NurdRage - 2009-12-26
How to make sulfuric acid by electrolysis of copper sulfate 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. Keep in mind that it will take a long time for the solution to go clear. if after filtering it's still blue, you'll need to keep electrolyzing it. You'll need over 60 amp hours of current per mole of copper sulfate, and usually more since the process is not very efficient.
Really nice! I tried this one and it worked well - then I simply used a ceramic pot on the stove to boil away most of the water. The problem is as described to find a good electrode for the anode - even carbon rods rapidly get pulverized into particles so fine it's hard to filter out (perhaps easier if using something better than coffee filters). As the water is boiled off - even the dirt gets concentrated and the finished acid will end up rather dirty.
Although the corrosion of the anode does not seem to be affected very much by the current. Of course - for example twice the current cause it to erode away twice as fast. But the conversion from copper sulfate to sulfuric acid also goes at twice the speed (so electrode consumption is not higher). It does however, corrode faster and faster as the process go on - the acid seems to have worse effect on a carbon electrode, than the sulphate. I did put a coffee filter over the electrode during the process - that collected most of the carbon particles and maked the sulotion stay clear enough to watch the process going without the need to stop and filter out carbon residue, all the time.
Same thing seems to apply to the hydrogen production. The amount of energy wasted on hydrogen production is determined by the ratio between copper sulphate left and already reacted acid. There is no hydrogen being produced at start - then it start's bubbling more and more at the cathode as the reaction goes on.
Only thing that happens if you turn down the current once the bubbles start coming is that you slow down the reaction so much that you don't notice the bubbles any more (but the same amount of hydrogen is still produced - just at a slower rate). After a while, it starts bubbling again - and you turn down the current even more. That happened to mee. I was starting at about 5 amps, then gradually dropped down to 1 amp during 12 hours. After that - the sulotion was still slightly blue and some bubbles where coming from the cathode anyway.
Then I turned the current up to about 10 Amps, just to see what happens and there was a lot hydrogen fizzing from the anode, but it went clear in a little over 1 hour - and the electrode didnt corrode faster than it did with 2 amps during 5 hours.
According to my other experiences with electrolyzis as well (I have made hydrogen/oxygen production and iron oxide production) - the speed of the process is directly set by the current. Current density doesn't effect the speed of the reaction - but it do affect the efficiancy and shud be kept as low as possible. Bigger electrode surface area allow for that, and put them closer together decreases resistance. The thing is that the voltage that needs to be applied to get the desired current shud be as low as possible. Every volt above the minimum needed to keep reaction going is just a waste of energy. It doesn't speed up the process - that energy is just turned to heat.
What an amazing video. Can hardly wait to try this process. Fantastic job, keep up the great work!
Great experiment! Do you know if there is any method to do the same with nitrate salts and nitric acid? If yes, could you make a video showing it? Thanks!
Somehow you've made science so much more interesting. and simple. Thanks!
@nurdrage I covered my graphite electrode with filter paper (2 layers, wrapped around) and prevented the C particles contaminating the product. Thanks for this video; I've now reclaimed my excess CuSO4 and have smelted the Cu :)
As always, many thanks for pointing me in the right direction. I hope I never tire of learning new things.
The old ways involved high temperatures. While not too hard most hobbyists prefer not to deal with them. Check out "lead chamber process" and "contact process" for sulfuric acid production.
Hey, been enjoying your videos for a week now, just wondering if a magnesium electrode could be used to perform the same reaction but from magnesium sulphate? It is slightly cheaper to purchase, but you say other electrodes work terribly, did you just mean for copper sulphate solution specifically, or this reaction in general?
Love it. It's great to be able to make these acids without having to buy them. About a year ago I made copper sulfate from Magnesium Sulfate (Epson salts) so it would be nice to say that I could get H2SO4 from something you can get down the local grocery store.
Although impractical, would it be possible to use MgSO4 in some sort of a biphasic apparatus with the cathode in a layer of CCl3 or a mixture of ethers to "trap" the reactive Mg(s) at the cathode and away from the aqueous phase while still allowing some salts to pass such that the electrolytic aspect of the reaction would still work?
Hi, I see your videos for every experiment I attempt to do. Where did you find the platinum electrode? can I find it in a local store or do I have to order it online? THNX
There are two competing reactions at the cathode: reduction of metal ions into the metallic form, and the reduction of water. Electrolysis reactions will prefer the reaction that requires the least amount of energy. Thus, with magnesium requiring 2.38 Volts, yet water only 0.82 Volts, it is clear that you would not plate out any magnesium. But let's assume that, for some reason, some magnesium actually plated out. Magnesium reacts vigorously with acids back to ionic form, so MgSO4 wouldn't work
I wish I had the money and time to get into stuff like this. This is just awesome. Good video OP.
I got my anode in today, I tried the carbon anode a few weeks ago and it worked.
Got it wired to an atx power supply's 5 volt rail rated for 22 amps and its working nicely.
This is a really good method to making Sulfuric acid and copper metal but I'm still wondering from where you got the second electrode? P.S. Nice video though, keep up the good work. I'm looking forward to watching more of your videos.
What was your source and cost for your Pt coated Ti electrode? I'm assuming its a MMO electrode, but most suppliers I've found only supply the raw Ti mesh with or without coating, not affixed to any sort of support.
I've noticed many of these acid creation processes require another acid in turn (basically shuffling between nitric, sulfuric and hydrochloric), or like this one use electrolysis. I've always been curious though how the aspiring 18th/19th century chemists would "start from scratch" if you will without the benefit of electrolysis or another starting acid. This might be a rather basic *rimshot* chemistry demonstration, but I'd enjoy a video showing such a process under those limited conditions.
I've found that the carbon in pencil graphite works fairly well. It's not the best though because the clay used to form the "leads" raises the resistance a bit. This clay might help to make the electrode last a little longer though, I don't know.
Excellent video. It would be interesting if you could do a video on sodium hypochloride generation and what are the best electrodes to use...
As for platinum plated titanium electrode being the most efficient, how about using a MMO electrode instead? Would it also erode fast?
i had a question for you, Nurdrage. i would first like to say i absolutely love your videos. I would like to know, after you shut off the reaction and filter the solution, wouldn't the sulfuric acid react with the filter paper? or is it not that concentrated yet? this question is open to anyone really. thanks a lot
Hi excellent video, by electrochemical synthesis is my favorite because it allows many substances to easily and inexpensively, congratulations
Nice video. What is the maximum current that titanium electrode can support?
Excellent reversal of the previously shown video of creating copper sulphate using electro-chemistry. Thanks as always and Merry Xmas Nurdrage!
interesting! 5 stars! i did not know that one could make H2SO4 like that. i do have one question about the platinum electrode; is it possible to reclaim or extract the platinum from scrap catalytic convertors and somehow get pure or nearly pure platinum from it
gardening and hardware stores have it, some will sell it by the bag-load (>10kg) its used to kill roots in drain pipes, and kill algae in ponds. also used as a fungicide.
Do you think the same would be possible with epsom salt(mg2so4•7h2o)?
It would be much cheaper than cuso4
i am currently trying it with the carbon rods he describes. so far it is working very well at a current of: 3v, 300milli amps. it is also eroding quite slowly too.
i tried doing this one with a tungsten electrode and it worked really well.you can buy a rod online but i made mine from a bunch of old lightbolb wires
I had a question about electroplating, does the amount of voltage affect the efficiency of electroplating?
Ok. questions. Could you use a gold electrode instead of platnium? Is it possible to make nitric acid using sulphiric acid and copper nitrate? And if so, is it possible, with the addition of electricity to create a cycle between nitric acid, sulphiric acid, and the element copper that never ends?
I found that a lead metal strip seems to work pretty well for an anode. The surface just oxidizes to PbO2 and keeps liberating oxygen without corrosion. A cheap alternative if you can't get platinum or don't want to take apart a battery.
Wouldn't it be a better Idea to add the dioxide layer in a separate solution so there's no Lead contaminants in your Acid? I'm not a chemist so correct me if I'm wrong, but it seems logical.
I also tried that and it does work but occasionally it will have PbO2 flaking off and some lead sulfate contamination. Good thing it's just used for making nitric acid.
I made my own lead dioxide anode and it works great
You bring up a valid point, I'm trusting the supplier to give me a platinum electrode as described but i don't have an independent test to confirm that is indeed what i received. I'll have to look into this further.
I've tried this with a lead dioxide anode and works great.
Hey I'm fairly new to electro chemistry and really want to make sulfuric acid this way also I was just wondering can I use a piece of copper wire as an electrode or what can be used as copper electrode? would it still be possible to get excess copper in the first method? If anyone can help with these questions that would be greatly appreciated thanks.
This gave me an idea to use gypsum (reclaimed drywall), CaSO4, to make CuSO4, then make H2SO4 using copper as an intermediary. It may be too slow, but hopefully the low-solubility Ca(2+) would go into solution as needed.
First, in the electrolysis cell, anodize the copper:
CaSO4 + Cu + 2 H2O --> CuSO4 + Ca(OH)2 + H2
Then I suppose heat it to 100 °C to precipitate the Ca(OH)2 and filter it out (so that it doesn't react later with the H2SO4 to make gypsum).
Then plate-out the copper:
CuSO4 + H2O --> H2SO4 + Cu + 1/2 O2
The above 2 reactions overall:
2 H2O --> 4 H(+) + 2 OH(-)
Ca(2+)SO4(2-) + 4 H(+) + 2 OH(-) --> Ca(OH)2 + H2(2+)SO4(2-)
overall: CaSO4 + 3 H2O --> H2SO4 + Ca(OH)2 + H2 + 1/2 O2
Or just use a galvanic cell with magnesium sulfate and an appropriate separator
https://postimg.cc/gX7QXTRJ
Managed to make 30% sulfuric acid from this method.
It took a long time but I got it. I used a lead fishing weight as an anode and it worked great. The solution has a pH of 1 (now i have to boil off the water because it's very diluted) For current regulation i used a nichrome wire in series with the electrodes and it worked great too (it's not the most power efficient solution but it's simpler than building a regulated current source :P)
hey, these videos are exactly why ive been subscribed to your Chanel. It seems like making any strong acid takes another, hard to obtain strong acid... This really is a useful video. I dont know how i would find/make a platinum electrode. Oh well, keep up the awesome videos. You have like the only cool chemistry Chanel on youtube.
@yodarox89 Thanks, its just that he made it sound like carbon really wasn't good, and that its highly recommended that a different material be used like the platinum, so I'll definitely give the carbon a try. Also, what exactly is an inert metal? and what determines the cathode material? sorry if I'm asking a lot of questions, I'm new to electrochemistry like this, but i enjoy learning it.
Dr. Lithium (heh), I have a question. Will the amount of CuSO4 in the solution affect: A) The time it takes to convert the solution into H2SO4 OR B) The purity of the acid Thanks!
This is a great video of what not to do when plating lol very informative! Thankyou for making it!
If anyone wonders I just calculated that 750 grams of cupper sulfate pentahydrate should give a theoretical yeld of 161 ml of concentrated sulfuric acid. Just saying...
Do i can use gold electrode and titanium electrode ?
Could you end up with 99% acid if you use anhydrous copper sulphate? It seems that about 1/3rd of the weight of copper sulphate pentahydrate is water and must be almost impossible to achieve a concentrated acid from electrolysis alone. I might actually try it with anhydrous and just keep adding it until no more dissolves and see how much I get.
@mrdojob Whether you dissolved anhydrous copper (II) sulphate or copper (II) sulphate pentahydrate into water, the copper (II) sulphate will dissociate into the solution. Sadly, it won't make a much of a difference if you dissolved anhydrous copper (II) sulphate instead of copper (II) sulphate pentahydrate. You eventually end up with Cu(+2) and SO4(-2) ions in the water.
So basicly one would need about 3 liters of water to dissolve 1000grams of CuSO4 at roomtemp. to yield about 210ml of conc. H2SO4. For this you will need some serious equipment, like a very big reaction vessel with a fitting lid, a big enough PSU and some very big anodes. PbO2 will be very suitable for this.
It is about the same setup as one would need for making (per)chlorates, like in the video’s from ytmachx.
https://youtu.be/O1aWzrRBMjk
Costs for acquiring these materials range between $500 - $2000, depending on the size and source, not mentioning the energy or time thats needed for this. I’ve seen some 10L RB Vessels on Chinese webshops for about $350,-.
https://nl.aliexpress.com/item/4000005330723.html?spm=a2g0o.productlist.0.0.30ee7b3fL8y5h2&algo_pvid=b83e34ff-596c-45e9-805e-55f61d6d4b6e&algo_expid=b83e34ff-596c-45e9-805e-55f61d6d4b6e-7&btsid=0b0a0ac215829078257557356ead54&ws_ab_test=searchweb0_0,searchweb201602_,searchweb201603_
Copper crystal growers report a very long time (several weeks / months) for growing very nice crystals. However they are using mili-amps to go slow. For acid production, one could easily up the ante and go as far the electrodes can handle and downplay the time needed to maybe several days of electrolysis.
The upside is that one could grow very impressive copper crystals, which could be sold and / or melted down to earn a bit back on your initial investment.
CuSO4.H2O consist about 25,5% by weight of copper, that is about 6,25kgs of copper per one 25kgs bag. Right now about $4,- / kg.
Where i live (The Netherlands) they will ban the sell of +15% H2SO4 to the general public within a year from now.
I do see this as a very viable way to obtain H2SO4 although somewhat expensive. One 25kg bag of CuSO4 will cost me about $70.- that would yield about 5 liters of conc. H2SO4.
Agreed. For every pound of copper sulfate I get 100 ml of concentrated H2SO4. Lead dioxide anodes are cheap, easy to make and work efficiently.
I suggest that it will be really cool if you will make the video about obtaining a pure crystals of peroxomonosulfuric acid!I have made some by myself and should say that it is more useful than any other chemical in the world(except nitric acid and sodium hydroxide) at least for dealing with e-waste!And it is the perfect oxidizer for making advanced propellents!
I saw that aluminum resists sulfuric acid in another one of your videos. Would using electricity break the resistance?
@coplants you can go further, but hydrogen production increases, so you need to perform this in a well-ventilated area to prevent hydrogen build-up. Other wise use a sealed cell that you can direct the hydrogen and oxygen gases outside and away from your work-area.
Dear NurdRage, I have greatly benifited and been entertained from your videos. i have a question about the copper sulfate solution. you say the stronger the solution the better. does this mean that a saturate solution will work? or at some point does the solution become too strong? Think you, Amsoil5
This has to be very fast. I couldn't believe how quick you were de-ionizing the copper.
i used a 1-molar solution of CuSO4 and want to share the information, that up to a certain concentration of acid (about 5%), the Copper in solution reacts back to Copper Sulfate. I would recommend using a lower molarity
@m8teseven Same thing. But i got around that problem by lowering the voltage. For example at the beginning i had at 6V and no bubbling occurred at the negative electrode but as the solution got lighter the bubbling appeared.I lowered the voltage to about 1.5 V and the bubbling stopped.I hope this helps.Read the fourth paragraph of the video description!! I hope this helps!!:)
The Thought Emporium - 2011-04-09
i switched the carbon electrode for a graphite one and it worked considerably better. the graphite didn't erode and it worked very quickly and very well