Yep your right. It's all pretty new to me big learning curve here. I will take the time to view that video. Thank you.
sulfuric stripping cell: My basket got eaten What did I do wrong.
- Thread starter gregory-d
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Thank you I will... am that is fantastic
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Thanks. Yes that was one thing I omitted the mesh was fine. It seems that each person works toward a work flow that suits them. Thank you for this it is helping me clarify and improve my own trials.
So what I am starting to think is that slowly heating the sulfuric below 300C will evaporate some of the water but once you get to a certain point no more water will come out and you need to boil it to get it to 98%. So buying sulfuric in smaller quantities and having a mostly sealed and dry stripping cell and working reasonably quickly would be ideal to keep the water out in the first place.
I'm also starting to think the refrigeration Idea might work well.
Fridges tend to dry the air and some of the cooling coil could be directed around the bath itself to extract the heat at the same time.
This would also have the added benefit of allowing you to run the system faster.
I will in the mean time experiment with wattage to work out which works.
My thinking here is watts tell the actual current occurring in the reaction, and as I saw somewhere here the resistance in the bath has an effect as well. Watts should sort of auto include that AFAIK.
Thanks everyone for your information ideas and help. I will come back to this thread often and follow each lead.
I'm also starting to think the refrigeration Idea might work well.
Fridges tend to dry the air and some of the cooling coil could be directed around the bath itself to extract the heat at the same time.
This would also have the added benefit of allowing you to run the system faster.
I will in the mean time experiment with wattage to work out which works.
My thinking here is watts tell the actual current occurring in the reaction, and as I saw somewhere here the resistance in the bath has an effect as well. Watts should sort of auto include that AFAIK.
Thanks everyone for your information ideas and help. I will come back to this thread often and follow each lead.
Martijn
Well-known member
The volume of acid greatly inlfuences how much current you can run. The voltage will follow, wattage does not matter much, it's the current causing heat.
If there is gold in contact with the anode basket, there will be current. Once the current stops, you need to check and shake it up if needed.
I found that a 100ml glass cell can take up to 750mA and not overheat above 35 C(95F). That's my limit i like to stay under.
A 400ml glass can take up to 2 to 2.5Amps, but if you don't watch the cell continuously the current will drop below that point and create less heat.
A large lead cathode sutface also helps keeping the heat down i think.
I stayed away from cooling, as it creates condensed water on tgevcool parts and you need to keep water away from the concentrated sulfuric. One drop of water can cause serious problems.
You also need to vent gases like Hydrogen off.
Setting the cell on a big metal plate might give enough heat loss to crank it up a bit higher.
Thanks Martijn really useful info again.
I am doing this all in the fume hood so the off gasses are getting removed and diluted straight away.
Just to be clear as watts is simply volts x amps and the voltage in the circuit is variable, then watts can provide a better reflection of the actual current in relation to the power being consumed.
"In electrochemical processes like stripping baths, the power (watts) directly correlates with the energy being supplied to the bath, which influences the rate of the electrochemical reactions. By controlling the watts, you're effectively managing the total energy input, which can provide more consistent and predictable results compared to just controlling voltage or current alone, especially when these can vary."
That is why I am going on about watts.
Yesterday I had a lump of gold plated stuff and keeping the watts at about 5 seemed to work well dropping to about 3 when most of the gold was gone. At that rate the temperature seemed to stay low (IR temp sensor is on it's way now).
I set the limits of volts and amps so they don't go over 6 watts and it seemed to work well reasonable bubbles on the lead side and not too much heat.
Today I will try another more robust basket and see if it erodes.
Time and experimentation will tell
On reflection and as people have suggested this may work in my setup but may be completely off for someone else
As you suggested yesterday I am pretty sure I'm dealing with a lower concentration (forgot to buy that battery again so I am still not sure I will also get a proper 100ml volumetric flask so I can get a more accurate value in the future).
So the result is that even with an empty basket I am getting some current with pure copper.
This is a lot of fun and even more fun with everyones help.
I was feeling totally lost but now things are starting to make some sense.
I think....
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I just had another idea that people might find useful. I use these for my photography chemicals they allow you to evacuated the air from the bottle and I think when my new stuff arrives I will store the Sulfuric in something like that between uses.
You have to be really careful though as the liquid will spill out if you compress them.
think think think .... edit post.
Naah on second thoughts I'll just stick with the pyrex containers that come with a lid and store them like that.
I can then basically use the container as the bath and don't risk spills.
You have to be really careful though as the liquid will spill out if you compress them.
think think think .... edit post.
Naah on second thoughts I'll just stick with the pyrex containers that come with a lid and store them like that.
I can then basically use the container as the bath and don't risk spills.
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Ok that worked.
The basket is still intact and the gold is gone off the bits.
With the basket the only use watching the watts really ended up begin was
to reflect how aggressive the reaction was.
Keeping it around 6 kept the temperature nice and low so I didn't have to stop.
Thanks everyone .
Now I have a lot of black sulphuric acid to deal with
The basket is still intact and the gold is gone off the bits.
With the basket the only use watching the watts really ended up begin was
to reflect how aggressive the reaction was.
Keeping it around 6 kept the temperature nice and low so I didn't have to stop.
Thanks everyone .
Now I have a lot of black sulphuric acid to deal with
Martijn
Well-known member
Thats a good problem to have. Let it settle over a week and siphon off the clean acid to reuse.Now I have a lot of black sulphuric acid to deal with
I always boil the black goo with the sulfuric acid left in it with some rinse water to dissolve as much salts in the dilute H2SO4. Then go for AR. you could do a HCl wash first or a nitric bath if silver or Pd is expected.
Once your acid gets more contaminated with base metal salts, it takes a lot longer to strip a batch so it's time to replace the acid.
I save almost all my sulfuric to reuse for other purposes. It's a very usefull acid.
Thanks Martijn that is really helpful.
This process is really fun and fits nicely into the way I do stuff. I'll get better at it as I go.
It would be really cool to know exactly what is going on at different amps, voltages, and concentrations.
I have a theory that a certain temperature, current, in a certain concentration is the key to selectively stripping the metals.
But as usual I'm possibly missing the point.
The higher the ampere's the faster the temperature will rise, also the gold removal will be faster.
You got to find a happy medium so you can complete the tasks at hand.
How much material you will run and watch temperature Martijn mentioned earlier.
You got to find a happy medium so you can complete the tasks at hand.
How much material you will run and watch temperature Martijn mentioned earlier.
Well amps doesn't directly tell you current unless you consider the voltage as well.
5V @ 1 amp = 5 watts
10V @ 1 amp = 10 watts
5V @ 2 amps = 10 watts
This much I do know for sure.
The actual current flowing in the reaction is the watts.
However as much as I can reason here.
The more aggressive the reaction the more other material will be stripped.
So current and temperature will have a role in that level.
This is the rabbit hole I am interested in exploring.
What is the ideal temperature and current to strip only the gold at the optimum speed.
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Well the Amps are the current and vice versa.
But the product of the amps and voltage is the Watts.
What strips the Gold are the PerSulfuric acid generated by what I would guess the voltage.
This is a highly instable compound that are created in a thin later around the electrically charged component.
PerSulfuric acid can dissolve Gold and dislodge it from the component.
As it goes back to Sulfuric it loses this ability and drops the Gold.
My guess is that this layer is a few microns thick, not much more.
Edit for spelling
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this is what I was starting to understand after searching this forum.
Understanding the PerSulfuric formation would better would really help.
This patent (https://patents.google.com/patent/WO2005016511A1/en) suggests the temperature needs to stay below 20C if that is true high current reactions will be less than ideal as the local temperature at the formation site will be raised above that thus other chemicals may be being formed.
I haven't yet read the whole patent. Edit: actually I don't think this is the right patent. but US patent # 2,185,858 suggests staying under 37.8C 100F
Also I am now thinking that if the H2SO5 is formed at the surface (as I read somewhere here) then slowly lowering the material into the liquid would be more efficient.
WTF are you on about WATTS for Gregory
Using just amps to explain current is like using km to describe speed. It only tells half the story.
Yeah you went 100k but how long did it take.
or You traveled for an hour but how far did you go?
I used 2 amps but at what voltage.
Or I used 12 volts but at what amps.
using watts gives useful information that will more clearly reflect to others what is going on.
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Martijn
Well-known member
Don't over do it. You need to understand the basics, and not dive in to deep.
Current means gols is stripped. Current stops: gold is stripped or not in good contact.
You can measure or calculate how much gold is stripped with how many watts, but in yhe end you will have the physical results to see if you calculations were true.
And when you start, the current is maxed out to the limit, but slowly drops. The voltage fluctuates as well during operation.
I leave the cell alone for some time in between checks and shakes.
I never calculated anything beforehand, the proof is in the pudding.
The power consumption will not influence my electrical bill very much.
Mind you, I have not read the patents, but I assume that is to get stable(ish) PerSulfuric acid.
The beauty if the Sulfuric stripping cell is that it creates the PerSulfuric where it is needed and then it reverts back as soon as it leaves this zone, stripping and precipitating at the same time.
By the way I did finally get a battery and measured the sulphuric acid 100ml = 183g so considering the potential errors of cheap scales and old eyes it is in the paddock. So I will keep using the stuff.
The one about the process we use (the second one) was for stripping gold before re-plating (musical instrument refurbishing) suggests 37.7C the other was the more permanent kind.
goldsilverpro shared the patent here https://goldrefiningforum.com/threa...detail-at-the-moment.27219/page-2#post-288533
Yeah temporary is good. It looks like pure stuff is a tad explosive.
Haha over thinking is what I do best.
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Oh yeah and watts are whats happening in the moment. It just relates voltage to amps ie the current current
That's not watt hours which is what watts are used over a period of time.
Try and say that 5 times fast.
Edit 2:
chatGPT did a better job of explaining what I'm trying to say here
- Amps represent the flow of charge.
- Watts represent the energy being used or transferred by that flow of charge, depending on the voltage
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Martijn
Well-known member
Consider this: When the cell starts, voltage is extremely low as there is a lot of golden surface for electrons to escape in the solution and oxidize gold in a zone as described.
I can imagine and am pretty sure that at this time the most gold is stripped. As lesser surface remains available after some time, the voltage rizes. With the current staying maxed out at it's setting.
I find it hard to believe that when most gold is stripped which makes the voltage rize, also more gold per watt will be stripped.
Current still running at max setting.
According to your theory: the power consumption is greater after most of the easy to get gold is stripped, but i'm pretty sure at the beginning the most gold per Amp is stripped.
The voltage rizes once it is harder to get the current off the stripped parts.
This would mean less gold per Amp per Second.
That is the opposite of what you're trying to prove or figure out with watts.
It's the high resistance of copper to concentated H2SO4 making the voltage rise. Until there is no more current.
My 2 cents.
