# precipitating gold with SMB



## sander (Mar 11, 2014)

So I have done a lot of reading and searching around this forum and other gold refining web sites and books. I am slightly confused with 2 items. 1st being what is the proper amount of SMB to use? From what I gather from reading up on this forum you should use roughly the same amount that you plan on getting in gold returns? I have also read that you should use the same amount as the total amount of dissolved metal not just gold. Which one is correct? I am a relative newbie to refining gold but I have done it a few times with success. But I wasted money using the Shor kit the first time. It worked but it was pricey for the yield you can acquire with the chemicals provided. 
Also when neutralizing with urea this is done to eliminate the nitric acid only correct? There is still a strong smell of HCL after using the urea. Also can you use too much urea where it effects the ph to an extent as to where it will not be in the proper range for gold precipitation to occur? 

One last question to ensure I am doing everything right. What is proper ratio of sodium nitrate nitrate to HCL to create aqua regia? I have gathered that you use 4:1 ratio Nitric to HCL but I was slightly confused on the sodium nitrate. 

Any info would be greatly appreciated from you well informed individuals!

Sander


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## rickbb (Mar 11, 2014)

Rule of thumb is same amount of expected gold plus 10%.

If your expected yield is unknown, then use less than you think you might need. 

Let that settle overnight and test again with stannous chloride to see if any more gold is in solution.

Repeat as necessary until the stannous test shows no more gold in solution.


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## joubjonn (Mar 11, 2014)

if you look around this forum a lot more, you will find the answers to your questions

here is a quick recap

us here like to remove as much base metal as possible, pretty much all of it for most reactions. 

1.2 times the amount of SMB to gold weight. 

urea is not recommended here for AR. search the forum "urea" and see, it's very popular method on YouTube, not here

I like HCl/Cl instead of AR for dissolving gold foils or powders, not good for karat gold

check the guided tour here on the forum and read a book by a lady named Hoke. many references here to that. it's all about research on this forum. all your questions have been answered many many times on here

good luck


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## sander (Mar 11, 2014)

I do not doubt these questions have been asked and answered many times. I found conflicting information hence why I asked. I have read and researched quite a bit and feel quite comfortable with the process but when I feel I might be going astray some direct reassurance is comforting is all. I appreciate your input. I have heard of this book by Hoke I have not read it but it is referenced a lot so I suppose I should. 

I had 3 lbs. of gold plated fingers from main frame boards in this batch so the only other metal would have been the copper and/or zinc I am not sure if they were pure copper or alloy beneath. I would estimate that half of the copper was dissolved into the acid perhaps less along with the gold.

Just out of curiosity what would you guys predict the recoverable amount of gold would be from 3 lbs. of gold fingers from early 2000's server boards? I honestly had no clue I added 1.3 ounces of SMB perhaps that was little much huh? 

Thanks for your help!


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## sander (Mar 11, 2014)

Another question I had a hard time finding an answer ... Can you reuse the HCL for another batch of aqua regia after gold precipitation has occurred?


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## joubjonn (Mar 11, 2014)

impossible to estimate. so many factors. 3lbs could yield 3 grams or maybe more. maybe less. depends on your method and skill. I wouldn't use AR for foils. I only use AR when I have thick gold. foils will dissolve nice in HCl and small amounts of Clorox. then all you need to do is heat a little to drive off extra Cl gas or wait overnight and it's ready for SMB. AR is harder to deal with. using too much nitric is very very common and once that happens it takes some work to use it up for SMB to work. Hoke explains it. and no I would not reuse AR.


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## butcher (Mar 12, 2014)

sander, 
All of the questions you have so far, have been answered some many many times, it is hard to answer a million questions, and answer them again and again for every new member, aqua regia once mixed is active (it is the gases created by the reaction of the two acids that do most of the work to dissolve the gold (not just the acids alone), this is why you cannot make a batch of Aqua regia and store it, and expect it to react to dissolve gold later (at least effectively), once you use Aqua regia to dissolve gold it is no longer Aqua regia, gold chloride (with other metal chlorides) with possibly some free acid depending on working conditions, then this solution is de-NOxed to rid free nitric and oxidizer, then you add a chemical (or metal) to precipitated gold (depending on which chemical or metal you use will depend on the chemistry involved) but it is definitely no longer aqua regia, more of an acidic salt solution of chlorides and sulfates and...


My opinion using Urea can be dangerous (even in the waste solution later), and can give problems with certain metals, if you understand how to use aqua regia you will have no need for urea, and if you need to de-NOx the solution chemically, sulfamic acid would be a good choice, as it is safe and has benefits in the process, to help remove lead from solution.

As far as adding so much urea to effect the pH to where you could not precipitate gold, I do not think that could happen, actually urea will not destroy nitric acid, (it will destroy NOx gas), depending on how you used your acids it could or could not work at all, although a dangerous solution of urea nitrate can be made in solution.
Urea can also decompose to form ammonia or ammonium solutions, which can also become a danger with many metals, (even in the waste stream), and urea can complicate some recovery of precious metals like the platinum group.

The whole idea of using Aqua regia is to refine the gold (not to recover gold, for that you need to use a different process) so why would you want base metals involved with aqua regia? Base metals for the most part should have been removed from the valuable metals as much as possible before aqua regia is even used, and why would you want to add a chemical that would add more contaminates to the solution you are trying to remove the contaminates from, A chemical that will add these contaminates that may or may not work to get what you are trying to do done (like removing free nitric acid from the gold chloride solution), why wash the baby in muddy water?

Keep reading and searching for those answers, you will learn much more about these questions, and many more things you have, and answers to questions you have not even come up with a question for yet, most of the the answers will easily be found with some study.

If I have a question and ask it in a post I may get one partial answer, and some opinions, (Example: My question is fire hot, how hot, will it melt gold? First answer: Yes. Second answer: Sure it is hot, and it is hot enough to burn you. Third answer yes, you can melt gold with fire). 
This answered my questions but I did not get much of an education by fire, or about fire.


But if I search for the answer to my questions, I learn many things to answer my questions, I can even learn much more than I would if someone just gave me a simple answer, and I can keep studying my question to learn even more about this subject, until I am satisfied, and ready to study my next question. I almost never ask questions with something I wish to learn, I find a source to study, and study to find the answers, so I can answer my question and I can learn more. If I limited my study to a few questions with partial answers that is all of the education I would get, but If I study myself and find the answers I can get a very useful education, that I would not have gotten from a few questions and half baked answers. Oh by the way fire is hot and it can burn you, and if you get it hot enough you can melt gold.

I hope this helps to answer a little bit of your questions, but more important it help you to get started on finding the answers to your questions through study where you will get more of an education on these subjects, than if you just got one half baked answer from me or others.


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## nickvc (Mar 12, 2014)

I had 3 lbs. of gold plated fingers from main frame boards in this batch so the only other metal would have been the copper and/or zinc I am not sure if they were pure copper or alloy beneath. I would estimate that half of the copper was dissolved into the acid perhaps less along with the gold.


Thanks for your help![/quote]


If you had a good understanding of the chemistry of refining this would ring alarm bells.
If you have any undissolved metals your gold will not be in solution and with pins you could have tin in the mix, that's fun...NOT.
Put the acids safely away and get the books out you have some serious reading to do to recover let alone refine your gold.


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## joubjonn (Mar 12, 2014)

for me when I first came here and searched "Aqua Regia" or "gold foils" in the search bar you get like 200 pages of posts. but instead of thinking "my god I don't want to read 200 pages worth, I want the answer now!" I though "that's awesome, I'm really going to get a good understanding of these process's" that's what it's all about. not about finding the answer to a specific question but also the who, where, what and why. 

shoot, I find threads with actual chemical reaction's I remember seeing in organic chemistry in college. that's when you know these people are looking at this to the molecular level, amazing stuff really. sure you can do a fly by over this site and probably get by, probably make a mess and most likely not get yourself very far but then what's the point? use the search bar, it's your friend.


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