Sciencemadness Discussion Board - Silver anode for making sulfuric acid?

Hello,

I've recently started getting back into amateur chemistry, and I need some sulfuric acid. Since it's not obtainable anywhere near where I live or even online, I figured I'm going to have to make some myself. I'm looking at the electrolysis method where a saturated solution of copper sulfate is electrolysed with a copper cathode and an inert anode. The acid can then be filtered out to separate the copper metal, and then boiled to obtain >50 % concentration.

Problem is, you can't use ANY metal/material for the anode. Platnium, lead dioxide and carbon are known to work (though the carbon will likely erode into the solution). I know that gold is supposed to work as well, and if all else fails I might just use a gold plated wibut I'm here to ask if anybody has tried using a silver anode? Silver won't react with the sulfuric acid. Perhaps one can minimize silver erosion (provided it does work) by limiting the current and/or voltage?

Any ideas or comments would be helpful.

Regards,
- mateo

This is my method of getting sulfuric acid.
Look at Nurdrages video on this.
https://www.youtube.com/watch?v=5dUSF9Gl0xE

You put a copper electrode on the negative terminal and connect a carbon electrode obtained from some batteries on the positive terminal.

Electrolyse the solution and leave it for 3 or so hours it will be all black. Filter this and you will have a clear solution of Sulfuric acid.

My only problem with this is that when I go to concentrate it inside in my garage I shit myself thinking of those acid fumes.

mateo - 3-1-2013 at 16:12

I've seen the video and I know how it is done, however I specifically want to avoid using a carbon electrode. I've done this before and there's much hassle in separating the carbon particles from the acid. Using a high-quality inert anode would be more suitable, and therefore I am asking to see if anyone has used silver for the anode, as it is cheap and readily available.

Manifest - 3-1-2013 at 16:15

I've seen the video and I know how it is done, however I specifically want to avoid using a carbon electrode. I've done this before and there's much hassle in separating the carbon particles from the acid. Using a high-quality inert anode would be more suitable, and therefore I am asking to see if anyone has used silver for the anode, as it is cheap and readily available.

Yes. That would work however it would be more expensive and I don't see you getting a bunch of silver easily.
Of course the silver would corrode aswell but slowly.

What's so difficult about seperating them? You just filter the solution. It's worth going an extra step and filtering rather than using expensive silver.

[Edited on 4-1-2013 by Manifest]

elementcollector1 - 3-1-2013 at 16:18

I do in fact have a one-troy-oz. bar of silver, .999 fine. Could this method really work? It's got a fairly high surface area, and I can match that with a copper PCB to make current flow easier... plus it would be oh-so-much better than a platinum one...
Is silver really resistant to sulfuric acid? Or would it form a precipitate of silver sulfate, analogous to lead?

Manifest - 3-1-2013 at 16:22

I do in fact have a one-troy-oz. bar of silver, .999 fine. Could this method really work? It's got a fairly high surface area, and I can match that with a copper PCB to make current flow easier... plus it would be oh-so-much better than a platinum one...
Is silver really resistant to sulfuric acid? Or would it form a precipitate of silver sulfate, analogous to lead?

No it would not form silver sulfate since copper is more reactive than silver.
It would still corrode and stay in solution though, but not react.

However silver reacts with hot concentrated sulfuric acid.
Using this method, dilute acid is formed.

[Edited on 4-1-2013 by Manifest]

mateo - 3-1-2013 at 16:24

That is what I was thinking. A one ounce silver bar isn't expensive and it's really easy to come by. I'm thinking of using one for an anode.

For what I know, silver by itself does not react with sulfuric acid, nor does it react with hydrochloric acid. Silver at standard conditions will only react with nitric acid, which is irrelevant in this case anyway. However, I'm not sure of what will happen with the silver under the combined influence of the acid AND the electric current...

[Edited on 4-1-2013 by mateo]

Manifest - 3-1-2013 at 16:29

I'm not sure of what will happen with the silver under the combined influence of the acid AND the electric current...

Like I said above. It will corrode slowly but not react at all.
I'm not sure how much it will corrode.

Test it and see.

mateo - 3-1-2013 at 16:35

I'm not sure of what will happen with the silver under the combined influence of the acid AND the electric current...

Like I said above. It will corrode slowly but not react at all.
I'm not sure how much it will corrode.

Test it and see.

Probably, yes. I'm try with a gold-plated anode as well and see how well that works. I will update you all on this topic once I've had time to try out some electrodes.

My approach for now will be using a silver bar for the anode, and reducing erosion of the bar by electrolysing with the lowest possible current.

D-glucose - 3-1-2013 at 16:36

I've actually tried this, and the results weren't great as i didn't let it finish. But it worked, the solution was clearing and the silver anode was corroding with black silver oxide, but it could be scraped off. The copper was depositing quite well on the copper cathode. I won't try this again because I'll find sulphuric acid elsewhere. BTW i was using a 9 volt battery as my power supply

elementcollector1 - 3-1-2013 at 16:36

I'm not sure of what will happen with the silver under the combined influence of the acid AND the electric current...

Like I said above. It will corrode slowly but not react at all.
I'm not sure how much it will corrode.

Test it and see.

Current basically equates to electrolysis speed...
Grab some popcorn and settle down.

Manifest - 3-1-2013 at 16:38

I'm not sure of what will happen with the silver under the combined influence of the acid AND the electric current...

Like I said above. It will corrode slowly but not react at all.
I'm not sure how much it will corrode.

Test it and see.

I had previously tried this with a gold plated earring.
It obviously wasn't plated very well as it corroded in the inside.

mateo - 3-1-2013 at 16:39

I'm not sure of what will happen with the silver under the combined influence of the acid AND the electric current...

Like I said above. It will corrode slowly but not react at all.
I'm not sure how much it will corrode.

Test it and see.

Current basically equates to electrolysis speed...
Grab some popcorn and settle down.

Yeah, that's the con of it. Limiting the current probably makes the anode erode les, but then it'll take much more time. But hey, the good things in life are the things worth waiting for, they say...

virgilius1979 - 4-1-2013 at 07:51

Silver is not that cheap to loose it this way. Better react it with HNO3.
I have produced some H2SO4 with PbO2 anode and it was a pale yellow solution (about 15% concentration). After boiling, I got about 250ml concentrated (90%) H2SO4 (from 1kg of CuSO4.5H2O), but it was a bit darker. The impurities could come from the CuSO4.5H2O or from the PbO2 anode itself; so it looks similar to drain opener. I'm going to distillate it to concentrate and purify.
The PbO2 anode I have it from China (I bought 15 of them

) and I want to try them for perchlorates too. From the thread dedicated to making such an anode I deduced it's not worth the effort. Platinum is too expensive (by the way, chinese were making custom electrodes, coated with many types of metals, I wanted to buy a Pt one, but at $300 a piece I decided it's too much).

Manifest - 4-1-2013 at 14:00

Jesus, am I missing something here?
What is so hard about filtering the solution after using a carbon electrode.

The filter paper doesn't clog up or nothing.

elementcollector1 - 4-1-2013 at 15:23

Carbon tends to dissolve somehow in H2SO4...

cyanureeves - 4-1-2013 at 15:26

a silver anode hooked to a 9volt battery in hydrochloric acid with dissolve into milk and sand within seconds. i have done this when i was trying to make silver chloride half a troy ounce and a couiple of years ago.used battery acid from a junk yard is the way to go then boiling it down in a backyard about three houses down from yours because it will fume like mad.some people probably aint back from the holidays yet.

Manifest - 4-1-2013 at 15:30

Carbon tends to dissolve somehow in H2SO4...

No, it doesn't dissolve as such. Carbon doesn't react with Sulfuric acid.

It just sits in the solution, you can just filter it out.

mateo - 5-1-2013 at 04:50

Carbon tends to dissolve somehow in H2SO4...

No, it doesn't dissolve as such. Carbon doesn't react with Sulfuric acid.

It just sits in the solution, you can just filter it out.

You are correct, however usually I get these tiny nanoparticles of coal that gives the solution a dull color. These are very hard for me to remove from the acid.

plante1999 - 5-1-2013 at 05:03

When the acid is boiling hot, add 1 to 3 ml of 30% hydrogen peroxide. It used to do the trick when I was making my acid myself from copper sulfate. Now I have better processes... The acid will become water clear in a few seconds after the peroxide addition.

[Edited on 5-1-2013 by plante1999]

mateo - 5-1-2013 at 09:30

Quote: Originally posted by plante1999

When the acid is boiling hot, add 1 to 3 ml of 30% hydrogen peroxide. It used to do the trick when I was making my acid myself from copper sulfate. Now I have better processes... The acid will become water clear in a few seconds after the peroxide addition.

[Edited on 5-1-2013 by plante1999]

You are welcome to share any processes you consider superior to the electrolysis of copper sulfate. Thanks for the tip, by the way!

plante1999 - 5-1-2013 at 09:53