# issue with gold drop



## Mr_Snow (Nov 20, 2013)

Hi there,

I'm a Pure Science undergrad from London. I've been interested in gold extraction for a while, and have been reading up on it since September (between studies). 

I spent as much as I could on it, but after a while found a great deal of inconsistencies with different people's methods/explination due to a lack of practical knowledge on my part, and so I thought I'd try and get some hands on experience to help contextualise what I'm reading on this forum.

So for my first experiment I took 512g of gold fingers dissolved that in [100ml nitric acid / 300ml HCL ] 
I got a positive test with Stannous solution 
I then neutralised with sodium carbonate and added some food grade sodium metabisulfite dissolved in water to precipitate 4.42g of a murky grey brown powder.
[for context the SMB was purchased from a chemical supplier]

I then tested this with Stannous to confirm a gold content, and it was positive.

I then dissolved in Aqua Regia [ 25ml nitric / 75ml HCL ] and filtered out the flakes of plastic


I now had a dark tan solution testing positive with Stannous, and neutralised this slowly with urea until it stopped bubbling.
I filtered to remove the dead urea left floating and on the bottom and was left with a transparent yellow solution.

This is where i'm slightly lost, I decanted 10ml into a seperate beaker and added some Sodium MetaBisulfate dissolved in water, and there was no reaction. 
[This SMB was purchased in the form of Campden tablets from Wilkinsons]

I added some sodium bicarbonate and it fizzed up white foam with what appeared to be patches of dark purple/red in parts of the foam.
The clear liquid now had several small flakes of an almost black substance floating in it but nothing else. 


I then went back to the Laptop and tried to read my way out of it, to no avail. 
so I went back and added some SMB dissolved in water to the main solution, there was a quick almost explosive bubbling from the point where the SMB sol. hit the neutralised AR, but no foam and it quickly stopped. I then added more but there was no reaction.

I left it overnight in the windowsill while i read up more about it, and with no progress went to retreive it today and it's now slightly paler, with a full growth of 2cm long very thin crystals on the bottom.

Can anyone offer any pointers on where i've gone wrong here? 
Does anyone recognise any of the symptoms?

Many thanks
Mr.Snow


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## moose7802 (Nov 20, 2013)

Sounds to me like you have to much SMB in your solution which is forming the white crystals on the bottom. How many times have you tired dropping the same solution? Also with fingers there is no reason to go straight to AR. Soak them in AP then decant solution and you are left with pretty clean gold flakes that need a little washing then dissolve this with AR. 

Tyler


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## Pantherlikher (Nov 20, 2013)

Hi...
Sounds exactly to me like you need to learn what you are doing.
Begin with reading Hoke's book to get the basics down. Make special note that Urea will NOT neutralize Acid.
sodium carbonate is not a good way either. Do a search and read up on how to expell excess nitric.

Your first mistake is putting fingers in AR... Waste of acid as you need to get as much copper out as you can...See Acid peroxide method in forum.

Then, you added too much nitric to the AR...It's definately not a measurement strick rule. Only add alittle nitric at a time and wait for reaction to stop..

You can use Urea for testing purposes so look into that.
Now you added unknown measured amounts of SMB to get something to drop. 
There is a formula here to know exactly how much SMB will drop gold expected.
What did you test with Stanus? the spent solution? or what dropped out? Did you properly wash what dropped out?

You then dissolved it again and now have a problem with nothing happening except fizzing.... 

You say you are in the learning stage of your life. Complete with books and all.
If true... You should have a working knowledge of what to do. Meaning, you should find the right information and study it untill you feel confident you can handle anything that might happen as you should already know what to expect.

Not to insult you or anything...not ment to be.
Everyone begins here with basically the same problem, question. Gold wont drop why?...

Please store everything in a safe place and begin reading here in the forum. Start at the beginning...Welcome section and then on to safety. 
Just like starting a colledge edumacation thingy.... begin at the beginning.

Good luck and hope to see your first gold button...

B.S.


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## niteliteone (Nov 20, 2013)

If you used SMB (Sodium Metabisulphite) to drop what ever from a dirty gold solution, Why didn't you use the same Sodium Metabisulphite to drop the gold from a cleaner second solution :?: 

Sodium Metabisulph-*i*-te will drop gold 8) 
Sodium Metabisulph-*a*-te will make a mess :shock:

edit to add;
It is never a good idea to dissolve gold in any solution that also contains base metals. That's a good way to make messes and possible loose your gold :shock:


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## butcher (Nov 21, 2013)

Mr_Snow,
I would like to help you get started learning, this is a field of science, and there are sometimes more than one method to get to an end, sometimes one method may work better than another method, as a Pure Science undergrad from London, you should also understand that chemical reactions, and results of chemical processes will work in certain ways, chemicals react with each other in certain ways, to get through a process using several chemical reactions, the process used will need to be performed in a manner which will react as expected throughout the different processes to give the desired results.

In the chemistry of recovery and refining of metals, it is not like cooking, where we may be able to put a whole bunch of vegetables in a pot add some salt and heat and end up with a delicious meal.
We also cannot just go by a recipe.

We need understanding of the procedures, need to understand the basic concept of what we are trying to do, throughout our several processes, and with each step in each of these different processes used to recover and refine the metal, we will also need to have a fairly good idea of what will, or is supposed to happen, how each of the chemicals or metals react, and have a good understanding of why the reactions work one way, but will not work another way...

At this point from reading your post, I feel you do not understand the basics, or even the procedures, or the concept of how gold is recovered or refined, much less the chemistry involved with what you wish to do here.
To me it sounds like you read a little bit, and now think you can just throw a bunch of stuff in the pot and get something good out of it.

I feel you need to stop, and rethink how you are approaching this, step back and take a scientific approach, get the education first, get that understanding of the basics principles, and learn how the chemistry should be performed, learn the procedures needed, and get a good understanding of the chemistry involved in these procedures. Getting a good understanding so that you will understand not only how to do a procedure, but you will understand each step, and why it is done or a certain way, or a certain chemical is chosen over another one. Understanding why each step in the process is used, and why, and what to expect in each step performed, and understand why it works, or did not work the way you expected it to, understand how to fix a problem when it does occur.

In my opinion right now you have a mess, there are several ways you could get your gold back out, I would use a clean thick piece of copper metal and cement any gold out of solutions, collect any powders of anything you have, and put them in a jar with a plastic lid, then treat your waste solution.

If you do not know how to treat your waste properly, read the thread in the safety section titled dealing with waste, this is one of the more important things you should understand, along with the safety of dealing with the chemicals and chemical reactions involved in recovery and refining.

Like any scientist having trouble, going back to the drawing board and starting from the beginning is our best bet to get our desired results. Going back to the beginning, and learning the basics, Hokes book will help you understand the basic principles and concepts needed, practicing the getting acquainted experiments in the book will give you a much better understanding of the chemistry involved, and what to expect in the reactions. These experiments also give you a better understanding of what combinations will cause trouble, and how to keep you out of trouble with your recovery and refining methods, practicing testing for metals and the other experiments will be valuable tools to you later as you begin to recover and refine your valuable metals.

Study the different methods used to process your scrap, study the processes used recover your gold, or other precious metal, and then study how to refine that metal, understand each step in each of these procedures, and get a good knowledge of how each of these steps work, and why they work the way they do, or why one method may be chosen over another method, understand each of the processes you plan to use, and the whole process, before you begin.

You did pick an easy material to work on, and an easy material to help you learn with (gold foils), but you did not spend enough time studying to learn how to recover or refine your gold from this material.

Take the guided tour (general chat section).

Take a scientist approach to learning, and to the recovery and refining ,not like just some ole cook in a dirty kitchen. 

Study, and understanding is the biggest step you can make towards getting that pure gold into your melting dish.

I hope this helps you to get started, welcome to the forum.


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## rickbb (Nov 21, 2013)

From you post I see 2 things you could have done differently.

First you put the fingers in AR, you didn't need to and you will get less pure gold that way. As well as being more costly. As others have said, use the AP Hcl/bleach process, it's less costly and yields very pure gold from fingers.

Second, you state you used Sodium Metabisulfate, wrong stuff. You should have used sulfite, fite, not fate. One letter makes a BIG difference in results.


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## moose7802 (Nov 21, 2013)

Well one time he says metabisulfite and then the second time he says metabisulfate. He needs to clarify which one it is that he used. 

Tyler


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## butcher (Nov 21, 2013)

Putting fingers in aqua regia, you will dissolve all of the metals into solution, the gold should be free from base metals before dissolving gold.

You used about enough acid to dissolve about an ounce of gold, I do not know if that 512 grams of fingers were removed from the circuit board material but You most likely had no where near that amount of gold, it sounds like an overuse of acids.

No mention of De-NOxing the overuse of nitric in solution.
Diluting or filtering.

Using NaCO3 sodium carbonate, A big mistake here, unless you used a very large amount, I doubt you lowered PH much, and even if you did that will not help much, as all your doing is changing your free nitric to nitrate salts, and your HCl to sodium salts, and if you lower pH that much making insoluble base metal carbonates, SMB at this stage will not help much either in this mess.

Redissolving this back into aqua regia, adding more SMB, then dumping sodium bicarbonate in and more SMB in excess...
Just sounds like a big mess to me.



The only mistake I see here is you have not spent enough time studying, and studying the right information to learn, and you are trying things before you have an understanding of what you are doing, or learned to use better and even proper ways it should be done.

There are much easier ways to do what you are trying to do, you just need to spend a little time to learn it.


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## moose7802 (Nov 21, 2013)

Off topic but Butcher I like you! Lol. You always take the time to help someone or put your knowledge out there for others to read. I for one truly appreciate all that you contribute. That being said Mr_Snow take butchers advice and the rest you have been given. With your understanding of chemistry already it should be pretty easy for you to sit down read and get these basic processes down. 

Tyler


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## Palladium (Nov 21, 2013)

Butcher makes a mighty fine teacher and moderator!


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## Mr_Snow (Nov 21, 2013)

Thank you for all your comments.

I'm finding it quite difficult to "just read" as many of you have kindly suggested; 
as I mentioned before, different people have different opinions on what does and does not work, so there's a lot of juxtapositions in people's guides out there.
Obviously there is a correct way to do this, and I'm more than happy to hold off experimenting until I read up a little more.

If anyone has any resources on what chemical reactions these processes work with I'd definitely be interested in reading it, 
every guide I've found so far basically explains what you should do, and not how or why it works 
(making it hard for me to learn the type of reactions I'm working with, and is possibly why I'm getting so far ahead of myself and trying to work it out like I am, making a mess)

What's the best method for retreiving the gold in the over-SMB's solution containing all the salts?


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## Geo (Nov 22, 2013)

im coming late to this post but i agree with Butcher. the amount of nitric used was way in excess of what you actually needed to dissolve all the metal present. a 2g yield on gold and maybe 20g of base metal is what you were working with. a very important part of the equation is knowing what you are working with. more study on the material you are working on would be advised in this case. remember, AR is a refining tool and should be used for refining. recovering plated gold is just that, recovery. recovery and refining are two different things. you should recover the gold from the fingers first and then refine it to a more pure state.


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## butcher (Nov 22, 2013)

Mr_Snow,
It takes a little time learning the basic principles, it is not that they are that hard as it is it just takes time for them to sink into our brains.
This is one reason Harold has harped for years for us to "read Hokes and keep reading it as many times as we need until we understand what it says", we can read her book the first time and learn a thousand things which will be very helpful to us, but the simple basic principles can go over our head, until we read it several times, then when you see it, it is like a light bulb comes on in your head and lights it up for you.

Hokes book is a great place to learn the basics, and by reading the forum you will gain more knowledge in these basic principles, as well as methods for recovery and refining.

Collect scrap material, you will be piling up your values, hold off on recovery and refining process at first, (so you do not lose that value), start with Hokes book and the guided tour, work with Hokes doing the aquianted experiments (these experiments can be performed with in very small amounts, like test tube experiments), if you combine your study of Hoke's book with what you are learning from the guided tour, your gold recovered from memory cards can be used for these doing acquainted experiments and the other things you learn in her book. 

The main thing is to study until you understand and it is clear in your mind.

Trying to process (before you study to understand), as a way to try and learn, is just a good way to learn how to lose your gold.

But studying to learn to process, and using that (understanding) to process in small experiments (like test tube size), is a great way to learn more about what you are studying.

Before you know it you will have gained enough understanding to do the simple processes, then building on those skills, and understanding you can go onto other more complicated processes studying them and learning and using your skills, and knowledge you are gaining to help you with them.

A good scientist is not born overnight, a gold refiner is a scientist who must study, and gain skill, and continue to work to improve his skill and work habits, and he will not do this overnight or by reading some step by step process, or watching a few thousand videos.
recovery and refining precious metals is a very vast and fairly complicated science, you do not learn a science like this overnight.


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## Mr_Snow (Nov 22, 2013)

Thank you Butcher.
So Hoke's is the best resource to learn this process?
Is there any other resource that describes the reactions in enough detail to give me a full understanding of exactly what's happening in my reactions?

That said I also would like to try and recover the gold at this point, so is adding a copper cement to the solution the best way to recover the gold?
How much copper do you think it will take? 
and is there any other metals I can introduce to the solution to cement instead of Copper?

Best
Snow


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## moose7802 (Nov 22, 2013)

There is no need to measure out an amount of Cu just take a nice big piece of copper and drop it in and let it sit for a few days this will cement out all valuables. I personally would take a piece of copper pipe hammer it flat and stick it in your solution. Then ounce you have read and studied a little more you will know what to do with the cemented PM's. Zinc would also work.

Tyler


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## nickvc (Nov 22, 2013)

Snow a good background in chemistry is very useful when your refining but the truth is that refining is such a massive subject that I doubt anyone knows it all. The basics are taught by Hoke and gives anyone a way to follow the processes that are common to most of us but in her day plated scrap and e scrap didn't exist or was ignored as too low value to bother with but now it's worth the extra effort to recover those values. The inventive minds here on the forum have found methods to make it cost effective and possible even for a home refiner and some are extremely effective while others offer safer methods to recover and refine but you need to learn from the ground up even with your chemistry degree there's no shortcuts but perhaps a quicker understanding, fet reading it's all here and for free.


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## eeTHr (Nov 22, 2013)

Mr_Snow said:


> So for my first experiment I took 512g of gold fingers dissolved that in [100ml nitric acid / 300ml HCL ]
> I got a positive test with Stannous solution
> I then neutralised with sodium carbonate and added some food grade sodium metabisulfite dissolved in water to precipitate 4.42g of a murky grey brown powder.
> [for context the SMB was purchased from a chemical supplier]
> ...




First, what I see strange, is your second use of stannous. Stannous chloride is used to test for gold solution. It can't test for metallic gold, which is what the powder would contain. It _is,_ however used after a drop, to see if any gold is still in solution. So if it tested positive after your drop, then not all of your gold precipitated and there was still some left in your solution.

Secondly, I recommend reading this post, to help decide when to use recovery processes, and when to use refining processes, and the reasoning behind their differences.

Third, this post might help with the concepts to consider for different methods of separating solids from solutions.

Finally, some things to think about when precipitating with SMB, and when cementing with copper.

P.S. The yellow highlighting in the linked pages was added by the Search feature (link at the top right of every page), which marked the search terms that I used to locate those pages.


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## Anonymous (Nov 22, 2013)

Mr_Snow said:


> So for my first experiment I took 512g of gold fingers dissolved that in [100ml nitric acid / 300ml HCL ]
> I got a positive test with Stannous solution
> I then neutralised with sodium carbonate and added some food grade sodium metabisulfite dissolved in water to precipitate 4.42g of a murky grey brown powder.
> [for context the SMB was purchased from a chemical supplier]
> ...



Yes mate - fellow UK guy here so I'll be blunt because I know you'll be able to handle it!

You dissolved and of course you will get a positive stannous test. Then you precipitated, which I also get. The bit I don't get is why you then redissolved. Also how you got a positive Stannous test on the powder is a tad concerning.

I think you're over complicating the process because to my mind you got it right the first time around by getting the powder out.

Your thoughts? Have you got some of the process of recovery mixed up with the refining bit?

Regards

Jon


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## butcher (Nov 22, 2013)

Cementing gold out of solution is a replacement or displacement reaction, or an oxidation/reduction reaction, basically gold in solution is in an ion form (missing electrons), the copper metal (atom) will gladly donate its electron to the gold ion, the copper is thus oxidized and the copper atom goes into solution as an ion, replacing the gold from solution as it gains that electron and reduced back to a full atom of gold, the black powder that is formed in the reaction.

You want a large excess of copper atoms, a clean thick bar of copper metal, so you do not end up with small pieces of copper metal mixed with your gold powder, as if you used a thin or a finer copper metal, it would drop of small pieces of copper metal, as all the atoms of copper bar will not just dissolve off evenly.

In this case I would not use zinc to cement the gold, when you look at the reactivity series of metals, you will see that zinc a much more reactive metal would cement out most of the base metals with your gold.

Copper although will not give you pure gold from solution would not cement out all of the base metal, giving you a cleaner gold (that would still need refining) to deal with later.

As the guys have stated so well. Hoke's book will not cover this particular process, but she will teach you basic principles, and facts you will need to understand in any type of recovery or refining that you will do, it is also invaluable information for much of the work you will do, and learning how to process the higher grade scrap like karat gold and PGM's, it is just a must read...

The forum will help with understanding of her teaching, and the many different processes to recover gold from other scrap she does not cover, that and other research, and with your background in chemistry you should have no trouble understanding.

But as nickvc has so well put it, we have to start at the ground and work our way up.

Understanding the chemical reactions to the letter is not necessary, although it can be very helpful.

But not understanding the basic chemistry of these reactions would only result in lose of your gold.

I do not know exactly how to say what I am trying to say, but once you learn more you will understand what I am trying to tell you. 

Harold has proven his scientific knowledge in this field, and I do not know if he can write a chemical equation, but he darn sure knows what is going on in solution, and understands its chemistry, and He can explain it to most any scientist that would wish to learn himself.

We do many times discuss the chemical formulas and what may be occurring in the chemical reactions on the forum, so by reading the forum you will improve your knowledge in this area.

Hoke was a chemist and she taught the chemistry, but did not go into the chemical formulas, or long explanation of chemical reactions, in her book, she was teaching the basic principles to the laymen in the field, so she teaches the chemistry, but in an easy, but very practical way, so even the non chemist could understand the chemistry involved, without going deep into the chemistry side of the discussion.


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