# Insight to old problems and help on new project!



## daytona69us (Jun 10, 2009)

Let me start by saying GREAT SITE!! I have been reading your forum for bout 2 years now and have learned a great deal. Unfortunately this is my first post. I ran across a large amount of PCB's for the aerospace ind last winter. Several different types of boards, 7 x .5 x .25 aluminum core with layer of copper, nickel(???), gold(thick 22k) next 7 x 5 x 1/8 copper bar with thick plastic, with gold plated contacts, glued on one side, trick is the gold on the plastic does not contact copper. Others were fiberglass boards which I used hcl to remove foils. I also picked up a bunch of stuff used for plating(titanium screen, flat titanium, electro-plater 50amp power supply, circulatory pumps, heaters, etc.). Thanks to the info here I have been processing these for many months now. I have produced more than a pound so far.

ARA in Dallas is a GREAT refiner 2% fee that's it, our numbers matched all the way.

Ok hears the deal..
Made a cell using carbon rods(dry cell, 6 or 7, spaced bout an inch) suspended from titanium for cathode(tried shallow and deep), made titanium clips for anode, liquid fire for electrolyte, electro-plater power supply(0-25v - 0-50amp). When I first started everything went fine, as I started my next batch things were a bit different, and so on. First it doesn't take long for the amps to start getting high like 30+, and hot of course, have to turn voltage way down when I do after a minute or so the amps will go close to 0 and the gold remaining stops coming off(no bubbles, black powder or circulation), I tried wide dish, narrow dish. I can only do 2 maybe 4 boards at a time. First time got a nice chunk bout an ounce, second time less and so on. First time purity was good 22+ second time lotta copper bout 18K and so on. Tried reusing acid at first that definitely didn't work amps would go too high, been using fresh acid each time(liquid fire). Tried freezing acid to drop out metals didn't work. Powders still appear and disappear sometimes. Usually when cell is full(amps high 30+),after I rinse all the sulphuric out, what powder is there is what I wind up with. I still do a Hcl was n rinse then do an ammonia hydroxide wash n rinse. The hcl does not discolor at all(maybe a bit yellow) but the ammonia turns dark blue(beautiful), but very very little of the amount of powder changes. As mentioned the boards have a layer of a shiny silver metal between the gold ad copper I am supposing this is nickle. It comes off in the cell before amps go to zero or near, but by then its getting into the already exposed copper layer. The longer I use the cell and as acid heats up I have to turn volts(amps) down. Got good filters, vacuum system, centrifuge, all kinds of lab stuff. Haven't thrown anything away.

Have almost 20 gallons of spent Hcl(black, clogs filter fast). Plate out metals?
What is recommended max amperage( I can hit 50 and make it sizzle)?
How do I clean metals(copper) from acid(suppose this is what is making it so conductive)?
How can I recover this silver metal?
Is there enough chlorine in tap water to react with Hcl and dissolve gold?


Next problem:
I have 2 types of the copper boards mentioned earlier the other one is basically the same except twice as wide. These boards have the least amount of gold on them. I have been heating them(too slow) to remove the plastic with gold contacts of which I put in hcl. Then run the boards thru the cell 15+ at a time, in a makeshift titanium plating basket(too slow, amps runaway). The deal is I have 6 or 7 5 gallon buckets(several thousand, over 150lbs per bucket ) of these boards, each solid copper. I also have some titanium(like expanded metal) plating baskets 3' x 8" x 4". I can fit the narrow boards thru the slots of this. I have plastic 55gal drum to cut for a tank(it will handle 400+F). Have 2 2' x 2' pieces of stainless(like corrugated) cathodes (from the same place), one had a layer of copper probably a mil thick on it that pealed off fairly easy. Was thinkin cut the drum, shove boards in the basket anode, drop in the SS cathode, and shoot the juice to it, ELECTROLYTE! Gotta have a bunch(20gal+) of it(limited budget) I have to get this wrapped up in the next three weeks.

Was thinkin saltwater?
Any ideas for that large amount?
Large membrane?


I was in Taiwan last month and carried a 87g 22k chunk with me. Went to a shop and did some horse tradin. He tested the purity by putting water at precisely 25c(?) in a beaker, placing this on scales, suspended the piece of gold in the water from a thread, did some math and viola he said it was 22k.
I guess this was based on specific gravity?
Is anyone familiar with this method?
Could you elaborate on the details?


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## leavemealone (Jun 10, 2009)

Good morning daytona and I would normally say welcome to the forum,but in your case I'll say welcome to posting....lol. The gold in the water trick is based on the displacement of the water compared to the weight.I don't know of anyone that uses that method anymore(except for your guy of course),stone testers are so readily available these days but maybe they don't have access to getting those over there.Anyhow, Are you purchasing any material? I'm in Cocoa and would love to have someone that is close.Ok well have a good day,
Johnny


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## daytona69us (Jun 10, 2009)

Hello Johnny. The guy that did this test told me it was the only way outside of assay that you can tell 100% for sure. Said acid and stone, and machines are not 100% accurate. Anyway what type materials? Always on the lookout for things


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## leavemealone (Jun 10, 2009)

Mostly boards and pins.I have a lot of boards,but I do most of my own recovery,except for motherboards.We come up there quite often,and I'd love to have a reason to come up even more often....lol.Do you participate in the shootout GSBS ?If not let me know I can tell you about it.Its the largest metal detecting competition in the U.S.and its held every year right there.Me and a lot of friends of mine enter it.Anyhow,If you ever come down you are more than welcome to come over.
Johnny


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## goldsilverpro (Jun 10, 2009)

Daytona,

I deleted the identical post you made under Other Processes. Please don't make duplicate posts. It confuses things.


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## daytona69us (Jun 10, 2009)

leavemealone said:


> Mostly boards and pins.I have a lot of boards,but I do most of my own recovery,except for motherboards.We come up there quite often,and I'd love to have a reason to come up even more often....lol.Do you participate in the shootout GSBS ?If not let me know I can tell you about it.Its the largest metal detecting competition in the U.S.and its held every year right there.Me and a lot of friends of mine enter it.Anyhow,If you ever come down you are more than welcome to come over.
> Johnny




The boards I do are specific, they don't come from computers. The only thing I process from computers is processors and fingers. I do have 3 or 4 drums of motherboards, cards, all kind of stuff, hate to throw it away(parts..haha). I have never entered any detecting competition though I am a very avid hunter. I have been foolin around with LRL's and built one(already had everything, I have been in electronics for many years). Seems to work but not for sure(I know where the gold is..LOL). Have never put it to a blind test yet, got sidetracked, theoretically it makes sense, reality- I kind of see how it MIGHT work. Have traveled all over Florida, lived in Vero Beach for a few months(Scuba Diving Instructor training at EASE).


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## daytona69us (Jun 10, 2009)

goldsilverpro said:


> Daytona,
> 
> I deleted the identical post you made under Other Processes. Please don't make duplicate posts. It confuses things.




My apologies, kind of a old newbie here, definitely don't want any confusion. Thanks


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## leavemealone (Jun 10, 2009)

Sounds like I may be interested in the barrels of boards you have if you want to sell them cheap enough.
I'll PM you with my number.
Johnny


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## goldsilverpro (Jun 10, 2009)

By weighing the gold in both air and water, the specific gravity can be calculated. The thread was used because it is too small and weighs so little that it won't produce a noticeable error. From the S.G. calculation, the gold karat can be estimated. Since 22K is popular in the Far East, the man probably did this so often and knew the S.G. of 22K gold. However, the accuracy is dependent upon the impurities. I would guess that the S.G. of 22K is about 17 to 18. The S.G. of pure gold is 19.3.

Here's a pretty good discussion. Notice how he jury-rigged the balance to make the weighings.
http://www.lnhs.org/hayhurst/geology/specific_gravity.htm

S.G. = (weight of gold in air)/(weight of gold in air - weight of gold in pure water)

As far as your cell is concerned, I'll have to wade through your post a couple more times to try and figure out exactly what you are doing. I have 1000s of hours of production experience using this cell and we should be able to figure out your problems. Off-hand, I think you are overloading it - too much metallic sludge buildup can cause a partial short, which would give excessive amperage. How large is the cell? You also say that you are running boards. If so, putting organic materials in the cell could cause problems. If you are running boards, how are you making contact to each isolated portion of gold plating that you want to strip?


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## daytona69us (Jun 10, 2009)

goldsilverpro said:


> By weighing the gold in both air and water, the specific gravity can be calculated. The thread was used because it is too small and weighs so little that it won't produce a noticeable error. From the S.G. calculation, the gold karat can be estimated. Since 22K is popular in the Far East, the man probably did this so often and knew the S.G. of 22K gold. However, the accuracy is dependent upon the impurities. I would guess that the S.G. of 22K is about 17 to 18. The S.G. of pure gold is 19.3.
> 
> Here's a pretty good discussion. Notice how he jury-rigged the balance to make the weighings.
> http://www.lnhs.org/hayhurst/geology/sp ... ravity.htm
> ...



Thanks for your response. The boards are specific and do not even closely resemble a standard PCB. They have no coating, the only thing besides metal is a plastic face(for lack of a better term) its all connected, they are from the Q.C. lab of a belly up manufacturer, and I have found several references to aero-space companies. For the cell I have home-made titanium clip(anode) and an adjustable holder, just clamp it on and lower it in, 2 at a time. I usually use a full quart of acid and have tried the lil pyrex meatloaf dish(deeper but less distance between anode and cathode) up to the big casserole one(shallow, but more distance). Have had better luck with the deeper one. Keeps boards outta the sludge. Even after settling and drawing off the clean acid, it doesn't seem to want to work right. Could it be the silvery metal(nickle??) that is between the layer of gold and copper. It comes off with the gold(when amps go to 0). A couple of times I managed to recover this silvery Pearlie sludge, but when I tried to dilute and rinse and it disappeared into solution. Haven't been able to get it back. I'll try to post some pics this eve.


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## leavemealone (Jun 10, 2009)

Hey daytona,I sent you a private message with my numbers,
Johnny


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## goldsilverpro (Jun 10, 2009)

Daytona,

Can you provide a couple of photos of those parts. I can't visualize them by your description.

I ran the same solution for several years, 10 hours a day. I collected the gold (about 50 - 100 oz) every week, or so, and put the same solution back in the tank. It was a 50 gal steel tank and I made the tank the cathode. It was run at 250 amps (5 A/gallon) and, even then, it would normally heat up to about 10 F above ambient. If it got much hotter, it started attacking things that I didn't want it to attack and creating other problems.

The boiling point of your H2SO4 is about 500 F. That means that, if you continue pouring the amps to it, it will keep getting hotter and hotter. Have you checked the temperature? I think that is your main problem, considering that little dinky quart of acid you're using and the huge amount of amps you're applying.

Here's how I would do it. Before putting the parts in, turn the rectifier knob to zero. After the parts are in, adjust the amps to about 10 max (from 2 to 5 would probably be better for your little tank). The voltage will be about 2, or so. When the amps start dropping, increase them back to 10 (or, from 2 to 5). Continue this until the voltage is about 12 - 15 and stop adjusting. You have to stay with it. The amps will soon go to zero. Using this method, average gold plating will take about 2 or 3 minutes. I was stripping 1 mil thick gold/tin braze (that's 30 times thicker that the gold on fingers) and that took 15 minutes. Don't overload the tank with parts. Run fewer parts and more batches. If the temperature reaches about 130 F, let it cool off. Either that or lower the maximum amps. When you reach a point where the amps won't go to zero, that means that there is so much metal powder floating around in there that you have a partial short - it's time to harvest the gold. If you do what I'm suggesting, I think that things will go faster, things will be safer, and you'll be able to re-use the solution. Just be patient and try it once my way.

I know of no 55 gallon plastic drum that will go to 400 F, unless it is made from something like teflon. I would figure about 170 F before it starts to get soft. Also, hot concentrated H2SO4 tends to remove the plasticizers from plastic and it starts cracking.


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## daytona69us (Jun 11, 2009)

Once again many thanks for your input. I'll start with tha pics(I hope I do this right)View attachment 4

The first board from top to bottom yields the most, the first three are on Aluminum core, the next two with the black front are on a solid copper bar, the top gold does not contact copper(remove and put in Hcl), It appears to have been plated copper on the bar before the gold, when I was heating them to remove the thin plastic with gold on top it would bubble on the bar itself. When examining these bubbles it was a layer of copper, nickel(I guess), and gold on top. When running the boards I could only do 2 - 4 at a time. If I keep amps at 10 or less it takes nearly 10 minutes plus to do 2, there is a silver metal between the gold and copper, the amps will not go down till this is gone as well, is this nickle? It goes into solution, any that is left dissolves in the rinse.
You are right about high amperage, I have been in a hurry and kind of experimenting(learning) and run it so long it got so hot the pieces would make a sizzle sound going into the rinse water, sometimes rush, rush(If a little is good, a lot is better, right?) What about ice in the outer container around the acid keeping it cool? I have a large amount of these boards and not enough time, I need to upscale! I live in the boonies and have had a hard time locating that much H2SO4, any other ideas for electrolyte? Can hit the scrap yard for a ss container. Did a heat test on a plastic drum that lye was shipped in, and the hard thick swimming pool plastic, the pool plastic didn't start getting soft til 196c . Had heat gun on high 4" away, took over 15 minutes before it even started getting soft. Didn't get the drum right due to severe weather.

The rest are of my lab in my soon to be dissolved metal shed, have good ventilation(also wear respirator), Cell with carbon attached to titanium cathode, small batch of powders for a lil boil in HCL, Harvest - the silver was scrap I purchased, also a button or two was from purchased gold, rest is reclaimed.


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## daytona69us (Jun 11, 2009)

Oooops missed one!


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## leavemealone (Jun 11, 2009)

Good morning daytona,
Very nice pictures.The ice trick wont work for very long,the heat generated from the acid will eventually raise the temperature of the water to the temperature of the acid.I can get you a 55 gallon steel drum if you want to try GSP's method,but I don't know if it needs to be a specific type or style of drum.The drums I have access to are just ordinary shipping drums that are relatively thin.Chris do you think one of those would work for what he needs?If not you can put your drum inside another container and keep fresh water circulating through it.That should keep the temp of your acid way below the melting point of your plastic drum (just make sure none of the water comes in contact with your sulfuric).
Johnny


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## goldsilverpro (Jun 11, 2009)

Don't use stainless. When I first started experimenting with this, about 38 years ago, I used a 4 liter stainless beaker. In a few days, it ate some holes in it, especially at the solution level. The H2SO4 tends to leach out the chromium and/or nickel in the stainless. The 50 gal tank I ended up using was made of welded mild steel. When I had it made, I made sure they used welding rod that contained no nickel. Nickel is a bad actor in this system. If enough gets into the solution, it will stop working. After several years of use, there was no noticeable attack on the tank. Like I said, I made the tank the cathode. You should be able to find a variety of sizes of steel boxes that could be used as tanks in a scrap yard.

The parts I was mainly running were these;
http://www.cpu-galaxy.at/

We had heated rails, with a good temp controller, that melted the Au/Sn braze on the lid and the Au/Si braze holding the chip. We then plucked off the lids and chips with a vacuum probe. The lids were stripped in the H2SO4 in a barrel plater similar this one. The chips were run in aqua regia.
http://www.singletoncorp.com/portable_barrels.html

To strip the main parts, I made a bunch of stripping racks from bare 1/4" square brass rods. They were assembled with SS screws. There was no coating on the racks. They looked similar to the rack on the right.
http://www.philipmachine.com/racks.html

Screwed onto the cross members was a series of piano wire spring contacts that held and made multiple electrical contacts to each of the parts. Each rack held from 300-500 parts, depending on their size. We ran about 4 racks per hour per tank. If we kept the temperature of the solution down, there was no attack on the brass racks, the stainless screws, the contacts, or the non-gold coated portions of the parts, such as the Ag/Cu braze used to attach the legs. The parts were then re-plated on similar racks that were coated and the parts were inspected and returned to Intel or AMD for re-use. At full production, we ran about 100,000 parts per week. The gold we got from the parts was a bonus. The main purpose of the business was to restore the packages for reuse. The parts we ran were not rejected because of package problems but because of chip problems.

In 1974, or so, the idiot Nixon devalued the dollar 10%, twice, and also that year, there was a 6 month dock strike in the US. The parts we ran couldn't be shipped from the overseas assembly plants and the entire electronics industry fell flat. We shut our doors and concentrated on just refining.

In about 1980, I set up a similar system to recycle hybrid packages, mainly from the microwave and fiber optics industry. This didn't last long because there was so much gold and silver scrap at that time that we had to concentrate on refining.
http://www.electrovac.com/sprache2/n168286/i234370.html
http://www.army-technology.com/contractors/data_management/schott/schott2.html

I know this isn't exactly pertinent to this discussion, but I wanted to show ways that the stripper could be used.


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## leavemealone (Jun 11, 2009)

Good morning chris,
How did you hang the material from those hooks?Or where there clips on them? I love that post,it was very informative and I appreciate the help.I'll start looking as soon as I can for some steel plate,as Im sure the drums I have will not work.I have one last question though.How were you able to run at that high of amperage? Power supply or welder maybe?
Thanks again,
Johnny


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## goldsilverpro (Jun 11, 2009)

leavemealone said:


> How did you hang the material from those hooks?Or where there clips on them? I love that post,it was very informative and I appreciate the help.I'll start looking as soon as I can for some steel plate,as Im sure the drums I have will not work.I have one last question though.How were you able to run at that high of amperage? Power supply or welder maybe?



They weren't hooks and we didn't hang the parts. We had a spring manufacturer make the spring contacts in lots of about 10,000. Each part used 4 springs. Two were formed so they gripped the parts, usually in a non-conductive area (the ceramic), and the other two made a spring contact to the lid ring and the chip pad. Some parts were a little different and required more contacts. For the hybrids, each spring both held the part and made contact at the same time. In the case of the CPUs, we had 2 or 3 girls loading and unloading the racks.

Before you think about having a steel tank built, look around in the scrap yards for steel boxes, at least 1/8" thick. The 50 gal tank we had was 1/4" thick. You may be surprised what you'll find. Were I to do this again, I would probably mount a good steel valve, that doesn't leak, a couple of inches above the bottom. The valve could be welded on or mounted with teflon seals. That way, you could let the gold settle and then drain the solution off. That would be a lot safer and faster than using a siphon hose, at first, and finish it off by dipping, like we used to do.

Like I said earlier, we used 250 amps. It doesn't seem to make much difference how much current, a little or a lot, is applied to the parts. There probably is a limit to how much current density (amps/sq.ft. of gold surface area) can be used, but we didn't reach it in this operation. As a guess, we were using about 150 amps/sq.ft. or 1 amp/sq.inch. The main thing is to use a large enough tank so the solution doesn't overheat. We used a standard 12 volt, 250 amp plating rectifier. It was almost identical to the one at the bottom of this page. They're not cheap but I've seen a lot of used ones. I prefer the analog meters rather than digital.
http://www.caswellplating.com/kits/rect.htm


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## leavemealone (Jun 11, 2009)

I can't thank you enough for the information.I feel like a kid on christmas eve again.Can't wait to get something like this golng.I'll probably go to napa next week and start getting my sulfuric.I assume the normal 90% is what you used? I wonder if I could get away with going down to about 75%.Any ideas on that?
Johnny


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## goldsilverpro (Jun 11, 2009)

> I assume the normal 90% is what you used? I wonder if I could get away with going down to about 75%.Any ideas on that?



Although the original patent on this used H2SO4 as low as 75%, I wouldn't use it. I have had problems at that level. I used the standard tech grade of 96-98%, by weight, and added 5-7% water, by volume. Also, you must consider that strong H2SO4 is a desiccant. It will absorb water from the air. I did this with 2 goals in mind: to strip the gold without attacking the other metals and to be able to reuse the solution many times. The weaker the sulfuric, the more it will attack base metals.
http://www.google.com/patents?id=L3FVAAAAEBAJ&printsec=abstract&zoom=4


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## leavemealone (Jun 11, 2009)

The only reason that I considered going down to 75% ,is because I'm starting with about 30% and boiling all of that down will be extremely time consuming.I can get that kind of volume of "Rooto" but of course the financial expense would just be rediculous,30 gallons would be around $900,where as the 30% in 5 gallons quantities would be about $550


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## goldsilverpro (Jun 11, 2009)

*The Nickel (or, Cobalt) problem* The standard H2SO4 solution will dissolve nickel somewhat. If too much dissolves, the solution will stop stripping gold and the solution will have to be changed. The parts I ran had the standard nickel plating underneath the gold plating and I had no problems with this small amount of nickel. However, when stripping gold from high nickel or cobalt alloys, such as Inconel or Stellite, the solution stopped working after a couple of days. I've never tried this, but I've always thought that a small addition of potassium dichromate would prevent the Ni or Co from dissolving. Were I to try this, I would start with a small sample bath and, at first, would add about 1 oz/gal. The combination of acid and dichromate tends to passivate base metals. It might even work with a weak aqua regia to dissolve gold plating from copper, without attacking the copper very much. It wouldn't work using nitric on silver plate because silver dichromate would form as a solid and you would have a mess.


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## leavemealone (Jun 11, 2009)

The help and information you have given thus far is priceless.I won't ask for anymore.I appreciate you patience.
Johnny


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## AurumShine (Jun 11, 2009)

Thanks goldsilverpro I have same problem about nickle plated pins but now this problem is solve :idea:


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## daytona69us (Jul 2, 2009)

Hey guys I'm back home and online. I've given a lot of thought to all of the excellent info from everyone. So I am going to do numerous changes and try to start back up this week. In the meantime I ran across this guy yesterday that claims to have a lot of plating solution he wants to get rid of both 22 and 24k. Roughly 50 gallons, says its cyanide free. I have not seen it yet but plan on checking it out in the next couple of days. I really don't know much about it so I'm gonna turn to the Gurus of Gold. Got any knowledge or experience with this stuff? My main question is how do I test to calculate the actual amount gold. The next one would be how to get it out? Plating I know, what about evaporation or precipitating? If plating it out what would be the best for anode and cathode?


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## goldsilverpro (Jul 2, 2009)

He probably has some written instructions on how to use it. Find out the names of the 2 solutions and maybe we can figure out what's in it. How you analyze it and how you get the gold out can be dependent on what's in it.


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## daytona69us (Jul 2, 2009)

He lives in a nearby to and I hope to hook up with him in the next day or two. He mentioned that he has some small amounts in quart jars and would let me have a couple of samples for testing.


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## goldsilverpro (Jul 2, 2009)

These things crossed my mind.

Due to the fact that they are designated as 22K and 24K, they sound like they are plating solutions that are sold to jewelers. When new, these usually run about 1 gram/liter, or less. I may be wrong about this, since 50 gallons is a lot for a jeweler to accumulate. 

This may come from a company that plated costume jewelry. They also buy their solutions based on karat. They would also generate a lot more solution. The solutions they use can run from 1 to 8.2 grams/liter, when new, depending on how thick they are plating.

If this solution is stolen, it could run high. It is not uncommon for employees to take a little good solution home each day. If it is not hot, it could be that the company plated the solution until it stopped working and replaced it with a fresh solution. In this case, the gold could be quite low.

If you are buying this solution, I would be very careful about the sample he gives you. Something he has sitting around in a quart jar is meaningless as far as values are concerned. Ideally, all the solution should be put together and well mixed before the sample is taken. 

If there are solids on the bottom of the solution, that complicates things. The solids may or may not contain gold. We used to heat the solutions to dissolve the solids before sampling. In your case, I wouldn't worry about it. Base everything on the liquid. The solids may be a bonus.

I suggest that you be present when all this is done. Don't be embarrassed about asking for a good sample. It makes you sound more knowledgeable and professional.


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## daytona69us (Jul 18, 2009)

More questions for the pros. OK I finally found out a bit more about the plating solutions. They came from a supply place in Louisiana called Swest inc. that was going out of business. It is new and he has 18 and 24k solutions(about 20gal 24k, 10gal 18k). I have a gallon sample with label. It's TivaGlo-Free 18k, cyanide free and ecologically friendlier by Tivian Ind.. I figure I got two choices for recovery, one plate it out, two quick evaporation in the hot Texas sun. The directions for plating on the label is, stainless anode, heat to 140f, 3-4 volts for 30-45 seconds. I can do this, but wouldn't evaporation insure I recovered 100% of the values? What are the chemical(s) and how well will they evaporate. I haven't had time to do a bit of research so I do not know the total yield per gallon thus far.


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## goldsilverpro (Jul 18, 2009)

I couldn't find an MSDS or a data sheet for the TivaGlo solutions but I did find a price - $771 for 5 gallons for all the various karats. That figures out to $40/liter. Therefore, you can't expect the gold content of a new solution to be more than about .8 grams/liter. It could be less. No matter what the karat is, they should contain the same amount of gold, when new. The lower karat colors are obtained by adding certain base metals, like copper, to the solution. 
http://www.goldtouchinc.com/tankplating/TankPlatingChemicalPrices.html

Although there may be exceptions, most all of the non-cyanide gold solutions I've seen are made from sodium gold sulfite and operate at an alkaline pH - usually about 9.5. The gold complex is unstable at an acid pH and will decompose. When the pH is lowered to the acid side, the gold will drop out as a fairly pure brown sponge that is very easy to filter. As a sample, I would take about 100-200 ml of the gallon sample and add 10%, by volume, sulfuric acid to it, under a fume hood. When diluting the sulfuric, add the acid to the water. You can also use battery acid (about 35% sulfuric - buy at an auto parts store) diluted about 4 or 5 times with water. Add the sulfuric to the gold sample, in small increments, with a little stirring, and see what happens. If this is a normal sulfite solution, the gold will all drop out at some point. It shouldn't take much acid. Once you reach a certain pH, brown powder should start forming in the solution. Since there is no simple way to test the solution for gold, it's hard to estimate how much acid you'll need. Also, the solution may be buffered in order to stabilize it at the operating pH. It may take a little extra acid to overpower the buffer. I don't think a little extra acid will hurt. 

I have read that there are some newer gold sulfite solutions that can be operated at an acidic pH. If so, it is possible that the sulfuric method given above may not work. If this is the case, I would lower the pH of a small 200 ml sample to about 2, or so, with weak sulfuric (maybe 5 or 10 ml of 10% sulfuric acid to your 200 ml sample) and add some 325 mesh zinc powder. The 325 mesh zinc powder is available from Ebay in 1# units and is inexpensive. Buy only 325 mesh. Add the zinc in small pinches, with stirring, since it can react violently, especially when you add too much at one time or, if you have started with too much acid. Wear gloves and a face shield. The zinc should precipitate all of the gold. Use a slight excess of zinc. You can tell this when the zinc no longer reacts with the acid and the precipitate appears as a gray powder. Filter and rinse. Transfer the powder to a beaker, cover with water, and add a little full strength battery acid. The acid will dissolve the gray zinc and you will be left with brown gold powder. It helps to heat it slightly at the end.

If you try to plate the gold out, I doubt if you'll be able to get it all. These "color" gold baths have very little gold to start with and most are only designed to plate for short periods of time. As the gold content gets lower, the plating efficiency gets lower, and the current splits more and more water at the cathode. At some point, all the current will be used in water-splitting and almost none will be used to deposit gold.

If you evaporate the solution, you will end up with all the chemicals in a dried out condition. In order to recover the gold, you will have to redissolve them and will probably then have to use one of the methods above. In other words, you will be right back to where you started from.

Try the sulfuric method first. It is by far the simplest method and I would expect it to work. Use small samples in your experiments. You don't want to screw up the entire solution, in case the method doesn't work. Let me know what happens.


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## Palladium (Jul 18, 2009)

Chris, You never cease to amaze me.

You can't buy knowledge like that. 8)


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## goldsilverpro (Jul 18, 2009)

Thanks, Ralph. Been there, done that.


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## Palladium (Oct 28, 2009)




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