purple HCl

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M

mjgraham

Well-known member
Joined
Feb 11, 2012
Messages
217
Location
Pennington Gap, VA
Hi, I have been trucking along doing pretty good, I won't say I have a problem just curious if anyone has seen this. I have a 4 gallon bucket I have a 50/50 mix of HCl and H2O to remove solder. Been doing batches of ram sticks and all has been doing good. My last batch I noticed that when I opened the top it was light green as if I have made an AP solution, did not think much of it, after I siphoned it out and filtered the sludge the mix went back clear after a few days. Last week I had a batch of 60 sticks in it and I noticed when they were done and I collected the sludge there was some copper in the mix along with the sludge but the solution was a slight yellow to clear, like normal. Well in the mean time I decided to heat the batch, I have constructed a double boiler kind of set up for it had it running for an hour popped the top and it was purple, not expecting that at all. The only other difference I just realized is that I had been removing all the parts off before with a torch this time I decided to let the acid do the removing, humm just realized there may have been some other metal in the mix now..

i-QQCkKFQ-L.jpg
 
Don't know about the purple, Looks like a stratified layer in solution so it could be anything besides a solid. But i can tell you what i see wrong. First you should clip them fingers off the boards before you do this. Why? refining is about segregation. The cleaner you can keep something the easier the process, the cleaner the end result. Those should be done in a separate batch. Trying to remove and wash foils from all that material is not going to be easy. Why create extra work and make your job harder? Next you should soak them in just straight hcl, not hcl / h2o2. That's the acid peroxide method you just created. Tin and oxidizers ( h202 ) for some reason act funny from what i have observed. Don't ask me the chemical side, i don't know. All i can say is what i have observed. What likely happen was the tin went into solution as well as the cooper from the ap like process you created. That's why it was green. Once the oxidizer was gone the tin precipitated the copper back out the solution giving you the clear again and your copper precipitate because all the oxidizers were gone. The stratified layer you see is likely a tin copper mix or a colloidal of the same. Next Time just pour the hcl in the bucket with the boards and the fingers removed from the boards and sit it in the sun to do it's work. After the boards are clean of solder and components then you can proceed to remove the solder mask if there is gold under it. Then you can go to ap.
 
Harold schooled me to the fact that silver can appear purple. it may be a colloid of silver from the solder. it could also be the small capacitor bodies left on the sticks dissolved into solution.
 
Yes it is a little out of the norm for me to do this. I had been clipping the fingers off of most of the sticks that I process if they don't have anything else that is gold plated, on these the vias are plated, I agree it may not be the best way to do it but I am new and was just tring to save two seperate batches. As for the H2O2, I didn't have any in it but I was wondering if the H2O I used to make up the batch. I only put in 12 out of the mass just cause this was a different idea, good thing looks like. I'll keep the acid seperate and figure out what to do with it later on.

Here is one of the sticks I stripped just to check the traces, is there a better way to handle sticks like these with so many little plated holes? I know they don't always come with out help, the copper is gone but just need labor.
i-Ps4bRLm-L.jpg



Edit. I am on here many times a day, somehow I missed this thread, seems to be a good chance what I am seeing.
http://goldrefiningforum.com/phpBB3/viewtopic.php?f=49&t=14661&hilit=colloid
 
yea that is what I was thinking too, somehow I overlooked all the recent posts on this, The only thing is this time I heated the solution to about 80C, before it had just been outside temp, but I had no parts on the boards just eating old solder off so has to be in the parts on the boards. I will do like suggested and just cut the fingers off anyway before the solder leach. I am glad I didn't try a mega batch, I guess I thought all the pieces are going into HCl at some point why not all at once when I know better... At least I didn't put the whole things in AR like a lot of new people then ask for help.
Thanks everyone for your input.
 
While I know that HCl will knock Silver out of Silver Nitrate, I thought it had no effect on Silver metal. Silver Nitrate will turn purple in the sun. Are we getting these two things confused or am I missing something?
 
Silver chloride will turn purple with direct exposure to the sun also. It is formed when hcl comes in contact with the metal surface.
 
My bad! Your right after i read it again you didn't have any h2o2. I read that wrong, sorry. :cry:
 
I don't want to derail this thread but are you saying that HCl will create AgCl on the surface of Ag? Kind of like an oxide layer that prevents further reaction with the metal? If I placed Ag in HCl and then removed it, rinsed it and placed it in HNO3, would it dissolve the Ag and leave the AgCl?
 
I don't think hcl alone will create silver chloride. Then again i might be wrong. Don't know about just the two of them alone in a solution. It's like hcl and copper in the ap process. Hcl in and of it's self does not have the oxidizing potential to do dissolve copper, but add oxygen to the mix and the surface creates an oxide layer that easily dissolves. Then you add other metals into the mix and it allows for a whole bunch of other kinetics to form or develop. I'm not sure of the chemistry or the how's i just know it happens. Here's something interesting i read earlier. http://books.google.com/books?id=F7p7W1rykpwC&pg=PA205&lpg=PA205&dq=silver+surface+oxidation+chlorides&source=bl&ots=fiUOsY0x3h&sig=4m6gMSsq-LbVKUKknJbs0F6pksM&hl=en&sa=X&ei=yvEaUO_XJ6XD0QHgo4CQAQ&ved=0CGMQ6AEwCTgK#v=onepage&q=silver%20surface%20oxidation%20chlorides&f=false
 
That looks like a good read. I will have to check that one out later. I am sure alloys such as solder will react differently than their constituent metals too.
 
Palladium, read my recent post on the next thread down (HCl Leach). I know that HCl will absorb O2 directly from the air. Most of the time I regenerate my AP by simply leaving it exposed to the air. It turns a nice emerald green all by itself without any added air.
 
maynman1751 said:
Palladium, read my recent post on the next thread down (HCl Leach). I know that HCl will absorb O2 directly from the air. Most of the time I regenerate my AP by simply leaving it exposed to the air. It turns a nice emerald green all by itself without any added air.
Click to expand...
I have noticed this also, I wondered if the water I put in was enough of an ozidizer to get it started, I had previous RAM sticks in for days mostly due to the fact I was busy. I thought it may have formed a weak AP. I am doing some tests have a few test tubes with the capacitors and HCL, 50/50 mix etc, so far no color change on heating. I had these sitcks in a day or so w/o the purple color change then when I heated it I got that stratified layer. But as many have said there are a lot of complex things going on so it is hard to say. For me it was moslty unexpected to see purple, my first though was collodial gold like I had just dumped stannous chloride in my auric chloride. It is a pretty purple, since I have filtered it out and seperated the now bare sticks out. all the parts are removed, the capacitors have just turned into silver sheets, or at least I hope there silver at the moment I don't have any way to work with silver. All in all it was more labor intensive to use a torch to remove all the parts then sort the ICs from the rest, I think for me at least it is easier, now I have this to clean up.
i-qjMmsGL-XL.jpg
 
Palladium,

Don't feel bad, I originally thought the same to. It looks like a stratified layer of silver chloride that has been exposed to the suns radiation and turned purple. But HCl alone should not make silver chloride. Also the material doesn't look like material that would have silver on the boards, and the chips/ICs/Eproms whatever they are, do not look like they have been broken into parts so I'm not sure where the source of silver would come from. But I did think the same thing as you, and I'm sure other people who have dealt with silver thought something similar.

But considering the material, and the fact this is an HCl leach, I think I would be inclined to go with others have said about Tin, it's almost certainly involved in the material's matrix.

Scott
 
RESET said:
I don't want to derail this thread but are you saying that HCl will create AgCl on the surface of Ag? Kind of like an oxide layer that prevents further reaction with the metal? If I placed Ag in HCl and then removed it, rinsed it and placed it in HNO3, would it dissolve the Ag and leave the AgCl?
Click to expand...

If there is silver present, and you know it, then HNO3 is the best way to remove it, it's easier to deal with silver nitrate, rather than silver chloride. But you also have to consider the other base metals, I assume that's why you are asking about first using HCl to strip the unwanted base metals, then wash and move to HNO3 to remove the Ag and Pd if any exists. The problem is that if there is even small amounts of HCl, adding HNO3 will dissolve small amounts of Au into solution. The only way to insure that doesn't happen would be to incinerate, washing will remove almost all the HCl, but it never seems to remove it all unless you soak it for a long time in water, and even then you probably still would have small amounts of HCl.

I look for silver, if I find none I depopulate the boards first and reserve the material I pluck from the boards for processing using another method. Then I give them a soak in HCl to remove any base metals, etc. Then I put them into an AP tank to foil the gold, the collect the foils and process those with HCl/Cl. It might take a little more time, but I believe in this way I circumvent many of the problems I might have otherwise.

Scott
 
I get that purple colour every time I dissolve the solder off the SMD capactors.
It gives off a strong distinktive, but not offensive, smell.

Its the smell of the school chemistry labs, from memory.

When I decant the liquid off & then add water, it turns clear & lots of 'suger like' crystals appear on the bottom of the beaker.
 

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