Non-Chemical Pins in A/P

[rewalston]

I'm going to be doing a crockpot AP later this week on some pins I have. I'm not expecting much, but any is better than none. Would it be a good idea to incinerate the pins before putting them into AP?

Rusty

 

[Smack]

It sure couldn't hurt.

 

[Geo]

Unless the pins are oily or trapped in plastic, I don't really see a need to incinerate. If the pins were soldered, you may run them through a hcl bath first to remove as much tin as possible. When you incinerate things like pins, the gold shell cracks along weak points from the thermal expansion and contraction. Don't incinerate and wait to process because the gold will start flaking off almost as soon as the metal cools.

 

[rewalston]

Thanks guys, I've got a few pins with just a speck of plastic, but with the amount there it shouldn't be a problem. I'll just crockpot everything with some AP and let it run. I've got a few more pins to recover from some dips witches (those are where the plastic is from). I'll post a picture once I get it "rolling". Thanks again.

Rusty

 

[Pantherlikher]

Warm HCL to make sure there is no solder. Then AP with an air pump and time will work great.
Certain plastics can be a problem which will be extracted and incinerated. Some soften to a thick mush and is tough to work with.

To prolong you solution, you may want to take out the magnetics as that will fowl when enough builds up. Allot that is. I ran a bunch through mine and the only reason I treated mine as waste was because winter was coming. Anything magnetic can go into your waste pot where it will remove everything but PMs, copper and maybe tiny amounts of base metals.
Again, this depends on how much you intend on putting into the AP soak.

B.S.

 

[rewalston]

I'm running about a pound of pins.

Rusty

 

[rewalston]

Well, I ran all my pins for 2 days on high in the crockpot, still a lot of copper undissolved, and a lot of gold flakes. I'm assuming that I'm going to need to dissolve all the copper before I can do anything with the gold. I moved the solution to a bucket with my air pump. And added about two more cups of HCl.

Rusty

 

[Geo]

If you force a volume of solution to dissolve more copper than it can hold (sounds impossible but it happens all the time) the copper metal will continue to dissolve but copper(I) chloride will precipitate out. It will look like cloudy green mud. If this happens, add fresh hcl and the solution will turn deep emerald green and go clear.

 

[rewalston]

If you force a volume of solution to dissolve more copper than it can hold (sounds impossible but it happens all the time) the copper metal will continue to dissolve but copper(I) chloride will precipitate out. It will look like cloudy green mud. If this happens, add fresh hcl and the solution will turn deep emerald green and go clear.

Yep it went clear. I have a bubbler in the bucket now and it's more of a greyish clear blue instead of green. Still have a lot of undissolved copper and lots of gold flakes.

 

[Geo]

The thing about AP that some people overlook commonly is assuming the volume of solution needed to dissolve a certain amount is less than it actually is. I confuse myself when I'm sleepy. Theoretically, One gallon of 32% muriatic acid will dissolve around 2 pounds of copper as copper chloride. So 1 pound of pins should require somewhere around one half gallon muriatic acid as copper chloride. Starting from basic components (hcl,peroxide,etc.) nearly 100% of the acid will be needed in the reaction. Given time needed and evaporation of the solution, any evaporation of the solution below the original amount of concentrated acid and the solution will be losing acid in fumes. Diluting the hcl before starting the process is better than adding water later which will weaken the acid further and make it drop out copper(I) chloride. Also, this just accounts for the copper and nothing else. If the pins have springs or are springy themselves, chances are they will be phosphor bronze which contains tin.

 

[rewalston]

Theoretically, One gallon of 32% muriatic acid will dissolve around 2 pounds of copper as copper chloride. So 1 pound of pins should require somewhere around one half gallon muriatic acid as copper chloride.

Geo, that was what I was looking for. I haven't checked the bucket today. How long should it take to dissolve the rest of the copper? Or should I put it back into the crockpot? I have quite a bit of gold flakes and black powder but with the pins still somewhat intact, I have no way to separate the flakes and powder from the pins. They just fall through my colander.

 

[maynman1751]

In my own experience, heat definitely accelerates the process.......so I'd say crock pot.

 

[rewalston]

In my own experience, heat definitely accelerates the process.......so I'd say crock pot.

Thanks maynman. I'm leaning towards that. I love your sig line...the only thing I would add is "you can't fix stupid...but a 2x4 helps"

 

[Geo]

If theres gold still on the pins, you will have to finish the dissolution of the pins. If the gold has already come loose from the pins and now you have flakes and bare pins, you can use hcl/Cl to dissolve the loose foils. You will have to work quickly because the base metal will start cementing gold as soon as it goes into solution. With the excess chlorine still in the solution, you will have time to decant the solution from the pins before the gold cements out. If you do it this way, wash the pins twice in hcl/Cl to be sure you got all the foils.

 

[rewalston]

Thanks Geo, I'm pretty sure that all the gold is off the pins and is either in the form of powder or foils. For a pound of pins how much HCl/Cl would you recommend?

 

[Geo]

Since nearly all the base metal will be present, do this as quickly and safely as possible.

(1) have all the chemicals poured and handy in separate containers.
(2) add enough hcl to completely cover the pins.
(3) add 10ml's of bleach and swirl for a count of ten.
(4) add 10ml's of bleach and swirl for a count of five and immediately decant solution into an clean vessel leaving the pins behind.
(5) replace fresh hcl and repeat the steps above.

If you can see any foils or black soot when you add clean water to the pins, repeat once more leaving the water on the pins the final time.

If the pins were a good quality, there should around 1g +/- of gold from a pound.

 

[dannlee]

when you add clean water to the pins

In your list of steps.. where is water mentioned?

(I just happen to have 120g of nice pins waiting)

 

[rewalston]

Thanks Geo, I'll let everyone know how I do. I'm not going to hold my breath. I'll be happy with whatever I get, it's all a learning experience and that experience is priceless.

Rusty

 

[Geo]

when you add clean water to the pins

In your list of steps.. where is water mentioned?

(I just happen to have 120g of nice pins waiting)

Water is not in the dissolution of the foils but the rinse after.

 

[rewalston]

I have a quick question. I have some classifiers that fit the top of a 5 gal bucket. I can't remember what size they are, but they are plastic with stainless (I think) mesh. Would AP be a problem with these. I figured that I could stack them together (smallest size on bottom and larger on top) and take my pins that I've been working with and put them on the top screen and this should allow the sediment and foils wash through. Rather than washing them with HCl/Cl to dissolve the foils mixed with the pins.

Rusty