Db33
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2 different buchner funnels. please help
i have 2 different glass buchner funnels. One of them has about a 1cm think very hard whats called #3 course filter and looks like this.
and i have another one that just has a clear bottom with a bunch of holes that i assume i put filter paper on top of. here it is
my question is, for the top one with that thick course filter already in it, do i use filter paper on that? and how do i clean it after? Am i suppose
to use filter paper for both of them? Any help would be appreciated. are they meant to filter differnet things?
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DDTea
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For the fritted funnel (top), cover the frit with celite. This will pre-filter any coarse particles, keeping them from clogging your frit. After
filtering your mixture, chase it with solvent to wash anything that may be clinging to the celite. Cleaning frits can get hairy. In the simplest
case, it involves washing with solvent and maybe some dilute acid. Some people like to use piranha fluid to clean their frits, but this is really
asking for trouble: a clean frit is not worth the risk of injury/death.
If your goal is to collect the solids, I recommend using the bottom buchner funnel + filter paper.
"In the end the proud scientist or philosopher who cannot be bothered to make his thought accessible has no choice but to retire to the heights in
which dwell the Great Misunderstood and the Great Ignored, there to rail in Olympic superiority at the folly of mankind." - Reginald Kapp.
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macckone
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There is a thread on cleaning fritted filters.
General rule is don't use frit with metal ions that
form insoluble sulfates. Then clean with pirhana
which will dissolve anything but those ions.
This including your eyes and skin so use proper
protection.
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aga
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I think i bought what mostly looks like the bottom photo, but with the filter shown in the top photo.
Hasn't arrived yet.
Basically you just need to experiment with them, use some common sense, and see what happens.
The funnel in the bottom photo definitely needs filter papers.
I got a similar (plastic) buchner and cut the required filter paper size from 'normal' 100mm ones with scissors.
Amazingly not everything gives in to vac filtering, which was a surprise.
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DDTea
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Quote: Originally posted by macckone  | There is a thread on cleaning fritted filters.
General rule is don't use frit with metal ions that
form insoluble sulfates. Then clean with pirhana
which will dissolve anything but those ions.
This including your eyes and skin so use proper
protection.
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Piranha is corrosive, but the bigger problem is that it causes explosions on contact with organics--which results in lots of flying glass from the
apparatus that was being cleaned. There was an infamous incident at Cornell stemming from piranha mixture.
"In the end the proud scientist or philosopher who cannot be bothered to make his thought accessible has no choice but to retire to the heights in
which dwell the Great Misunderstood and the Great Ignored, there to rail in Olympic superiority at the folly of mankind." - Reginald Kapp.
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ahill
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I actually broke my glass frit buchner last night - (I am still in morning) and I will definitely be getting another one - I think it was my favourite
bit of glass.
TIP - the center tube (at least on mine) is very fragile - I connected a hose to wash trapped particles back out (squirting water thru it in reverse),
and as a wriggled the hose to remove it, the tube just snapped near the base.
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Db33
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damn is there anything else i can use other than piranha to clean it? i dont wanna worry about explosions.
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DDTea
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apologies, i forgot to actually mention what to use! after discarding the celite, washing with water, then acetone, then hexanes, and drying in an
oven usually works for me. nitric acid if you need to get more aggressive.
"In the end the proud scientist or philosopher who cannot be bothered to make his thought accessible has no choice but to retire to the heights in
which dwell the Great Misunderstood and the Great Ignored, there to rail in Olympic superiority at the folly of mankind." - Reginald Kapp.
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Texium
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One time when I was inexperienced and decided to filter out very fine carbon with my fritted funnel I ended up having to use chromic acid to clean the
frit (also something that you definitely don't want to use on a regular basis, but it works when desperate measures are called for).
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Db33
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so which one should i use most of the time? the sintered filter or the one that takes filter paper?
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XeonTheMGPony
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As others have said if you can not disolve it don't use it on a frit, use it on the cellulose filter
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Melgar
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You should use a paper filter for everything that doesn't dissolve paper, especially if you want to keep the solids. Fritted funnels, I believe, are
better for when you want to get rid of the solids and keep the liquids, and want to do a really good job filtering any precipitates out of your
liquid.
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Db33
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thank you Melgar
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TheNerdyFarmer
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Can't you use filter paper on a fritted funnel?
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aga
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You could, but that kinda means that you should not have been using the fritted one.
Mine arrived today 
Surprising how big the 200ml version looks.
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TheNerdyFarmer
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I was wondering because I just have a fritted one and not a regular cellulose Buchner funnel.
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XeonTheMGPony
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I've don that, some stuff all ways makes it past the sides a bit, but got to make sure the cellulose is finer then the frit or there is no point!
I need to get a disk style funnel here my self as I don't want to subject the more valuable fritted ones to mechanical wear when unnecessary.
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barbs09
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Hello, I intend to filter a gold chloride (Au in aqua regia) from insoluble sediments (quartz mainly) using a buchner funnel. My aim of course is to
collect the valuable solute rather than the solids. Given the solution will stream past the vacuum side arm I suspect some droplets will end up in
the vacuum stream. Does anyone know of a standard way of setting up buchner funnel with the goal of retaining the liquid? The problem I see is that
most buchner funnels have short stems.
Thanks in advance.
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j_sum1
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Well I have never heard of that being a problem. You could always put a trap in.
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Sulaiman
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there is virtually no airflow in the side arm, (if there are no leaks), the volume of gas is equivalent to the volume of solute filtered 
for dense precipitates I find gravity, patience and decanting is best for precious fluids as some gets lost when filtering.
I do not own a large fritted funnel, just tiny ones,
but (ideally) you know what you are filtering and so can determine the least hazardous way to clean the filter
most things can be cleaned with water, detergent, petrol, .... household stuff.
CAUTION : Hobby Chemist, not Professional or even Amateur
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barbs09
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Thanks guys, good advice. Sulaiman, I should have thought of that
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