Unknown Liquid

[NGfan]

I have an unmarked brown glass bottle (big) next to two identical, labeld bottles, nitric and hydrochloric acid. I would like to know the contents of the bottle but do not know the proper tests. I have pH paper and many chemicals. All help welcome.

[ultma]

First off find out as much basic information as you can. colour, pH, density, is it viscous, does it have an odour (be careful), does it fume.

Is it likely to be a mineral acid also i.e. is your lab well organised with incompatible chemicals kept separate.

Find out as much information as you can before you start testing.

Be careful it could be anything.

Links to some tests.
http://www.wpbschoolhouse.btinternet.co.uk/page13/ChemicalTests/ChemicalTests.htm

[knowledgehungry]

There are many chemical tests, but first I would advise you notice the physical properties of the liquid, i.e. color, viscosity, density etc.

I have a feeling it is sulfuric acid, just because acids are normally stored with acids and Sulfuric is the missing acid of the 3 most common for synthesis.

Find the mystery liquid's density and then look up the specific density of H2SO4 I would imagine that they will be very close. Even if they are not it doesn't mean that it is not H2SO4, it could just be a lower percentage. If the density is higher than that of H2SO4 it is fairly safe to bet that it is not Sulfuric acid as diluted H2SO4 has a lower density(if diluted with water, the only common diluent for H2SO4).

EDIT: Sorry my post was semi-redundant, Ultma beat me to the punch. I am still sticking to my advice though.

[ultma]

Yeah I was thinking H2SO4 swell

Also are you a university student do you have access to an I.R spectrophotometer.

If you can a boiling point or melting point can help.

[stupid939]

Here is a link to a chart for the specific gravity of sulfuric acid.

http://frogfot.com/stuff/h2so4.png

If you go to the previous page, there are other charts for nitric acid, salts, etc.

[NGfan]

Thank you for the help so far, you guys, and good guess. The third IS H2SO4, I just ommited it as it is not in an the same glass bottle as the other acids. It is in a plastic container. I will update with info on viscocity, etc.

I love how everyone on these forums are so helpful. Reputation additions all round.

[NGfan]

Viscocity is low, it fumes whiteish and is a clear liquid. pH paper(litmus) in the fumes turned red and dipping in the -acid?- produced darker red that turned white over time, Indicating from Ultma's generous link that there is chlorine, or chlorine gas... I wonder if it is HCL...

[ultma]

Viscocity is low, it fumes whiteish and is a clear liquid. pH paper(litmus) in the fumes turned red and dipping in the -acid?- produced darker red that turned white over time, Indicating from Ultma's generous link that there is chlorine, or chlorine gas... I wonder if it is HCL...


As soon as you said fuming I knew it was Fuming HCl it should be around 37% so it should have an approximate density of 1.19 g/mL. It could be more or less but most likley 37% weigh up a mL.


Edit: Another more fun test will be to put a small square of Al foil 1cm2 in a beaker with a small amount of acid in a fumehood away from anysource of ignition and watch the violent reaction that will take place if it is indeed HCl

[sprocket]

The fastest way to tell the mineral acids apart is probably using your body's own analytical instruments. Based on smell and taste as well as physical appearance any true chemist could tell you which it is. Obviously you'd dilute the sample before tasting it and don't swallow. Perhaps it's not such a good idea to taste random things if you have anything very toxic in your lab...

While acids initially taste sour, they have their more or less unique aftertaste.
Sulfuric acid - doesn't smell much, but has a sweetish aftertaste.
Hydrochloric acid - pungent smell, tastes like puke (and for a good reason)
Nitric acid - also pungent smell, but doesn't quite have the sting of hydrogen chloride. Haven't actually tasted it, but it probably has the 'round' aftertaste typical to the nitrate ion.
Perchloric acid - Don't know, but I would love to try!
Acetic acid - ick (everyone knows this one)!

If it is indeed an acid (as the litmus test would hint at) then hydrochloric acid seems to be the best bet. Try puffing ammonia at it. It could be oleum, but it is a noticably viscous fluid that usually has a slightly yellowish tone. Maybe tasting it isn't such a bad idea... What's the worst thing that could happen? ;)

[NGfan]

OR, I could just play russian roulette with a fully loaded pistol. Seriously though, I will test the tastes, and the aluminium foil, although is the reaction specific to HCL?... and what IS he reaction? Well I'll just have to try and see. I am considering just good old dipping my finger in. Nah, not really, although nitric acid DOES make your skin gowonderfully yellow and fall off... Ah the joys of youth...

I don't know if you're a science god or what, Ultma, but you named exactly the concentration of my labled bottle of HCL.

Also, my lab has very toxic ingredients, 98% and 100% nitric and sulfuric acid, Bromine, sodium hydroxide, and a drawer full of chemicals with mostly eroded lables saying things like:
USE EXTREME CAU...MELY TOXIC...KNOWN CARCINO..
I tentativly peer into the bottle with my full face gas mask on and am dissapointed at the liquid that appears to be water. Taking a sip, I realise it to be, fluoroantimonic acid. I very quickly and painfully die...
- extract from 'Writings of a K3wl'

Regretfully, since the posting of this article, the author of 'Writings of a K3wl has passed away. Let this be a lesson to other K3wls evrywhere; Drink fluoroantimonic acid.

[ultma]

Don’t taste them use your brain instead physical examination followed by chemical tests, you will also learn more.

Weigh out 1mL.

Also add some weak 0.1N AgNO3 soln to your HCl if a white precipitate forms (AgCl) your in business. It’s HCl.

[NGfan]

Fine, I will. Even if it means dissolving that pure silver spoon given to me on my first birthday by my godmother, I will.

You so clever Ultma, if only my dad were more like you...:rolleyes:

-The silver spoon thing is true, but she's dead now, so won't come round asking to see it... Tee Hee...

[sprocket]

While silver chloride itself is highly insoluble that's not the case for the complexes formed in high chloride (or other halides for that matter) concentrations. If you add a small amount of silver nitrate to conc. hydrochloric acid it might initially precipitate, but only to redissolve as complexes. Explore the equilibrium:

AgCl(s) + (n-1)Cl- <=> AgCln1-n

lg K
Ks1 -6.75
Ks2 -4.75
Ks3 -4.75
Ks4 -4.45

These complexes are quite soluble! Therefore it is very important to do the silver nitrate test correctly. That is, if your sample most likely contains high halide concentrations it needs to be diluted.

Considering that you do in fact have toxic chemicals in your lab (but I would not count sulfuric/nitric acid as such) it might not be such a good idea to taste random solutions. Although having unlabeled potentially highly toxic substances in the first place is just as bad an idea.

The fact that it is stored in a plastic bottle is quite interesting. It would suggest that it cannot be stored in a glass bottle, which leads us to hydrofluoric acid. This is quite the beast! Even the most seasoned chemists are reluctant to use it. It is readily absorbed through the skin and causes very nasty and painful burns. Death through systemic poisoning can occur even if as little as 2% of your body is exposed to it.

It's easy to test if it's indeed hydrofluoric acid though. Just place a drop of it on a piece of glass and see if it etches the glass.

[ultma]

While silver chloride itself is highly insoluble that's not the case for the complexes formed in high chloride (or other halides for that matter) concentrations. If you add a small amount of silver nitrate to conc. hydrochloric acid it might initially precipitate, but only to redissolve as complexes. Explore the equilibrium:

AgCl(s) + (n-1)Cl- <=> AgCln1-n

lg K
Ks1 -6.75
Ks2 -4.75
Ks3 -4.75
Ks4 -4.45

These complexes are quite soluble! Therefore it is very important to do the silver nitrate test correctly. That is, if your sample most likely contains high halide concentrations it needs to be diluted.

Considering that you do in fact have toxic chemicals in your lab (but I would not count sulfuric/nitric acid as such) it might not be such a good idea to taste random solutions. Although having unlabeled potentially highly toxic substances in the first place is just as bad an idea.

The fact that it is stored in a plastic bottle is quite interesting. It would suggest that it cannot be stored in a glass bottle, which leads us to hydrofluoric acid. This is quite the beast! Even the most seasoned chemists are reluctant to use it. It is readily absorbed through the skin and causes very nasty and painful burns. Death through systemic poisoning can occur even if as little as 2% of your body is exposed to it.

It's easy to test if it's indeed hydrofluoric acid though. Just place a drop of it on a piece of glass and see if it etches the glass.


True about the AgCl test but it will still make a white cloud when added to 37% HCl which will dissolve quite quickly however as you said. but if your not to lazy to dilute it do it as sprocket said.

It’s not in a plastic bottle it’s in a big brown glass bottle.

HF goes through your skin and dissolves your bone as well doesn’t it? Well at least that’s what I was told once.

I have a very old HF plastic bottle in my lab (tucked away in an expired chemicals cubby) double bagged but it has crystallised on the outside of the bottle in the bag I am too scared to even touch it. :eek:

[FUTI]

HF goes through your skin and dissolves your bone as well doesn’t it? Well at least that’s what I was told once.

No. IIRC it penetrate skin, cause mussle cramps and unbelievable pain, artery shrinking that can cause gangrenous limb (the one affected), your nails fall out etc. So bone and teeth problems are least to worry about.

[sdjsdj]

Hydroflouric acid is one of the few chemicals I am genuinely afraid of. I wouldn't want to work with it without full protective gear, if at all. Sorry to spoil your fun, but - if all else fails - send a small sample to a university, or somewhere else with a mass spectrometer; that should tell you its PRECISE composition within . . . let me see . . . oh, about a minute.
If they agree to test it.
And you find a way to get it to them without the postal service having several dozen fits.
And you can find a good excuse for having it in your posession.

Good luck with the identification.

[NGfan]

Hmm, I could give some to The Technicians... They give you anything, as long as it has a teachers name at the end of the sentance, you wouldn't believe the stuff I get... Won't let me go near the radioactive stuff, though.
I don't know if they have a mass spectrometer, and would feel that fuss would probably be created if I had a particulary dangerous chemical. I think I should do the silver nitrate test... I'm unsure if I should take pictures/video of the entire experiment (making of silver nitrate would be included) and post it on the forums. What do you guys think?
Btw, this would have to be in two weeks time, as I am studying for really important tests.

[knowledgehungry]

The Al test is particularly easy to do I recommend it. Although it is not a definitive test, if it fails to react than you know it is not HCl. Remember to do this in very small amounts wearing appropriate safety wear.

Does HClO4 fume?

[ultma]

The Al test is particularly easy to do I recommend it. Although it is not a definitive test, if it fails to react than you know it is not HCl. Remember to do this in very small amounts wearing appropriate safety wear.

Does HClO4 fume?

Yes i think it can fume if concentrated enough? it also has a strong odour.

yeah Al + HCl is great fun Al wont react with HNO3 or H2SO4


Also have you weighed the liquid what is its density?!!!

[NGfan]

As I have no indication of concentration I have decided measuring density will probably be misleading. Will be back with the results of the Al test tomorrow (UK time)

[Bert]

As I have no indication of concentration I have decided measuring density will probably be misleading.

You do not understand how concentration of acid are determined from knowledge of their densities then. Several people have posted tables or links to tables showing concentration of acids vs. their densitites here. SEARCH. I think you'd better leave your new chemistry set alone untill you learn the basics.

[ultma]

measure the density its probly 37% HCl but still it will help

Standardisation of HCl
assuming 37% (12.1M)
weigh out three 24.2-29.04g of di-Sodium Tetraborate add d.H2O warm to dissolve add some 0.1%w/v methyl red in methanol then titrate with acid until endpoint (pink colour)

reaction: B4O(2-)7 + 2H+ + 5H2O --> 4H3BO3

Molarity = ((1000x g tetraborate)/(mL HCl))/190.72

[NGfan]

You do not understand how concentration of acid are determined from knowledge of their densities ... I think you'd better leave your new chemistry set alone untill you learn the basics.

I know how density works, I have just been over the topic in my physics class. But, if I do not know the chemical or the concentration then density would be pretty useless.
I read emotion really badly over the internet, so there are two responses to your refrence about my new chemistry set with vaccum distiller;

- If you were patronizing - I don't care what you or anyone else grades my ability to be, as I know myself and only tackle what I feel I can handle, which includes random liquids. Don't judge me solely based on one post.

- If you were concerned for my health - I see the point you make. If the density corresponds to 37% HCL, then I may safely assume it is before further experiments. Although slightly misguided, I realise your intentions were
benign. After confirming what it is, I will follow your advice and find it's concentration by it's density.

When/if you respond I may edit one of the options out to seem less weird.

[NGfan]

Well I tried the Al method - not foil, though, powder, using tiny amounts. After a few seconds, a fizzing could be heard and the fumes increaced greatly. Does this mean it if HCl for sure? If so, can someone tell me how to close this thread because all it will do from then on is use unnecessary bandwith.
Thank you all.

[knowledgehungry]

You can't close a thread, only mods can do that, people will eventually lose interest in this thread and let it die.

This does not mean it is HCl for sure but I would bet a good sum of money that it is HCl. Assume it is and check the density of it if it roughly matches 37% HCl then I would consider the case solved. The reason everyone keeps telling you to check the density and compare it to 37% HCl is that fuming HCl in a lab is almost always about 37%. 37% is standard concentrated HCl.

[ultma]

Did you measure the density, is it similar to 37% HCl.

Chemical tests can be fun how about you do the same HCl test with Al in a test tube and do the pop test to see if H2 is evolved

(anyway how did you get your lab tech job grandfathering nah just a joke, but sweet you have a rotavap)