# How do I drop only the gold? Precipitation Questions



## BangBang (Sep 17, 2012)

Hi all, somewhat new here. 
I am in the process of reading Hoke's book, which looks to be exactly what I need. Been searching for answers and learning the hard way for about a year now (on and off) The first few pages of that book was like someone turned on a bright light and exposed all the answers. So needless to say I have high expectations for the rest of the read. 

Anyway - If this is covered in the book, please forgive me for jumping ahead. 

I have been separating gold (foil fragments) from PC boards with Hydrochloric acid (32% Muratic Acid) and Hydrogen Peroxide solution (3%) 1:2 ratio. I do this as a means of having the least amount of unwanted metals in my gold when I use Aqua-Regia to further separate the gold from other unwanted materials. 

I am at the point now where I have a small stash of gold fragments mixed with various ..stuff. 
Some of the stuff is just board fibers and other junk that the AR will ignore. I am sure other components of the stuff contains metals that will be dissolved by the AR. 

My question(s) are these: 
1- Should I neutralize the AR prior to precipitation? (I am sure that's ahead of me in Hoke's book) 

2- What should I use to precipitate the gold from the AR? I've read lots of threads that suggest almost anything from Magnesium, to the aluminum tabs from a soda can, to Storm Precipitant (what ever that is). 


3- Without being a chemist, is it as simple as picking something with a lower oxidation state? Say for example, I have Gold and Lead-solder dissolved in AR. If I want to drop the gold and not the lead, would I add something with an oxidation state between gold and lead? If I used something beyond lead would the lead also drop? 

Please forgive my ignorance for what may be very stupid questions. I am looking for an understanding as much as I am looking for a way to drop just gold. 

With Advance Appreciation, 

BangBang


----------



## Geo (Sep 17, 2012)

very simple questions with somewhat complex answers. the term you are looking for is the electromotive series of metals. a metal that is more reactive will cement metals that are lower on the reactivity scale. this is referred to as "cementation" cementing metals is not the best way to precipitate PM's from solution. there are several precipitants that are selective for gold. the most common is sulfur dioxide gas. most members use sodium metabisulfite to precipitate gold and can be used to produce gold that is 99.9+. sodium metabisulfite will decompose in water forming salt and sulfur dioxide gas.


----------



## BangBang (Sep 17, 2012)

Thanks for your reply. 

Sodium metabisulfite? Do you know if that's the real name of Storm Precipitant? From what I've read it precipitates "almost pure gold" but they don't say what it is.


----------



## philddreamer (Sep 17, 2012)

> From what I've read it precipitates "almost pure gold" but they don't say what it is.


That's shor for you! :roll: 

http://goldrefiningforum.com/phpBB3/viewtopic.php?f=49&t=7746&p=71240&hilit=bonide#p71243
Take care! 8) 
Phil


----------



## Geo (Sep 17, 2012)

storm precipitant is sodium sulfite which is basically the same thing and works the same way. sodium metabisulfite is (or was) easier to source because it is used as a food preservative. people used it for canning meats and soup. it can be sourced from some high end canning shops as well as wine and beer making supply houses. a common source of sodium sulfite is "Bonide" brand "stump out" some stump removers contain potassium nitrate and some contain sodium sulfite, so be sure to check the labels if you decide to source your precipitant from these.


----------



## butcher (Sep 18, 2012)

BangBang, 

Keep reading Hokes book, until you get an understanding of the principles, you may need to read the book more than once as there is a lot of detail that you may not see at first, things like she removes the base metals before putting gold into solution, so she did not have hardly any in solution with her gold, and this way when she precipitated the gold with one of the several chemical precipitants the gold would precipitate leaving the minute amount of base metals in solution essentially giving more pure gold than was dissolved, she also shows what metals are actually trouble like tin (from solder which can rob you of your gold.



For foils you should look into using HCl/NaClO (hydrochloric acid and bleach) to dissolve your clean gold foils, aqua regia is very difficult for a beginner, many details sound easy but take some experience to master.


My question(s) are these: 
1- Should I neutralize the AR prior to precipitation? (I am sure that's ahead of me in Hoke's book) 

My answer: No do not neutralize, this would precipitate everything putting you back to where you began, the nitric would need to be removed from the gold chloride solution, Details you will find in Hokes book, in her book she may say boil but notice she was using a steam bath which would not boil the solution but would slowly evaporate off the nitric, if you got the temperature to the point of boiling the solution you would loose some gold (do not boil, just heat to evaporate). 
With HCl/NaClO method this is much simpler.

Another note: only use the amount of nitric acid needed to dissolve the gold, our Gold Silver Pro taught us this trick and you can read details about it in several of his excellent post.

2- What should I use to precipitate the gold from the AR? I've read lots of threads that suggest almost anything from Magnesium, to the aluminum tabs from a soda can, to Storm Precipitant (what ever that is). 

My answer: No only if you had problems, then copper metal would be a better choice, there are many chemicals that can precipitate gold, some of the more popular are sodium metabisulfite or ferrous sulfate, Hokes will list others.


3- Without being a chemist, is it as simple as picking something with a lower oxidation state? Say for example, I have Gold and Lead-solder dissolved in AR. If I want to drop the gold and not the lead, would I add something with an oxidation state between gold and lead? If I used something beyond lead would the lead also drop? 

My answer: No lead is insoluble as a chloride (you may have some in solution but most will stay behind as a white powder, the little that follows the gold solution is precipitated with a few drops of sulfuric acid.
You should not have any solder in aqua regia, this is where you will loose your gold from colloidal solutions, troubles filtering and just a mess, solder should have been eliminated mechanically or with HCl alone before putting any gold into solution. Do Hokes experiments this will give you more of an understanding of these metals in solution, and the related troubles if they are in solution with your gold.

Please forgive my ignorance for what may be very stupid questions. I am looking for an understanding as much as I am looking for a way to drop just gold.

My reply: nothing stupid about question, Understanding will come with more study and getting some experience, but Note you should study first to gain an understanding of the processes before beginning, if you try and get experience before studying you will most likely loose most of your gold trying to learn the hard way through making all of the mistakes, most of which could be avoided by gaining the understanding through study, keep reading Hokes book you have a lot to learn.


----------



## BangBang (Sep 20, 2012)

Thanks to all for taking the time to answer my questions. 
I am several chapters further along in Hoke's book and, as expected, finding it to be a priceless work. 
I did find a thread describing the Gold & Silver Pro's process for adding just enough nitric without going overboard. Again - Very valuable. 

What upsets me - and I include this with hopes of preventing someone else from making the same mi$takes, is the amount of time, money and precious metals I've wasted prior to finding this forum. 

I first found "Instructions' for sale on E-bay. Like a fool for $15.00 I purchased a copy. They sounded easy enough, and "lucky me" the pointed me in the direction of Shore international where I could buy the chemicals. (and find the same instructions for free I might add). 

I did so with very high expectations. Spent countless hours mixing up slop (various PC components & chemicals) with no understanding of how difficult I was making things. 
Needless to say, I exhausted my stash of CPU's and other potential sources learning how NOT to do it. 

With renewed expectations, Hoke's book, this Forum and a greater understanding, I start anew. 
Thanks again.


----------



## glondor (Sep 20, 2012)

Butcher, you are a fantastic moderator.


----------



## butcher (Sep 20, 2012)

Thanks glondor,
I feel I am just another member doing what any of our good members do, trying to help make this the best place to learn from our friends, I do hope I do not let anyone one down.
Although it seems as though some people think of me as an enemy (like the banned Hacker trying to destroy my computer).

BangBang, keep studying until it is clear what to do, you have great resources here on the forum, work on lower value scrap, small experiments, until you understand the processes well, this will help from losing money while learning the ropes, also remember to keep a healthy stock pot as Hoke suggests.


----------



## Alkymida (Oct 1, 2012)

Hi Bangbang

I´m new here too and have nearly been on this site since i joined.
Experimenting, reading, making mistakes and learning by doing.

But with small portions of everything so i don´t make expensive or hazardous mistakes.

Until now i have gathered about 0,5 g of PGM black powder from only 2 RAM-sticks and the last 24 hours i have reverse-plated an object i nearly threw away.
It has given me 3 g of golddust so far, and i´m looking forward to purify this and melt it down to a nugget. :0)

Best regards
Peter


----------

