unknown precipitate in AP

[Geo]

i have been using AP to digest gold clad pins and have come up with what appears to be sand in the reaction container.it is insoluble in HCL and i even tried hot HCL with no effect.it has a large amount of my gold foils trapped.i havent tried any other acids yet or water because of copper II chloride.my chemistry is lacking to where i cant figure out where these crystals come from.the pins are mostly brass and half has solder.if it were tin HCL would clear it up.the clean sand (crystals) do not react at all with fresh HCL so copper is out.from six US pounds of pins there's over one US pound of these crystals.i really need some help because i have about twenty US pounds of high grade military pins and would like to process them this way.any help would be greatly appreciated. thanks.

 

[Barren Realms 007]

Wash a few times in water then try a wash in ammonia and see if this clears you up.

 

[Palladium]

If it won't dissolve in hcl then try processing the foils with the acid/bleach method. Once the foils are dissolved you can filter the trash out and then precipitate.

 

[Lino1406]

The "sand" is probably Tin dioxide - SnO2
to avoid it dissolve 1stly the solder

 

[Geo]

The "sand" is probably Tin dioxide - SnO2
to avoid it dissolve 1stly the solder

thanks for the info.that describes what i have very well.i looked it up online and since it isn't reactive to most acids except sulfuric, hcl+chl should work just fine.for future reference how would i dissolve just the solder first?

 

[butcher]

Solder should be eliminated mechanically as much as possible, Acid peroxide will dissolve the small amount of solder you miss, dissolving solder,copper, brass or base metals, gold will not react as long as you do not add too much oxidizer (H2O2), bubbling air with fish tank air bubble maker helps, and you cannot seem to over do it, this should give a mix of gold foils, in a copper chloride and base metal solution, most of the tin from the solder would dissolve into the chloride solution, lead will be as white lead chloride powders, boiling water washes of foils will make these lead salts soluble, HCl wash will help to rid other contaminate like any tin oxides.


Tin with nitric is the nightmare, send them powders to hells fire in incineration.

Edit to addthis note : HCl will breakdown lead dissolving tin and making lead chloride salts, heating helps, air from environment(can absorb into solution) with very hot concentrating solution can act like acid peroxide, and even possible to dissolve some of the fine foils or plating of gold. the base metals will push it out into the insoluble lead salts, or plate to copper base metals, if this happens.