CharlisonX
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unknown substance
Hello, Sciencemadness! I am Charlison, a long-time lurker of this forum(~2 years) and small-time chemist, amongst other hobbies.
I finally decided to create an account for a question i had for a long time ago.
this '?' labeled dust is a pure lab reagent, i forgot which one.
what i know is that i got him together with sulphuric acid, nitric acid, potassium iodide, NaOH pellets,metallic iodine and sodium sulphate.
it's not lead nitrate, my teacher didn't let me touch that one
how can i know what is this dust?
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Maroboduus
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Go get, or download, a Quantitative analysis textbook.
Read it.
Buy the reagents they use.
Do what they tell you to do.
Alternatively you can try and find some lab to analyze it for you at a reasonable fee. Or it may be easier to try and find some lab to analyze it for
you for a hefty fee.
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TheMrbunGee
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You need to do some tests, I assume you will not get and read Quantitative analysis textbook.
As I understood - it is one of "sulphuric acid, nitric acid, potassium iodide, NaOH pellets, metallic iodine and sodium sulphate" correct?
sulphuric acid, nitric acid - liquids, so no.
NaOH pellets - not dust so - no!
"Metallic" iodine I think you mean crystalline, but it is dark colored, so no!
So it is either sodium sulphate or potassium iodide?
Easy test is to try dissolving it! If you can dissolve 10 g of it in ~50 ml fridge temperature water - then it is Iodide, if you can’t - it is
sulphate!
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aga
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Put a tiny amount on a spoon and tip the dust into a flame.
See what colour it makes.
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CharlisonX
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i did try dissoluting it, it is lighter than water, and it didn't reacted until i mixed manually. it's heavier than 98% ethanol tho, and soluble on
the latter, i don't have a scale so i can't say how much.
also, i put it in the spoon and pointed a flame, besides the blue color of the flame, i didn't saw any particular color, i mean, the dust started
glowing bright yellow, so maybe that caused some interference
EDIT: i'll point out that i think it's talc, and if it is, i'll be so disappointed that i'll make sure the sample never existed
also, i have matters to attend later so i can't do any experiments after a hour or two from now
[Edited on 23-11-2016 by CharlisonX]
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Maroboduus
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Quote: Originally posted by TheMrbunGee  | You need to do some tests, I assume you will not get and read Quantitative analysis textbook.
As I understood - it is one of "sulphuric acid, nitric acid, potassium iodide, NaOH pellets, metallic iodine and sodium sulphate" correct?
sulphuric acid, nitric acid - liquids, so no.
NaOH pellets - not dust so - no!
"Metallic" iodine I think you mean crystalline, but it is dark colored, so no!
So it is either sodium sulphate or potassium iodide?
Easy test is to try dissolving it! If you can dissolve 10 g of it in ~50 ml fridge temperature water - then it is Iodide, if you can’t - it is
sulphate!
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If it is in fact one of those chemicals then you're certainly right.
It was my impression from his post that he was telling us he bought this along with those other chemicals, and that he had no idea what it is.
Can't imagine why he wouldn't say it's one of those chemicals if it is, in fact, one of those chemicals. However the only other bit of information he
gave us is that it's NOT lead nitrate. Why would he point out it isn't lead nitrate if he's telling us it's one of those other chemicals?
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aga
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Heigh-ho. Best of luck with it then.
Some Qualitative analysis might be easier to get started with.
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Maroboduus
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| Quote: Originally posted by CharlisonX | i did try dissoluting it, it is lighter than water, and it didn't reacted until i mixed manually. it's heavier than 98% ethanol tho, and soluble on
the latter, i don't have a scale so i can't say how much.
also, i put it in the spoon and pointed a flame, besides the blue color of the flame, i didn't saw any particular color, i mean, the dust started
glowing bright yellow, so maybe that caused some interference
EDIT: i'll point out that i think it's talc, and if it is, i'll be so disappointed that i'll make sure the sample never existed
also, i have matters to attend later so i can't do any experiments after a hour or two from now
[Edited on 23-11-2016 by CharlisonX] |
Talc is much higher in density than water, and is not soluble in water or ethanol. This should be good news, as it will relieve you of the necessity
of making sure the sample never existed.
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CharlisonX
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oddly, the alcohol-? solution went grey in the meantime
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CharlisonX
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i'm leaving now, as an extra i'll leave my last two tests:
added silver nitrate on the two solutions: no change
added '?' on vinegar: insoluble, no reaction
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TheMrbunGee
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| Quote: Originally posted by CharlisonX | i did try dissoluting it, it is lighter than water, and it didn't reacted until i mixed manually. it's heavier than 98% ethanol tho, and soluble on
the latter, i don't have a scale so i can't say how much.
also, i put it in the spoon and pointed a flame, besides the blue color of the flame, i didn't saw any particular color, i mean, the dust started
glowing bright yellow, so maybe that caused some interference
EDIT: i'll point out that i think it's talc, and if it is, i'll be so disappointed that i'll make sure the sample never existed
also, i have matters to attend later so i can't do any experiments after a hour or two from now
[Edited on 23-11-2016 by CharlisonX] |
It is probably floating in top of water because it is fine powder and there is air trapped within the pile.
So it is soluble in water? Is the solution clear and colorless?
Talc will react with strong acids.
| Quote: |
oddly, the alcohol-? solution went grey in the meantime
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Did the powder just sank to the bottom? Alcohol might have extracted some impurities from the powder if so!
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Bert
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Potassium iodide is soluble in methanol, and PROBABLY in ethanol. Your sample dissolved in alcohol?
Take a few ml of alcohol, dissolve as much chemical as will easily do so in it. Ignite the solution on a CLEAN surface. Does it have a lilac/lavender
colored flame (Potassium spectrum).
https://youtu.be/jJvS4uc4TbU
[Edited on 24-11-2016 by Bert]
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Bert
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Thread Moved
24-11-2016 at 08:02 |
NitratedKittens
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The only thing about potassium flame test is that it is very easily contaminated with other compounds, However if it is a pure reagent, and it has
been stored properly then it should work.
Basket of kittens for you ........BOOM
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Texium
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There was no precipitate with silver nitrate. Potassium iodide has already been disqualified by that test. Plus he said from the start that he got it
with KI, not that it could be KI.
I'm wondering if it's an organic compound, perhaps a sugar. Try adding a drop of conc. sulfuric acid to a pile of it, carefully, and see if it
carbonizes.
Otherwise, just test an aqueous solution of it using a bunch of different qualitative tests if you have the materials. See if you get a precipitate
with chloride, sulfate, carbonate, barium nitrate, etc. See if it will reduce a dichromate or permanganate solution.
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NitratedKittens
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Get some distilled water, and dissolve the substance then test for electrical conductivity, if it is ionic it will disassociate and start conducting
electricity. if it is covalent the conductivity will not change.
Basket of kittens for you ........BOOM
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CharlisonX
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| Quote: |
I'm wondering if it's an organic compound, perhaps a sugar. Try adding a drop of conc. sulfuric acid to a pile of it, carefully, and see if it
carbonizes
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i added a drop of sulfuric, but there was no reaction,
I suspect my acid absorbed atmospheric water, as i tested it with regular sugar and didn't carbonized. too
| Quote: |
Otherwise, just test an aqueous solution of it using a bunch of different qualitative tests if you have the materials. See if you get a precipitate
with chloride, sulfate, carbonate, barium nitrate, etc. See if it will reduce a dichromate or permanganate solution.
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ferric chloride: no precipitate
sodium carbonate: no precipitate
copper sulfate: it seemed the compound flaked but I tried again with a new sample after the insoluble part went to the bottom. no precipitate
barium nitrate: I don't have BaNO3, but I tried with silver nitrate: no precipitate
potassium permanganate: no reduction, at least not any bubbles or precipitate,
(my pernanganate is part reduced to MnO2, but it still can draw oxygen from H2O2)
sodium hydroxide: no precipitate
i also felt all mixtures, there wasn't any significant change of temperature at all
| Quote: |
Get some distilled water, and dissolve the substance then test for electrical conductivity, if it is ionic it will disassociate and start conducting
electricity. if it is covalent the conductivity will not change.
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i don't have distilled water, but I have a multimeter, and I made some tests:
tap water: 115k ohms
tap water with '?': 200k ohms
tap water with table salt:12k ohms
tap water with sulfuric acid: 0,8k ohms
i also apologize for almost necroing the thread, but my laptop died when i tried to open it later that day, fixed it today.
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phlogiston
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If it was organic, very likely you would have observed it decomposing and/or melting when you heated it directly in a flame. However:
| Quote: | | also, i put it in the spoon and pointed a flame, besides the blue color of the flame, i didn't saw any particular color, i mean, the dust started
glowing bright yellow, so maybe that caused some interference |
With 'glowing bright yellow', do you mean you saw the powder sitting there on the spoon emitting a yellow glow, or do you mean the flame itself turned
yellow, possible from vapor from the powder or particles being blown into the flame?
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"If a rocket goes up, who cares where it comes down, that's not my concern said Wernher von Braun" - Tom Lehrer |
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NitratedKittens
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also, did some sooty smoke come from the compound when heated.
Basket of kittens for you ........BOOM
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CharlisonX
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No. It was the powder that was glowing, like a piece of charcoal. It cooled very fast when I stopped heating,
No soot either, the dust was as white as packed.
Except for some dark in the vicinity of the flame(probably from the butane flame itself, i didnt pointed at those areas)
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Harristotle
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Titanium dioxide powder glows yellow when it is heated up, and loses it when it is cold.
Test by adding 0.5g to 5ml conc sulfuric and heat until fumes are formed. Dilute to 100ml, then add 6% H2SO4. Should turn orange-red if TiO2.
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phlogiston
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So, it is likely to be an inorganic compound.
What is puzzling is that it dissolves in ethanol, but not in water.
TiO2 nor any other metal oxide I can think of has that property.
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"If a rocket goes up, who cares where it comes down, that's not my concern said Wernher von Braun" - Tom Lehrer |
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