# Sulfurdioxide, sodium sulfite, sodium-meta-bisulfite



## freechemist (Mar 6, 2011)

Sulfurdioxide, SO2, is a toxic irritant gas, fairly well soluble in water, giving an aqueous solution of sulfurous acid, H2SO3: SO2 + H2O => H2SO3. The acid is stable only in diluted aqueous solution and decomposes easily back into it's constituents, SO2 and water. It has two reactive protons, which can be neutralized stepwise with alkaline reagents (NaOH):
H2SO3 + NaOH => NaHSO3 (sodium hydrogensulfite) + H2O
and NaHSO3 + NaOH => Na2SO3 (sodium sulfite) + H2O.
Concentration and evaporation of aqueous sodium-hydrogensulfite solutions leads to solutions of sodium-meta-bisulfite (SMB):
2 NaHSO3 => Na2S2O5 + H2O.
On concentration of such solutions to dryness SO2 volatilizes slowly, and the solid residue consists of a mixture of sodium sulfite and SMB. Thus solid SMB can be regarded as the addition-product of sodium sulfite and SO2.
All three reagents can be used to reduce gold in acidic solution and to precipitate it as the metal:
2 HAuCl4 + 3 Na2SO3 + 3 H2O => 2 Au(metal) + 6 NaCl + 3 H2SO4 + 2 HCl.

To precipitate 1.00 gram of metallic gold one has to use 1.15 g of solid sodium sulfite or 0.87 g of solid SMB. The quantities of reducing agent given above correspond to a 20% excess over the calculated stoichiometric amount.

freechemist


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## goldsilverpro (Mar 6, 2011)

> To precipitate 1.00 gram of metallic gold one has to use 1.15 g of solid sodium sulfite or 0.87 g of solid SMB. The quantities of reducing agent given above correspond to a 20% excess over the calculated stoichiometric amount.



Nice to know the numbers. I've been using photo grade sodium sulfite for about 30 years and I used it on Friday. For some reason(s), I always like the way it works better than SMB. Don't ask me why. SO2 is great, especially for large amounts of gold.


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## Richard36 (Mar 7, 2011)

I've read that the gas produced by cutting onions is SO2, 
and produces sulfuric acid when it comes in contact with the moisture of our eyes. 

That being said, would it be possible to pulverize some onions in water to produce H2SO3, then filter the solution and use NaOH to produce sodium hydrogensulfite, and sodium sulfite, as well as sodium-meta-bisulfite by concentrating and evaporating the solution?

I've also read that SO2 can be produced by reacting sulfuric acid with copper to produce SO2 gas.
Could this gas be bubbled through an aquarium pumice stone in water to produce H2SO3, and use NaOH to produce the above chemicals?


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## shyknee (Apr 12, 2011)

can sodium-hydrogensulfite precipitate gold directly.
If so I stumbled onto a source of cheap and readily available sodium-hydrogensulfite
I have not tried it yet (I seek approval first)


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## Irons (Apr 12, 2011)

Making SO2:

http://www.youtube.com/watch?v=V1sQO91UvFI


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## shyknee (Apr 12, 2011)

shyknee said:


> can sodium-hydrogensulfite precipitate gold directly.
> If so I stumbled onto a source of cheap and readily available sodium-hydrogensulfite
> I have not tried it yet (I seek approval first)


I just realized I need to reword .
I meant to ask If sodium-hydrosulfite (Sodium dithionite) can be used.

cool video Irons


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## dtectr (Apr 12, 2011)

Richard36 said:


> I've read that the gas produced by cutting onions is SO2,
> and produces sulfuric acid when it comes in contact with the moisture of our eyes.
> 
> That being said, would it be possible to pulverize some onions in water to produce H2SO3, then filter the solution and use NaOH to produce sodium hydrogensulfite, and sodium sulfite, as well as sodium-meta-bisulfite by concentrating and evaporating the solution?
> ...



Onion processing plants (don't laugh - they process TONS of onions in a 2 month season, especially in the SW states of the US) send TONS of rejects to dairies, including skins, chunks, & debris (yeah - that's why your milk tastes the way it does ...) its CHEAP for the dairies, most of whom have HQs in California, USA, (check them out) whose water-quality standards are stricter than the states in which they operate. They save literally millions of dollars U.S. in excise taxes/fees/etc. (per corporation, multiple corporations)in such a way. 

Lye is a simple end product of wood ashes & water ... 

If we could create a different, more PM-centric initiative ... ???

Who do YOU know ...


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## Oz (Apr 13, 2011)

dtectr said:


> Onion processing plants (don't laugh - they process TONS of onions in a 2 month season, especially in the SW states of the US) send TONS of rejects to dairies, including skins, chunks, & debris (yeah - that's why your milk tastes the way it does ...)


Do you like a bit of onion or garlic powder on your eggs? Chickens love eating both, and your eggs will have the taste of what they have been eating. Pre-seasoned eggs. 

I can't say I have ever had my milk taste or smell like onions though. Then again I live out east and our milk does not come from the "land of fruits and nuts” California. The only dairy livestock I have kept was dairy goats. I never tried feeding my milk goats onions or garlic either, so I can’t say if that also comes through in the flavor of the milk.


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## freechemist (Apr 13, 2011)

Hello shyknee,

Sodium dithionite, Na2S2O4, is a strong reductant, stronger than sodium sulfite. It is produced by reduction of sodium sulfite, Na2SO3, and therefor more expensive. As a colourless cristalline powder it dissolves readily in water, giving solutions not stable against oxidation through atmospheric oxygen. As a solid it decomposes on heating to about 80oC in an exothermic reaction, giving off gaseous SO2.
Surely metallic gold could be precipitated with sodium dithionite, but there is always the risk of coprecipitation with other precious metals present in solution. As an example sodium dithionite can be used in reclaiming metallic silver from used fixing solutions, whereas sodium sulfite does not reduce dissolved silver in these solutions.

freechemist


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## shyknee (Apr 13, 2011)

Freechemist, I just want to say how thankfull I am for your presents here on this forum.
And for so freely giving of your wealth of knowledge and taking the time to answer what may seem as a simple question.
Humbly thank you ,
shyknee


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## winterssoul (Jun 14, 2011)

Richard36 said:


> I've read that the gas produced by cutting onions is SO2,
> and produces sulfuric acid when it comes in contact with the moisture of our eyes.
> 
> That being said, would it be possible to pulverize some onions in water to produce H2SO3, then filter the solution and use NaOH to produce sodium hydrogensulfite, and sodium sulfite, as well as sodium-meta-bisulfite by concentrating and evaporating the solution?
> ...



hello all and might i add a thank you to you all, why not just bubble the SO2 gas though the pumice stone in your gold bearing solution then collect the unused gas and bubble that through either water to produce H2SO3 or regenerate your sulphuric acid by bubbling though H2O2 it would seem more efficient this way and I've been working on a scrubbing system for this


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## Harold_V (Jun 14, 2011)

winterssoul said:


> why not just bubble the SO2 gas though the pumice stone in your gold bearing solution


Not a good idea at all. It makes no sense to put anything in the solution that can absorb values, and a stone to diffuse the gas is clearly not a requirement. 

A glass tube inserted within ½" of the bottom of the vessel in use is more than adequate. Even when using a cylinder of SO2 without a regulator, it's dead easy to introduce the gas at a rate that is totally absorbed by the solution before a bubble can hit the surface. When precipitation is complete, the tube is easily cleaned of traces of gold by simply pushing a small wad of paper through the tube with a small diameter rod. I used 1/16" wall 3/8" diameter Pyrex tubing for the purpose. 

Harold


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## Militoy (Jun 15, 2011)

dtectr said:


> ... Onion processing plants (don't laugh - they process TONS of onions in a 2 month season, especially in the SW states of the US) send TONS of rejects to dairies, including skins, chunks, & debris (yeah - that's why your milk tastes the way it does ...) its CHEAP for the dairies, most of whom have HQs in California, USA, (check them out) whose water-quality standards are stricter than the states in which they operate. They save literally millions of dollars U.S. in excise taxes/fees/etc. (per corporation, multiple corporations)in such a way...



Interesting idea - I'm curious where you read or learned the info on the onion / dairy connection? As it happens, I live in a rural desert area of California with a lot of local ag activity. The main crops here are carrots, alfalfa hay, potatoes and especially onions. Hundreds of acres of onions growing almost year-round. I don't doubt your report of onion scraps being sold to dairys - I've heard of cows and pigs back east being fed fish meal; and down south (happy) cows being fed the remains of the corn used to make Tennesee whiskey. Around here though, they feed the cows alfalfa. I was under the impression that the green waste from our local operations was plowed back under. I would be interested in hearing what you have read though. BTW - the main local onion co-op marks their product with the "Antelope" brand name - hope that's not the operation thats "onioning" up the milk!


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## winterssoul (Jun 15, 2011)

Harold_V said:


> winterssoul said:
> 
> 
> > why not just bubble the SO2 gas though the pumice stone in your gold bearing solution
> ...



Thanks for the input harold but what say you on the rest of the process it seems this is the only way I have since I can't find any other precipitants except the metals that hoke's described


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## Harold_V (Jun 15, 2011)

winterssoul said:


> I can't find any other precipitants except the metals that hoke's described


Check with garden supplies for ferrous sulfate. The container is likely to be marked simply as iron (for plants). So long as the crystals are green, they'll work just fine. 
By the way, in case you didn't make the connecton, ferrous sulfate is copperas, as noted in Hoke's book.

Harold


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## dtectr (Jun 15, 2011)

Militoy said:


> dtectr said:
> 
> 
> > ... Onion processing plants (don't laugh - they process TONS of onions in a 2 month season, especially in the SW states of the US) send TONS of rejects to dairies, including skins, chunks, & debris (yeah - that's why your milk tastes the way it does ...) its CHEAP for the dairies, most of whom have HQs in California, USA, (check them out) whose water-quality standards are stricter than the states in which they operate. They save literally millions of dollars U.S. in excise taxes/fees/etc. (per corporation, multiple corporations)in such a way...
> ...


The knowledge is first hand - The farmers, onion-shed operators (who were often the farmers), the dairies they sold to and the people who hauled away & spread the waste - direct from the "cow's" mouth so to speak. They were all my customers & friends when I sold industrial fasteners, cutting tools, chemicals, etc.

Another favorite fodder was the debris from cotton gins - seeds, hulls, bits of stems, trash, basically, as long as it was plant-based in form. Also, debris from red chile processing (If I'm lyin' I'm dyin'!) goes there. Its all filler for the cows, who are ruminants, and need material to be processing through their 4 stomachs to stay healthy. Their nutrients/food is usually in the form of concentrated feed supplements, which do not contain enough cellulose bulk to keep rumination running smoothly.

BTW - Antelopes are ruminants, too, as are deer & sheep, I believe.


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## winterssoul (Jun 15, 2011)

Harold_V said:


> winterssoul said:
> 
> 
> > I can't find any other precipitants except the metals that hoke's described
> ...



Yup I did a detailed search of the places that I could think about but they either didn't know what I was talking about (I used both names) or they just didn't have it but ill keep looking around


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## goldsilverpro (Jun 15, 2011)

In garden supplies, it might be called iron sulfate or sulfate of iron. Like Harold said, just make sure it's green.


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## Oz (Jun 15, 2011)

You could also just make your own copperas with some battery acid and low carbon iron laminates. I think Butcher wrote a rather thorough description of how he makes his.


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## Richard36 (Jun 15, 2011)

Oz said:


> You could also just make your own copperas with some battery acid and low carbon iron laminates. I think Butcher wrote a rather thorough description of how he makes his.



I made mine by using 1 part Sulfuric Acid to 15 parts distilled water, and a couple 16 penny nails.
It took about 4 days for the Iron to completely dissolve, and produce the green crystals.
I then filtered the solution to recover the copper sulfate, and dried it.

Just my thoughts on the subject.

Sincerely, Rick. "The Rock Man".


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## Barren Realms 007 (Jun 16, 2011)

Richard36 said:


> Oz said:
> 
> 
> > You could also just make your own copperas with some battery acid and low carbon iron laminates. I think Butcher wrote a rather thorough description of how he makes his.
> ...



That is interesting how did you get copper out of iron?


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## Oz (Jun 16, 2011)

Barren Realms 007 said:


> That is interesting how did you get copper out of iron?


You don’t. It is just one of those old quirky words that make you wonder why they called it copperas of all things. It is actually iron sulfate.


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## Barren Realms 007 (Jun 16, 2011)

Oz said:


> Barren Realms 007 said:
> 
> 
> > That is interesting how did you get copper out of iron?
> ...



Yea I was poking fun at Richard. 8)


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## Richard36 (Jun 16, 2011)

Barren Realms 007 said:


> Richard36 said:
> 
> 
> > Oz said:
> ...



Lol!!! That's funny! Copperas, Copper, my mistake, Duh!!!!
I meant Iron Sulfate.

You're all welcome for the laugh.

Sincerely, Rick. "The Rock Man".


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## Oz (Jun 16, 2011)

Um... You had it right Rick.


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## Irons (Jun 16, 2011)

shyknee said:


> shyknee said:
> 
> 
> > can sodium-hydrogensulfite precipitate gold directly.
> ...



Thanks, I thought it was pretty neat. It goes to prove that, sometimes the simplest solutions are the best. SO2 is so easy to make, just by burning sulfur, that, other than convenience, it's the cheapest way to go.
I read somewhere that some companies that use large volumes of SO2 have gone to generation on site, rather than dealing with the cost and hazards of shipment and storage of liquefied SO2..


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## butcher (Jun 18, 2011)

Sodium thiosulfate, can be made boiling sodium sulfite Na2SO3 and sulfur together, Na2S2O3 sodium thiosulfate is used in photography to dissolve unreacted silver halide from film.

Sodium thiosulfate is also used to leach gold and silver from ores. Usually as ammonium thiosulfate and copper sulfate basic PH.

From what I understand cementation is used or electrolisis to recover silver, and I wonder on effieciency from what I have studied.

There is also a patent on recovery of silver using sodium hydrogen sulfide and regenerating the thiosulfate for reuse in photography.


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## winterssoul (Aug 3, 2011)

winterssoul said:


> Harold_V said:
> 
> 
> > winterssoul said:
> ...



yup thanks again but i found an industrial raw material chemical supplier that sells a 50lb bag of sodium metabisulfite (i stressed the spelling to them) for under $5000 jmd(a little over 50 dollars but i haven't been able to pick up this bag yet i also checked out a school lab supplier which sells it for $2750 Jamaican dollars for 500g of the stuff


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