cnidocyte
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Thermal decomposition of KNO3
I saw on a youtube video, a boiling tube of NaNO3 converted to NaNO2 by flaming the boiling tube:
http://www.youtube.com/watch?v=L7qRoYQEBPk
I don't have any NaNO3 so I tried this with KNO3 instead but got different results. I heated the boiling tube on a gas stove but the KNO3 turned black
as it melted so I couldn't use this change from cloudy white to clear as an indicator that the reaction occured. Why would the salt turn black like
that? Potassium oxide is pale yellow so thats not the cause of it.
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Picric-A
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Because either your KNO3 had impurities in it that were oxidised to carbon or the glass had impurities on it that oxidised likewise.
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Retard-3000
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Recrystalize it and try again
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cnidocyte
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I recrystallised from tap water and got the similar (turned brown instead of black this time) when I melted it. Shoulda used distilled water but the
impurities from tap water wouldn't be enough turn the salt brown would it?
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not_important
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Describe your recrystallisation process in detail. Too often I've seen someone "crystallising" a product by boiling off all the solvent and frying
the solid. There's plenty of 17th and 18th century texts describing the purification of saltpeter, worth a bit of digging on the Internet Archives,
Google Books, and elsewhere.
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ScienceSquirrel
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Anyone planning on a recrystallisation should consult a solubility table.
This is the one from Wikipedia;
http://en.wikipedia.org/wiki/Solubility_table#P
Recrystallising potassium nitrate should be a breeze and it gives really lovely needles if you do it right.
I would dissolve about 60g in 100ml warm water and then cool it slowly in the fridge.
[Edited on 8-2-2011 by ScienceSquirrel]
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The WiZard is In
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Make a saturated solution and put in your freezer... works wonders.
djh
---
Cunning, Care and Sheer Luck Save Rare Map
NY Times 17i11
White lines were visible where the map had ripped, the brighter
inner fabrics of the paper standing out from the stained surface.
Mr. Derow visited Argosy Book Store on the Upper East Side and
bought a handful of obscure old books - among them, for
example, "The Select Dialogues of Lucian, to Which Is Added, a
New Literal Translation in Latin, With Notes in English," from 1804
- that were printed on cloth paper, like the map, and not wood
pulp.
He performed on them a technique that should chill the blood of
any author, wondering where his books will be in 200 years: he
baked them in his kitchen stove and boiled them in water. He
painted the resulting brackish stew onto the white lines, matching
them to the rest of the map.
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cnidocyte
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Quote: Originally posted by not_important  |
Describe your recrystallisation process in detail. Too often I've seen someone "crystallising" a product by boiling off all the solvent and frying
the solid. There's plenty of 17th and 18th century texts describing the purification of saltpeter, worth a bit of digging on the Internet Archives,
Google Books, and elsewhere. |
I added boiling water to a few grams of KNO3 until it was fully saturated then I put the solution in the freezer and let it cool to around 3C then
filtered out the large crystal shards. Maybe the boiling tubes themselves are dirty.
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