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Purify Sulfuric Acid by Distillation


Warning this experiment handles boiling sulfuric acid. This must be performed with gloves, outside or in a fume hood. Greetings fellow nerds. In this video we’re going to purify sulfuric acid by distillation using the heating mantle we built in a previous video. Now sulfuric acid can be made in various ways or obtained from some types of drain cleaners. But often times it’s not very pure and contains contaminants, particularly water. Now you can boil it down to remove some of the water. But the most effective way to purify it is to distill it. So let’s setup our apparatus. We start with the heating mantle that we built in a previous video. Mine is connected to a variac off camera. Now we get a condenser. Mine is connected to a water supply also off camera. And here is a 100 mL round bottom flask filled about halfway with sulfuric acid from drain cleaner. As you can see it’s quite dirty. Remember to clamp it into the stand so there is no chance it will fall over and spill. Now we connect it to the condenser using an elbow joint coated in high temperature grease. At the other end here we put some beakers to receive our distillate. And we’re ready to start distilling. Let me zoom in. First turn on the water flow and then turn on the power. Start on low power and gradually ramp it up until you can see stuff condensing. If you look closely at the acid, you can see it expanding as it heats up. This is why we fill only fill half way and not completely, to allow for thermal expansion. Eventually volatile organics and water should start condensing. The distillate will also have small amounts of acid but this is rather dilute and not worth saving. We need to collect when the acid concentration is fairly high. A simple way to find out when the acid concentration in the distillate is high enough is to take a small sample and apply it to a tissue. If it’s mostly water then nothing will happen and the tissue will just get wet. You can discard the distillate you’ve collected up to that point. Keep running this test and eventually the distillate will burn the tissue, this is a strong indication that we have more acid than water at this point. Change out the receiver and start collecting your acid. Here is a close up of the tissue with the acid having burned clean through it. Now while the acid is very concentrated, it’s not yet the common 98% concentration that corresponds to azeotropic sulfuric acid. To know when we’re at that concentration, pay close attention to the distillate in the receiving beaker Here is a separate run with smaller beakers for clarity. Anyway, as the acid distills, if the concentration is still increasing then you’ll get these distortions as light refracts through the changing density of the acid. It’s best to have a picture or something behind the beaker to easily see this. Now if you do see these distortions then change out the receiving beaker. When we’ve reached 98% pure azeotropic sulfuric acid then the distillate will be clear and homogeneous without any distortions. This is because the density is now uniform. The acid from here on in will be the highest purity you can get by distillation. Just keep going collecting the clean acid until you have about 20% of residue remaining of the dirty acid. I don’t recommending going further as the distillation tends to bump and boil uncontrollably when it gets this low, spitting dirty acid over the condenser and into your clean acid. Before it gets that far, turn off the power and let everything cool. And there we have it, purified 98% sulfuric acid. The less pure, but still clean acid can be applied to uses where you can tolerate water or where you’re going to dilute it anyway. Alternatively you can add it to future distillation runs to get higher purity. Anyway, if you want to test your 98% pure sulfuric acid, a fun thing i like to do is the classic sugar carbon-pillar experiment. Just mix the acid with an equal amount of sugar and wait. Concentrated acid will dehydrate the sugar and convert it carbon that should form a pillar that rises out of the beaker. Anyway, that’s how you purify sulfuric acid by distillation. Thanks for watching. In this video we’re going to make a heating mantle.

100 thoughts on “Purify Sulfuric Acid by Distillation

  1. Holy shit, did anyone else notice that the pillar at the end looked like a dragon? It's almost symbolic 

  2. Can someone explain the squiggly stuff in the breaker. He said something about distortion with light. I also seen these squiggly stuff when I mixed something like alcohol into water.

  3. So, you're from Canada? I wonder if this distilled Sulfuric Acid is going to be the same quality as industrial one? Or is sulfuric acid always sulfuric acid no matter where you got it from?

  4. NurdRage, when are you going to make that video about making potassium chlorate via electrolysis that you said you were gonna do a long time ago?

  5. Is the sugar/carbon snake reaction unique to sulphuric acid? What happens if you mix in hydrochloric acid, or nitric acid or something?

  6. Use the mantle to also purify nitric acid, maybe make an updated complete guide to making nitric acid video.

  7. awesome.  Re: the sugar and the Sulfuric Acid – How strong a reaction is that? if you were to contain in in a pressure vessel what sort of pressure would result?  Does it heat up?  It was such a quick aside to the video – it could have used its own video!

    Glad to see you're back!!!

    Is there anything you need? User submissions? Materials? neat… stuff?

  8. If you go to enough garage sales you will find crazy stuff.  I found some good sized glass bottles of 93% pure Sulfuric acid once.  I don't do these kinds of experiments or have any use for it so I left it.

  9. "Outside or in a fume hood" refers to 'outdoors', right? Not that you can choose whether to have a plan for where the fumes go, right?

  10. Can you make a video on purifying OTC muriatic (hydrochloric) acid? Its cheaper to buy OTC HCL for $7.29 per gallon versus $30.00 for 1 Liter. 

  11. Awesome video! Cant say I'd ever distill sulfuric…. I've distilled bromine several times, but boiling sulfuric is truly nasty stuff! Have you ever looked into Rooto drain opener? It has been titrated by several amateur chemists to be approx 95-98% purity, depending upon the batch (and exposure to atmospheric moisture I would guess). Its surprisingly clear as well. Would be great if you could do an analysis on Rooto to determine purity, and what impurities are present.

  12. Great video.  There are a lot of experiments on youtube that call for H2SO4 so a purification method this easy could really come in handy.

  13. Concentrate sulfuric acid boils at 330*C, isn't it dangerous to distill it with water condenser, it cant break easyly from temperature ?

  14. GREAT video!
    I like to use a thermometer to set what boils off. Lower temps to remove VOCs, and gradually increase until the boil point of the acid, around 650 (330C). Temps outside a +10 range are contaminated. It is a hand built electric kiln, Kanthal A1 wire. :)

  15. I was wondering if its possible to make potassium nitrate using potassium chloride without ammonium nitrate I can't seem to find any cold packs that are made with it and was looking forward to using it for smoke bombs

  16. I have a question! Im want to produce elemental silver from silver sulfate via electrolysis. currently im using pencil leads as electrodes. One of them is corroding. what electrodes should i use beside copper or metals that would contaminate the solution?

  17. At 3:51, what is that wavy-looking effect in the acid called? I learned the name for it a long time ago but I can't remember what it's called.

  18. Dr N. if you don't mind me asking this how many videos you make when you make then and when should I be expecting these amazing videos to come out?

  19. I have had some questions on Distillation; how is it that the acid remains in solution if the the water becomes vapor? I know a similar method is used for extracting essential oils out of plants. What determine weather a compound will remain in solution when it is a vapor?

  20. Hey man I just want to thank you, I learn so much from every single video that I cover my arms with notes after about 10 videos, what I learned from you has actually helped me qualify for the second part of the american chemical association exam, by the way I'm a tenth grader from the states.

  21. Nurdrage.. im so confused why you didnt perform vacuum distillation to avoid the high temperature and be quick on purification.

  22. Hi, Just wondering: is there a method for vacuum distillation of sulfuric acid? Are there any problems you can foresee with that?

    Undoubtedly some risk due to sulfuric acid getting into the air and vacuum might pose a problem, but is there any way to neutralize the gas and still be able to do distillation under low pressure?

  23. I was thinking of getting around to doing this, but I've seen that temperatures get quite insane…

    @NurdRage
    I've been wondering, have you considered some sort of CPU thermal paste as a sealant? They're silicone based and should be pretty inert (not sure about sulfuric acid tho 😀 ). Ofc. a "server class" grease would have to be used as the standard PC grease can only take about 100-150 degrees C. But it might be doable?

    Also, I've been ebaying and came across some "break pads" grease. Supposedly they take temperatures up to 1000C. No idea what they're made of tho.

  24. Yeah I'm ready to fill a barrel with this stuff and keep it in my bunker so that I can disolve my waste when the aliens come.

  25. @NurdRage: I'm trying to distill some 38% battery acid to gain some nice, clear concentrated sulfuric acid. But I always fail – because when the acid is getting near to it's azeotropic point, it tends to superheat. So when the superheated acid abruptly goes into the gas form, its eruption will come over the condenser, contaminating the destillate. This happen every time im trying to distill 🙁 I've also added some shattered glass & ceramic dishes to act as boiling stones – but the superheating still happens. Any Ideas on that? Maybe there is some type of magnetic stirring rod available, that can withstand the high temps of the boiling acid? (The PTFE ones wont do)

  26. Question: if i need to add 3% of Sulfuric Acid in 10 liters of water, can i use 1 liter bottle ( battery acid) of 30% Sulfuric Acid and add 9,3 liter water? Thanks

  27. I used a sand bath and started distilling the sulfuric acid with a condenser running ice water at 0degrees celsius. The sulfuric acid (drain cleaner) started boiling and a white gas started running through the condenser but did not condense and only a white smoke came out of the condencer. I tried to lift the round bottom flask higher from the heat but it did the same. Any help? I did it before and it worked perfectly but this time it doesn't. Its the same acid from the same bottle of drain cleaner.

  28. Can some1 Please Help me out, currently i have 93% sulfuric Acid, i want to obtain 98% sulfuric Acid from my current 93% sulfuric Acid?!?! When i heat The acid "too drive off The Water" i start getting Lots of sulfur Fumes???

  29. How do I separate sulfurous acid from sulfuric acid? I made mine by mixing hydrogen peroxide with sulfur dioxide gas.

  30. At 2:58, what is the name for the distortions? I remember there being a name but I can't remember what it is. (I know why it happens , refraction but I remember there being a different name when it happens in water or liquids)

  31. Great Video. I've been using Sodium percarbonate to clean drain cleaner to produce clean sulfuric acid. After an exothermic reaction, I usually end with very clear viscous H2S04, with a precipitate of what I believe is sodium sulfate. I was wondering, being sodium sulfate is hygroscopic, couldn't I just reduce the temperature of the solution close to freezing then pour off the acid and filter with fiberglass to get anhydrous sulfuric acid? (BTW I know I probably have peroxymonosulfuric acid after the reaction, but from what I understand it's fairly unstable and reverts to sulfuric acid) EDIT:Sulfur Trioxide SO3 is anhydrous H2S04 (dehydrated, i.e.-H2O) which is not sulfuric acid at all. It was a little confusing.

  32. Hey Nurdrage if been watching this video a lot, but I have one question instead of a heating mantle can you use an oil bath or just a hot plate? Thank you

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