After a calcination analysis there was an orange mass sticked in my ceramic containers. It is supposed to be some V(V) oxide since the sample was a
V(IV) complex. I have already treated it with regium water and sulphocromic solution and still it won´t clean. I was thinking that maybe I need a
reducing agent instead of an oxidizing agent. Can someone help?microcosmicus - 13-2-2008 at 13:50
Since it's in already a crucible, maybe try reducing it at high temperature
with carbon, hydrogen, or magnesium. For what it's worth, vanadium is
commercially reduced using calcium metal.
Instead of using an acid, try an alkali. Mixing with NaOH should give
you Na3VO4, which dissolves in water:
Looking at the reactions mentioned in those articles should also give
you some other ideas of things to try.
[Edited on 13-2-2008 by microcosmicus]not_important - 13-2-2008 at 20:37
Going after it with alkali is the best. Even boiling aqueous Na2CO3 should do it. An alternative is hydrochloric acid plus alcohol or sugar, this
reduces V2O5 to V(IV), breaks up most insoluble vanadates and V-S-P based compounds.
If it's really tough try doing a Na2CO3 fusion, followed by extraction with warm water. Any stains remaing are then likely to yield to HCl (aq) +
EtOH.Klute - 14-2-2008 at 13:48
You could try giving the pirahna solution a try: conc. H2SO4 with 30% H2O2. It's a powerfull oxydant AND reducer, but be very carefull the stuff heats
up considerably, and can eat through anything in a matter of seconds.
Espceially don't let even trace amounts of nitrates/ nitric acid approach the stuff, I've had a very frightening experience that way.not_important - 14-2-2008 at 20:39
I'd try alkali, and the HCl + alcohol, before piranha, and I use piranha more than a lot of people do. Less potential for "exciting action", and I
think a better fit for the material in question going by its origins. If it was calcined then it's likely purely inorganic, and possibly fused. It
might have reacted with the ceramic, in which case it may not be completely removable.Klute - 15-2-2008 at 03:37
Quote:
I'd try alkali, and the HCl + alcohol, before piranha, and I use piranha more than a lot of people do.
Yes, you are right. Better stay on the safe side; and it is more adapted to (very small amounts of) organic materials. I usually use it on fritted
filters when aqua regia doesn't work.
