Sludge in gold filled solution, advice needed please

[delboy9891]

Hi Folks, I just refined a 400 gram gold filled chain with brass as the base metal, after multiple ntric acid boils I ended up with some lovely gold foils, I filtered off the last acid boil and kept it for my next dirty refine as it has excess nitric in it as I was advised before, when it was filtered I had a thick sludge at the bottom if the buchner funnel, I tried to boil the sludge in distilled water but would not dissolve, before I proceed any further If anyone has experienced this before advice would be greatly appreciated as you can see from the pics the gold foils are suspended in this sludge, i dont want to lose them and not too keen on going to Aqua Regia until I get some advice, Derek.

 

[Yggdrasil]

Hi Folks, I just refined a 400 gram gold filled chain with brass as the base metal, after multiple ntric acid boils I ended up with some lovely gold foils, I filtered off the last acid boil and kept it for my next dirty refine as it has excess nitric in it as I was advised before, when it was filtered I had a thick sludge at the bottom if the buchner funnel, I tried to boil the sludge in distilled water but would not dissolve, before I proceed any further If anyone has experienced this before advice would be greatly appreciated as you can see from the pics the gold foils are suspended in this sludge, i dont want to lose them and not too keen on going to Aqua Regia until I get some advice, Derek.

I'm fearing Metastannic acid.

 

[nickvc]

You may need to incinerate the sludge carefully but I would advise a good water rinsing first.
Once incinerated put the remains in a beaker and add HCl if indeed you had metastannic acid present this should remove it, test the solution before disposing of it safely if barren of values.

 

[delboy9891]

I'm fearing Metastannic acid.

Again!!!!!! thats the second time and Ive only done three small batches, I know how to deal with Metastanic but I wish I could avoid it in the first place

 

[delboy9891]

You may need to incinerate the sludge carefully but I would advise a good water rinsing first.
Once incinerated put the remains in a beaker and add HCl if indeed you had metastannic acid present this should remove it, test the solution before disposing of it safely if barren of values.

Thanks nickvc Ive rinsed it several times but I will go with your suggestion of drying out the sludge and incinerating but wish I could avoid it in the first place

 

[Lino1406]

Seems the "brass" is bronze, a tin copper alloy

 

[delboy9891]

Seems the "brass" is bronze, a tin copper alloy

Could very well be, the base metal did have a bronze colour

 

[Yggdrasil]

Could very well be, the base metal did have a bronze colour

Bronze comes in many shades, so I would not go by that alone.