Make Sulfuric Acid by Copper Sulfate Electrolysis





Introduction: Make Sulfuric Acid by Copper Sulfate Electrolysis

How to make sulfuric acid by electrolysis of copper using an inert anode. Copper sulfate is very easy to obtain in large quantities at gardening and hardware stores and provides a convenient route to sulfuric acid if the appropriate anode can be obtained.


Warning: This should be done in a well-ventilated area as hydrogen gas build up is explosive. Copper sulfate is toxic and sulfuric acid is corrosive, wear gloves when handling them.


The procedure is extremely simple, just get a copper sulfate solution, insert two electrodes and run a current through them. The anode, the positive electrode, must be an inert material that can withstand extremely oxidizing conditions. Very few materials meet this condition, platinum, lead dioxide, and carbon among them. Other metals, even stainless steel, are quickly destroyed under these conditions and cannot be used. The cathode, the negative electrode, is exposed to reducing conditions so the metal requirements are must less stringent. Copper is the best choice here since it has high electrical conductivity.


When applying power, the current should be adjusted so that corrosion at the positive terminal and bubbling at the negative terminal are both minimized. The bubbling at the negative terminal is hydrogen production and that’s wasted energy that should have gone into reducing the copper sulfate.


After the solution has gone clear, filter off the particles and the clear filtrate is dilute sulfuric acid that can be boiled down to obtain concentrated sulfuric acid. It will have trace amounts of metals but for most purposes this is not an issue.



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    so the cathode and anode can be used what types of material when the electrolyte is copper sulfate ?

    once the dil sulfuric acid forms .... shouldn't i be able to dissolve more copper sulfate for further electrolysis??

    As benzeen, I would like to know if gold anodes would work for this. Gold is more electronegative than platinum. That probably means that it would be more difficult to oxidize than platinum. Am I right?

    but it will still dissolve. keep your voltage below 5v to minimise electrode erosion.

    all gold oxides will decompose into gold and oxygen below 160 degrees celcius. gold sulfate which somehow magically forms is too unstable and converts to gold again. but thats just gold troxide, the most stable. its likely it will form lesser oxides which decompose at lower tempuratures.

    If you have a butane torch (purchaseable on ebay for under $3), and a mould, and a source of clean copper sulfate, as well as a fiberglass or cellulose sock to put over your gold rod, you can reuse your gold over and over again!

    asuming though that no oxide drops off, going over the rod with a blowtorch or even a regular cigarette lighter, should destroy all oxide and hopefully it will stick back onto the rod!
    i personally dont know how gold will work, so try it out for yourself, i can guarantee that if you run it at 3v, your results will always be good!

    Lead on the other hand erodes about as fast. best of all the exact same proccess which erodes the lead making it brittle, converts it into lead dioxide which is more inert than platinum (if completely beta), but since it is about 50:50 alpha and beta, the alpha will slowly flake off with the bubbles. over time, but thats about it, and that will take ages!

    When i say inert, i mean inert under these circumstances. unless voltage goes too high, say over 5v, or no current passes through the anode, then it will become lead sulfate.

    I am currently proving my point by using a preused (in making copper sulfate) lead rod to electrolyze some copper sulfate completely into sulfuric acid and copper.

    Hell noo! Are you sure of that? Lead is incredibly cheap! I'll try that later. Even though it is very cheap, it is quite hard to get. At least where I live. But i'll give it a shot. I'm actually waiting for my 5v 50a psu to arrive. Would it work? The voltage is quite low, but the current is pretty high. I've heard of someone saying that lead dioxide are not very good as anodes...At least for chlorate synthesis. Just more one thing: Can I use another electrolyte other than sulfuric acid? That stuff is very hard to get here. We need tons of paper for getting our hands on that. Thank you very much.

    what i did was get some copper sulfate and electrolyze it like nurdrage did, filter it, then it was suitable to use. its only a catalyst, so only very little is needed, also your dead wrong, people i know go through allot of trouble just to get lead dioxide anodes specifically for making chlorate and perchlorate, i dont know where you heard otherwise, but it was wrong!

    Keep in mind though, the lead dioxide coated anode is only been displaced by the lead dioxide, not fully converted, in the same way copper sulfate will do to iron, it only has a surface coating, using it for anything other than electrolyzing copper or magnesium sulfate, will just not work.

    also another electrolyte you can use is nitric acid, but thats it.
    You dont need much sulfuric acid. just a 50ml solution of acid that is about as sour as lemon juice will do it. siphon a little bit from a car battery and your good to go, you can return the acid later.

    also, about that powersupply, try and use a regulator to drop the voltage to 3-4v because these kind of reactions use very little current. more amps wont to skwat!
    Ive been running mine overnight and the amperage hasnt exceeded 1A and it has a 28A potential.

    Will the process get screwed if I use that psu? I'll buy a 3v 1a. I'm not sure of what I'm thinking is correct, but that is okay....Erm....The idea of making lead dioxide coated anodes from lead is just oxidizing it using an electrolysis that generate oxygen gas on the anode, right? There is a large number of electrolytes that, if electrolysed, will release oxygen at the anode. Electrolysis of aqueos sodium bicarbonate will release oxygen at the anode. Can I use that? Electrolysing a solution of copper sulfate will actually release oxygen at the catode as well...That would probably be able to oxidize lead to lead dioxide, right? Would it work?

    since youll never get a current draw over 1A/100ml, a good resistor will work fine to cut down the voltage.

    What i find happens, is that if there is too much bubbling at the cathode, like nurdrage says, you will loose sulfate ions, which generally form sulfur trioxide!.

    Many a time i have detected sulfur like smells coming off my electrolysis , at 5V!

    Also, the answer is no, no other electrolytes short of a few very strong acids harder to get than sulfuric acid.
    it isnt the fact there is oxygen bubbling out. This type of reaction is fairly unique between lead and sulfuric acid, even more so because its the cathode which is going to oxidize, which eventually does though, into lead tetroxide, in carbatteries and such.
    Another thing, dont touch the lead dioxide coating, its alpha and weak, so much bubbling such as with 5v, which rip off the Lead dioxide.

    at 5v i calculated, i lost 30% of the sulfuric acid that there should have been there! at 3.5v i lost almost none!
    just get a 3.5v regulator or proper resistor, dont pass up on the PSU.
    regulator chips only cost $2-3 and thats in packs of 10!

    By the way, the lead dioxide coating, i find i have to reapply once ever day or two, which is ok since it only takes about 5 minutes in a solution of sulfuric acid made from 50ml saturated copper sulfate!
    On 3v, i havent once had to reapply, which is good since i dont have any acid right now!

    how can lead get oxidize at the cathode? Is there any way to avoid lead dioxide oxidize to lead tetroxide? using 3v 1a would reduce its erosion? how would that work? i am really trying to understand the process, but it sounds really confusing....

    I wouldnt bother learning how it works, i didnt.

    Also, lead tetroxide, is Pb2O3, which is NOT a higher state of oxidization, despite having more oxygen.
    PbO2 --- 2 oxygen per Lead
    Pb2O3 ---1.5oxygen per lead

    PbO2 is the higher oxide, and in a cell will not decompose into teroxide, despite what you may see occur when you run the electrolysis. Lead on its own will convert to teroxide, any exposed lead, for obvious reasons will form orange-brown teroxide.

    What happens in a car battery, is, when the battery becomes discharged, the acid , with the aid of the electron flow, can react with the lead, now, both electrodes become lead sulfate coated.
    This will happen automatically even if there is no lead sulfate to begin with, it is really just skipped when there is no sulfate. anyway, imagin it does form sulfate,
    here is the reaction that occures.
    Anode Reaction: PbSO4(s) + H+(aq) + 2e− → Pb(s) + HSO−
    Cathode Reaction: PbSO4(s) + 2H2O(l) → PbO2(s) + HSO−
    4(aq) + 3H+(aq) + 2e−

    In an ideal reaction, no oxygen or hydrogen will escape , which is the case with my current electrolysis, though a small bit of hydrogen is escaping as the copper sulfate levels drop, and it burns my lungs every time i breath in without the fan on (breathing in hydrogen gives a false burning feeling in the lungs much like chlorine, or hydrochloric acid, but not in the nose).

    the reaction that goes on is very unique in the case of sulfuric acid and lead .
    Its best you not worry about it.

    both the anode and cathode are reacting with the acid, the only difference is that the cathode is using oxygen from the water to complete the sulfate - ions, rather than the two which made up the sulfate to begin with