jgourlay
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KN03 ---- or not???
I bought some "potassium nitrate" off of ebay. Now I'm wondering if I got pranked.
A million years ago my 7'th grade science teacher did the demonstration where you put a match to sugar (nothing), put a match to kno3 (nothing), mix
them together and put a match to it (slow burning pile making massive smoke cloud).
I was passing that onto my son yesterday, and it was nothing, nothing, nothing. This make me think it's not KNO3. Is there any way to allay
suspicion short of the extreme sports of making gunpowder or boiling it in sulfuric acid to make nitric?
Will (attempted) crystallization or putting some on a toothpick over a flame tell me anything?
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ScienceSquirrel
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You can try the flame test for potassium followed by the brown ring test for nitrate.
It will not tell you how pure it is though
http://library.thinkquest.org/2923/tests.html
Recrystallisation is very easy and potassium nitrate forms distinctive needles.
The crystals are not hydrated so taking a few grams of the dry recrystallised salt and heating it gently will cause little or no loss of mass.
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Saber
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how fine was the sugar you mixed it with?
Normally you either mix it with icing sugar or melt granulated sugar with the nitrate carefully.
If this still doesnt work hold a few crystals of it in a blue flame (of a bunsen burner), If it gives a purple/lilac colour you have a potassium salt,
if not, if its a orangey colour, then you have been tricked.
Next make a solotion of the salt you are testing. Add a soloution of FeSO4 and then drop conc sulphuric acid into the two soloutions... brown rings
should appear if there is a nitrate anion present.
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jgourlay
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Thanks Guys, I'll try that. I could also be due to using "suganot" which is some unrefined, brown, large crystal crap my wife buys instead of sugar.
I say "crap", actually it's got a much better, richer flavor that Imperial Pure Cane Sugar.
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jgourlay
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Okay, I'm now more certain I was pranked. I put a little pile of "the stuff" next to a little pile of Alum on a stainless steel plate and played over
them them a propane flame.
The alum has a color I wouldn't call "lilac", at least not the flaming Liberace purple I would expect, sort of a yellowy orange with just a hint of
blue. "The Stuff", otoh, has a definite sodium orange. I'll do it against salt tonight just to confirm, but I'm pretty sure it's a sodium compound.
I don't have any ferric sulfate for the nitrate test.
I have some black phospated deck screws. Could I dissolve one in some H2SO4 to get close enough? Unfortunately I just cleaned up the garage over the
weekend, so I don't have any of the typical steel chips laying around next to the lathe.
Also, "the stuff" melted immediately and turned to a glassy substance. This makes me think it's not NaCl. I took the glass and dropped it in a
little dish of hot water on the way out the door to work. When I come back this afternoon I'll see if any kind of crystallization has occured--enough
at least to see needles vs cubes or dendrites vs crust.
If this stuff turns out to be sodium nitrate, could I take equal weights of "the stuff" and road salt (KCl), dissolve in water and recrystallize to
get KNO3 and NaCl?
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ScienceSquirrel
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Alum will not give a good potassium colour in a flame test as it is a hydrated salt and has aluminium in it as well.
Potassium sulphate or potassium chloride give an excellent lilac shade.
You need ferrous sulphate (iron II sulphate ) not ferric sulphate ( iron III sulphate) for the brown ring test.
The easiest way to make it fresh is to add a little fine steel wool to dilute sulphuric acid, warm and filter.
I can't see you getting very far with a black phosphated deck screw
You reallly have to make a hot saturated solution and let it cool to do the crystallisation test properly.
[Edited on 9-9-2008 by ScienceSquirrel]
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jgourlay
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Why didn't I think of that?
Geez...steel wool. I'm such an idiot. I have packs and packs of that that I bought for furniture refining before I discovered abralon pads.
"dilute" H2SO4: I really need to go back and review molarity and the definitions of "dilute" and "strong" and "holy crap!" with respect to
acids/bases.
Recrystallization: I'll do that. matter of fact, I should go through all this from the beginning with my son. What a great lesson!
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ScienceSquirrel
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If you have a look at the solubility table here.
http://en.wikipedia.org/wiki/Solubility_table
You will see that you can dissolve ca 15g in 25mL of water at 60C. Try that using a warm water bath, then you want to get it a little hotter than that
to stop it dropping out in the filter, say 80 - 90 C. Filter and cool in ice to produce a crop of needles ca 12g.
This extreme solubility curve of potassium nitrate was used to purify it in the old days when it was made from urine etc and also to estimate its
purity.
A mass of good saltpetre would disssolve in a certain volume of water at a certain temperature.
If it did not and you were selling to the king then 'a taste of the lash' awaited you.
The concept of dilute sulphuric acid is a bit nebulous, but 2 -5M is about right
[Edited on 9-9-2008 by ScienceSquirrel]
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MagicJigPipe
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If you have even technical grade KNO3 mixing it w/ normal granulated sugar will cause it to be sensitive to flame (i.e. it will burn). Period. If it
doesn't burn it's either not KNO3 or it's so impure it might as well not be KNO3.
Yes, there are other ways to test but, like I said, if it doesn't burn you got jipped.
"There must be no barriers to freedom of inquiry ... There is no place for dogma in science. The scientist is free, and must be free to ask any
question, to doubt any assertion, to seek for any evidence, to correct any errors. ... We know that the only way to avoid error is to detect it and
that the only way to detect it is to be free to inquire. And we know that as long as men are free to ask what they must, free to say what they think,
free to think what they will, freedom can never be lost, and science can never regress." -J. Robert Oppenheimer
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jgourlay
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Right, I got jipped. Now I need to find out what the stuff really is. Maybe it will be useful, or maybe it will laundry detergent.
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Magpie
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Maybe you can turn this into a real learning experience for you and your son - identifying an unknown! 
1. Is it soluble in water, dilute H2SO4, alcohol, etc ?
2. Is it flammable? What kind of flame?
3. If an inorganic do flame testing for cations.
4. Then if you can get the test reagents do some standard qualitative analyses for cation and anions.
5. Determine melting point if organic.
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kilowatt
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| Quote: |
Also, "the stuff" melted immediately and turned to a glassy substance. |
Sodium tetraborate? See if you can acidify it to precipitate boric acid, identified by a green flame test.
[Edited on 9-9-2008 by kilowatt]
The mind cannot decide the truth; it can only find the truth.
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jgourlay
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<<See if you can acidify it to precipitate boric acid, identified by a green flame test.>>
Can I drop some H2SO4 in there and achieve that?
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ScienceSquirrel
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If you have sulphuric acid then adding dilute and then concentrated sulphuric acid to small portions of the material and then heating the samples
would be interesting.
It would certainly give you a good indication of the anion.
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not_important
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borates and phosphates come to mind for making glassy melts. Dissolve a small amount of the stuff in water, add a drop of hydrochloric acid and mix,
let sit and pour the liquid into another container. Add some concentrated calcium chloride solution, a precipitate could be phosphate, borate,
sulfate, or a few others. Adding a little HCL to make it strongly acid will dissolve calcium borates and phosphates. The green flame test for
borates can distinguish the two. If adding HCl gives bubbles the likely carbonate or bicarbonate, a drop of lime water on a glass rod held in the
off-gas will confirm.
A little of the stuff in a strong warm solution with some strong H2SO4 added would form nitric acid if the material contains a nitrate, dropping in
some bits of copper wire would result in the wire quickly dissolving with the formation of brown NO2. If adding the H2SO4 gave a precipitate and
copper indicates a nitrate, it could be a fertilizer containing calcium and nitrates, some of these mixtures aren't very energetic when heated with
fuels and will 'melt' when heated.
A strong heating - red heat - will fully decompose such mixes, when cooled the solids likely will not be very soluble and the solution will test
alkaline. Phosphates and borates and halides will melt, but don't change much and their water extract will not be strongly alkaline.
Almost any organic will char or vapourise, salts or organic acids will burn to carbonates and oxides, and will have an alkaline water extract, or
sulfates from sulfonic acid salts (detergents) with near neutral water extract; most of these won't melt but char instead.
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Phosphor-ing
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Please say you gave the seller a negative feedback on ebay!
"The nine most terrifying words in the English language are: 'I'm from the government and I'm here to help.'" -Ronald Reagan
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jgourlay
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Unfortunately no. I bought this over a year ago, and just now got into the bag. I don't have a record of the seller.
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