ssdd - 26-8-2007 at 16:06
So I am wondering if I were to take a metal sulfate in solution (Mildly acidic due to excess sulfuric acid.), what would be the best way to take the
metal through different oxidation states yielding the different colors.
Just wondering if there are any general methods that tend to work for most metals.
-ssdd
*** Also what metals would be good for this? Exotic metals welcome. (Looking at a few of the rare metals on unitednuclear, would some of these work?)
[Edited on 26-8-2007 by ssdd]
Ozone - 26-8-2007 at 18:48
This is cool; there's a lot of neat stuff on this site.
http://www.cci.ethz.ch/mainpic.html?expnum=108&ismovie=1...
and:
http://www.cci.ethz.ch/mainpic.html?expnum=115&ismovie=1...
Also see Woelen's website, which is extremely well done.
Cheers,
O3
ssdd - 26-8-2007 at 19:07
Thanks, the one using the zinc is interesting.
I have done one in the past using KMnO3 solution poured into a second solution of Sucrose and NaOH. This takes the Mn ion through a great range of
colors. (Found this on Woelen's site some time ago.)
I love the transition metals and the experiments you can do with them. Makes for some impressive stuff.
-ssdd
woelen - 26-8-2007 at 22:42
Yes, transition metals make beautiful colors. Most remarkable are vanadium, chromium and iridium (the last one unfortunately is very expensive).
For vanadium experiments, the best start is the use of V2O5 from a pottery/ceramics supplier, dissolved in moderately concentrated warm solution of
NaOH. After acidification and addition of zinc powder this will go through all oxidation states, starting at +5, ending at +2.
For chromium, you can start with a compound like K2Cr2O7 and reduce this, using mild reductors (e.g. acidified sodium sulfite). The resulting color
strongly depends on the acid used, and on the reductor used. Any color from deep green/blue to red/purple can be obtained. This is due to excellent
complex formation properties of chromium(III). With zinc powder and HCl as acid, you can even go to the +2 oxidation state.
Another neat property of chromium in its +6 oxidation state is its reaction with hydrogen peroxide. Depending on pH, you can get many amazing
compounds, with colors ranging from red/brown to deep indigo/blue. Some of these can easily be isolated, but be careful with these. Peroxo chromates
are rather unstable and having them in solid pure form is not without risk.