riedmur
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acid i d
Now, let's see if I can get this posting stuff done right. How's it goin', eh? My first post.
Here is my problem: I have several bottles of acids which have been in storage since the last century. The acid fumes have totally destroyed the
labels. There is nitric, sulfuric & maybe hydrochloric acid, but I have no idea which is which.
There may be acetic acid also. I need a simple test to i.d. these acids. I want to avoid messy & dangerous determination of specific gravity.
Something involving a few drops. TNX, R
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Bot0nist
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Start by just observing the physical properties. What color is each liquid? Put a small drop of each on a piece of glass. Which evaporated to dryness
with no residues. The nitric acid should react with copper producing orange brown gasses. HCL(aq.) With ammonia, white fog. Acetic acid will freeze
in most freezers I believe.
I'm sure some very simple and elegant way exists for all three, that escapes me. This is the type of question that many here love juggle with, so just
wait around a bit.
[Edited on 23-2-2015 by Bot0nist]
U.T.F.S.E. and learn the joys of autodidacticism!
Don't judge each day only by the harvest you reap, but also by the seeds you sow.
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j_sum1
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Some precipitation tests may be in order -- depending on what other reagents you have. Only small dilute amounts of the acids will be needed.
Addition of barium hydroxide or calcium hydroxide will give a ppt with sulfuric acid.
Addition of silver nitrate will show up hydrochloric acid.
Acetates and nitrates are both soluble so precipitates won't help you much there. However, if you have narrowed it down that far, you should be able
to determine acetic by its odour. Nitric if concentrated will react with copper as previously stated.
Is there any chance that you have phosphoric acid or hydrobromic or any other acids? A wider set of options may be harder to narrow down.
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Bert
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Thread Moved
22-2-2015 at 22:16 |
Amos
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First I would suggest doing any reactions with your unknown acids in a fume hood, just as a precautionary measure.
Acetic acid can be neutralized with the correct amount of sodium hydroxide or sodium carbonate, and afterwards the addition of some iron(III) chloride
solution should produce a red color.
In case some of these other acids are present:
Hydroiodic acid can be oxidized by hydrogen peroxide, giving a red solution of iodine in water and a precipitate of elemental iodine.
Hydrobromic acid can be oxidized with potassium permanganate, and will generate fumes of bromine(which may require some heating).
Phosphoric acid is viscous and, at least in my experience, always seems to form soapy-looking bubbles or foam when shaken up. It will react with
copper(II) oxide or copper carbonate to yield an insoluble light blue solid.
If you think for any reason you might have hydrofluoric acid stored here, I would postpone testing any of these acids until someone more knowledgeable
than me tells you how to handle that. Any glass containers, however, will not contain it.
[Edited on 2-24-2015 by Amos]
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Molecular Manipulations
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This is really easy to find out without any tests except your nose. Of course dont put your nose to the neck of the bottle, just open the lid and wave
the smell toward your nose.
Ok, the one that smells like strong vinegar is acetic acid.
If you've never smelled hydrochloric acid before, that's fine, the one that has a strong smell, but not like vinegar is HCl. The one that has no
smell or a very weak smell is sulfuric acid.
-The manipulator
We are all here on earth to help others; what on earth the others are here for I don't know. -W. H. Auden
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Zombie
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If he doesn't post back I will fairly assume the "smell test" did not go so well.
Why would you post that MM? 
I work w/ HCL in gallons for washing fiberglass, and I wont go in the storage shed with out a mask on.
I'm mostly joking in my reply but not completely.
No offense.
They tried to have me "put to sleep" so I came back to return the favor.
Zom.
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Amos
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The OP also mentioned nitric acid, which similarly has a strong smell, so "strong-smelling, but not vinegar" does not automatically mean HCl; plus,
glacial acetic acid really doesn't smell much like distilled vinegar. Besides, I would imagine that we're looking for more definitive proof than what
most people can provide by nose alone.
Oh, and Zombie, since when are there hills in the Florida panhandle? If you count these, then I'm laughing, as a resident of Kentucky.
[Edited on 2-24-2015 by Amos]
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Texium
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A smell test is really not a bad idea. If you carefully waft, it won't hurt you. Sure, HCl vapors suck, but smell just a bit and it's instantly
recognizable. (Although I'm not sure if the other hydrohalics have similar odors, as I've never worked with any of them. That might make it more
problematic.) Impure HCl may be yellow colored from dissolved iron. Another possible way of identifying HCl would be adding some copper wire and a bit
of hydrogen peroxide. An emerald green solution should form after a few minutes due to the presence of the tetrachlorocuprate ion.
Nitric acid may have an odor of nitrogen dioxide if it isn't completely pure, (which has a unique smell, slightly like chlorine, except more thick and
cloying) and if it does it will also likely be slightly yellowish. Testing with a piece of copper, as Bot0nist suggested, is definitely the easiest
way to determine which is nitric, as it is the only one that will react with copper on its own. Make sure to test outside though, since the NO2
produced is quite toxic and smelly.
If your sulfuric acid is in a plastic bottle, it may have degraded the bottle, turning the acid and sides of the bottle yellow or brown depending on
the level of degradation. If this is the case, be very careful with the bottle as it may have become brittle and fragile. Concentrated sulfuric acid
(93+%) will char paper and cotton unlike the others, so you could identify it by putting a drop or two on a paper towel to see if it will make a
charred hole. It should also be very dense and oily compared to the other possible acids. Note that if these tests fail, it could still be sulfuric
acid albeit less concentrated. Then the only way that I could think of to identify it would be to add some to a solution of a soluble barium salt. A
white precipitate of barium sulfate should form, even if your acid is quite dilute.
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Zombie
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Quote: Originally posted by Amos  | The OP also mentioned nitric acid, which similarly has a strong smell, so "strong-smelling, but not vinegar" does not automatically mean HCl; plus,
glacial acetic acid really doesn't smell much like distilled vinegar. Besides, I would imagine that we're looking for more definitive proof than what
most people can provide by nose alone.
Oh, and Zombie, since when are there hills in the Florida panhandle? If you count these, then I'm laughing, as a resident of Kentucky.
[Edited on 2-24-2015 by Amos] |
You caught me off guard with the hills... HillBilly, I get it.
Well I do actually live on top of what would have been the first of two off shore sand bars when Fl was under water.
Does that count? ( I guess it has to )
They tried to have me "put to sleep" so I came back to return the favor.
Zom.
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Molecular Manipulations
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Hmm, somehow I over read the nitric acid part. Yeah the smell of nitric and hydrochloric acids, although not really similar, are kind of hard to
discribe, and to somone who's never smelled either could be confused.
As for the fact that the smell is overpowering Zombie , perhaps I've had too much exposure, cause I feel great after a whiff or ten!
But really I think it's safe cause the acid is so old, I doubt it's very concentrated. Hydrochloric acid is quite notorious for escaping it's
container.
So my suggestion is, after you've eliminated all but nitric and hydrochloric acid, add silver nitrate solution, if a precipitate forms, it
hydrochloric, if not it's nitric.
If you don't have silver nitrate (get it! It's awesome) just see if copper will dissolve. As mentioned earlier, nitric will dissolve, hydrochloric
will not.
[Edited on 24-2-2015 by Molecular Manipulations]
-The manipulator
We are all here on earth to help others; what on earth the others are here for I don't know. -W. H. Auden
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j_sum1
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The thing is, a process of elimination is easier if you have a starting list. If one of your bottles was aqua regia and you hadn't included that as a
possibility then you would have all kinds of fun identifying it.
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Darkstar
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Reminds me of the time I took a nice BIG whiff of 10M HCl (the 31.45% stuff you buy at the hardware store). Like an idiot, I opened the one-gallon jug
and stuck my nose right in and inhaled deeply. I instantly got a lung full of HCl vapors (which was now acid due to all the moisture in my lungs and
throat) and started choking and gagging. Shit burned like a mother and I could barely breath for several minutes..
I have no idea why I did it, either...
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Bot0nist
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Did the same with cleaning ammonia solution as a kid, but just once... Some things are easy to learn the first time.
[Edited on 24-2-2015 by Bot0nist]
U.T.F.S.E. and learn the joys of autodidacticism!
Don't judge each day only by the harvest you reap, but also by the seeds you sow.
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Zombie
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Got out on a chilly morning, dew on everything, and dump a gallon into a five gallon pail.You better be on the upwind side of that cloud.
I use a nylon brush on a broom pole to wash the dark water stains from boat hulls as prep for painting.
The HCl burns all the organic material out of the pores in the gell coat.
You don't want to smell test the stuff. It can kill you. DEAD!
They tried to have me "put to sleep" so I came back to return the favor.
Zom.
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woelen
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A simple test:
Take 2 ml or so of each of the acids in a test tube.
The one which smells like vinegar (carefully sniff each test tube) is acetic acid. Put that aside, no further tests needed.
To each of the remaining ones add a piece of copper (remove some isolation from electrical flexible wiring). The nitric acid dissolves the copper
quickly, gives a blue solution and a brown gas. This is a very clear test and in the small quantities involved not dangerous. The other acids only
react very slowly with the copper and have no clear effect (at least not in minutes).
What remains are sulphuric acid and hydrochloric acid.
Take a few drops of ammonia (plain 5% household ammonia is OK and if there is some detergent or colorizer in it, no problem) and let this run along
the inside wall of the test tube. In the tube with HCl you get a dense white smoke, in the one with sulphuric acid the air remains clear, but the mix
of liquids can get quite hot.
With these few tests you have determined all of them, without using large amounts and without doing dangerous things. Perform the tests in a
well-ventilated room and always point the test tubes away from yourself and from other persons.
If you have no test tubes, then use small glasses (e.g. for drinking strong liquor) and put 2 or 3 ml of acid in the glasses. None of the said acids
is really toxic and after they are rinsed away again with lots of water you can use the glasses again for the purpose for which they were made.
[Edited on 24-2-15 by woelen]
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riedmur
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Thanks to all that posted. I will post results when I have tested the acids
I failed to mention that these are 1 liter bottles. These bottles were filled from a 4 liter bottle, thus no nifty color coded caps. I have some brown
bottles with a PTFE cap liner which is supposed to be acid resistant. I will transfer the acids sometime when I get around to it. I have a plastic
cabinet from the Target Store. This is presently used as acid storage. For some reason, no matter how acid bottles are sealed, some fumes always get
out & damage wood lab cabinets or burn the paint off metal ones which then rust.
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Texium
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The destructive vapors are primarily from concentrated hydrochloric acid. It's quite volatile and can permeate bottles that aren't sealed well. A
glass bottle with a PTFE lid should contain it though. Since I got one for mine, I haven't had any more problems with it.
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