PINS IN AP

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When you have lot of tin in auric chloride solution your solution will be yellow but when you attempt to drop gold with SMB you will get dark brown/black solution which will refuse to settle. I have one jar with dropped gold say about 4 days and only small part 1/5 is clear on top, rest of gold still hang in solution. I did this just to see how long it will take. If you want to speed up things you will need to heat that solution to slowly evaporate liquid. As it will become hot your gold will settle on bottom faster. Melting this powder will result in silvery button. I recommend to just incinerate powder and put it in fresh HCl to get rid of tin.
 
hello everyone
the solution is now 2:1 HCl:H2O2. The air pump is running continuously.
it is still very pale green after 36 hours, is that normal color or am being impatient?
regards
 
andees78 said:
hello everyone
the solution is now 2:1 HCl:H2O2. The air pump is running continuously.
it is still very pale green after 36 hours, is that normal color or am being impatient?
regards
Click to expand...
yes, pale green is good for 36 hours. the whole process will take 7-10 days. depending on how much material you are working with and how much liquid you have, the solution may never saturate with copper. after you do this process two or three times you will learn what to expect. its my experience that it takes 1 and 1/2 US gallons of acid to digest 1 US pound of pins in 7-10 days depending on the weather. hotter weather equals less time. i dont heat my solution but some others do.
 
thanks Geo,
i read somewhere that diluted HCl is better,
is that true, and how much diluted?
regards
 
andees78 said:
thanks Geo,
i read somewhere that diluted HCl is better,
is that true, and how much diluted?
regards
Click to expand...

I don't think so. It will be working but it will take longer. I use 10-20% HCl as I cant get the proper stuff. Maybe you confused this information with diluted nitric which is 70% HNO3 diluted to 30-35%.
 
it is true nitric acid will dissolve the brass in the pins faster but it is much more expensive than hcl acid because of the volume needed. it takes 1 US gallon of 70% nitric acid to dissolve 2 US pounds of copper and if you dont have a reflux on your apparatus to collect the nitrogen dioxide to convert back to nitric acid your process will become very expensive very quickly. hcl acid on the other hand is fairly cheap to purchase and can be re-used over and over again without special equipment.
 
hello
are the square pins harder to dissolve?
because all of them are still goldish, and all reactions seems happening
to the little slim ones from ram sockets :?:
regards
 
that just means the plating is thicker on those pins, not to worry, the reaction is taking place under the gold foil where you cant see it.
 
My choice would be cell. Amount of gold on them will not be worth hassle and cost of chemicals by dissolving them whole.
 
cell. absolutely, as a matter of fact i dont use AP for pins unless im just way behind. you really need to stay with a cell when operating and with AP you just set it and leave it alone. i can run about 5 US pounds of pins through my cell in a few hours and reclaim 85%-90% of the gold on the pins. i always go back through my pins and pull out the pins that didnt strip all the way. there are always some that dont strip due to bad conductivity or unclean pins (oil or other deposits).
 
Thanks Patnor and Geo. Now all I need to do is get the materials for EVERYTHING. Still doing a lot of collecting and pre-processing but it's slowly coming together.

Rusty
 
Hello All
the solution is getting darker green. there is white dust on the bottom, although the
pins where free of solder. :?:
regards
 
andees78 said:
Hello All
the solution is getting darker green. there is white dust on the bottom, although the
pins where free of solder. :?:
regards
Click to expand...

I can't answer your question andees78, but would like to hear it if someone else can.

I started my second, larger batch of pins in AP with an air bubbler a week ago, about 200 grams in a 600ml beaker. When the white dust (salt?) builds up as it has been the last three days I have been adding more HCl, about 25ml a day. The beaker is full up to about 450ml, the level of AP is about the same as when I started because I am using a 100watt warming pad underneath and it is slowly evaporating. I suspect that the pins might take another week to disolve, but can I just keep adding acid? Adding a drop of water does not form a white cloud, so I do not think the solution is saturated with base metals, but it is dark green/brown. Should I pour some of it off through a filter to add more fresh 32% HCl?

Of course, the pins are mostly kovar and I should have tried nitric. Thanks-O.T.
 
the composition of the base metal will shed light on this. brass is an alloy of copper/tin in different ratios depending on the application of the metal involved. some alloys have more tin and others dont. the whiter the brass the higher content of tin. the white dust is more than likely tin(II)chloride from the tin in the brass.
 
Geo said:
brass is an alloy of copper/tin in different ratios depending on the application of the metal involved.
Click to expand...
Uhhh---no, it isn't. Technically, brass is an alloy of copper and zinc. The line gets real fuzzy, however, in that there are alloys that contain both zinc and tin, and may be addressed as brass or bronze (which is the alloy that contains copper and tin).

the whiter the brass the higher content of tin.
Click to expand...
You can't generalize that way. There are bronze alloys that are quite white that contain no tin at all---aluminum bronze, for example. In addition, yellow brass has no tin and is quite light colored. It contains 33% zinc.

Harold
 
Pins are (or say that most of them) tin plated - there is thin layer of tin on them anyway. To keep solder out brom base of pin is just reducing raio of tin in your solution and making things easier. Your white powder may be copper chloride.
 
for some reason i always have tin in my solution from pins, even if there's no solder. not sure if bronze is used in the composition of the pins or its used as a shield to keep the gold from migrating to the base metal but the tin is always present. sorry about not making the distinction between brass and bronze. even though i have dealt with bronze in my scrapping days it almost always went into the brass unless it was a large piece like an impeller or propeller and its just a bad habit to refer to bronze as brass.
 
I experienced the phenomenon you spoke of when I processed escrap, which was only on rare occasions (only for myself). I can't help but wonder if, maybe, some of the trouble comes from zinc.

Regardless of the source of the problem, one thing that worked for me, and saved me on many occasions, was to incinerate after processing with nitric, then to give the solids a prolonged boil in HCl, then to rinse until the solution was free of color. Regardless of what the problem material is, it should no longer be troublesome. Please understand, I'm speaking from the perspective of filtration, and nothing more. I found some solutions bordered on the impossible to filter, which I attributed to the presence of tin. Maybe it was, and maybe it wasn't, but the process worked.

The plating found under gold is typically nickel, which is there to prevent migration of gold in to the base metal. That phenomenon is well documented.

Harold
 

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