Swede
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Registered: 4-9-2008
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Reflux setup for valve metals
I'm looking for suggestions from the hive mind... Electrochemistry is my bag, organic chemistry (or chemistry requiring mucho glassware) generally is
not.
My task is to strip oxides from valve metal strips for various formulations of mixed metal oxides, MMO, and other deposited solid solutions. Usually,
this calls for hours of immersion in near boiling mineral acids, like 20% HCl. I really need some sort of a reflux setup to do this properly.
Can something like this be jerry-rigged? Would a round-bottom flask filled with crushed ice over a beaker be adequate?
If not, how do I reflux so that the heated acid, the container itself, can accept moderately sized Ti samples? A typical ground-glass joint is too
small.
Thanks.
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smaerd
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Mood: hmm...
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Are you planning on refluxing HCl or getting it below its boiling point?
Reactor flask would accept bigger items but it seems like flask abuse especially if the metal is heavy.
Ex: http://i00.i.aliimg.com/img/pb/354/743/465/465743354_227.jpg
Do the acids need to be heated? Could the oxides be stripped with a bit more time at room temperature?
Another option would be to use a big pyrex beaker or flask put it on a hot-plate and turn on the fume-hood or do it outside?
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Swede
Hazard to Others
Posts: 491
Registered: 4-9-2008
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Thanks, Smaerd, the procedure calls for "near boiling" HCl for a several hour period. No specific temperature specified, just hot. No doubt, it
could be done at RT, just slower.
Another choice mentioned is oxalic acid, which I have in some quantity.
The valve metal substrates are first abrasive-blasted with aluminum oxide, silica, or similar, and small fragments embedded in the valve metal must be
removed as well as the oxides of the substrate.
A reaction flask like that pictured would work, but would be overkill for what should be a simple process.
I am attempting to first replicate Henri Beer's ruthenium-based MMO, then begin work on the addition of Bi ions into the mixture, eventually to create
a BiRuO pyrochlore, sintered into the substrate with high heat. This is one of those things where if the substrate is not correctly prepped,
mechanical coating failure is almost assured.
I may simply have to do it outside, unless I can come up with some sort of reflux rig that minimizes the fumes. Unfortunately I don't have a fume
hood.
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