KaliyaK
Harmless
Posts: 15
Registered: 10-2-2016
Member Is Offline
Mood: No Mood
|
|
Potassium nitrite solution
Hello everyone! I have made some potassium nitrite but i cant seem to be able to dry it. I thought on dissolving it all and make a stock solution. How
will i be able to determine the concentration of the final solution? Thanks!
|
|
|
Bert
|
Thread Moved
15-12-2016 at 11:59 |
Scalebar
Hazard to Self
Posts: 54
Registered: 6-5-2016
Location: Europe!
Member Is Offline
Mood: Looking for a way out
|
|
There's probably easier ways but boiling a known volume down to constant weight ( ie. really really dry )would be one way
|
|
|
Eddygp
National Hazard
Posts: 858
Registered: 31-3-2012
Location: University of York, UK
Member Is Offline
Mood: Organometallic
|
|
If it's wet, it will be very difficult to determine the exact concentration without a margin of error. Is there no way you can dry it with drying
agents and the sort?
Otherwise, there must surely be some conductivity test with a KNO2 solution to determine the concentration. Either that or check molar UV absorbances
of nitrite, check UV and use Beer Lambert Law. From that stock solution of, once you do the UV thing, known conc., you can proceed normally.
[Edited on 16-12-2016 by Eddygp]
there may be bugs in gfind
[ˌɛdidʒiˈpiː] IPA pronunciation for my Username |
|
|
JJay
International Hazard
Posts: 3440
Registered: 15-10-2015
Member Is Offline
|
|
I recently saw a procedure on potassium nitrite titration with sulfuric acid and permanganate. It said that it is ordinarily possible to obtain
results within 1% if the nitrite is added to a measured quantity of a standard permanganate / sulfuric acid solution.
It should be easy enough to dry potassium nitrite over calcium chloride.
[Edited on 17-12-2016 by JJay]
|
|
|
KaliyaK
Harmless
Posts: 15
Registered: 10-2-2016
Member Is Offline
Mood: No Mood
|
|
I have tryed to dry it with sodium hydroxide but it forms a dry layer on top and provents the rest from geting dry. Even with regular steering it was
non efective. And heat it to dryness i'm afraid to burn it... Maybe theres a best drying agent, will magnesium chloride be any better? Maybe try to
spread the nitrite on a petri dish to have more surface area?
|
|
|
Magpie
lab constructor
Posts: 5939
Registered: 1-11-2003
Location: USA
Member Is Offline
Mood: Chemistry: the subtle science.
|
|
You should be able to dry your NaNO2 under gentle heat as I did here: http://www.sciencemadness.org/talk/viewthread.php?tid=52&...
And, you should be able to titrate your solution with KMnO4 as already mentioned.
The single most important condition for a successful synthesis is good mixing - Nicodem
|
|
|
JJay
International Hazard
Posts: 3440
Registered: 15-10-2015
Member Is Offline
|
|
Quote: Originally posted by KaliyaK  | | I have tryed to dry it with sodium hydroxide but it forms a dry layer on top and provents the rest from geting dry. Even with regular steering it was
non efective. And heat it to dryness i'm afraid to burn it... Maybe theres a best drying agent, will magnesium chloride be any better? Maybe try to
spread the nitrite on a petri dish to have more surface area? |
You'd want to get it fairly dry first and then spread it out. A petri dish would work, as would the bottom of a large beaker.
You could then put that beaker into a bucket with calcium chloride on the bottom and seal the bucket, stirring the nitrite occasionally. It could take
a few days or weeks to obtain a really dry product.
|
|
|
woelen
Super Administrator
Posts: 8014
Registered: 20-8-2005
Location: Netherlands
Member Is Offline
Mood: interested
|
|
Potassium nitrite is much more hygroscpoic than sodium nitrite. If you keep potassium nitrite in contact with air it may even liquefy, but at least it
becomes wet through.
Drying it by spreading it in a petri dish is not going to work. You can heat the material and drive off water, but the disadvantage of this is that
part of the material may be oxidized to nitrate. Humid/wet nitrite is slowly oxidized by oxygen from air to form nitrate. This will not destroy all of
you nitrite, but it may become impure.
Maybe apply some gentle heating, driving off most of the water and then dry the remaining part in a closed vessel over NaOH or H2SO4? Maybe even CaCl2
works, but I don't know that. Just try it.
|
|
|
JJay
International Hazard
Posts: 3440
Registered: 15-10-2015
Member Is Offline
|
|
PrepChem suggests rinsing off water with ethanol and using calcium chloride as a dessicant: http://www.prepchem.com/synthesis-of-potassium-nitrite/
I can't say with 100% certainty that the procedure works, but it seems reasonable.
|
|
|
![[*]](images/xpblue/default_icon.gif){kind=icon}
