SomeDude
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Mysterious White Powder
Hey, I got two different white powders from my friend (not drugs), both of us couldn't figure out what they could be and I was looking to use some
chemistry techniques to figure out what these powders are. What chemistry techniques would I use to figure out what these powders are made of. besides
chromatography cause that's too expensive
So far this is what I got
Powder A:
Physical Properties: White, Shiny, Flakes, Oder less, Insoluble in water almost feels like fake snow, tastes sour/bitter
Powder B:
Physical Properties: White, dull, Oder less, bitter, Insoluble in water, numbs the tongue (once again this is not an illegal drug such as cocaine)
How would I find the pka of a chemical which is insoluble in water (for instance if it was soluble i would just use mix it with water and check it
with ph paper, but since it isn't soluble in water do I have to try and mix it with another solvent and if so wouldn't that the ph of the mixture come
up more or less the same as the solvent that I used?)
Also, If I'm trying to find the melting point, would I simply just put the powder on a hotplate and keep turning up the heat until it starts melting?
[Edited on 1-10-2012 by SomeDude]
[Edited on 1-10-2012 by SomeDude]
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Nitrator
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If you don't know what it is, than you should never taste it. You're still alive, so apparently it's not acutely toxic, but it could be carcinogenic
or have a certain threshold limit.
Don't ever taste anything you make in the lab, period! (Especially if you don't know what it is).
[Edited on 10-1-2012 by Nitrator]
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IanCaio
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Nitrator is right, its basically number 1 rule on labs, never
taste reagents, smell gases, specially if you dont have a clue
what they are. Imagine if you had some sodium hydroxide,
your tongue would be completely burned because you tasted
it.
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Nitrator
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lol, burned out tongue. 
But seriously, that would not be cool.
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phlogiston
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If there is absolutely no further clue as to what these materials might be, this is not nearly enough information to make any guess.
Where did you get them from?
The fact that you tasted them suggests to me you knew in advance that they are not fatally toxic. How did you know? How do you know they are not
illegal drugs?
I guess that what I am trying to say is that is clear you know more than you are sharing and you are likely to get a more helpful answer by revealing
a bit more than you have.
-----
"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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ElectroWin
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Quote: Originally posted by SomeDude  |
Also, If I'm trying to find the melting point, would I simply just put the powder on a hotplate and keep turning up the heat until it starts melting?
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that's most of it. but don't forget, you still need an instrument that measures its actual temperature, as it reaches the melting point.
those new infrared thermometers are neat, since they don't need to touch the surface of the material
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tetrahedron
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thread from a few days ago:
http://www.sciencemadness.org/whisper/viewthread.php?tid=215...
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sargent1015
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Well, if you have a little extra cash and want some absolute melting point precision, you cannot go wrong with the Mel-Temp:
http://www.ebay.com/itm/Mel-Temp-200W-Melting-Point-Apparatu...
But, if you are on a budget and still want accurate results, I recommend getting these for sure:
http://www.amazon.com/Pyrex-Glass-Capillary-Tubes-Melting/dp...
and setting up a hot water bath (0-100C mp range) or an oil bath with a thermometer in it. Place your compound in the tube and place the tube in the
bath. Slowly increase the temp and observe the mp (Or melting range as it will appear).
I am not sure if this technique is fully outlined in Bromic's and my book (see my links), but it sure will be!
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bmays
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On a hotplate with some sand you can get a general idea of the melting point, boiling point, decomposition temperature. Inorganic compounds generally
have higher heat tolerance in all aspects while many organics will melt, boil, and decompose easily. Inorganics will possibly decompose into more
easily identifiable elements or other compounds while organics will turn to soot (leftover carbon). Put an inorganic in a strong acid or base might
yield a useful decomposition/color change/observation etc. My guess is you have an organic compound. Try obtaining the freebase compound (is it a
liquid, melting, etc, etc), try making an hcl salt, test solvents, melting points, etc. You could find its density. It would also be possible to
determine its molar mass by finding how many moles hcl (for example) are needed to salt 1 gram of your unknown. You are going to have a heck or a time
if it is organic with no ideas and no infrared spectrograph.
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bfesser
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| Quote: Originally posted by Nitrator | If you don't know what it is, than you should never taste it.
. . .
Don't ever taste anything you make in the lab, period! |
<strong>Wrong!</strong>
<underline>Always</underline> taste unknown white powders! It's our best hope of ever being rid of idiots like you.
P.S. Did you know that KCN tastes like candy?
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SomeDude
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thanks for all the professional advice, gonna check the melting point with hotplate and then I'm going to try to mix it with some sulfuric acid/sodium
hydroxide to see what happens. Just to clarify (if it dissolves easily in an acid then the powder is acidic? i.e. low ph levels)
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sargent1015
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Not really, if it dissolves or reacts (gas given off or something) it is likely basic. If it is an organic compound with a site to protonate, adding
an acid may dissolve it or adding a base could remove a proton and dissolve it.
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