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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.
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.
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.
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!
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−
4(aq)
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
Also, current limiting is no real problem , just try to keep the voltage below 5v, and let the current do whatever if you are electrolysing less than 200ml water, otherwise try to keep the current under 2A/100ml all asuming youve dissolved as much copper sulfate as possible . no fancy equiptment needed for that though, just move your anode and cathode further apart to lower the current!
the requirements change with the situation. most often only as much current is drawn that is needed, not as much as the power supply can supply. for example. my powersupply can deliver 28A, but the load is only taking 500mA.
as a general rule. if its bubbling violently , reduce current or space out the electrodes. no bubbling should be occuring at the cathode. and very little should be occuring at the anode. If you can manage it, use 5v and sace the electrodes really far apart so that the cathode is not bubbling at all. the cell resistance will be cutting the voltage down to about 4v anyway.
The cathode bubbling is fine though in the first 6 hours or so. after that, try and prevent it, or risk loosing acid. which you can tell by the stench of burning rubber (sulfur dioxide/trioxide).
Also yes, both electrodes must be lead when making the lead dioxide coating.
when you are using your lead dioxide coated electrode to electrolyze copper sulfate solution, you should use the lead dioxide coated cathode, as an anode, and copper wire as the cathode.
one last tip. cover up the container you plan to use!
I just finished my electrolysis, and i have sulfuric acid spattered everywhere, and sulfuric acid doesnt just dry up like water does. it becomes stronger and stronger, as water evapourates, and then once it hits about 50%, it sucks water from the air (being hygroscopic), and stays that way for a long time! it evaporates at the same rate as vegetable oil, so dont expect it to go anywhere fast!
also protect your electrical connections, acid is corrosive.....duh!
fear not, in a few days you'll have an example to copy off!
I dont think the MMO will hold out well against the acid, though platinum will work. and so long as you dont exceed 3v, the platinum will last forever.
you know how i made my lead dioxide coated anode?
I got a carbon rod and electrolysed copper sulfate into a 3% solution of sulfuric acid. then i filtered it, and electrolysed the lead and BAM done.
The reason i use lead with an oxidized layer of lead dioxide is because i dont want to get platinum, if you have platinum, then you dont really need to worry about using lead!
But if you do want to use lead as an anode, you can tell when all the lead dioxide that can form, has formed, when it turns completely black. having said that, try to keep your amperage very low when making the lead dioxide layer because it is alpha, the weak form of lead dioxide (not like beta, which is what proper lead dioxide anodes are made of). once an hour slightly wipe of the lead dioxide that forms, and eventually you get lead dioxide pores forming which will hold it better.
To concentrate sulfuric acid, just boil it.
it boils at 300 celcius,
i wouldnt risk distilling it because allot would decompose at that heat.
water boils at 100c, sulfuric acid boils at 300.
use glass, on an electric stove and youll be fine.
and yes, this is good. more bubbling can be expected as the reaction goes on.
be sure though to cover up the container the reaction is going on in, since you get acid mist setting everywhere around, even though you cant see it, its happening.
Aluminium undergoes a displacement reaction with copper that replace aluminium metal with copper metal, and you end up with copper coated aluminium and aluminium sulfate. later as the acid strengthns, it will eat away the aluminium.
DO NOT USE ALUMINIUM IN THAT CELL! THE COPPER SULFATE WILL DISPLACE THE ALUMINIUM FORMING ALUMINIUM SULFATE AND PLATING THE ALUMINIUM IN COPPER, AND ALSO IT WILL REACT WITH THE SULFURIC ACID AS IT FORMS.
it might look like a normal copper plating reaction, its actually not!
copper sulfate reacts with all more reactive metals (lead, iron, zinc, magnesium, aluminium, potassium, sodium ect), in a displacement reaction, which exchanges the copper in copper sulfate, with the reactive metal, which means you get the surface coated in copper, and a reactive metal in solution will be likely to ruin the anode, as well as affecting the cell current load capacity.
use copper wire as the cathode, or anything less reactive that iron, excluding all forms of steel!
nothing but copper , lead or graphite should be left in the cell while it is off.
take the aluminium out immediately, also, word of warning. this will happen eventually, the solution will bubble a
and how could you do this to get magnesium out of magnesium sulphate??
the electrode worked fine as a cathode for several days of non stop electrolysis before the inevitable happened, the lead dioxide coating was reduced into lead tetroxide (Pb2O3) and no longer worked, until i cleaned it with steel wool and electrolysed it again!
all in all, lead dioxide works, and soon ill have the video to prove it.
best of all, there is almost no corrosion or polution at all, which has yet to be identified. a very small amount of a heavy insoluable sludge wa sleft at the bottom of the electrolysis, which i may add went clear overnight. it is either calcium sulfate, which is understandable since im using a copper sulfate i bought for $25 as horse food, i didnt expect ti to be clear. or it could have been lead sulfate, though it may have only been converted lead sulfate from the exess alpha lead dioxide in the rod.
my point is, lead dioxide works, but it stain the lead dioxide layer (which is ok since its only really less than a millimeter thick, so only use a cathode plated one , not an expensive solid lead dioxide electrode!
wrong because my electrodes did somewhat dissolve, though i was making sodium chlorate, using the power supply for my lcd tv which was 12v 5.5a. it filled y room up with a chlorine smell which was annoying and my mum thought something in my room must have been on fire.
anyways i was also right because i tested this twice (two simultaneously off the same supply)
only they werent cleaned, and what happened was that the water was full of black gunk, though i had previously given it a good wiipeing.
so i think its better applying some heat to the carb0on rods to remove the wax that is inside it
I think the best way to settle this is with an experiment, treat the carbon electrode the way you described and run the electrolysis and observe the results.
Lots of us have more scientific interest than we have money. You help us get a handle on basic chemistry and do it well within a po' boys price range.