Precipitants in general

[Lou]

Yes.

Then you have to deal with molten sulfur. A sulfur burner is easy enough to make, pretty blue flame. For small operators, best to stick with sulfites unless you can justify the purchase of a cylinder of SO2, a cabinet, and a dedicated exhaust for "just in case" something goes wrong. Also, there are certain reporting requirements (under CERCLA/Right-to-Know) for the installation of even a 150# cylinder here in the US. If you insist on making SO2 g, then you can do it as per kadriver.


Lou

 

[Richard NL]

he precipitates with Nitrogen gases

If he did not eliminate the excess nitric, he precipitates with (oxidized) Nitrogen gases NO_x.
LOL

Best regard,
Richard.

 

[MarcoP]

Then you have to deal with molten sulfur.

I'm doing my homeworks on this but all I could gather is that molten sulfur is simply elemental sulfur heated to 240°F (115°C) and it seems to still produce S02(g). I could not found any resource with a complete equation of the cumbustion process, not even a line about the left over of the combustion.
Could you pass me a link where I could study on it or gether some hints?

If you insist on making SO2 g, then you can do it as per kadriver.

Really interesting but expensive, I wanted to avoid using SMB as it is expensive in my area and hardly available. Sulfur here is really cheap and easily available.

Thanks.

 

[Richard NL]

A equation of the combustion process of sulfur: http://www.tigurl.org/images/tiged/docs/activities/431.pdf
You can study this google search or similar ones:
http://tinyurl.com/o9p6mjt
http://tinyurl.com/pxvms6m
http://tinyurl.com/lo5x9nk

Or wait for Lou.

Good luck with your homework

Best regard,
Richard.

 

[MarcoP]

Thanks Richard, I actually came to read the same PDF you posted and that's why I'm still perplexed as it seems that all sulfur combust to the dioxide and no solid remains thus I don't quite understand Lou's comment about dealing with molten sulfur which I initially believed to be the remaining solid. Bad luck my dad never wanted me to help him he used to burn sulfur.

The other three links seems to take me on a "Discussion" search, will try to open them when back home.

 

[Shark]

Lou made a pretty good point. If you dig deep enough you will find information on kadrivers method scattered around the internet. Some pretty good information on generating your own sulfur gas, and how to do it. I have been slowly working my way into trying it. Still need just a bit more information yet.

 

[butcher]

http://goldrefiningforum.com/phpBB3/viewtopic.php?f=48&t=17070&hilit=sulfur+dioxide

Kadriver made a great video of his chemistry setup to generate the SO2 gas, I am not sure how to point you to the video.

http://goldrefiningforum.com/phpBB3/viewtopic.php?f=48&t=17070&hilit=sulfur+dioxide

 

[MarcoP]

Thanks gentlemen, I've read the topic and watched the video of this nitty closed system as soon Lou mentioned it but I think I can produce SO2 gas by burning sulfur in a closed system and still in a fume hood but as Lou pointed out I might end up with molten sulfur to deal with, which should still be sulfur but in a liquid form and that will solidify on cooling to a really hard solid sulfur.
Not sure how much is correct in infos gathered from internet.

I'm only asking for any type of details about the mentioned residue.
Will letting the combustion continue to it's end eliminate most of the residue? (as it is always done in some of it's multiple uses - never tried on first hand and not going to try until I know what I'm dealing with)

Being aware of it will let me study on the disposal, complications or other possible uses of this still unknown to me by-product. Then and only then i'll be able to decide to go into overusing SMB route to obtain SO2 gas, or none at all.

Basically if someone can overuse smb, in fact there are no complications on doing it, should be doing it Kadriver's way, still in a closed system.
I can always keep going between copperas and smb depending on the feed stock, and i'll keep using oxalic acid for the second drop, still some issues but i'm getting the hand of it.

What i just learned about elemental sulfur, on a complete combustion with pure oxygen:
S(s) + heat + O2(g) --> SO2(g) [dioxide]
2S(s) + heat + 3O2(g) --> 2SO3(g) [trioxide]

But if i take easy on the oxygen, slowing down the combustion, I should mostly get the dioxide.

But none of those equations reports any particular material left to deal with, that's where I'm stumbling.

This will off course be done in future inside a fume hood as I'm aware of the enormous dangers of the reaction of the trioxide with water. Breathe it and it will use the water in your lungs!

Normal air oxygen supply will be enough to reduce the trioxide. Limiting the source of oxygen to further slow down the combustion will keep it to the minimum, if any will be produced, and in any case it will end up in the chloroauric acid to form sulfuric acid.

If you read till here and you are a moderator feel free to split this part of the discussion to resume another thread or create a new one. Originally about a precipitant but not anymore.

P.S.: I even fall at sleep writing this, hope you don't when you read it :lol:

 

[solar_plasma]

Burning pure sulfur there is not much left over, if anything at all. In a more or less closed reaction chamber you might observe sublimated sulfur condensing at the colder glass areas. Very hard to remove. If this vapor is condensing on the surface of water you get some chewing gum-like form of elemental sulfur there, which is going back to a hard form after some days.

You don't need pure oxygen, just air flow.

If you want to heat in a closed vessel like a quartz tube or a borosilicate test tube you should make sure those sublimates will not reach the precipitation vessel.

Instead of burning sulfur you could also burn (roast) metal sulfides (with "D"!).

You could use the generated SO2 to make sulfurous acid or sodium sulfite by scrubbing through water or NaOH.

 

[Shark]

A equation of the combustion process of sulfur: http://www.tigurl.org/images/tiged/docs/activities/431.pdf
You can study this google search or similar ones:
http://tinyurl.com/o9p6mjt
http://tinyurl.com/pxvms6m
http://tinyurl.com/lo5x9nk

Or wait for Lou.

Good luck with your homework

Best regard,
Richard.

Thanks for the document link, it has gotten me closer to the information I have been looking for.

Edited for spelling

 

[solar_plasma]

In the first link there is a typo:

, where it forms calcium sulfate hydrate

but CaSO3 is sulfite, not sulfate.

 

[Shark]

In the first link there is a typo:

, where it forms calcium sulfate hydrate

but CaSO3 is sulfite, not sulfate.

Thanks, I will add that change to the document I have.

 

[MarcoP]

Thank you solar_plasma, I guess using SMB or scrap copper with sulfuric acid will eliminate the hard-to-remove condense issues.
If so, I'll avoid the sulfur and try to get some glassware when it's time.

 

[Richard NL]

Some more Literature about burning elemental sulfur/sulphur to get SO2.
Because it is nice if you have another tool at your disposal.
Mainly the first part of this book, the second part is also fun to read (producing small bubbles of gas in liquids by submerged orifices).
I hope that this book still tells the truth (because i like it)!
https://www.scribd.com/doc/250829045/The-Ferric-Sulphate-sulphuric-Acid-Process

Second book: https://www.scribd.com/doc/250853307/Recovery-of-Manganese-From-Low-Grade-Resources

Third book: https://www.scribd.com/doc/250840257/SO2air?secret_password=yDoDZwHBBnMjdsJXw9Q6

Best regard,
Richard.

 

[MarcoP]

Richard, I'm at the first one, thank you!

Reading more and more about it but I just realized that if using sulfur dioxide, independently how it's produced, in a concentrated gold chloride solution might produce less sulfuric acid. Will search on this to make sure if it.

 

[kadriver]

Copperas (ferrous sulfate) (FeSO4), easy to make works good if PGM in solution, will precipitate gold and not platinum, (SO2 or SMB can carry down PGM), I have not heard of trouble with Iron being dragged down as stated above, I believe the iron should stay in solution, (I would like to learn more about how the iron would be dragged down).

Refining twice using a different precipitant than was used in the first refining will greatly improve the quality of gold.
From above we see copperas would make a good choice for the first refine if PGM was in solution, and SO2 the second refining.

Butcher, I have recently started using ferrous sulfate for the first refining, and SMB for the second refining.

The gold powder from the second refining comes out looking real good, that nice light colored tan look, and the gold always tests three nines via XRF.

I did notice that the barren solution (tested with stannous chloride) from the second (SMB) refining was tinted yellow so I did a third refining using SMB and the barren solution was then colorless. But before this third refining I put a few drops of the yellow barren solution in a spot plate and added a crystal of ammonium thiocyanate.

Sure enough it turned red indicating the presence of iron. If the pure gold powder was not properly washed free of this yellow solution then wouldn't this cause a slight bit of iron contamination in the gold? Of course it would not be "drag-down" of the iron, but if ANY of the yellow tinted iron solution remained in the gold powder, due to poor washing, and the gold powder melted, then the iron would report in the gold, correct?

The reason I bring this up is because I turned in some gold once, precipitated with ferrous sulfate, and the tech said that the gold had some iron in it.

Also, I use copperas from the hardware store. I dissolve a couple of pounds in a little hot water to make a concentrated solution, and filter. THERE ARE BITS OF IRON IN THE COPPERAS that filter out as well as other solids. If one was to try and add the dry copperas, right out of the bag, then these bits of iron would contaminate the gold powder for sure.

I then pour the filtered concentrated ferrous sulfate solution into a large PYREX dish and let it evaporate to a hard green solid.

I keep the solid in a covered dish until I need it. To use, I put some of the green solids in a beaker, add distilled water and a little hydrochloric acid, then heat it on a stirrer until it dissolves.

Thank you,
kadriver

 

[kadriver]

Kadriver made a great video of his chemistry setup to generate the SO2 gas, I am not sure how to point you to the video.

The video is here on the forum somewhere. Doing a search for "precipitating gold with sulfur dioxide" on YouTube will pull it up also.

I used sodium metabisulfite and dripped sulfuric acid on it in a gas generated setup in the video. It worked quite nicely, but using SMB is much easier.

kadriver

 

[g_axelsson]

If the pure gold powder was not properly washed free of this yellow solution then wouldn't this cause a slight bit of iron contamination in the gold? Of course it would not be "drag-down" of the iron, but if ANY of the yellow tinted iron solution remained in the gold powder, due to poor washing, and the gold powder melted, then the iron would report in the gold, correct?

I thought that was the definition of drag down.

Mechanical inclusion of contamination when precipitating a product.

Göran