Precipitate+Heat.........

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goldfever007

Active member
Joined
Mar 22, 2018
Messages
39
Dear member:
First of all let me thank you all for sharing the knowledge.....
Second i was always wondering ,when we add copperas or SMB to AR ,why we have to wait till tomorrow or hours ? why don't we use heat so we can recover the gold quickly?
 
Heat and agitation help. Precipitating from a concentrated solution also helps. Gold reduced from a dilute solution will have a more difficult time agglomerating into large particles that will settle quickly. The extreme example of this is a solution in which the gold forms a colloid, which may never settle until the colloid is broken.

Dave
 
I use a beaker with plenty of head room and heat my AR. On the same hot plate I heat my precipitant dissolved in water, like wise with plenty of head space. Once the two reach near identical temperatures I mix them in which ever beaker has the most head space. This usually boils up pretty good, so mix slowly.
 
Shark said:
I use a beaker with plenty of head room and heat my AR. On the same hot plate I heat my precipitant dissolved in water, like wise with plenty of head space. Once the two reach near identical temperatures I mix them in which ever beaker has the most head space. This usually boils up pretty good, so mix slowly.
Click to expand...

Yeah this is true but make sure as heck you have no Nitric left otherwise it's gonna go volcanic on you.

I usually add a bit- see gold precipitate out without trying to go back into solution - and THEN add more.
 
anachronism said:
Shark said:
I use a beaker with plenty of head room and heat my AR. On the same hot plate I heat my precipitant dissolved in water, like wise with plenty of head space. Once the two reach near identical temperatures I mix them in which ever beaker has the most head space. This usually boils up pretty good, so mix slowly.
Click to expand...

Yeah this is true but make sure as heck you have no Nitric left otherwise it's gonna go volcanic on you.

I usually add a bit- see gold precipitate out without trying to go back into solution - and THEN add more.
Click to expand...

My usual description would use the term "a whole lot of head space". I thought "plenty" sounded nicer though. :D

To be more exact I usually have around 3/4 to 4/5 of the beaker reserved for head space. Yep, I am a bit paranoid of those boil overs, even when using heat and chemicals to denox with. While I have never had one to boil completely over the side, I have been close enough to go into panic mode a time or two. :mrgreen:
 
I always dilute the strong AR 3 to 1, with tap water, then dd a little sulfuric, filter, then drop with sodium sufite or SMB at room temperature. The gold always drops immediately. Of course, I always add the nitric in increments to the AR and rarely, if ever, is there enough excess nitric to interfere with the drop of the gold.
 
I think it depends on the base material Chris.

If there's no silver or lead in there then I wouldn't dilute or add Sulphuric but then again I denox with Sulphamic so it makes Sulphuric as a by product of the reaction.

On a recovery process with 20 litres of liquor I'd rather filter well, drop the gold and then deal with the small amount of silver before refining the gold properly in a smaller amount of liquid rather than making 60 litres of waste when I don't have to.

For smaller volumes then for sure the 3:1 dilution works however it doesn't make practical sense on large volumes. To be frank the gold dropped from a "dirty" recovery is going to need refining anyway so I just hit it again with AR after cleaning it up, all in one go.

We all have our own preferences I guess.
 
hmmm. Okay I am a bit confused here. I thought I always see you guys adding ice to the solution before dropping. Or perhaps I am wrong, and you do it at a different time. The dropping from a concentrated solution to get bigger clumping sounds like it makes sense. I think I've made the error of over diluting, and my precipitate is too fine, much of it going through any filter I use. Could someone please remind me why use ice. I can't seem to recall.

I think I will reduce my auric chloride by heating before I drop next time.

Sorry I'm such a newbie still. :mrgreen: :oops:
 
The addition of a small amount of sulfuric acid and heating helps the particles coalesce into larger particles and thus allowing the precipitate to settle faster. I believe the sulfuric acid helps clean the surface of the precipitated powder allowing other gold particles to stick to it.
 
Main reason for adding sulfuric acid is to remove any lead. Even small amounts of lead in otherwise clean gold creates a brittle alloy that can't be worked and that breaks easily. Lead sulfate can be filtered off with silver chloride and other contaminants before precipitating the gold.

Ice is usually used to lower the solubility of silver chloride before filtering the gold chloride solution. Some people adds it to the gold chloride if they have large amounts of gold (kilos) in solution. Precipitating is an exothermic reaction so there are a lot of heat released.
If you want to add ice or not is a personal preference and not a rule.

Göran
 
Nice video, I would suggest one change for your own protection. Spill containment. A pyrex dish between the heat and the beaker would catch any boil overs or glass breakage. If your flask was to shatter from the heat the gold would be quite difficult to recover.

A lot of the "scientific glassware" out there from smaller suppliers are not true borosilicate glass! Be safe with containment.
 
4metals said:
Nice video, I would suggest one change for your own protection. Spill containment. A pyrex dish between the heat and the beaker would catch any boil overs or glass breakage. If your flask was to shatter from the heat the gold would be quite difficult to recover.

A lot of the "scientific glassware" out there from smaller suppliers are not true borosilicate glass! Be safe with containment.
Click to expand...

Thank you for the advice! In fact the hotplate itself sits inside a large cooking tray(my first line of defence) , but I guess another pan in the "line of fire" as suggested by you, will make the things even safer.
 
Owltech said:
How about enamelware, any cons?
Click to expand...
For me, any metal container, preferably copper or aluminum, covered with a layer of epoxy, does the trick quite well, and cheaply. Cover everything but the bottom where you apply the heat. Even a direct flame can be used. You can lower the temperature, so that the epoxy does not burn, adding some motor oil.

I had never witnessed the "ripening" effect of the precipitates, like you show in your videos, for both oxalates, and SMB. Thanks again for sharing. :G
 

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