a new plan

[g_axelsson]

ORP = Oxidation Reduction Potential (http://en.wikipedia.org/wiki/Oxidation_reduction_potential)

Göran

 

[waltao]

We thank you, however I also had done some research and I found this as well as make an instrument to measure the ORP, it is only a millivolt meter the problem will be the salt bridge and the platinum wire
Walter

 

[solar_plasma]

you can buy those electrodes cheaply on ebay, I think I paid around 10€ - can't say how exact it is....probably better than nothing

 

[solar_plasma]

solar,

Which method do you recommend to ppt the gold after it is in the thio leach? As I understood it the sodium sulfide was used to drop ALL metals from solution and leave nothing behind. So in boiling the black sponge are you saying that the gold is now in solution? I did notice the solution is now a nice yellow color but testing came up negative with stannous. And again there is some black powder that never went into solution.

Maybe, I stay corrected (mostly page 4): http://goldrefiningforum.com/~goldrefi/phpBB3/viewtopic.php?f=44&t=7938&start=60
sodium sulfide for precipitation - one member wrote, he tried all possible precipitants described in the literature and sodium sulfide worked best
sodium sulfite against the rotten eggs odor of H2S and/or for regeneration

maybe more important notes, I thought page 2 is interesting, but confusing too): http://goldrefiningforum.com/~goldrefi/phpBB3/viewtopic.php?f=37&t=12284&start=20
Dr.Poe states that iron wool or zinc powder are the best to cement the gold from this solution. Confusing.

wiki says both monovalent and trivalent gold sulfide is black-brown
the first link says sodium sulfide will "not precipitate all the other crap"
=I would assume the precipitate, that you got, to be gold sulfide

sulfides are normally roasted (though there are also threads about smelting silver sulfide) to remove the sulfur (evolves SO₂), aren't they.. So, more reading is needed, but if I am right, after roasting it should be possible to dissolve the powder and test it.

(only some ideas for further reading and searching, not meant as a practical advice)

 

[g_axelsson]

maybe more important notes, I thought page 2 is interesting, but confusing too): http://goldrefiningforum.com/~goldrefi/phpBB3/viewtopic.php?f=37&t=12284&start=20
Dr.Poe states that iron wool or zinc powder are the best to cement the gold from this solution. Confusing.

Warning! Poe turned out to be a charlatan and certainly not a doctor. Some things (a lot) he said was just garbage told in a way that he would look like a professional. He was later exposed and ported from the forum.

In my opinion the signature of Poe should have a warning attached to alert people of this.

Göran

 

[solar_plasma]

I have found a nice text about thiosulfate leaching of cell phone boards. Most interesting: The conclusion in the end.

http://article.sapub.org/10.5923.j.ijmee.20120102.02.html#Sec5