Some questions regarding Nitric acid digestion

[yossarian]

In my OP I said that I was confused by some results I had in 2 different Nitric Digestions. Here are the pictures of the pins I used and the results.

Pic 1- the first pins I used (1 gram)
Pic 2-The results after Nitric bath
Pic 3-The second Pins I used (3 grams)
pic 4-The results of Nitric bath

The first batch of pins (in the first picture) are a much deeper yellow and are darker than the second batch of pins which are brighter and shinier. I also realize That the first acid Digestion was not done to completion, but it was my first ever experiment, and that was the whole point of starting with an experiment, so that I can make mistakes.

Anyway, I am confused why the results are so different. The first batch was only 1 gram and the second was 3 grams. Is the brown powder in the 4th Pic gold?. also the second batch had little particles suspended in it that would not settle, even after sitting for over 24 hours, could that be some gold powder that I lost? Is gold not too heavy to float indefinitely?

 

[qst42know]

I have had some solutions that were visibly clearer after a week than after setting for a day. Dirty solutions can really slow down the speed at which the finest stuff settles. That is the purpose of the stock pot so the tiniest particles and other traces of values are accumulated into a meaningful amount.

Yes the brown powder is your gold. The appearance of foils aside from possibly being an incomplete digestion, could be a function of plating thickness or of the violence of your reaction. Stirring can break up foils as well as a rapidly fizzing reaction. Processing larger amounts you should have both powders and foils.

 

[goldpete]

i have a question which may or may not be related to this conversation . but before i ask it , ill explain the process ive been doing so far which i think i have right and is what ive obtained from hokes book.

my scource of material is cell phones and curcuit boards / pins from computers.

first i soak my material in nitric , then i filter it and discard the liquid.
then i keep spraying water into the filter over a couple of days till only clear liquid comes through.

then i place the filter and its contents into approx 120mls of AR , made from 1 part nitric and 3 parts hcl.

after a couple of days ,i add a little sulfuric acid (approx 30mls) and i evaporate the AR down to a syrup , then i add hlc (approx 10mls). then i avaporate again down to a syrup and add more hcl. i do this 3 times.

once i think all nitric is expelled , i then add 3 times its volume of hot water. after it cools , i filter which usually leaves me with a nice gold coloured solution . and then i add smb.


ok here is my question .......going back to where i have soaked my material in nitric and then filtered , i see in the filter plenty of gold flakes and lots of grey sludge which i assume is silver cholride .

what i want to know is how can i get rid of that grey matter before proceeding to AR ? AND I SHOULD NOTE THAT I DONT HAVE A BLOW TORCH OR ANY WAY OF INSINERATING

 

[Geo]

goldpete, when you say you filter and discard the liquid, do you mean you discard the spent nitric acid? first, if you dissolve whatever will dissolve in nitric acid, there will be no silver chloride. there will be silver nitrate and thats what you are discarding. you are tossing away perhaps half of your values in the bath water (so to speak).why not use a piece of copper to cement your values out of the nitric acid before you discard it. not to mention the palladium, but since i did, why throw it away? second, after you release the gold from the boards, why not use hcl/Cl (hcl and bleach) to dissolve the gold foils. theres no need to evaporate and add hcl and evaporate and.... you just let it sit out over night or gently warm it and let it steam for about an hour and cool it and drop your gold. why make things harder than it needs to be?

 

[DarkspARCS]

goldpete, when you say you filter and discard the liquid, do you mean you discard the spent nitric acid? first, if you dissolve whatever will dissolve in nitric acid, there will be no silver chloride. there will be silver nitrate and thats what you are discarding. you are tossing away perhaps half of your values in the bath water (so to speak).why not use a piece of copper to cement your values out of the nitric acid before you discard it. not to mention the palladium, but since i did, why throw it away? second, after you release the gold from the boards, why not use hcl/Cl (hcl and bleach) to dissolve the gold foils. theres no need to evaporate and add hcl and evaporate and.... you just let it sit out over night or gently warm it and let it steam for about an hour and cool it and drop your gold. why make things harder than it needs to be?

ok, so the white cloudy crap when using nitric is silver nitrate, while the white cloudy crap when using hcl is silver chloride.

why does it only appear right when i wash with water lol? and... after a nitric bath, placing copper directly into the 'spent' blue nitric cements other pm values?

 

[Geo]

ok, so the white cloudy crap when using nitric is silver nitrate, while the white cloudy crap when using hcl is silver chloride.

why does it only appear right when i wash with water lol? and... after a nitric bath, placing copper directly into the 'spent' blue nitric cements other pm values?

i believe something got lost in translation. :lol: silver nitrate should never present as white and and cloudy (unless you add hcl to it). if you are processing cell boards in nitric acid and your getting white crap thats hard to filter, its more than likely stannic acid (tin dissolved in nitric acid). cell boards contain a lot of silver bearing components (solder,capacitors,connectors) also palladium. none of this should turn white or cloud the solution by just being there. if the tin isnt removed first, that is the source of the white crap.

as far as precipitation when you add another liquid, concentrated solutions will hold metals like tin and lead better than a dilute solution. when you dilute with water the tin and lead cant be supported because the acid is too weak and will fall out of solution. this is the reason for diluting AR solutions before filtering. it also works with hcl/Cl solutions and many others.

adding a piece of copper to your spent nitric solutions will cement any silver or palladium or any other metal of value out.