Sciencemadness Discussion Board

Mysterious White Powder

SomeDude - 30-9-2012 at 19:46

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]

Nitrator - 30-9-2012 at 19:55

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]

IanCaio - 30-9-2012 at 20:10

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

Nitrator - 30-9-2012 at 20:19

lol, burned out tongue. :P

But seriously, that would not be cool.

phlogiston - 1-10-2012 at 01:35

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.

ElectroWin - 1-10-2012 at 05:15

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?

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

tetrahedron - 1-10-2012 at 06:44

thread from a few days ago:

sargent1015 - 1-10-2012 at 19:13

Well, if you have a little extra cash and want some absolute melting point precision, you cannot go wrong with the Mel-Temp:

But, if you are on a budget and still want accurate results, I recommend getting these for sure:

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!

bmays - 1-10-2012 at 22:30

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.

bfesser - 2-10-2012 at 11:12

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!

<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?

SomeDude - 2-10-2012 at 20:51

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)

sargent1015 - 2-10-2012 at 21:07

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.