021)

You normally find silver/palladium alloys in contact points. I have never even heard of platinum/iridium alloy in contact points. Do you happen to have any pictures of the points before processing?


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## Yggdrasil (Nov 9, 2021)

Geo said:


> You normally find silver/palladium alloys in contact points. I have never even heard of platinum/iridium alloy in contact points. Do you happen to have any pictures of the points before processing?


I know it has been used on high end spark plugs and such.
Maybe the same for rotor contacts for the ignition?

In the 70s I was not quite in the teens yet, I was playing a bit with a blob of Mercury. Makes me shiver now.

But I had dismantled a relay from a 60 something model VW and they sank like rocks in water. Lead was floating on top, fascinating for a boy around 10. 

My sentiment is that it had to be Pt, Ir or some alloy of them or something like that.
Age matters in these cases.


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## Lou (Nov 9, 2021)

I've processed magneto contact points that were platinum. I believe they were 95% Pt 5 % W mounted to a ferritic base. Boil in HCl then just melt the Pt in lime and the W is gone.


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## butcher (Nov 9, 2021)

Lou ,
That sounds like the older style tractor's magneto points.


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## stoneware (Nov 9, 2021)

Like these Lou.


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## stoneware (Nov 9, 2021)

Geo said:


> You normally find silver/palladium alloys in contact points. I have never even heard of platinum/iridium alloy in contact points. Do you happen to have any pictures of the points before processing?



Unfortunately not, but will post pictures next time.

This is what ended up in the filter.


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## Lou (Nov 9, 2021)

Nope. Mine were out of aircraft motors. Nothing to do with tractors. They were threaded on one end and a platinum nub on the other. Probably already deleted the photos after more came in.


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## stoneware (Nov 9, 2021)

Geo said:


> You normally find silver/palladium alloys in contact points. I have never even heard of platinum/iridium alloy in contact points. Do you happen to have any pictures of the points before processing?


Visited a couple of landfills, today's pickings.

The oven thermostat, heating elements and those from electric water heaters have the largest contacts, washing machine and dryer timers from the older models are smaller but reasonabaly heavily plated.


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## stoneware (Nov 12, 2021)

Finding tungsten powder after leaching the appliance contacts, there is some tungsten powders left in the beaker.

Adding HCL into a small leach sample did not produce any silver chloride, which prompted some research.

Alloys of Platinum and Tungsten

Alloys were prepared by thoroughly mixing appropriate quantities of high purity platinum and tungsten powders, and pressing the mixture into compacts.


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## stoneware (Nov 21, 2021)

With base metals removed, after boiling in AR for several hours I'm left with many contacts which have not dissolved.

Side cutters make an indent, one other on the anvil flattened out to several times its original size before breaking.


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## Yggdrasil (Nov 21, 2021)

If it is Silver AR won't have much effect.
The HCl will passivate the Silver.
Try dilute hot Nitric.
Regards Per-Ove

Edit for spelling:


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## kurtak (Nov 21, 2021)

Stoneware --- First I need to tell you that the VAST majority of contact points you are going to find are going to be silver --- very rarely are you going to find points that are made of PGMs (platinum group metals) &/or for that matter points alloyed with PGMS - though there are of course exceptions - but it is VERY RARE

contact points that are made with PGMs &/or there alloys are only used in "*very specialized*" applications such as *OLD* telecom gear (before the world went digital) &/or as Lou pointed out aircraft motors (& other "*specialized*" applications) 



stoneware said:


> The oven thermostat, heating elements and those from electric water heaters have the largest contacts, washing machine and dryer timers from the older models are smaller but reasonabaly heavily plated



You will NEVER find PGMs in the points that come out everyday consumer appliances like this stuff --- they will ALL be silver points !!!

For what it is worth - in the something like 12 years I spent *making a living *recovering & refining PMs the VAST majority of the silver I processed came from contact points 

to put it in perspective I processed literally TONS of *whole* contactors from magnetic disconnects, relays, & stuff like in your picture (from your landfill score)

out of those tons of "whole" contactors I recovered on an average (plus/minus) 2,000 ozt silver per year (or "about" 60 kilos/year)

Out of the many MANY tons of (whole) contactors I processed - only once did I run across points made with PGMs - those came from some OLD telecom gear

I posted about them here









Three types of contacts


Folks I've got three types of contacts here on a batch of telecoms equipment that's landed with me today. I may be wrong and I'm happy to take some advice but I think that the dark contacts (corroded) on the right are silver, as they polish up. I think the grey contacts on the left may be...




goldrefiningforum.com







stoneware said:


> Finding tungsten powder after leaching the appliance contacts, there is some tungsten powders left in the beaker.



What makes you so sure the powders in your beaker is tungsten --- it could be anything depending on "other" metals involved & or acids --- meaning different acids react differently with different metals & when it comes to contact points the metal(s) the points are attached to (bus bars) could be just about anything - so depending on the acid used to remove those metals you may dissolve some metal but not all metal leaving you with a sludge of who knows what - & you can not determine what these sludges are simply because of there color

Concerning tungsten/silver points - they are almost always found in hand thrown "circuit breakers" like the ones found in the electric panel in your house although you can also find them in large industrial size hand thrown circuit breakers

these type points generally run "about" 40% silver & 60% tungsten & they need to literally be *boiled* in nitric acid for *hours* in order to leach the silver out of the tungsten (sintered) matrix at which point yes you will get a tungsten sludge in the bottom of your beaker - meaning - unless you boil them in nitric - you will not leach enough silver out of them to get much if any tungsten sludge in the bottom of your beaker

Bottom line - although you may run across contact points that are made of PGMs &/or alloys of PGMs it will be very VERY rare & almost never (if ever) points that come out of normal everyday consumer products 

Kurt


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## kurtak (Nov 21, 2021)

Yggdrasil said:


> If it is Silver AR won't have much effect.
> The HCl will passivate the Silver.
> Try dilute hot Nitric.
> Regards Per-Ove
> ...



Actually - running the contact points in AR to get rid of the base metals (the bus bar metals the points are attached to) would be "one" way of getting rid of those base metals leaving you with just the silver points to then process with nitric

The down side would be that you are likely to see "some" silver lost in the fact that the nitric in the AR is likely to react (at least) on the "surface of the silver contact but then the HCl in the AR will turn that (nitric reacted) silver to silver chloride & as you say will cause the silver to passivate (prevent the acid from further reacting with the silver)

Some of that silver chloride is likely to flake off & end up in the bottom of the beaker as a sludge

Depending on light exposure - that sludge could end up as normal white silver chloride - or it could "photo gray" thereby ending up as a gray sludge (most likely) being as silver chloride does not take much light &/or time to photo gray

so unless you put the sludge through the process of reducing silver chloride to actual silver - you are going to see at least "some" silver lost

In fact - it least "some" of the sludge stoneware is seeing - & "thinks" is tungsten - could well be silver chloride

Because there are so many different metals involved in processing points - the sludge could be "anything" including but not limited to silver chloride (if AR is used to remove base metals) stannic tin (nitric used on phosphor bronze buss bars - which would include nitric used in AR) or lead used in solders - or ???? (other metals involved)

As I told stoneware - different acids react in different ways with different metals (&/or there alloys) AND when processing contact points - you are going to run into just about any & every combination of metals you can imagine so you are also going to run into just about any & every result (metals in solution &/or sludges produced) when processing contact points

Kurt


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## Marcel (Nov 22, 2021)

Tungsten has a melting point of +3400 °C. Which should be unreachable with any standard torch. I know you should not melt scrap together to separate it, but in this case, I would give it a try.
Apply heat around 1200°C , your silver and any gold should come out, and the tungsten remains intact. Maybe add some collector metal as well (Ag?)
I would not expect any Pt in those contacts.


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## Lou (Nov 22, 2021)

As usual Kurt, thanks for the contribution.

One thing I might add, as someone who works with many tons of W a year...when the W contacts are "done" you should have a yellow powder of WO3 left behind.

W is some tricky stuff and I've learned quite a bit about it dealing with aerospace superalloys. It will slowly cement Pt out of solution because even aqua regia doesn't readily act on it.

Better solvents for W are NaOH + NaOCl, NaOH + dropwise H2O2.


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