Concentrating Sulfuric Acid

[Nehebkhau]

I did a search for this and there was just one thing I didn't understand. Apparently you heat the acid at around 100 degrees celsius until white foam, then distill. How exactly do you distil, and will it make that much of a difference in the purity of my acid? How greatly will it affect my explosives? I kno this question is kind of vague, any advice is appreciated. If you could link me to a thread that discusses this further, and maybe a simple way to do the distillation without expensive equipment? Thx

[Wild Catmage]

I guess you've been reading this thread:
http://www.roguesci.org/theforum/showthread.php?s=&threadid=1908

When the concentration reaches < 98% thick white fumes appear. Purification-The concentrated impure acid is then distilled at 340C at normal atmospheric pressure. The result should be < 98% pure sulfuric acid.

I can see little point in distilling something that is more than 98% sulphuric acid to get a new substance that is more than 98% sulphuric acid. :confused:

This is a thread on concentrating sulphuric acid from car batteries here: http://www.roguesci.org/theforum/showthread.php?s=&threadid=2660

[kingspaz]

well atleast its in the water cooler....:rolleyes:

[Nehebkhau]

One last question. I'm using a coleman backpacking stove to heat my sulfuric acid at around 110 degrees Celsius. Placing the beaker directly on the stove gave me uneven heat so I placed an aluminum plate under the beaker. Now I have a very* steady temp. of around 110. Is it better to turn up the stove and let it boil over a little onto the pan, or to let the reaction continue slower at the current speed?

[Nehebkhau]

I started with 500 mL of 33-38% acid and was expecting to see white foam when the acid level reached somewhere around 150 mL. Well the acid kept boiling down to around 100 mL and I finally shut it off because the vapor emitting from the flask was just too heavy. I never saw even the tiniest bit of white foam this whole time....Does the extremely heavy vapor mean it was done? Any ideas on what I might have done wrong?

[kingspaz]

its not white foam you should see, white 'fumes'.
ok, i have the same stove, if you put some sand in the pan also then that will increase the surface touching the beaker so heat it mor evenly and better. don't let the acid boil over since it will react with the Al as follows:

3H2SO4 + 2Al --> 3H2 + Al2(SO4)3

whats hydrogen do when it gets lit? BANG!

what temperature does pure sulphuric acid boil at?
what temperature does water boil at?

once you've answered those questions you will realise what you are doing wrong.

[frogfot]

When the concentration reaches < 98% thick white fumes appear

This can't be true, at least with my battery acid.. Fumes appear at about 50% after which they increase. ..this maby depends on how one inerpretate word "thick" :)

[kingspaz]

in my interpretation thick = decomposing sulfuric acid. means its at 98% then :)

[Nehebkhau]

Wow, so aluminum not safe then, lucky that didn't boil over, what about stainless steel? The aluminum pan burnt pretty bad too, it has holes in it now so its going in the trash. Stainless steel would hold up better, but safety is the priority soo.....If not stainless, what should I use? Thx

[kingspaz]

what is stainless steel made of? at what rate does it react with H2SO4? does H2SO4 react with sand?

answer those and you'll find the answer. i'm not doing this for all your questions, use some initiative! as i've mentioned in other threads, if you learn some basic chemistry then it'll stop you making elementary mistakes.

[Nehebkhau]

Ok, for some reason I have sulfuric battery acid manufactured by the exact same company reacting differently to heat. When I bought the acid, the guy said he'd give me a gallon for 4 bucs. He actually ended up giving me closer to 2 gallons, around 7 or 8 small containers (same electrolyte containers used when you buy your own battery and fill it yourself). Some of the containers are different sizes, for instance there were around 3 of the following sizes 32 oz, 50 oz, and even larger containers that looked to be around 100 oz but don't say the exact measurement on them. Now, both the 50 oz and 32 oz containers have the exact same company name and protection label and all that good stuff on them. The larger containers however, do not have any label except for a small protection label. Now, here's where this gets interesting....

When I heat 300 mL of sulfuric acid from the 32 oz container, everything is fine, it boils until it reaches around 100 mL at which point I cease adding heat, and allow it to cool down. In other words everything works fine with the acid from these particular containers.

When I heat 300 mL of acid from a 50 oz or 100 oz container, the acid doesn't appear to boil evenly, it kind of hesitates like it tries to bubble, then all of a sudden will erupt in a quick bubble sometimes shooting acid out of the beaker and onto the stove. This puts out the flame and causes a huge mess. I've had to use the whole, pan with sand technique under the beaker to keep the acid from getting into the stove when the miny volcano blows. Any idea on what might be causing this?

[Anthony]

The problem you're having is "bumping". Why it would be different for acid from the different bottles, I don't know. Try some boiling stones such as borken glass and see if that helps.

[Nehebkhau]

srry for my ignorance, but are you saying to just place some broken glass in the bottom of the flask while im heating the acid?

[knowledgehungry]

Yeah thats what he was saying.

[AsylumSeaker]

Originally posted by Wild Catmage
I can see little point in distilling something that is more than 98% sulphuric acid to get a new substance that is more than 98% sulphuric acid. :confused:

I believe he means that the acid in the solution was at 98% concentrated. The distillation is to remove the impurities insn't it? The stuff you can't boil off?

I actually tried concentrating my own acid the other day from a car battery. I just did a small amount in a beaker to see how concentrated the stuff was. It was boiling for ages before the fumes appeared. And those fumes really are noxious. Even with my mask I could feel my lungs getting itchy and I started to cough. So I just held my breath and put it in something and plugged it quick and got out of that room for a while. My point is to take precautions even with tiny amounts. It was about 8 mls of stuff that I had and I still thought I was going to die.

When the acid reached 98% concentration lumps of black metalic looking stuff formed in the mixture. I assume this was the lead from the battery or some such. It looked really cool when it just sprung out of nowhere.

[Nehebkhau]

When I purify mine white fumes are present almost the enitre time. Because of that, I go more by the amount left in the flask than the fumes. For instance starting with 300 mL and then turning the heat off around 100 mL. There are actually less white fumes coming off the flask towards the end of the process. I've never boiled it long enough as to create a solid in the acid such as you are talking about.

[FinnBell]

Last night I was attempting to distill some Hn03 and when I was finished I realized that the reason for the crappy yield might have been because my
H2S04 was probably not as pure as it could be. So I proceeded to try to heat it until "thick white fumes" appeared and my acid is drain cleaner btw so its got a yellowish brown tint to it. So I heated it for a couple of hours and it gave off fumes the entire time but when I stopped heating the acid had turned to a deep dark brown and Im not sure what has happened. Even after its cooled down, its still the same deep dark brown. Ive searched and havent seen anything about this. :confused:

[Viper3k]

I read something about this not so long ago. It could be the impurities in the acid turning to carbon from the heat. Hence the dark colour.

[FinnBell]

So I take it that's going to require filtering.

[knowledgehungry]

The discoloration of the Sulfuric Acid has never caused any problems in synthesis, at least not in my experience or in any I have read on the forum. I have always had discolored H2SO4 when obtained via the drain cleaner route. I would not worry about it, the reason your results were so poor IMHO is that you had a low concentration of Sulfuric. Low concentration will hurt your results far more than small amounts of carbon impurites.