# percipitate question



## dsinjc (Oct 25, 2007)

i am running my first batch ( woo hoo) i am using AR so far I have a very nice emerald green solution going.very dark.so I guess i need to reduce ph first with urea. I have been only able to find it in fertilizer ?? will that work cuz there is other stuff in it.also instead of sodium meta bisulfite, can I use sodium bisulfite ??.
So urea, drop, filter,wash, melt ??


----------



## Noxx (Oct 25, 2007)

Hello,
You must use +80% urea for neutralization. And if you get that stuff, you'll probably have a lot of impurities in it. Aim for 99%+ Urea (look on ebay)
Sodium Metabisulfite and sodium bisulfite are near the same. You will get the same results.
I hope it helps and good luck !


----------



## dsinjc (Oct 26, 2007)

thanks for the help. I am excited that all of the spare computer stuff that i have collected througout the years might pay a small dividend. The liquid is a very dark green I had some bigger chunks in it. I pulled one out after 12 hours and there was clean copper on one side and scaly gross lookin stuff on the other.hope i didn'r do it wrong.


----------



## Anonymous (Oct 30, 2007)

Sorry for speaking. Self edited. rf


----------



## Harold_V (Oct 30, 2007)

russford said:


> "Your green solution indicates copper, but you will probably have some silver in there worth recovering.



Wrong!

He clearly stated that he dissolved his material in AR-----silver will have already been precipitated as silver chloride, so nothing would be recovered, assuming there was any present in the beginning. Having started with AR instead of nitric, virtually none of the silver would have gone in to solution.

The problem I see with this entire operation is the fact that AR was used prior to eliminating base metals. The fact that there was base metal remaining virtually assures that there will be little, if any, precious metal left in solution. The crud described on the one side of the copper is likely the values, having precipitated on base metals. Why would *anyone* process by that method? 

I'm mystified by the lack of knowledge in folks that are attempting recovering precious metals. There's an abundance of good and proper information on this list, free for the reading, which makes mistakes like this not excusable. 

There is no good reason to process base metals with AR, with a few exceptions. If your material copper, or a copper based alloy, if you don't strip the gold, or eliminate the base metal by dissolving it in nitric, or an equivalent substitute, you're spinning your wheels and have much to learn about refining.

Harold


----------



## Anonymous (Oct 31, 2007)

Sorry folks. Self edited.....russ


----------



## Harold_V (Oct 31, 2007)

It may appear to be unfriendly, but the information you dispensed is not in the interest of anyone that wants to learn to refine properly. Something needs to be said that will keep people from chasing their tails, and I'm not the least bit shy about doing so. Sorry if it offends, it was not meant to, but I would go far out of my way to instruct others to ignore your process. Not because I'm an ass, but because you clearly do not understand acceptable procedures, and are muddying the water with information that isn't in anyone's best interest, regardless of how well you may feel it works. There are readers of this forum that have had endless difficulties following your prescribed advice. 

Refining isn't a stranger to me, having done so for a living for years. I am more than familiar with processes that yield excellent results and don't require endless roundabout methods to extract the values. Fact is, if you'd read some of the posts I've made regards procedures, you might learn a few things that will make your life much easier. 

It's obvious you need to do some reading. Given your self proclaimed experience, you would have never mentioned precipitation of silver from an AR solution. By its nature, it will have already precipitated the silver. That was my point. You should have also known that precipitating gold from dirty solutions yields dirty gold that is difficult to bring fine, even with considerable washing. There are far better procedures that insure good results. 

I'd like to recommend a book that will help you better understand acceptable procedures. It's titled Refining Precious Metal Wastes, written by C.M. Hoke. It will clearly state the reasons why your recommended procedures should be avoided. 

Harold


----------



## Harold_V (Oct 31, 2007)

russford said:


> “..He clearly stated that he dissolved his material in AR----silver will have already been precipitated as silver chloride..”
> 
> Not if he started with AR.



russford,

I apparently overlooked this portion of your post. 

To be perfectly honest, I am at a loss to understand your point. 

If you start with AR and alloyed gold, you'll create some silver chloride, but virtually NO silver will be in solution. That, of course, has already been addressed in a previous post, and can be verified by reading Sir. T.K. Rose's book The Metallurgy of Gold, or Hoke's book as well. Silver and gold can not be in solution at the same time in an acid. You may not like the news, but that's the way it is. 

I'd be in your debt if you would take the time to explain to me what your point is. One uses the process of inquartation to make it possible to dissolve gold alloy in nitric, eliminating base metals, along with silver, which can be, and often is, the added metal in the inquartation process. It need not be, although it is far easier and more economical to dissolve than copper or brass. The solids that remain after this process will be finely divided particles of high quality precious metal, and can then be easily dissolved in AR for final separation. The ultimate is when the particles retain their original form, so they are easily handled, but are honeycombed such that acid has perforated them to their core. 

Why would the novice avoid this procedure and go directly to AR, which tends to be nothing short of trouble, and yields less than good quality gold under most circumstances? 

Harold


----------



## Anonymous (Oct 31, 2007)

".."Your green solution indicates copper, but you will probably have some silver in there worth recovering.." 

I was referring to the sliver oxide sludge that was left when he disolved his batch - not the AR.

I will do as you say. I will become a lurker and read the back posts. I did not join this forum to engage the guru in debate. As you say I'm a novice! Let this be a lesson to other novice lurkers...... if you post anything here, you will be ridiculed instead of delt with in a kindly manner. I suppose that's not a bad idea on a forum such as this. At least that way you won't have a lot of misinformation or even alternative methods posted. I suppose there is truly only one acceptable way to skin a cat. :wink: 

Having said that and as I walk out the door......

I never said that silver and gold could exist in the same sloution. You said I said that. Could you have misunderstood what I was talking about? If you look at the other post I made on the Tutorials questions forum you will see that I said:

"..That is exactly what I wanted because all of this will be going into the Aqua Regia and the acid reacts much more quickly and thoroughly to small thin pieces of gold rather than say, a solid wedding band....By droping the gold into water I exposed a lot more surface area and that's why my next step was to put everything into a nitric bath on the hotplate and let it simmer until all the fumes were gone. I drained off the liquid and dropped in some talbe salt to see if there was any silver. I got quite a bit of white precipatate which I believe to be silver..."

Please pay attention to my words "that's why my nest step was to put everything into nitric" that means before AR!!!!!
I leave you to your kingdom with your crown in place. ....rf


----------



## Harold_V (Oct 31, 2007)

russford said:


> ".."Your green solution indicates copper, but you will probably have some silver in there worth recovering.."
> 
> I was referring to the sliver oxide sludge that was left when he disolved his batch - not the AR.



Having conveniently altered your original post, it is now a mute point, but you, indeed, did not say that, otherwise you wouldn't have talked about introducing salt to AR. 



> I will do as you say. I will become a lurker and read the back posts. I did not join this forum to engage the guru in debate.



Lurking isn't a bad idea for anyone that is new to a forum. It's a great way to conclude the level of information that is being dispensed by others, a measure, if you will, of where what you may know will fit with existing conversation. There are people on this forum that have dealt with the gold industry for more than 40 years. I am not one of them. They have brought to the table information that has been very revealing to the majority of readers----myself included. In some cases, processes that have been discussed are very foreign to others, and may not even make much sense until all of the equation is well studied. There's room for any and all procedures, as long as they are just that, procedures. The same does not apply to misinformation. 



> As you say I'm a novice! Let this be a lesson to other novice lurkers...... if you post anything here, you will be ridiculed instead of delt with in a kindly manner. I suppose that's not a bad idea on a forum such as this. At least that way you won't have a lot of misinformation or even alternative methods posted.



You just hit the nail right on the head. *Misinformation.* That is precisely what I corrected, and it should have been. 



> I suppose there is truly only one acceptable way to skin a cat. :wink:



Let me make one thing clear. One person doing something wrong for an endless period of time won't make it right. Nor will 100 additional people doing the same thing, still wrong, make it right. I dedicate far too much of my time to this forum, time spent with no hopes of any kind of a return aside from the possibility of helping others that are struggling with a procedure. To have someone come along and post misinformation that serves no purpose aside from clouding the water for others isn't very welcome, certainly not by me. This isn't a matter of finding a different mouse trap, this is a matter of insisting that a mouse trap that isn't functional being used to catch mice. 

One of the most difficult things I had to do when I started following this forum was to endure the work-arounds that have been so kindly provided by others. In most cases the processes are totally unrelated to those that I used in my more than 20 years of refining for the jewelry industry. Still, I persevered, and came to understand that these processes were not in contradiction with refining procedures, they were simply a different approach to the same problems I, and others, had been solving with conventionally prepared solutions, commercial acids. They are one of the best things to have been contributed to readers, for in most cases, certain acids are not available without considerable difficulty and expense. 

Unlike the above, you stated that one should precipitate silver from an AR solution. Perhaps it was in error on your part, that you simply stated your position incorrectly. If that was the case, you'd have gained considerably more respect by correcting your position instead of insisting that your way works fine and you'll continue to use it. The water had already been muddied by your erroneous comment, and you insured that it remained so. 

I have spent countless hours privately trying to help others on this board recover from bad experiences. To have anyone fuel the fires of misinformation and allow it to go unchallenged undoes all the hard work that so many of us have contributed to others----leaving me with the question-----why am I here? How much of my time am I willing to discard as trash------when all it takes is one misinformed person with an attitude to post misinformation------then refuse to accept the smallest correction, instead of taking it as a personal affront. 

Feel free to contribute to this, or any thread. Also, be prepared to hear from people like me that have invested a considerable amount of their time trying to be helpful, when your contributions are in error. 

We won't always agree-----and there are times when I must bite my tongue------not because the other person is wrong----but because the other person uses a procedure that I did not. A good example is the use of an electric furnace to cast ingots. I owned one, but quickly discovered it was far more inconvenient to use than a Hoke torch and a melting dish, even for casting large (10 ounce) gold ingots. That is my choice. It appears that several others find an electric furnace to be in their best interest. That's called personal choice-----there is no right or wrong in this case. I must respect the other person's contributions, for they are viable solutions to problems, whether I endorse them, or not. Adding salt to AR isn't one of them. 

Harold


----------



## NobleMetalsRecovery (Oct 31, 2007)

I have held back from commenting on the forum other than for specific technical issues, usually when I need to know how to do something.

I believe I can honestly claim to have had played an important role in the creation of the forum. Both NOXX and Lasersteve have told me that the info I published for years on eBay, "Refining Gold from Electronic Scrap" and "Secrets of Refining Gold from Electronic Scrap". helped to get them into this field. My emphasis was on the ins and outs of electronic scrap, and learning what parts had value, for resale, and what items were best for refining and well as other aspects of the trade.

I have never claimed to be very knowledgeable in this field as to the refining , but only that I knew how to get SOME gold off of electronic scrap. For 15 years I floundered on my own trying to improve upon the methods I was using with little success. Knowing that my ways were lacking, I never tried to do any "production" volume in refining, but was content to just dabble and get satisfaction in producing a nugget or two, while losing plenty of values in the process. Knowing the shortcomings in my ways I was content to glean some income from my CD's on the subject that I was selling on eBay.

I don't feel I was leading people astray, since I did NOT claim to be able to recover gold efficiently, but only that I could get some gold. Because my methods were simple, others found that they too could do the same and were generally satisfied. I've always offered full money back on my CD's and eBook, and have not had a single taker.

In all those years I never produced at one time as much as a single ounce of gold. Now, armed with the info found on this forum I've had the confidence to attack this problem with accurate information. I recently recovered my first full ounce of gold, and captured the silver as well (after using nitric acid to pre-treat the scrap). Now I'm almost done producing my second ounce of gold. 

I'm tired of doing things WRONG out of ignorance. I now turn to the seasoned experts on the forum who graciously give of their time and knowledge to impart info that is often well guarded from others. I am deeply indebted to contributors such as Harold_V, and Lasersteve, as well as many others.

Even though I still continue to sell my eBook on eBay, "Secrets of Refining Gold from Electronic Scrap", I have dropped the price down to $9.99, (I've sold it for as much as $50.00 for a time). Lots of people still find it to be a good introduction to the subject. I now tell all buyers of the eBook that they owe it to themselves to join the Gold Refining Forum, and that there they will find both BETTER and SAFER methods of doing this.

One thing I believe I can take credit for is the "Crockpot" method that is listed on the forum. As far as I know I am the originator of that method. I first tried it several years ago, and for over a year published the info on eBay for FREE. I came up with it as a way to do pins. If I'm mistaken in my belief of being the originator, I don't mind being corrected.

My goal has always been to find the best and safest methods, and to lead others to them as well. This continues to be my main objective and I am overjoyed that the forum exists for the benefit of all. I encourage you and other valuable contributors to continue to do so. Once again, my sincere thanks. 

Regards, Steve

Noble Metals Recovery, LLC


----------



## NobleMetalsRecovery (Oct 31, 2007)

I'd like to follow my own post with a technical question.

After processing some CPU's in nitric acid (with the metal plates removed) there's a fine white powder precipitate in the acid. I've added salt to drop the silver chloride, which formed the normal looking white curds. Now I have the white curds and the white precipitate mixed together after pouring off the acid and rinsing.

Any ideas as to what the fine white powder is, and how to separate the silver chloride from it?


----------



## lazersteve (Oct 31, 2007)

Excellent post Steve, 

Truer words have never been spoken here! :wink: 

It's true that the forum has your CD's in it's deepest roots. I'm sure a lot of the members have purchased your material.

Regarding the solution, if it was saturated with copper chloride the white salt you mentioned could very well be a cuprous chloride (copper I chloride- CuCl). It can also form if too much SMB is used when dropping the gold from solutions high in dissolved copper chlorides. It's soluble in dilute HCl. 

Other possibilities are for the unknown white powder are lead or tin nitrate compounds if solder was present in the source material. Lead will make more crystalline salts while tin will form a gel like material. Hot water should remove lead nitrate. 

You should have filtered the solution clear before dropping the silver to avoid mixing the two precipitates. Your best bet now is to rinse the silver chloride with lots of hot water.

Harold and some others may have more suggestions.

Steve


----------



## Noxx (Oct 31, 2007)

Thanks again Steve.
Without you, I wouldn't have come into this thing and this forum wouldn't exist  You can also add to your credits that is it gold refining who mostly made me choose my studies.

As a result, we both helped each other unconsciously.


----------



## NobleMetalsRecovery (Oct 31, 2007)

I would suspect that it is cuprous chloride, since I have not yet added any SMB. Would anyone know offhand how to dissolve the cuprous chloride away from the silver chloride?


----------



## NobleMetalsRecovery (Oct 31, 2007)

Is that what the hot water should do?


----------



## Harold_V (Nov 1, 2007)

Assuming you haven't introduced any sulfuric acid-----any lead present should still be as a nitrate, and would dissolve in hot water. It has to be introduced, thoroughly stirred, allowed to settle, and decanted before the solution cools, otherwise the lead precipitates again. In your favor, hot solutions tend to settle rather quickly. It may require more than one repetition. 

Harold


----------



## NobleMetalsRecovery (Nov 1, 2007)

There could be sulfuric acid in the mix. I used battery acid and sodium nitrate to make the nitric acid, so there could have been some free sulfuric acid which I guess would have produced a sulfate that doesn't dissolve in water, hot or cold.

This batch doesn't matter too much. I'll know what to do on the next one to avoid the problem of having an unwanted precipitate mixed with the silver chloride.


----------



## Harold_V (Nov 1, 2007)

If it's an issue, could be you can dissolve everything that can with ammonium hydroxide, then recover the silver from that solution. Any lead left behind as a sulfate won't go in to solution. 

Hoke's book discusses that as one of the testing methods when you are dealing with an unknown white substance, if memory serves. I haven't looked at my copy in years. I used the test on rare occasions, but I have never experienced silver recovery from ammonium hydroxide, so I can't report any experiences in that regard. 

Harold


----------



## lazersteve (Nov 1, 2007)

Silver is very easy to reclaim from ammonical solutions. 

Acidify the solution with HCl and you will have a nice white percipitate of silver chloride that settles rapidly. You must add enough HCl to the ammonia solution to convert all the ammonical silver to silver chloride. Add the acid slowly as the reaction produces lots of heat and thick white fumes (Ammonium Chloride). Don't breath the white smoke.

Pour off the liquid leaving the white powder (AgCl) and rinse with several washes of warm water. Proceed to converting the AgCl using 5-10% H2SO4 (twice the volume of AgCl) and an iron stirring rod. 

The silver changes from *white* to *dark gray* as it converts. The iron stirring rod (I use an old pc case support arm) pushes the silver out of the solution as it dissolves with stirring. The progress of this reaction can be monitored by the color change of the silver chloride in the bottom of the beaker. It's very interesting to do this reaction... almost magical. I was amazed the first time I ever converted silver chloride this way. I learned the second part of this method from Hokes book.

Steve


----------



## NobleMetalsRecovery (Nov 1, 2007)

Are we talking about common household unscented ammonia?

I recently did the iron conversion of silver chloride. It was indeed very fascinating.

Steve


----------



## Harold_V (Nov 1, 2007)

Thanks for the report on recovering from ammonia. It was never an issue for me, due to different procedures, but it would have been nice to have had that particular piece of knowledge tucked away in my mind. It makes lots of sense-----that's also one of the procedures for purifying palladium salts. 

I also never tried the iron (steel) rod conversion of silver chloride to elemental silver. Because I had an abundance of aluminum on hand, I started using that instead. In retrospect, I can't help but wonder if, perhaps, iron would have been a slightly better choice. My single complaint with using aluminum was the solution after the fact. It was very confusing to see-----looking almost like there was silver in suspension. It took considerable testing over a long period of time before I became comfortable with tossing the solution. I imagine that isn't an issue with iron. 

Back to my choice for using aluminum, I did all my conversions, such as they were, in a large handled Pyrex container. It was one I had managed to acquire in trade for a few ingot molds I made for another refiner. He didn't see a use for the container, but I had it earmarked for processing carpets, plus it was perfectly useful for converting silver chloride without fear of breaking, and was quite large in diameter, providing for a nice shallow layer of material that was easily visible. The last time I checked the cost of a replacement, it was well over $300, and that was many years ago, while I was still engaged in refining. To have risked breaking it with a steel rod wouldn't have been something I could have dealt with mentally. That would be my one and only reservation for not changing to iron, even today. 

Great report, guys. Now I wish I'd have at least given it a try, so I'd understand the ease by which you can convert the chloride. I am now of the opinion it is easier than aluminum. 

As I've said on countless occasions-------anyone that desires to learn refining is missing the boat without owning a copy of Hoke's book. There is so much useful information contained within that it makes it easy for most anyone to go from not having a clue, to being an astute refiner-------and it's all done in simple terms, easy to understand. 

Harold


----------



## lazersteve (Nov 1, 2007)

Steve,

I've used both types of ammonia (household 3-5% and concentrated 28%) for dissolving silver chloride. The concentrated works much better, but the household variety will work in a pinch. 

Be sure you use the kind without additional soaps or scents. Clear ammonia is best of the household types. Heating speeds the dissolution of the silver chloride and produces unbearable ammonia fumes so be sure to do this in a ventilated area or better yet under a good fume hood.

My first post in this thread assumed the silver chloride was already dissolved in the ammonical solution such as when you are removing the purple crusting from karat gold placed in AR without inquarting first. ammonium hydroxide is a solvent for silver chloride.

Steve


----------



## Platdigger (Nov 1, 2007)

Were do you get the 28% stuff Steve?
Randy


----------



## lazersteve (Nov 1, 2007)

Randy,

I got mine at an old job where we etched large quantites of circuit boards. I have about two or three gallons of it. It's reallly nasty stuff and will bring tears to your eyes (literallly) just opening the jug. It's nothing to play around with.

As for where you could get some today... it's hard to say with all the chemical controls in place. I know several ways to produce concentrated ammonia, but the methods are beyond the average gold scrapper.

Steve


----------



## NobleMetalsRecovery (Nov 1, 2007)

Maybe they still make ammonia for blue prints? I think it's pretty strong.


----------



## NobleMetalsRecovery (Nov 1, 2007)

Zinc will work in place of the iron, "it is more rapid than iron, and equally effective". It is done with zinc foil and dilute (10 to 1) sulfuric acid. This info is from, "Recovering Precious Metals from Waste Liquid Residues", 1920, by Geroge E. Gee.


----------



## Lino1406 (Nov 2, 2007)

I suggest this is tin dioxide. It can be dissolved
in 60% sulfuric, or hydriodic acids (what fits)
Lino1406


----------



## NobleMetalsRecovery (Nov 3, 2007)

Here are the results for the solution of silver chloride with an unknown white precipitate in the form of a fine white powder.

I added household ammonia and let it set for a day. A crystal like lattice formed on the top of the liquid, leaving the white powder still on the bottom of the coffee pot.

I assumed this to be the silver. I scooped the silver from the surface with a spoon and then converted the silver with zinc and then mixed it with soda ash and torched it to produce a nice silver bead.


----------



## NobleMetalsRecovery (Nov 3, 2007)

Here are the results for the solution of silver chloride with an unknown white precipitate in the form of a fine white powder.

I added household ammonia and let it set for a day. A crystal like lattice formed on the top of the liquid, leaving the white powder still on the bottom of the coffee pot.

I assumed this to be the silver. I scooped the silver from the surface with a spoon and then converted the silver with zinc and then mixed it with soda ash and torched it to produce a nice silver bead.


----------



## lazersteve (Nov 3, 2007)

Steve,

You should acidify the remaining ammonia solution after filtering out the white powder at the bottom. Silver should never be left in ammonia solutions because it can form explosive compounds. More silver chloride should precipitate from the filtered ammonia soluton after adding HCl. 

You can then convert that silver chloride to silver also.

Steve


----------



## Lino1406 (Nov 4, 2007)

I am not sure what you used ammonia for if the white
precipitate remained 
?Did you prove the nice silver bead is silver


----------



## lazersteve (Nov 4, 2007)

Lino,
The remaining white precipitate was the mystery material that was mixed with the silver chloride. The ammonium hydroxide dissolved the silver chloride and the white mystery powder remained. If you read the entire thread you will see what he's talking about.

Steve


----------



## Lino1406 (Nov 5, 2007)

Thanks steve, although it's hard to conceive
from the "scooping" description. I refer you
again to my former post, suggesting the
"mystery precipitate" to be tin dioxide.
Lino1406


----------



## Lou (Nov 5, 2007)

I don't know if you already checked, but try dissolving your mystery material in hot water. Silver chloride complexes with ammonia, but lead chloride (or any of the halides of lead) does not. So if you're left with a residue of white powder after ammonia water, try dissolving it up in hot water in which lead chloride is slightly soluble. 

Tin dioxide is not soluble at all in water.


----------



## NobleMetalsRecovery (Nov 6, 2007)

I have safely added the solution and unknown precipitate to my acid stockpot. I have not used ammonia in the past because of concerns of silver fulminate.

I did some testing to see if the bead is silver. I remelted it. No oxides formed. (I think the first time I melted it it did "spit" some). I then put the bead in boiling HCL. No reactions. If it were tin, zinc, or aluminum it would react strongly.


----------



## Harold_V (Nov 6, 2007)

Noble Metals Recovery said:


> I did some testing to see if the bead is silver. I remelted it. No oxides formed. (I think the first time I melted it it did "spit" some). I then put the bead in boiling HCL. No reactions. If it were tin, zinc, or aluminum it would react strongly.



A test with Schwerter's solution will determine, instantly, if you have silver. Schwerter's is made of distilled water, reagent grade nitric and sodium or potassium dichromate. It reacts blood red when applied to silver. 

Harold


----------



## eagle2 (Dec 5, 2007)

I would like to add that concd nitric acid produces an insoluble form of tin. Metastannic acid. I have found that it even is produced in somewhat dilute solutions and is one of my main bugaboos when preparing a gold solution for precip. This is a fine white powder that can pass through a coarse filter easily. It is also insoluble in ammonia. 

I believe those white crystals on top of the ammonia are a silver complex. Don`t let your solution sit overnight. Separate it while its still warm and those crystals haven`t formed yet. My method is decant as much as possible, then filter the rest into the same beaker. I`ll heat this solution right away and slowly add HCl until its slightly acid. You will get a much nicer precip. from a hot solution. Then let this sit overnight to cool and get all the AgCl to settle. Also, when washing AgCl, its somewhat soluble in hot water. I use warm water then let it cool before suctioning it off.

Steve! What a great tip on reducing the AgCl in sulfuric with a iron stirrer! 
 I have looked at many ways of doing this and this has to be the best and simplest. Can`t wait to try it. ---- Al


----------



## Lino1406 (Dec 6, 2007)

Or, simply tin dioxide
Is soluble in:
1)boiling caustic
2)60% sulphuric
which is a bit difficult to decant,
3)HI
If the HI contains free I2
it can also dissolve the gold,
so use what fits according
to the case involved.
Lino1406


----------



## eagle2 (Dec 6, 2007)

Thank You for the info Lino: 

Tin forms a lot of complex compounds. It seems every author has something different. It`s important to know something about its compounds, because we are always running into it. 

The formula for Tin Oxide (or Dioxide) is SnO2, mol wt 150.70. Metastannic acid is given as approximately H2SnO3, mol wt 168.71. One author claimed some nitric acid is carried along with it. Another states it carries odd combinations of hydrates (water).

Most of it forms when AR is used. Its in the insolubles at the bottom of the beaker. When pure its a white powder. When you see it on the filter, its off white because gold and other elements have cemented to it. If the off white has a tinge of purple, thats gold you`re losing. So I save it and reprocess it later combining several batches. 

Later on when I`m adjusting the Ph of my PM solution, it shows up again as a Tin oxide (and probably some Metastannic acid) precipitate and no doubt some cemented gold. 

I hate to filter! This is the first place you start to lose gold. 

The only reference to dissolving Metastannic acid I saw was prolonged heating in concd. HCl. (this would surely dissolve your gold precip), or heat it to break down the hydrate bond and produce a soluble form, or something called calcining. 

Heres a good link to tin and its compounds. 

www.1911encyclopedia.org/tin

Here`s a good tip on keeping your Stannous Chloride gold testing solution from going bad, Just keep a small piece of Tin metal in it.

Al


----------



## Lino1406 (Dec 7, 2007)

May I suppose new leadless
solder will enable getting
rid of tin at the beginning
of reclammation process,
before any HNO3 is introduced?
Lino1406


----------



## eagle2 (Dec 7, 2007)

Hi Lino; I think I have heard of it. Do you know the composition of metals in it?

Still tin will be on old boards your scrapping. Most times tin or nickel is also plated on copper, then a gold plate is put on. So you still have to contend with Tin. 

I think most go the easier route and just melt whatever is precip. and accept whatever their refiner reports. I fuss too much with my precips. I try to send 99.9+ to mine. Then I know I`m not getting ripped off. ---- Al


----------



## eagle2 (Dec 7, 2007)

Going back to the mystery white powder, If you used sulfuric acid to make nitric, there would be Sodium Sulfate in solution.

Besides Tin, The white powder could be free Sulfur. Maybe reduced by your SMB. I`m not sure of this, but you could test this by drying the precip and heating it. Sulfur melts and burns easily, the gas produced is SO2 (poisonous). The similar smell you get when using SMB. Be very careful with this. Use only a small sample. Sulfur is a part of old gunpowder formulas! -- Al


----------



## eagle2 (Dec 7, 2007)

Just want to add, if you didn`t use SMB yet, Its probably not sulfur.


----------



## Harold_V (Dec 7, 2007)

eagle2 said:


> I hate to filter! This is the first place you start to lose gold.



Only when you discard the filter. 

Harold


----------



## eagle2 (Dec 8, 2007)

Hi Harold. Thank You. I must have 20 pounds of filters I`ve been saving for years. 

I recently bought a large cheap household SS bowl. I guess you add a little alcohol and burn the filters and then AR the residues. Didn`t someone say you need to muffle this or cover this somehow, so the ash dosn`t float away? ----- Al


----------



## Harold_V (Dec 8, 2007)

I had a different approach, but my refining conditions were likely very much unlike yours. The vast majority of material I used to process was waste from the jewelers bench. As a result of processing alloyed gold, I inquarted routinely, and had traces of silver chloride in all my wastes. Rather than get involved in recovering the traces of gold chemically, I saved all my wastes, which were well incinerated, then stored dry. That's important if you don't want a rusty environment. 

To make a long story short, just before closing the doors on my refining business, I ran my many years of accumulated wastes by furnace reduction. The traces of silver chloride served perfectly well as a collector of accumulated values and helped affect a very good recovery. An assay of my slag indicated a value so low that it was not worth further processing----not even with litharge. The recovery of values over that long span of time was staggering---more than 200 ounces of gold, but bear in mind I processed a huge volume of gold annually. The losses, per filter, were relatively small.

Regards incineration-----my process was to heat the filters in a shallow pan, in my fume hood, using a gas hotplate. Once the material burned, I raised the heat on the pan until the bottom was red, at which time carbonaceous residues were consumed. It's virtually impossible to get compete combustion otherwise. It was much like watching charcoal burn, albeit in much smaller quantities. 

You are correct in thinking that there will be some losses due to smoke and other discharges. My hood was filtered, and was cleaned about every second year. The recovery of gold from the hood alone was well worth the effort. Losses to dusting should be expected----but--again, remember, I processed a lot of material annually. On a hobby basis, the losses would not be significant, although certainly worth recovering if possible. 

Given your circumstance, it might be logical to incinerate as best you can, then process with AR after a good wash with HCl. That will insure that the material will filter easily. Otherwise, you may discover that your gold chloride, recovered from the residues, won't filter worth a damn. I've had a liter of chloride solution take more than three days to filter-----which is the reason I came up with the HCl wash process. I never again suffered with filtration problems. 

In reality, there will never come a point where you should discard filters, or anything that makes intimate contact with your values. If nothing else, incinerate them and store them for the future, at which time you may do a furnace reduction as I did. You will be pleasantly surprised and rewarded for your efforts. 

Edited to include:
As an add-on-----a bowl isn't very good for incineration. You'll find the contents don't get enough oxygen. A fairly shallow pan serve much better. Go to any of the second hand stores (Goodwill, for example) and look for old fry pans. Steel pans work, but shed oxidized iron and don't have a long life. Stainless pans last for considerable time. Do not try aluminum-----it will melt at the temperatures involved in proper incineration. 

I removed the handle to avoid doing stupid things, like picking one up while it was blistering hot, and used a wheel weight pliers to handle my pans. The one I had was an early tap, with no hammer on the end. The strange offset of the pliers worked very well, and was the best thing I discovered for the purpose. 

Avoid even trying cast iron pans. Their mass will make it impossible to achieve a red heat, and it will likely crack from uneven heating in any event. Once you've given this a try, it will all make sense. 

Hoke talked of "pouring on the gasoline"------which is, of course, absolutely stupid. Do not use any accelerants----just get the pan hot and allow it to burn on its own. Also, be careful if you happen to incinerate any of the plastics, such as garbage bags. They appear, at first, to not burn well. They are reduced to oil upon heating, then when they're hot enough, they burn with a vengeance. Early in my learning curve, I set my garage on fire by that process. It resulted in building a fire-proof hood. Be careful!

Harold


----------



## eagle2 (Dec 8, 2007)

Thank You. Many good points. No doubt from hard experience. 

Your HCl wash. Did you use concd HCl or diluted like 6 Molar? Did you heat and filter that from a beaker, or soak and stir, then decant the solution. The PM`s would still be in the residues and anything that dissolved would be base metals? 

Also the carbon and the heat produced in the incineration would have reduced many compounds to their metals. So the HCl could redissolve some base elements. 

I wonder if a bit of H2O2 added to the HCl wash would improve the dissolution of the base elements?

Or did you just use the HCl wash to float away any fine ash that remained that would plug up the filter?

Al


----------



## Harold_V (Dec 8, 2007)

eagle2 said:


> Your HCl wash. Did you use concd HCl or diluted like 6 Molar?


Because I lack proper education, my approach was more of one from the perspective of a person following a recipe. Many of the things I did I did because I was so instructed. Perhaps that will help you understand that I did little of this from a scientific standpoint, although I was eager to follow prescribed procedures. So then, in answer to your question, I used tech grade hydrochloric for everything but the final wash when I re-refined my gold. As far as washing materials like your filters, I'd have incinerated them, screened to remove any potential large items, swept a small magnet through to remove any magnetic particles (which were all dumped in the stock pot), then the material would be placed in a beaker, and covered with roughly 50/50 HCl and tap water. I would then boil the lot for a period of time, usually simply making visual observations that the material had been changed. It's usually obvious. One thing to remember. When you're processing a large amount of material that is akin to dirt, it often will cook dry on the bottom of the beaker, which then forms a very hard deposit, a combination of previously dissolved elements and solids. That usually results in a broken beaker, so my advice to you if you decide to pursue this as I suggest, be certain to keep stirring your material as it heats, and even when it is boiling. Even then, the occasional hot spot will overheat the beaker, which will crack when stirred. 



> Did you heat and filter that from a beaker, or soak and stir, then decant the solution.


Once satisfied that I had dissolved anything that would, the beaker would be removed from the heat and filled with tap water, stirred well, and allowed to settle. Once settled, the solution would be decanted (siphoned, not poured, otherwise you stir up the solids), and rinsed (tap water) at least once, more if necessary. I allowed the color of the rinse water to determine if more rinses were required. My experience indicated that if the solution was reasonably free of color, the gold chloride solution that came from the next step was easily filtered, and that was my objective. 



> The PM`s would still be in the residues and anything that dissolved would be base metals?


You may even find some traces of base metals after the fact, but the majority of them appeared to be removed in that the gold chloride solutions from such an operation tended to be yellow, not green or brown. This system was very effective in removing base metals as well as compounds that were unknown to me that made filtration difficult. It's entirely possible some of them were not even metallic in nature, although I have no way of knowing that. 



> Also the carbon and the heat produced in the incineration would have reduced many compounds to their metals. So the HCl could redissolve some base elements.


I have to assume that's correct. For sure, you'd remove copper and iron. If the color was blue, I never bothered to test----secure in the knowledge that anything I processed would not be found in a blue chloride solution. 



> I wonder if a bit of H2O2 added to the HCl wash would improve the dissolution of the base elements?


You'd likely have to talk with one of the fellows that are well versed in chemistry. My personal advice, based on not knowing, is to not do so. What I did worked very well---and I can't see where anything you might do would improve the results. It was, for all practical purposes, trouble free. I used this method even when processing large volumes of eye glass frames, which can be very trying when run in concentrated solutions. 



> Or did you just use the HCl wash to float away any fine ash that remained that would plug up the filter?


As I've said, there are many substances that are dissolved, many of which I likely didn't understand. 

Remember----as long as you've incinerated well, nothing of value aside from palladium oxide can be dissolved in straight HCl (I'm open to correction if I'm wrong), so don't be shy about just attacking the lot as I described. If there's anything of value dissolved, it can be recovered easily in the stock pot, so you can't get in trouble with this process. 

When you boil and stir material of this nature, your stirring rod will tend to scratch the hell out of your beaker. If you have a variety of beakers (or other containers), it might be in your best interest to set one aside to be used strictly for operations of this nature. Once scratched, they are not well suited to precipitation. Gold tends to adhere doggedly to the scratches, making total recovery difficult. 

Harold


----------



## eagle2 (Dec 8, 2007)

Your remarks match my experiences, too. Gold does tend to start precip on scratches in the beaker!

I`m not a chemical graduate, but I did study my college chemistry books.

50/50 HCl and water is close enough to 6 molar for HCl. 

If you heat a solution with a lot of heavy residue or heavy gold precip, in the bottom to near boiling, It will "bump", so you better stir anyway. I`ve lost gold when a bump spurted a bit half way up the wall! Needless to say, I like to cover those beakers with a watch glass now. If you stop stirring for a moment keeping the stirring rod sitting in the beaker does help reduce this.

Thanks for all your help! Happy holidays! 

Al


----------



## Lino1406 (Dec 9, 2007)

Hello Al,
Sorry if I was misunderstood. I meant 
lead is preventing tin dissolution by HCl 
and therefore the new formulas may
help. Some that I saw include Sn-Bi
or Sn-Ag, where the co-element consists
less then 5%, against 37% of lead in
the classic solder.
Lino1406


----------



## eagle2 (Dec 9, 2007)

Hi Lino: Oh I think I see what you`re referring to. Doing the base dissolution with HCl instead of Nitric acid. Its not done with solid base metals, because its slow and many metals don`t dissolve. With just plated pins with a bit of solder on them nitric or a electro-strip cell is still my choice. You might try an experiment on the new solders and see if HCl will work. 

I didn`t know lead in solders was inhibiting dissolution in HCl. Merck`s index states lead and tin dissolve in hot concd HCl. I think, any silver in the solder would interfere or slow or stop this, anyway. 

You will still run into Tin plate under the gold plate and some Tin alloyed in the Copper. 

Boiling dilute Hydroxide will clean your scrap and prepare the surface for acid treatments. But you`re getting into so many pretreatments, a batch will take forever to finish.

Al


----------



## Palladium (Jun 9, 2011)

8) 8)


----------

