Eddygp - 25-5-2013 at 10:53
I have a black chemical and I would like to know if it is carbon or a black metal oxide. Without using a flame test due to obvious sodium impurities
(I used a lot of NaOH) and being a home chemist, how could I identify the nature of this compound? I actually want to know if it is carbon or not,
only that.
vmelkon - 25-5-2013 at 13:35
Test for conductivity. Do some acid test to see if you get a colored salt.
woelen - 26-5-2013 at 23:04
Mix some of the powder with KClO3 and ignite. If it is carbon, then the mix burns easily with a purple flame, if it is some metal oxide, then it won't
burn.
Another option is adding the black powder to conc. HCl and heating for a while. Does it dissolve? If so, then it is some metal oxide. If not, then it
might be carbon, but this is not a 100% certain thing. If you add the powder to conc. HCl and it floats on the acid and sticks to the glass
everywhere, then it most likely is carbon. Metal oxides usually are much more compact and quickly settle at the bottom if they do not dissolve.
AndersHoveland - 27-5-2013 at 01:47
I think I remember reading somewhere that boiling hydrogen peroxide with sodium hydroxide will attack organics, including carbon. (a variation of base
piranha)
Again, not really sure about this.
Of course, you would have to make sure that the sodium hydroxide would not dissolve the metal oxide in question. Some of these metal oxides can be
slightly amphoteric (such as CuO).
just a possible suggestion, something to think about
[Edited on 27-5-2013 by AndersHoveland]
AJKOER - 27-5-2013 at 09:05
Talk about complex solutions to a simple problem, this thread should win an award.
Weigh a small amount of the compound (make sure it is dry otherwise heated it in a closed vessel) and heat at a high temperature in air (or O2). If
there are a lot of fumes, best heat in a closed vessel. Now, if it turns to a fine ash and basically is reduced in mass, it could be Carbon.
If you see a glow and no loss in mass, it could be a metallic oxide or some other inert compound (at least to oxygen), an alloy or even an element,
just not Carbon. Make sure there is sufficient O2 per the equation:
C + O2 (g) --> CO2 (g)
where 12 grams of Carbon (1 mole) will require 22.4 liters of O2 (and not air), but less if you make some deadly Carbon monoxide gas. In air to make
CO gas, you will need around 4.4 liters of dry air per gram of Carbon. So for a half liter flask, use no more than .1 grams of C (forming CO and not
CO2, which would require cutting in half the dose of Carbon or doubling the size of the flask).
[EDIT] Upon completion, an exercise in more advanced chemistry is to place compounds sensitive to the formation of CO in the flask, for example, CuCl
in HCl or aqueous ammonia to form the colorless chloride-bridged dimer [CuCl(CO)]2.
[Edited on 28-5-2013 by AJKOER]