# Overuse of sodium metabisulfite in gold bearing solution



## majorazora (Apr 6, 2015)

Hello, and thank you for reading my thread. I have successfully dissolved gold using the clorox method, and moved right along to the dropping stage. I dropped successfully as well, the golden snow fell like a gilded winter, but it seems that I have overused the sodium metabisulfite, (and I will pace myself heavily from now on) as there is now a slush-like mixture of metabisulfite crystals and gold powder. I can clearly see the small gold powder glint and shine, and the metabisulfite crystals (which are usually stark white) have taken on a yellowish orange hue, indicating that I basically have a bunch of gold powder mixed in with these crystals. My question is, how can I separate all of this extra metabisulfite from my dropped gold powder? 

Thank you again for reading!


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## Barren Realms 007 (Apr 6, 2015)

Siphon off the solution and wash with warm water till you only have the gold powder. Be sure and let your powder settle well between washes so you don't pour it out with the wash water.


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## MrMylar (Apr 6, 2015)

What I would do at this point is add warm to hot water to the solution. Overshooting your gold drop with SMB won't actually hurt the recovery process, but it can hamper the recovery of the gold powder if the SMB is dropping gold but the outside temp is lower than the solution temp. If the outside temp is around 60+ degrees, the SMB tends to perform as it should.

I have realized that the gold powder is mostly heavier than the added water (approximately 19x heavier), it'll make settling of the gold that much easier. I just finished a batch of gold plated jewelry from a sulfuric cell, and even after filtering a few times, the gold is so fine, it keep showing up in my rinse water. That's where the term/use of "*decant*" comes in at. You vacuum out the liquid instead of pouring it out.

Some things to keep in mind:
It takes no more than 1 teaspoon of SMB to drop upto 7grams of gold. After that 1 pour and stir, test your solution with your Stannous and of you don't have 7+ grams in the solution, it might register very faint or not at all. In other words, If I have less than 7 grams of gold to drop (estimated) I will only use 1 teaspoon of SMB. You shouldn't have any buildup of the SMB in your dropped solution if you don't use more than 1 teaspoon per "up-to-" 7 grams of estimated recoverable gold.

Some people add 1 teaspoon of SMB to approximately 1/4 cup of water, let it dissolve, and then pour some of it into the gold solution to drop the gold. It works the same. 

One good way to make surre most of your gold is captured from the SMB drop and testing it with stannous, is to add some fresh warm water to the beaker and let it sit for about 5 minutes or less, depending on how big of a beaker you use and how much water you add to that beaker. If a solution is used up, and the powder (gold or silver) have been dropped, adding warm water may help in dropping powders that simply don't drop to the bottom of a beaker, and yet they will fall though a coffee filter. Either way, your material is at the bottom.

For me, adding water AFTER all the gold powder have been dropped with SMB, I add water to the solution to make the gold drop faster to the bottom. Also, adding more water than what's in the beaker also reduces the amount of times you have to rinse your powders. Keep a pH tester handy. Depending on the beaker I use for the powder I'm refining , I may have to rinse my powder out about 2 times, and test it with the pH tester and I can get a 7 on the scale for the most part.

Refining is fun and educational, along with dangerous too, yet it gives you that sense of pride when you've refined something that was considered trash and turned it into pure gold, silver, platinum, palladium, copper etc,.

Don't forget that "*twice refined*" is purer and more valuable too.


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## bswartzwelder (Apr 7, 2015)

Have you tested with stannous chloride? If not, why? It's easy to make and will tell you if you dropped all the gold. If you haven't dropped all the gold and have gotten rid of the solution, you may have thrown values away. 

Another thought also came to mind. Decant as much of the solution as you can then add more water to it and heat. Nothing will happen to the gold, but the excess SMB would most likely dissolve in the excess water. Problem solved.

The reason why I am so adamant about the use of stannous is because as a newbie I thought I was too smart to make mistakes. Then one day I tried it and discovered I had lost some of the values I was trying so hard to recover.


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## jeneje (Apr 7, 2015)

When heating solutions with SMB, do this in a well ventilated area or fume hood. You do not want to breath the fumes of the sulfur dioxide. 
Ken


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## kurtak (Apr 7, 2015)

I just recently posted my washing procedure on another forum (Kens forum) so here you go

My washing method goes as follows

Water washes - start with three - after third wash test with PH paper - if acidic - wash again - repeat till PH test is not acidic (usually takes 5 sometimes 6 washes)
decant washes into quart mason jar to let ultra fine Au settle out that pours off when decanting 

HCl washes - do this wash as many time as it takes till you see no color change in the HCl - could be as few as 2 or 3 - or as many as 5 or 6
decant these washes into it's own quart mason jar again for ultra fine Au settling - also test these decanted washes with stannous for PGMS (the reason for decanting to its own mason jar) that may have dragged down as traces when dropping your Au - if PGM positive use zinc to recover the PGMs

Water washes - again do this till PH paper test show no acid (usually takes 5 sometimes 6 washes) 

Ammonium Hydroxide wash - one wash (hot) this gets ride of any silver chloride - decant into beaker with enough HCl to acidify the ammonium & drop out the silver (as a chloride) 

Water washes - as many as it takes to rid the ammonium (PH paper does not show basic positive test) usually takes 5 or 6 - decant these washes into same beaker as first ammonium wash - make sure the ammonium is acidified & not basic

In other words - you want to do your water washes till testing with PH papers shows no more chem from the previous chem treatment & do your HCl wash till it has removed all base metals &/or PGMs (no color change in the HCl) that may have dragged down when dropping your gold --- meaning there is no "set" number for each wash - preform each wash till it has completed its intended task --- it could be just a few washes if it was a small &/or clean gold drop - or it could be a lot of washes if it was a large drop &/or a lot of BM/PGM drag down

I have had to do as many as 7 or 8 washes (each wash) on larger batches &/or the leach source was dirty to start with

Kurt


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## MrMylar (Apr 7, 2015)

jeneje said:


> When heating solutions with SMB, do this in a well ventilated area or fume hood. You do not want to breath the fumes of the sulfur dioxide.
> Ken


Oh boy it has an awful smell. When you smell it, you'll know it. Also, keep in mind that there is a difference in *smelling* fumes/gases and *breathing* fumes/gases. I have learned that here on the forum. You really do want to know the "_*smell*_" of your chemicals, but you *DON'T* want to "_*breathe*_" the chemical fumes and gases.

Another thing I've learned from being here on this forum and refining , is that I can now tell which chemicals is giving off an odor when working outside. Most newbies and even seasoned people with refining knowledge is *expected* to know how to control the use of the Nitric Acid you need to use. You are better off needing to add nitric acid than to have to cook off the excess nitric acid. This is for anyone that uses nitric acid in their refining process(s). Use it sparingly and add heat. 

Make sure you post a picture of the finished product in the gallery.


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## crgoode (Apr 18, 2015)

I have encountered this same thing. thanks for the incite.


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## pnavaie (Jul 13, 2021)

please someone help i confused
i made aqua regia and solve gold in it and filter it
after that i add some sodium bimetasolfite , i saw the brown thing created but after a second it disappear and nothing settle !!!!!!
what should i do


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## FrugalRefiner (Jul 13, 2021)

The brown disappeared because you had excess nitric acid in your solution. The excess nitric redissolved the brown precipitate.

You need to deNOx it, meaning you need to remove the excess nitric. You can search the term deNOx to find a solution that will work for you.

Dave


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