11 replies to this topic

[Pretty green flames]

I recently got some KNO3. And i only noticed today.
It smells of Cl. It's like that smell like in the swimming pools.

Is it supposed to smell of Chlorine or something else.
My first batch of KNO3 was odorless.

Anyway to test if it really is KNO3.

Take care

[neo]

taste it, if it taste salty the you've got the right thing

seriously I have now idea, but is there no other way to test than that david sad? because I don't know where to get or dear to use high concentrated H2SO4...

[Phoenix]

I don't see why it wouldn't be KNO3, if that is what it was sold as, but you could dissolve some it water and allow it to crystallyse out. It should form long needle like crystals. Here is a picture of some KNO3 crystals.

Here is W.V's chlorate and perchlorate page, which has pictures of these compounds on.

Finally do a flame test. Potassium compounds should, of course, turn the flame purple.

[richard2]

The best way to ensure that it is a potassium salt, without getting some other hard to find chemicals, is as mentioned above - to carry out a flame test. Take a piece of wire and if you have it dip it in some strong HCl then dip it in some of you chemical and hold it in a blue gas flame. If it turns the flame lilac/purple it is very likely to be a potassium salt if this is what you purchased it as.

There is also quite a simple test to ascertain that it is indeed a nitrate. Take a small amount of your chemical and mix it with a small amount of iron(II) sulphate. Make up a saturated solution of this in a test tube and gently drip some concentrated H2SO4 down the side of the tube - it will sit at the bottom of the tube. If a brown ring forms at the interface of the two layers you have a nitrate.

To determine if there is a chloride present mix a small amount of you sample with a small amount of manganese dioxide and add a little concentrated H2SO4. If there is chloride present chlorine will be liberated and this can be detected by wafting some towards your nose (carefully) or it will bleach damp litmus paper.

Warning: If you suspect the salt is a chlorate or perchlorate DO NOT add concentrated H2SO4 as it will form an explosive gas or solution.

You can probably test your KNO3 in a small amount of composition to find out if will work however I am not sure how a small amount of chloride contamination will affect it. I think that sodium chloride acts as a flame retardant and would imagine that this would be the case for other some of the other chlorides. Maybe someone else will know.

Also how dry is your KNO3 - has it been exposed to a lot of moisture.

Rich

Having thought about this a little more rationally in the morning without having had a few drinks it is unlikely to be a chloride that is the problem. It could however be a hypochlorite salt which can give off chlorine in the presence of any ammonia that could be formed by the reaction of nitrate ions with other impurities.
I do not know how a hypochlorite impurity would affect a composition however I seem to remember Big G advising against using it in a composition when it was suggested as a chlorine donor. Also I can't find a test for hypochlorite in my notes you could probably try adding a few drops of ammonia to a small amount to see if chlorine is given off.

Edited by richard2, 06 November 2004 - 08:33 AM.

[Pretty green flames]

Also how dry is your KNO3 - has it been exposed to a lot of moisture.

It's sealed in a Air tight container

[Stuart]

Chlorates and Perchlorates dont smell of Chlorine, I doubt that you have that in there. If I had to guess, I would say Hypochlorites would be the cause.

The easy test (if a bit crude) for this would be to put a layer of Potassium Nitrate in a shollow dish. Add some cold water so it just covers the Potassium Nitrate. Blow away any air until the area is clear of Chlorine and the water will stop any more getting to the air. Then add some Hydochloric acid and stir it a bit. It bubbles are formed and the gas smells like Chlorine, you probably have some Hypochlorite there. If nothing is given off, then you probably dont have any Hypochlorite in it.

[adamw]

Maybe it is just the container? Some plastic storage tubs sometimes smell quite chlorine-like

[bobconan]

Easiest way to tell if its hypochlorate is add soda to it. if it gives off chlorine then its hypochlorate. Regular coca cola soda.

[bobconan]

yes you are most right.