Help with botched refine

[bsrjack]

Hi There
I'm complete newbie so please take it in to account
Few months ago (after reading this forum and finding some extra info on the net) i did successfully refine some old jewelry i had around and ended up with beautiful piece of pure shine, all perfect.
Today i tried to do it again on another small batch of scrap using the same inquartation method but things went totally wrong.and i don't understand how and why.
today i smelted two separate batches of scrap, one made of good known quality gold and another made of some dubious jewelry found by my daughter, that jewelry looked so dodgy that i decided to smelt it in separate batch to not mess with first good known batch. of course both were tested with acid first resulted in 18k and 14k pieces the second 9k, i dropped the stuff into water nitric acid mix and placed on heat, after some time the good batch disappeared leaving very fine black dust and the "dodgy" batch didn't even change the color and stayed totally untouched by acid. i collected and washed black dust which by the way was far less then should be in gold
and tried to smelt it together with the filter but it gone leaving nothing in smelting pot.
So not i've got badly inquartated gold which don't dissolve in acid, acid in nice clear blue color and no gold from first batch. Where is the gold from first batch? and what to do with the second which don't dissolve? it keeps showing around 9k after inquartation!! is my 9k test plain wrong?
I'm glad batches where really small so lost is not that hard to swallow
Thank to you all in advance..

 

[FrugalRefiner]

First, you're melting things, not smelting things. Both are valid terms in refining, but they mean different things.

You mention inquartation. Please provide a little more detail about what you did.

Did you ever test any of your solutions with stannous chloride?

After trying to melt your black powder, what was left? Was there any discoloration in the pot? Any beads of metal? Nothing at all?

Give us some answers and maybe we can help.

Dave

 

[Geo]

Did you test the nitric acid leach with stannous chloride? As far fetched as it may sound, it sounds like you may have dissolve the gold.

 

[bsrjack]

No i didn't test acid with the chloride, used the same bottle of 60% nitric acid as at first successful attempt + equal amount of destilled water, black powder left no residue nor discoloration just burned out together with the paper filter.
For inquartation i used
first batch
3.91g 18k + 7.82g silver
1.21g 14k + 1.61g silver
second batch
6.31g 9k + 3.15g silver
i'm left with an around 8.2 grams of acid untouched gold

 

[g_axelsson]

The calculations seems right, makes me believe that the 18k batch was made out of gold filled or plated. The black powder is the gold, there was too much base metals present so the gold broke down into fine particles instead of porous pieces that we aim for when inquarting.

The second batch is more intriguing though. Aluminum or steel could resist nitric acid but steel is both impossible to mix with silver (at least molten iron is) and really hard to melt. Maybe an aluminium bronze alloy could resist nitric acid, but it seems odd to have an alloy that high in aluminium that it would protect the metal in nitric acid.
You could always add more silver to see if that would help. Another thing you could try is to scratch, cut or hammer the shots if there is a passivated surface stopping the nitric acid reaching the metal below.

Good luck!

Göran

 

[bsrjack]

The plot deepens (at least for me) i've been investigating a bit and 2nd batch is metallic on the surface only and quite brittle and porous inside i can definitely brake it between fingers so it looks it got treated by acid but somehow got covered by gold later? maybe it have something to do with saturation of acid solution?
I have tested both batches with acids on the stone, first batch came from rather reputable source and volume of black powder don't match wight of gold that went in, i gonna melt what is left and test karat out of curiosity, here is the photo of the stuff interior

 

[bsrjack]

Ok, melted the thing and result is white metal lighter then same size 24k gold and shows above 18k on the stone (i have no higher tester acids)