Which First Incinerate or HCl

[tesremos]

Okay, so after 200 cellphone boards in AP

Sadly, i left solder on some, yes yes i know. bad me, *slap on wrist*

this is left in my filter from the AP, (this is the last filter from the batch, most foils were lifted out of solution with a spoon)


Do i incinerate, or wash in HCl first?


if i incinerate, will any Sn (tin) or solder melt and cause one hell of a mess?

if i wash in HCl, will i end up with a Stannous chloride with gold in it?


Advice please.


and or i ask my self,

what would Harold, Steve, Sam, paladium, or GSP do...

WWHSSPGD for short....

 

[solar_plasma]

I would give it a hard incineration, then HCl washes till colourless and no tin present, then AR it until no more gold is dissolving (no more yellow and/or SnCl2 test negative).

 

[tesremos]

it wont melt the tin/lead into a clump ?

 

[solar_plasma]

there is no metallic tin anymore, only compounds. Btw metallic tin would burn to oxides sooner or later.

 

[tesremos]

thats mostly what i was thinking... but i wanted a second opinion.


incineration it is!

 

[Harold_V]

As it should be. There's nothing that will equal a proper incineration followed by a digest with HCl. I used that process on many things I refined, including gold filled objects, where you're likely to encounter tin and lead. Even eye glasses received that operation, after the initial digest in nitric acid. The resulting gold chloride solution filters with ease, and there's virtually no other metals in solution. Incineration is the magic bullet most folks seek, but aren't wise enough to understand its benefits.

If you've ever processed dental amalgam, you'd know of the difficulties of dealing with tin. I quickly learned that just incineration, after the retort operation to remove the mercury, was extremely beneficial. It should be accomplished in a fume hood, as there's always traces of mercury left behind, but by incinerating until the cake turns mushy, then stirring while it's in that state, the tin is quickly oxidized such that the next step, digesting in nitric, isn't troublesome. Needless to say, you wouldn't want to do the HCl wash for this material, but experience taught me that it also isn't necessary.

Incineration. The magic bullet.

Harold

 

[tesremos]

Incineration....


the answer to all of life's problems,
(i some how KNEW harold would say incineration)

so, oxygen rich incineration, or oxygen starved incineration?


to what temperature should i take this?

is 700c sufficent? or should i get the torch onto it and bring it to 1400c ?

 

[solar_plasma]

As the wise words of Rammstein in the song "Benzin" says: "Willst du dich von etwas trennen, musst du es verbrennen." (=means something like, if you want to get rid of basemetals, you have to incinerate it first) :lol:

 

[butcher]

tesremos,

Your goal is to burn off oils and carbonous trash and to oxidize the base metals in the incineration process, this requires an oxygen rich environment, you do not want to melt the metal, about 700 degrees and keeping that temperature till the metals are oxidized, also keeping the material crushed and stirred to get good exposure to oxygen is important.

Many times with material that has been exposed to acids , these will dry on low heat, and can be crushed to powders, but as they are heated they will again fuse the salts of these metals powders, and form a syrup like substance being wet again from the heat as moisture and acids burn off, if heat is too high this can bubble and splash out values as these bubbles pop in the syrupy mix, lowering heat to keep the mix from bubbling, and or spreading out the material in the dish, until the syrup drys again (as the previous acid gases off during the heating process) as the syrup drys it can harden into a cake making re-crushing back to powder a bit harder, stirring before it completely dries, can help to break it up, and making re-crushing easier later.

I use a Pyrex glass mortar to crush the clumps back into powder, at this point the dry powders have removed most of the previous acid, and the temperature can be raised to high, the powders are kept stirred in the heat and brought to a glowing red hot, and kept hot while stirring and exposing all of the fine power to air or added oxygen, towards the end of the process you will see less smoke or gases emitted from the material, , oils and carbonaceous material burns off, the moisture and acids are fumed off as gases, and the material can then absorbs oxygen to convert the base metals oxides, many times you will also notice a color change of the material as the metals oxidize.

Oxidation of the base metals helps in several ways, it can make some of these base metals easier to dissolve into the acid washes, it can make some base metals insoluble in acid, basically improving the material to help us separate the base metals from our values, and helping us to make the troublesome base metals (like tin) much easier to deal with.