# Smelting flux



## ruffneck84 (Nov 28, 2017)

Which to use ? Sodium bicarbonate ( baking soda) or Sodium carbonate (soda ash) in my flux. Pro's and Con's ?


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## jimdoc (Nov 28, 2017)

Joined: Sat Aug 24, 2013 6:06 am?
You have had over five years to study the forum, what happened?


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## ruffneck84 (Nov 28, 2017)

I do have a real job and a life that takes up alot of my time. But after 6 years of reading i am ready to start production. I have produced bars ranging from 2-4% Au and Pt, up to 34% Ir, with Rh, Pd, Ag running as high as 20%. Alot of Ag and Pt 1% to 3% ends up in the slag. Flux adjustment needed. Wondering if the baking soda or soda ash makes any difference ?


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## jimdoc (Nov 28, 2017)

I would think an assay would be a good idea, to make sure the XRF numbers are correct.
What is the source of the metals? This may do better in the "Prospecting, Mining, Ore Concentrates & Geochemical" section.


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## ruffneck84 (Nov 28, 2017)

This is straight head ore and it can not be concentrated. 48 Lb. run 1260 gram lead collector. End bar wieght 1668 gram. The XRF read is of this bar. The machine has been checked numerous times. Ive read alot and learned exceptional amounts of wisdom from this site. But there are little things that I have overlooked.


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## jimdoc (Nov 28, 2017)

I think a moderator may move this to the mining category for you. 
There are members that can help you, that may only check that section more than the rest of the forum. Lou is probably the person to help you if it is that much iridium.


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## ruffneck84 (Nov 28, 2017)

Thank you Jim, ive worked along time on this and i want to get it right.


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## nickvc (Nov 28, 2017)

The iron and lead readings look ok but the iridium is doubtful imho but I could be wrong, if you are finding that much iridium in your material it normally is very hard to melt into a decent assayable bar, PGMs normally cause bars to separate out when cooling, one side may be rich the other poor, it’s almost like a honeycomb inside.
Before you go any further get a proper assay done to confirm you are on the money and send a large sample of what you have like a good slice off one of your bars.
I hope you have found decent grade material but confirm before getting too excited...we rarely see or hear good news from our mining brethren.


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## ruffneck84 (Nov 28, 2017)

Yes Nick the PM's did separate it is the first picture. In the second picture as i was knocking the flux off of the bar it broke in half. All of the bars are real brittle. I am sending four bars to the refiners for final analysis. I am the kind of guy that likes to get it all. This is why I'm asking on the flux. I look at it this way if you're going to rob a bank get it all 8)


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## mls26cwru (Nov 28, 2017)

I am no expert in smelting, but I have been reading a bit recently on fire assays before I try to start smelting myself...

I ran across a tidbit about the differences between sodium bicarbonate vs. sodium carbonate and i believe the book said that bicarbonate is avoided if possible because it releases a larger amount CO2 which leads to frothing or boil-overs... I will double check tonight when i get home though just to make sure.


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## ruffneck84 (Nov 28, 2017)

Thanks mls that helps on making up my mind on which directon to go. I know that you can't recover 100% of PM'S so i have brought my percentage down to 99%. I would be happy with that. 8)


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## snoman701 (Nov 28, 2017)

The XRF is confused. Look at the probability.

While you CAN take very accurate XRF of powders, slags, etc...sample preparation is key. You have to grind to a uniform size. The sample must be homogenous.

In this case, the iridium is likely platinum. The lines in the spectrum nearly overlap and iridium and platinum are very difficult to tell apart without examining the spectrum AND having good known standards by which to compare.


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## ruffneck84 (Nov 28, 2017)

Snowman this maybe why im showing Pt in the slag and not in the bar, if so good call. They will be running ICP on the bars at refiney so that i get the whole story. Any input on the soda ash or baking soda ? Thanks for your input.


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## snoman701 (Nov 28, 2017)

ruffneck84 said:


> Snowman this maybe why im showing Pt in the slag and not in the bar, if so good call. They will be running ICP on the bars at refiney so that i get the whole story. Any input on the soda ash or baking soda ? Thanks for your input.



I don't, sorry. 

I didn't think that lead is the best collector for PGM's though.


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## ruffneck84 (Nov 28, 2017)

Yes i understand but I've had a lot of problems with PGM's volatilizing in the past so I have went with a lower melting point collector. Plus i strip the bar (around 2 kilogram) of lead comes out 99% pure + residual left in bar goes into the next smelt. I will catch the PM's sooner or later that way with no great loss. I've got my process down to the bare minimum, Crush, smelt, pour the bar, and sale. Just needing to tweak a few things in the process.


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## mls26cwru (Nov 29, 2017)

I checked the book last night and here was the passage in relation to sodium bicarbonate:

This passage comes from "A Textbook of Fire Assaying" by Edward Bugbee, on pg. 8.

"Sodium bicarbonate (NaHCO3): Is still used by some assayers as an alkaline flux, mainly because of its cheapness and purity. It is decomposed, however, when heated to 276C, forming the anhydrous normal carbonate with the liberation of water vapor and carbon dioxide. The large volume of water vapor and carbon dioxide released, passing up through the charge before it has softened, is bound to carry off more or less of the fine ore and thus contributes to the so-called 'dusting' loss. 
The bicarbonate contains but 63.1 per cent of Na2CO3 (sodium carbonate), and therefore when it is used as a substitute for the normal carbonate 158 parts are required for each 100 parts of normal carbonate. Because of the above serious disadvantages the use of the anhydrous normal carbonate is recommended in all cases. The only advantage witch can now be claimed for the bicarbonate is that it does not deliquesce." 

Hope this helps.


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## ruffneck84 (Nov 29, 2017)

That is great information to know, and thanks again for the help. I also come up with some interesting facts, soda ash/ sodium carbonate (dense) ph 11.3, baking soda / sodium bicarbonate pH 8.6. It looks like the soda ash (dense) will be a better acid neutralizer. Also soda ash is used in glass production, no information of using sodium bicarbonate for the production of glass was found. I want to thank all for comments and information.


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## Shark (Nov 29, 2017)

You can download or read that book from the link. Very good read with some useful information.

https://archive.org/details/textbookoffireas00bugbrich


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## ruffneck84 (Nov 29, 2017)

Thanks Shark, will do.


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