transformer
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filtering very fine particles
Is there any other way that is superior to celite for filtering extremeley fine carbon particles?
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Fleaker
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Have you tried using a very fine filter paper or fritted glass (heat it up to remove the carbon)? There are other methods of
separation...centrifugal...extreme density differences (i.e. thallium malonate solution, sand will float on it) etc.
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transformer
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Unfortunately there is no fine filter paper at hand or a good centrifuge and vaaguh was afraid of clogging his fritted glass funnel with the carbon
particles.
How does this removal process by heating the fritted glass work? Just heat and then shake the dry particles off?
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Eclectic
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If you can tolerate low levels of protein impuritys and you are working with an aqueous system, try mixing in a little egg white and boiling. The
coagulating egg will floculate extremely small particles into easily filterable scum.
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garage chemist
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I am also looking for a solution for the problem of filtering a fine precipitate.
My specific problem is the filtering of chromium(III)oxide from a solution of sodium perchlorate after destruction of dichromate with a reducing agent
and subsequent precipitation of Cr2O3 by adding NaOH.
The large amount of salt in the mixture (over 500g/L NaClO4) seems to prevent the coagulation of Cr2O3 into larger particles.
A coffee filter is actually fine enough to remove this precipitate, but clogs very fast and makes the process consume a lot of time.
My solution was to drop the liquid slowly into the filter using a dropping funnel at a rate of one drop every few seconds. This way the filtration is
done automatically overnight without having to add more solution into the filter every few hours.
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unionised
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"How does this removal process by heating the fritted glass work? Just heat and then shake the dry particles off?"
Carbon burns.
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vulture
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| Quote: |
...and subsequent precipitation of Cr2O3 by adding NaOH.
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How about (next time) adding KOH, filtering the resulting mix of KClO4 and Cr2O3, then wash with hot water? The precipitating KClO4 will also greatly
speed up the precipitation of Cr2O3.
As KClO4 is removable with hot water, adsorption and enclosure are reverted upon washing.
The only real problem I foresee with this is enclosure of KClO4 in Cr2O3. However, as Cr2O3 should precipitate first, this effect should also be
limited, no?
One shouldn't accept or resort to the mutilation of science to appease the mentally impaired.
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garage chemist
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I do not want to produce KClO4.
I want my NaClO4 solution as it is.
NaClO4 can be used for HClO4 distillation, KClO4 can't.
Or do you mean to add just a bit of KOH and remove the Cr2O3 with the subsequent precipitation of a small amount of KClO4?
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jimwig
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just for the record - increasing the number of filter papers does not the decrease the size of filtrate.
think about it.
one size fits all - so to speak.
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prole
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I have used a toilet paper plug in the neck of my funnel as an effective filter for fine particles. Don't laugh - it really works well. If you
don't already know how, just take a two-ply square and keep folding it in half lengthwise, so it ultimately looks long and thin, then roll it up
tight into a cylinder and carefully plug it INTO the neck of a funnel. It must not rest above the neck or it won't work. The only drawback is
time - it's very slow. Ideally the plug will be very tight, compressed, and compacted in the funnel's neck.
It's crucial that the plug keep its cylindrical shape while inserting it into the funnel's neck, don't let it uncoil. Also, one may
adjust the plug's size to fit the neck. This is pretty straightforward and simple, but I'm trying to decrease your trial-and-error time.
[Edited on 10/13/2005 by prole]
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