question about using HCl-bleach

xelexo
Shop deals on ebay
shop deals on amazon
Advertise with us
Gold Refining Forum

Help Support Gold Refining Forum:

This site may earn a commission from merchant affiliate links, including eBay, Amazon, and others.
archeonist

archeonist

Well-known member
Joined
Jun 27, 2012
Messages
286
Hi all, I'm new here and reading a lot of information on this great forum. I also started reading Hoke's book and I'm trying to learn as much as possible.
There are two questions I have. The first one is why should you use HCl-Cl instead or after AR?

The second question is that I have read that SMB is a selective preticipant for gold. I can imagine that SMB will precipitate the gold first and the less noble metals is order of less nobleness (probably not the right word but I'm dutch so english is not my base language)
 
HCl / Cl is a work around method for those who struggle to obtain Nitric acid for use in AR, therefore it is an alternative method which can be used. If nitric acid is available to you then the two methods are interchangable when dealing with foils or powders, although the HCl /Cl does tend to work slowly on larger pieces of gold.
Welcome to the forum and I hope that my post is useful to you.
 
as martyn said,hcl/Cl works better on foils and powder gold. larger solids will need to be dealt with in other ways. theres inquartering for instance.

SMB (sodium metabisulfite) is selective when precipitating gold. the SMB, when dissolved in water decomposes into salt and SO2 gas. its the SO2 that precipitates the gold. it does not precipitate other noble metals to any extent that will effect refining bullion grade gold.
 
scott, thats not entirely true.if it was, we couldnt use it to precipitate our gold. the reason gold comes out of solution impure using SMB is due to "drag down"effect. its a mechanical effect and not chemical.
 
Geo said:
as martyn said,hcl/Cl works better on foils and powder gold. larger solids will need to be dealt with in other ways. theres inquartering for instance.

SMB (sodium metabisulfite) is selective when precipitating gold. the SMB, when dissolved in water decomposes into salt and SO2 gas. its the SO2 that precipitates the gold. it does not precipitate other noble metals to any extent that will effect refining bullion grade gold.
Click to expand...
Guys, thanks so much for sharing this information!

Geo, as I understand does SMB preciptate gold very rapidly and easy. The other metals do react with SMB but very slow and very difficult. So there always precipitates a very small portion of the base metals together with the gold. Than this is why you are advised to more than once dissolve your gold in AR. Did I understand it a little? :roll:
 
archeonist said:
Geo, as I understand does SMB preciptate gold very rapidly and easy. The other metals do react with SMB but very slow and very difficult. So there always precipitates a very small portion of the base metals together with the gold. Than this is why you are advised to more than once dissolve your gold in AR. Did I understand it a little? :roll:
Click to expand...
I'm not Geo, but my opinion may help (or not!)
The bulk of contamination in precipitated gold, assuming the solution has been properly filtered, tends to be caused by drag-down, as has already been described. It is for that reason that one washes the resulting gold well, then, if purity is a requirement, it is re-dissolved and precipitated a second time.

By carefully washing the first precipitation, most of the entrapped contaminants will be removed, but some remain, due to the nature of the gold's ability to clump, plus some may be entrapped by the forming gold. By dissolving and precipitating a second time, the contamination is liberated from the gold. Considering that the amount of contamination present is drastically reduced, even though some may get dragged down yet again, there is so little present that the quality of the gold is improved. It is not unreasonable to expect greater than 9995 quality if good hygiene is practiced, and the gold is well washed.

A second refining may or may not be advised. If your objective is to recover gold for sale to scrap precious metal merchants, you are highly unlikely to receive a better price, but if you have hopes of becoming recognized as a refiner, perhaps with the opportunity to market your gold for spot, to consumers (manufacturing jewelers, for example), you are well served to go the extra mile to improve the quality. One bad experience as a refiner, as you start out, can spell the difference between success and failure.

Harold
 

Latest posts

Back
Top