Can I use Muric Acid To Disolve Concentrates and Leave Gold?

[Samauri-Ray]

Hi All,

This weekend went panning and have a some good concentrates that I need to refine better to bring out the gold.

I was thinking of using Muric Acid to try to eat away the bad concentrates and then leave the gold.

Has anyone tried this before and what was the success rate?

FYI... Muric Acid is used in masonry and stone work to eat away stone / concrete and such.

Thanks for the input.

Ray

 

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[Kenmitch]

Not sure on the acid question. Guessing you meant muriatic acid.

For me panning seems like the more rewarding/funner way to do it. You have a lot of material with really small gold? Maybe classify it down and then pan it out .

 

[rodoconnor]

Nope. Muratic acid won't do it. Hydroflouric ,super dangerous and expensive. " Breaking Bad". Probably other high molar acids or bases might work too. Develope a system that works for you with your cons, whether it's a bowl,a table , a clean up sluice or just panning. Glad you got some cons to work with Ray

 

[KevinInColorado]

Probably not. Muratic won't react sufficiently with rock unless it is lime based (similar chemistry to mortar or concrete) to my knowledge. There is an acid that will eat away the rock (hopefully someone else will remember which acid) but your acid costs will exceed your gold values in many cases going that way.

What's wrong with just classifying and panning?

 

[winners58]

so you are in south America? if its really fine gold and don't want to use cyanide or mercury
best way to get your concentrates worked down is a recirculating sluice ether miners moss or some felt or fiber
once you have it to just gold and black sands it can be fired with Borax
the heavy mineral concentrate is mixed with borax, blowtorch the mix the gold sinks to the bottom and forms a button.
https://www.911metallurgist.com/blog/mercury-free-gravity-borax-method-gbm

 

[arizau]

To echo some other responses....panning aided by classifying to like sizes is the "Least Expensive" and safest way to recover gold from placer concentrates. Depending on how much concentrate you are working with, a set of 4 or 6" screens sized 30, 50, 100 mesh will probably suffice. Check this link for some screen/classifier sources. https://www.google.com/search?q=pio...ome..69i57.27894j0j4&sourceid=chrome&ie=UTF-8

This video series shows a very effective method for handling/panning screened concentrate (not just this video but look for all 12 parts of "the fine gold challenge") to utilize the screens and pan the gold out.


Good luck.

 

[Laz7777]

muriatic acid = hydrochloric ..and like many other responses, the answer is no.
I pan 50 mesh clean. a little dish soap or any of the number of auto dishwashing additives like JetDri will help.
get the experience, it beats all the gadgets, gizmos and chemicals.
I'll lose a little, but that's what a safety pan or rubbermaid tub is for.
if you want a chemical seperation still, go see if you can find an answer on goldrefiningforum dot com. I've seen some discussion of this in the prospecting section.

 

[Oakview2]

. We use muratic excited with heat to remove host rock from specimens. Hydrofluoric will disolve rock and leave gold, but will disolve you as well. Find yourself some garage sale crockpots to clean specimens. I would not use acid on concetrates, when classification will work much better

 

[Hoser John]

Nitric is the acid of choice but err on the side of caution always. It also gets rid of the lead/tin. John

 

[Laz7777]

nitric is some scary stuff..the bottle said something like: "breathe the vapors, you'll feel ok fer a bit, tomorrow you'll be dead"
used some on some amalgam that was really old and had yellow/brown fumes pouring out my steel crucible...it didn't just fizz either, it turned the color of nose goblins and came creepin over the edge.

 

[bcfromfl]

Careful panning, coupled with the "blueberry bump" and a snuffer bottle will clean concentrates surprisingly well -- enough so that they can be sold as-is. It's all in the technique. Doc has some great videos demonstrating this.

 

[Crabs]

I'm surprised that no one has mentioned Aqua Regia.
It's a simple 1:3 molar solution of concentrated nitric acid and concentrated hydrochloric acid.
In a nutshell, aqua regia dissolves the gold leaving the impurities at the bottom of the vessel.
You then separate the aqua regia from the impurities and precipitate the gold using sodium bisulfite.
Sounds simple, right?
Uhhhh...no.
Gasses evolving off of the solution will melt your lungs and dissolve your skin.
A small drop on you or your clothing anywhere will ruin your whole day.
It smells really, really, really, really bad, and your neighbors will not be amused at all.
In fact, they will likely call the cops on you, thinking that you are (thank you Breaking Bad) making meth.
The good news is that it's really expensive and you've got to be a chemist (or have a very good reason) to be able to even buy the concentrated nitric and hydrochloric acid to make it.

'Crabs

 

[Hoser John]

hahahaha now the nitric/aqua regia monster.....use any chemical WRONG and kaka can happen. Acids are easily obtained in many places if need really be with decent equipment-John

 

[Bonaro]

No no no... First, don't play with acids with whom you are not trained to play with...they will kill you.
Second, acid is not a good way to get rid of the concentrates from your gold. Learn how to pan. Once you become good it is neither slow nor frustrating. Hand panning is ALWAYS the last step in any gold recovery process. You cant use chemistry to change this.
Finally, Muriatic is a fair acid but it wont do what you want to do and may actually badly discolor your gold depending on the other stuff in your cons.

 

[Bonaro]

nitric is some scary stuff..the bottle said something like: "breathe the vapors, you'll feel ok fer a bit, tomorrow you'll be dead"
used some on some amalgam that was really old and had yellow/brown fumes pouring out my steel crucible...it didn't just fizz either, it turned the color of nose goblins and came creepin over the edge.

The age of the amlagam has nothing to do with the "brown fumes pouring out". It's due to an out of control exothermic reaction created by improperly introducing the acid without dilution. You can't just pour it in and it sounds like you contaminated the whole area in the process.

 

[kurtak]

Hi All,

This weekend went panning and have a some good concentrates that I need to refine better to bring out the gold.

I was thinking of using Muric Acid to try to eat away the bad concentrates and then leave the gold.


Ray

Ray

I am not sure what you mean by "concentrates" but if you are talking about "black" sand concentrates that are holding your "ultra" fine gold fractions - then yes - HCl (hydrochloric/muriatic acid) can be used to "assist" in further concentrating it (it won't dissolve away all the junk - but will certainly dissolve away some)

Acids - when used properly - can be a very useful tool in the recovery of very fine gold from concentrates - the trick is knowing when, where, & how to use them (this is a very deep subject - certainly more then I can cover here in a single post & it is certainly not always the best choice)

Part of the trick of working with acids is knowing what &/or how different acids react with different metals &/or there oxides - an example of what I am saying here is aluminum - nitric acid will NOT react with aluminum & therefore will not dissolve it - but aluminum will react (quite violently) with HCl (hydrochloric/muriatic) acid to dissolve it

In the case of black sand concentrates HCl can be used to at least reduce if not eliminate the "magnetic" fraction of the black sands --- though this can be done with the black sands "as is" - it is best to first remove the magnetic fraction with a magnet to be treated with the HCl - & even then - the HCl will not dissolve away everything - it will just "reduce" it to a more workable concentrate due to the magnetite being complexes of other elements other then the elements of iron, nickel etc. that make it magnetic

The process is a bit more involved then just pouring HCl on the concentrates & then pouring the acid off & washing it out --- rather then posting details here & now I will wait to see if there is an interest in full details in which case I will post more details about the steps in the process - including safety concerns & treatment of the acid waste for proper disposal

My only point at this time is to point out that using acids - in "some" situations can be beneficial to the recovery of "fine" gold from concentrates

Kurt

 

[kurtak]

Nitric is the acid of choice but err on the side of caution always. It also gets rid of the lead/tin. John

This simply is not true --- Nitric acid is NOT the acid of choice for treating concentrates - HCl (hydrochloric/muriatic) is --- also - nitric will NOT dissolve (get rid) of lead &/or tin

In fact - if lead &/or tin are involved - trying to use nitric as your "first" choice of acids is going to create even greater problems in the recovery of your gold

The reason for this is that even though nitric will react with both lead & tin - it does NOT actually dissolve it - thereby putting it into solution that can then be washed/filtered out

Rather - what happens when you react lead or tin with nitric is it breaks it down into another state of oxidation that is still in a state of solids & a "very" messy one at that

Tin & nitric - in this reaction the molecular bond (that makes it the element of metal tin) is broke (but not dissolved) & what you end up with is a very ultra fine slimy white paste known as stannic tin - once this stannic tin is created it creates "all kinds" of other problems - one of which is that it is no longer soluble with other acids --- once stannic tin has been created with nitric - the "only" real way to get rid of it is to do a reduction roast in order to convert the stannic tin to tin oxide - which can then be dissolved with HCl which (HCl) is what should be used to eliminate tin in the "first" place as it is HCl that dissolves tin

Lead & nitric - produces some what the same results except that the lead nitrate does not break down to an ultra fine paste - rather it forms a hard crust on the surface of the lead & this hard crust passivates the lead under it - preventing the acid (nitric) from continuing to react with the lead under the crust - so the reaction of the nitric with the lead stops even though there is still "free" nitric to react --- in other words - adding more nitric won't help

So again - HCl is the acid of choice to dissolve lead - but - this reaction needs to be run "hot" & the HCl needs to be diluted --- the reason for that is because though HCl will dissolve lead - when it is cold the lead precipitates crystals of lead chloride which can again crust over the lead being dissolved & again passivate it - but lead chloride is very soluble when heated & when the solution is diluted

Tin (with HCl) will dissolve at ambient temps so it can be done in a plastic bucket (set out in the sun as warm helps - it just doesn't need to be "hot")

Lead because of the heat required needs to be done in "high" temp glassware like a beaker, an old (glass) coffee pot from a coffee maker or (if you can find them) Vision Ware cooking pots &/or pyroceram cook ware

Iron, stainless steel & aluminum pots wont work because HCl also reacts with these metals

Kurt

 

[dave wiseman]

Do like you outa,add acid to water...not the reverse.

 

[kurtak]

I'm surprised that no one has mentioned Aqua Regia.


'Crabs

AR (Aqua Regia) is rarely "if ever" a good choice for recovery (by way of leaching) of gold from concentrates - whether they be hard rock cons or placer black sands (not saying it can't be done - it is just a VERY poor choice)

I could post a whole thread on why this is not a good choice - but right out the gate - because AR is such an aggressive solvent it is going to want to dissolve a whole host of other elements other then the gold - this is going to require a great deal more AR then what is need to just dissolve the gold - if you don't dissolve ALL the elements the AR will dissolve - the other elements will cause any gold that does going into solution to do what is called "cementing" the gold back out of solution - this cemented gold will then be even finer then the gold that was in the original cons --- also some of the elements found in cons can prevent "full" recovery of the gold in the cons (& that's just the tip of the ice berg)

If you are going to go a chemical route with treating cons - you will be better served to first treat the cons with HCl to remove what the HCl will remove (dissolve) & then smelt what is left (there is more to it - but that's an on going discussion)

If you are set on a leaching process - then cyanide leaching is by far a better choice - with cyanide leaching your gold (partical size) has to be at the "very least" 100 minus mesh & better if its 200 or even 300 minus mesh

As an added note; - though the reference to the ratio of HCl to nitric in AR is often quoted as a 3/1 HCL/nitric ratio - that is not really true --- that is a "general" information that can cause problems if you don't understand how AR actually works

In many cases (more often then not) you actually want to use more then 3 parts HCl to one part nitric - for one thing - other elements that are needed to be dissolved may require that 4 or even 5 parts of HCl to 1 part nitric is used - or - even with the 3/1 ratio it can result in all the nitric not being used up & when that happens it will result in your gold not precipitating back out of solution when you add your SMB (or other precipitating reagent)

Kurt

 

[kurtak]

Do like you outa,add acid to water...not the reverse.

Although that is a general "good" advice - of the 3 commonly used acids (HCL, nitric, sulfuric) used by refiners &/or as home & construction cleaners sulfuric acid is the only one that is really a MUST add the acid to the water for safety concerns

NEVER add water to sulfuric acid - ALWAYS add the sulfuric to the water when diluting sulfuric acid - & even then you want to add the sulfuric to the water VERY slowly

The reason for this with sulfuric (unlike HCl or nitric) is that sulfuric acid is VERY hygroscopic - meaning it loves to take on water which is a hydration "reaction" that is VERY exothermic

What that means - is that when you try to add water to sulfuric (especially if it "concentrated" sulfuric) the reaction is in an equilibrium that favors the rapid protonation of water - this reaction is VERY violent & hot - in a word - "explosive"

On the other hand - when adding the (sulfuric) acid to the water - the addition of acid to the water ensures that the acid is the limiting reagent - meaning the greater volume of the water limits the acids reaction with the water --- the reaction is still very exothermic but much more subdued - as long as the acid is added to the water SLOWLY --- so though you wont have the explosive reaction - the vessel you are doing the diluting in will get hot - very hot

Though the reaction of nitric & HCl is "somewhat" exothermic it doesn't come even close to the reaction of sulfuric with water - nitric & HCl - both these acids can be safely diluted ether way (acid to water - or - water to acid) --- that said - as a matter of good safety procedure - Dave is right - acid should be added to water when diluting so that it becomes a matter of habit & a mistake is not made if/when working with the MUCH more dangerous sulfuric

Kurt