[jgaoxx06]

Hi,

Can anyone tell me how you would test for oxides of sulphur and nitrogen dioxide? I've searched on chemguide and Google, but didn't find anything. I know you use glowing splint for oxygen and limewater for carbon dioxide, but I'm stuck on these two gases.

[anarchron]

Sniff it.
Sulphur dioxide will stink.
Nitrogen Dioxide will make you laugh.

[Borek]

Nitrogen Dioxide will make you laugh.

Will make you dead.

[Will]

Can anyone tell me how you would test for oxides of sulphur and nitrogen dioxide? I've searched on chemguide and Google, but didn't find anything. I know you use glowing splint for oxygen and limewater for carbon dioxide, but I'm stuck on these two gases.

Oxides of sulfur:

• Have no color
• Turn damp blue litmus paper red
• Have a choking, lung-catching smell

and  SO₂ turns filter paper soaked in orange potassium dichromate(VI) solution green without the deposition of Sulfur, which is what H₂S does. I don't know about a specific test for SO₃, although I know lots of things it can do, just not on the scale of testing.

NO₂ has a very characteristic brown color which darkens on heating, and if, when it is dissolved in water and ammonium chlorde is added, a gas (which is N₂- you can test for that too as it does gives a negative result for every single test that I know of!) is evolved, then it is definately NO₂. If you still aren't 100% sure its NO₂ for whatever reason then you can always check its not bromine as it will do nothing when it is dissolved in water and AgNO_3(aq) is added. (Bromine would give cream precipitate).

NO₂ has a choking smell, it certainly won't make you smile, let alone laugh!

[pantone159]

Nitrogen Dioxide will make you laugh.

You are thinking of N₂O, nitrous oxide.

[mike]

Sniff it.
Sulphur dioxide will stink.
Nitrogen Dioxide will make you laugh.

Never do this test!

[jgaoxx06]

Wow, thanks everybody, you're all so helpful.

[Alberto_Kravina]

An easy (and safe) detection reaction of sulfur dioxide is to pass the unknown gas in H₂O₂. If there is SO₂ it reacts with H₂O and forms sulfuric acid which can be easily detected with Ba²⁺

[qlabel]

Never do this test!

Is it possible to do it carefully, or is it too dangerous?

Is it also possible to make a quantitative analysis with the method you described AK?

[Mitch]

Never sniff unknown gasses!

[Alberto_Kravina]

Is it possible to do it carefully, or is it too dangerous?

That can be pretty dangerous...don't try it

Is it also possible to make a quantitative analysis with the method you described AK?

I don't know, you could titrate the formed sulfuric acid with NaOH, however, I don't know if 100% SO₂ absorbs to the H₂O₂...so I'm definately not sure about the accuracy of this method

[Mitch]

Just take an IR if possible.

[Will]

Never do this test!

Is it possible to do it carefully, or is it too dangerous?

Not only is it dangerous, but it is completely inaccurate. There are many gases that stink- ammonia, H₂S, Cl₂, hydrogen halides, C(SH)₂(Me)₂, thioacetone, (E)-but-2-ene-1-thiol, the list goes on and on.

Just take an IR if possible.

But that doesn't really count as a test, though, does it?

[bramgo]

There are kits to do these kind of test. I did both an NO_x and a SO_x test about 4 months ago. Both are like little glass tubes. First you need to break of the top and next you need to suck air inside them with some kind of pump. Fast, clean and easy.

[Will]

There are kits to do these kind of test. I did both an NO_x and a SO_x test about 4 months ago. Both are like little glass tubes. First you need to break off the top and next you need to suck air inside them with some kind of pump. Fast, clean and easy.

Oooo cool ! But isn't that cheating !? I think  jgaoxx06 wanted to know about a specific chemical test for NO₂ and oxides of sulfur. My teachers wouldn't have been too impressed if I told them that a test for these gases was to test them with specific kits which test for the gas in question!