Sufuric Acid turned black!

[BigArt47]

My stock of H2SO4 has turned black!
What causes this and how do I fix it?
What is the best way to concentrate this to "fuming"?
I assume that the acid has taken in some kind of contaminate but I have been very careful not to allow any contamination so it must be either water or gas from the air or something in the bottle or lid:mad: !

[Cobalt.45]

Check the cap, under the seal.

[FUTI]

Did you foolishly tried rubber/wooden cork to seal the flask/bottle where you keep your stock? Manufacturers are obliged to sell the products in proper package so I assumed you have to resort to DIY technique for some reason. Describe how do you hold your acid.

[Universal]

I imagine that it is carbon, sulfuric acid is a powerful dehydrating agent that will react and extract the water out of carbohydrates and rubbers.

C6H12O6 ---H2SO4---> H2O + C

Not balanced but that is probably what is happening, filter it to get the C out, if you can find a suitable filter that is.

[a_bab]

Due to the dust, impurities of all kind, not a proper cap (rubber for instance) the SA has the tendancy to turn black. It's a prof you've got good acid there.

A suitable, resistant filter can be a wad of clean glasswool. It'll take long to filter due to the viscosity, so a vacuum filtering system would help.

On the other hand, depending on what you need it for, it'll still work and the carbon that contaminates it wouldn't produce side reactions (in a nitration for instance).

[PeterB2]

I had a sulfuric acid disaster! I was trying to condense my battery acid to a higher concentration of sulfuric acid (hopefully >90%). I used small, single tip acohol burner with 250mL florence flask on top of the burning stand with 250mL of battery acid.

I checked it periodically about every half hour. After about 1 1/2 hours, I went out to check on it (it had been moderately boiling) sulfuric acid was all over the place in about a 2 ft. radius. The acid was eating through my burner and stand leaving both severely corroded.

I was left with about 200mL of acid in the flask--the other 50mL must have partly evaporated from the boiling and partly dissipated from the explosion (dare I call it an explosion?). The flask seems to still be intact with no cracks or holes...and it holds water without any leaks.

Both the burner and the florence flask were brand new...what could have happened?!? I had done the same proceedure just yesterday on a smaller scale with about 100mL of battery acid leaving me with about 20mL of reasonably concentrated H2SO4 after about 4 hours using the same equipment. I am partly mad and partly flabbergasted ...

[Cobalt.45]

Sounds like a case of "bump".

Often. adding inert chips of ceramic material will prevent this occurrence.

[c.Tech]

Something probably fell into the concentrated acid causing it to boil over, like when you add water to acid.

And peter, please use paragraph breaks.

[PeterB2]

Ceramic material? With the sulfuric acid inside the flask? I'll have to make sure to do that next time.

c. Tech, I poured the acid that remained in the flask into a beaker for inspection and there didn't seem to be an contaminates. Why would not having ceramic pieces in the flask make it boil over the way it did?

Sorry about the paragraphs...I'll edit it. >_<

[c.Tech]

Maybe what fell in was boiled over or dissolved into the acid. It’s only a possibility, birdshit would be the most likely to drop into my flasks because they are always open outside.

[Cobalt.45]

Liquids often boil in an uneven fashion, or bump. They tend to bump when there aren't any scratches on the walls of the container where bubbles can form. Bumping is easily prevented by adding a few boiling chips to the liquid, which provide a rough surface upon which bubbles can form. When boiling chips are used, essentially all of the bubbles that rise through the solution form on the surface of these chips.


+++++++++++

You can't just post a quote, with no reply, as the software requires at least 20 characters of text to prevent +1 replies.

Also, make sure your posts are properly formatted before posting them, such as making sure quote tags are properly used. ;)
NBK

[DONMAN]

Does any one know the percent sulfuric acid that drain ro go drain cleaner is? Its sold in a jug in a bag. This cleaner also has some black dye added in. I was wondering does any one have an estaminet what percent this is?

[c.Tech]

>90% from what I heard, doesn’t it tell you on the jug?

[stupid939]

You usually have to look at the msds, but the stuff I get (Liquid Fire Drain Line Opener) is 88%. Most of them are in the range of 88-95%. Another is called something like Professional Drain Opener and IIRC it is 93%.

[PeterB2]

I got some Rooto drain opener. It says it contains concentrated sulfuric acid, but I checked the manufacturer's website and they do not have any MSDS's for their products--I'm sueing :rolleyes:

[stupid939]

Peter, I searched google for "rooto drain opener msds" and the second page I found had a msds that said 93.2% Sulfuric acid. Try a little harder next time because spoonfeeding can get you banned around here, as you probably know. If you would like it, the link to the pdf is:

http://www2.itap.purdue.edu/MSDS/docs/12070.pdf

Oh, and I forgot that most of the dyes in the drain cleaner sulfuric acid can be oxidized. I forgot where I read it, but you heat up H2SO4 on a hotplate or stove to about 100°C or so, and slowly add H2O2. I used baquacil (27%) and it worked well. I forgot how much was added, but I did it until it was kind of clear.

I started with Liquid Fire (dark brown color) and when I heated it and added the H2O2, it turned fairly clear for awhile and then turned dark again, but after it cooled down, it turned pretty clear again. The hydrogen peroxide breaks down into O2 (oxidizing dyes) and H2O, so it adds a little bit of water to your H2SO4, but it is better then doing some reactions with a dark liquid.

[PeterB2]

Opps, sorry >_<. Thanks for the link.

Is the H2O2 totally inert to the sulfuric acid? Still, great idea...and since its already hot anyway, it shouldn't be too hard to boil off the last little bit of water. As I found out the hard way, just be sure to put some sort of media in there (porcelin bits or boiling stones) so that the boiling liquid doesn't erupt. :o

[Cindor]

H2O2 + H2SO4 --- H2SO5 + H2O

Maybe the Peroxysulfuric Acid oxidize with the dye and the Sulfuric Acid come back.

[PeterB2]

This warrants some investigation. This source: http://chemistry.about.com/cs/toxicchemicals/a/aa603003a.htm (acessed on December 27, 2006) says not to mix sulfuric acid with hydrogen peroxide as it may spontaneously detonate.

[nbk2000]

UTFSE for "piranha fluid". ;)

[SafetyLast]

The "Rooto" brand Sulfuric that I usually buy is very dark, almost black.
I'm not sure what kind of contaminants it has in it, but I do know that it is 93% concentration and works for most nitrations except will sometimes make a product with slightly different color.
I'm reminded of that stupid book "Two component explosive mixtures" which was mostly a list of what chemicals will react violently with each other. I could have read that in almost any chemistry book!

[PeterB2]

Hmm...I didn't know piranha fluid was potentially explosive though. Corrosive and dangerous, definitely, but explosive? Also, from what I read, the concentrated sulfuric acid must be mixed with >50% conc. H2O2 in order to produce efficient amounts of Caro's acid. Would 3-10% H2O2 make a mixture that would "spontaneously detonate" (if the Caro's acid is indeed explosive in the first place)?

[nbk2000]

No amount of acid is going to turn 3% peroxide into piranha fluid.

[Sworn]

In my opinion, you had bought a cheap product or the industrial acid.
I didn't know what you want to use polluted sulfuric acid in sensible
liquids ? It turns black always when concentrated to fuming sulfuric acid.
The boiling point of sulfuric acid 100% is nearly 330 degrees C. Why don`t you
try to distill the acid in a high-quality distillation column. Concentrate
the acid much as possiple by boiling it and than distill gently that it not
decompose too much into sulfur dioxide.
I belive chilled piranha fluid will not spontaneously detonate, may it is usable
with sulfuric acid 95-99% and H2O2 >10%. You need a lot of sulfuric acid and the yield is very low.

[PeterB2]

I'm going to by doing a titration soon to find out the concentrations of my various samples of sulfuric acid.

However, I'm wondering what the best base is to use for such a project. I was thinking about sodium hydroxide, but I'm not sure which products the reaction thermodynamically favors : sodium bisulfate (NaHSO4) or sodium sulfate (NaSO4).

The balanced equation for each would be the following:

H2SO4 + 2NaOH --> Na2SO4 + 2H20

2H2SO4 + 2NaOH --> 2NaHSO4 + 2H2O

Another possibility would be that a significant amount of both sodium bisulfate and sodium sulfate is formed. If anyone knows, (or knows a good resource for thermodynamics tables) this would help immensely in my stoichiometric calculations. Also, any suggestions for an alternative base are welcome. (I suppose, this could be why my previous titrations with my battery acid didn't make sense.)

[c.Tech]

Although not as accurate you could always use a hydrometer to find the concentration. Should give you a close enough measure for its use in most explosives if that’s what you need it for.

[SafetyLast]

I didn't want to start a new thread about this since this one was already here.

I recently used a drain opener called "Liquid Lightning" which is labeled "virgin sulfuric acid". Now I've been using Rooto for a while which is dark color and works fine for most things but this "virgin sulfuric" seems to be a bit weaker.

I read on an msds somewhere that the concentration was 93%, but now I can't find that msds anywhere. So here's my question: what sets virgin sulfuric acid apart from the other concentrated drain opener variety? By the way this stuff is very dense and dark black like coffee.

[chemdude1999]

SafetyLast, "virgin sulfuric acid" simply means the acid is "first use" as opposed to regenerated acid. Users often sell "spent" acid to facilities that regenerate it, ridding it of contaminates. Virgin acid is supposedly higher quality. Honestly, it's just a selling point for the drain opener.

SA is naturally very dense and viscous. I would assume the dye is an indicator. For example, say you pour some in a tub and it is working its way into the clogged drain. Clear SA would not catch the attention of a person that might subsequently use the tub, thus harming them. Also, I think it might be used as a branding method. Not positive, though.

[Shalashaska]

I've actually been searching for an answer to this question for some time now, because Liquid Lightning is the brand available at Wal-Mart. The links when I search google are mainly all leading to this

The Section 261.4(a)(7) exclusion applies only to spent sulfuric acid used as a feedstock in an
industrial furnace for the production of virgin sulfuric acid and does not extend to spent sulfuric
acid recycled in any other manner. Spent sulfuric acid is frequently burned in industrial furnaces
to derive sulfur. As part of the same process, this sulfur is then purified, chemically converted,
and absorbed into existing sulfuric acid. EPA has concluded that spent sulfuric acid that
undergoes this process is neither regenerated nor recovered, but rather used as an ingredient in a
production process (48 FR 14487; April 4, 1983). On the other hand, spent sulfuric acid
recycled by another method, such as filtration, is not excluded under Section 261.4(a)(7).

[Alexires]

Shalashaska - What was the point of that little piece of legislation? Where did it come from? What does it relate to?

An answer without a question.