# Copperas or SMB



## alexander the Swede (Apr 11, 2017)

Hi all,

I have a question about why SMB is the dominant type of precipitation method and why i seldom hear of copperas being used? In Hookes this is the preferred way of precipitation.

I have myself used mainly SMB to do the gold drop with good results but out of curiosity i tried using copperas and found it to be just as effective, at least when it comes to the solutions i have had.
Is it because the dragdown is less with SMB?
Now i have only done small batches and mainly from gold foils ( meaning copper as main contaminant in the gold solution). 

If their is an existing thread that explains the difference and when you should use one or the other please advice me to that one. 

Now i have heard of that using different types of precipitants when doing the second refining is often resulting in higher purity end product. That´s one thing but otherwise some more information could be interesting.

Regards
Alex


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## Topher_osAUrus (Apr 11, 2017)

I like to use copperas on my recovery precipitation. Sometimes I just use smb both drops though. 

It depends on what the contamination is. If its copper in solution with gold, I will either cement on more copper, or I will use copperas, as it is less likely to drag down copper. Using copperas will, however, take a few rinses of HCl to get it clean afterwords because of the iron contamination.

Using smb the second time, there will be no copper in solution so the smb wont be able to drag it down with the gold, since it shouldnt be there.

Each one can be beneficial in it's own way.


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## Shark (Apr 11, 2017)

Both have their uses. If I had to choose just one it would be copperas, but that is based on the material I work on the most. Having more options to choose from can make it easier to deal with any mishaps that may arise. I like to use AR and drop with copperas for my first refine/recovery and switch to AR dropped with SMB or Hydrochloric/bleach dropped with SMB. It all varies by what I have seen happen in the first steps, and how clean the powders look from the first drop. As Topher mentioned, cementing on copper, more people should learn to use copper. It can save many headaches over adding more chemicals to a bad situation, and in the long run save time.


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## Lino1406 (Apr 12, 2017)

Advantage of copperas: does not have the SO2 smell
Disadvantage of copperas: needs 5 times SMB weight


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## anachronism (Apr 12, 2017)

Ferrous Sulphate/Ascorbic acid for dirty drops- clean up and then SMB for a further refine (if required.) You should be able to get to 99% plus on your recovery drop.


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## Geo (Apr 24, 2017)

I had an unusual experience. I leached some smelted material in nitric acid. After dissolving the left over solids in AR I tried to precipitate with SMB. A thick white cloud formed. I waited for the gold to drop and redissolved the gold thinking the white precipitate would stay put. The precipitate redissolved with the gold. I tried SMB again and got the same white precipitate. I changed from nitric to bleach on the next dissolution. It helped very little as most of the white dissolved. I tried to drop the white mess with sulfuric acid and failed but SMB brought it straight out. So it was the SO2 and not sulfuric acid. 
I finally dropped the gold with copperas and the white precipitate stayed in solution. I can only imagine that it was silica sulfate or something like that. Either way, the copperas brought the gold down without the mess. It was a struggle to figure this one out.


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## Lino1406 (Apr 24, 2017)

The white material precipitating with SO2 which I know is Ag2SO3


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## Topher_osAUrus (Apr 24, 2017)

Geo said:


> I had an unusual experience. I leached some smelted material in nitric acid...



What all was it that you smelted together?


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## Geo (Apr 24, 2017)

It was IC material with the iron removed with a magnet. It wasn't silver because I had leached with nitric and rinsed the solids really well.


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## Geo (Apr 24, 2017)

And too, it did dissolve somewhat in water. And, it didn't darken in sunlight. I really didn't dwell on it too much. It was only ten grams or so of gold but I finally got it out and cleaned up.


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## Topher_osAUrus (Apr 24, 2017)

Geo said:


> It was IC material with the iron removed with a magnet. It wasn't silver because I had leached with nitric and rinsed the solids really well.



I had a similar experience, but I did not smelt mine together.
I kind of chalked mine up to being a base metal that I didn't remove. Maybe some excess salts formed from using poorman ar or excess smb. I went directly to poorman ar after magnetic removal because this was well before I had good nitric. 

Hope you get it figured out, as it would be good to know for future use.


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