Sulaiman - 27-9-2015 at 02:04
My current filtration system is a pyrex conical funnel using folded (boring!) paper filter disks and gravity
... develops and tests patience in equal ammounts!
I have a cheap 20 kpa abs. vacuum pump and a 3 cfm 0.3 pa dual stage rotary
and I want to upgrade my filtration system.
I am considering this http://www.ebay.co.uk/itm/Glass-Suction-Filter-250ml-Buchner...
any comments?
I can't justify the cost of multiple filtration setups so this needs to handle everything from microscale to litres.
(for very small scale I have B10 funnel/glass nail/paper and for very big scale kitchen type sieves)
I also want some kind of vacuum dessication,
has anyone here integrated vacuum filtration with drying ?
P.S. the kit listed above does not even mention the frit porosity,
so assuming that it is 'medium',
what would I do for 'fine' particulates?
add filter paper?, buy another funnel (not likely)?
[Edited on 27-9-2015 by Sulaiman]
ave369 - 27-9-2015 at 03:48
I've got a Buchner set (flask + funnel + ring) and a makeshift hand vacuum pump. Everything works, depending on what type of filter I put into the
Buchner funnel. I don't have any Schott sintered glass filters, and if I need to filter something aggressive, I put one or two layers of
micropunctured polyethylene on my Buchner funnel instead of paper. Or a polyethylene-rockwool sandwich.
[Edited on 27-9-2015 by ave369]
Sulaiman - 27-9-2015 at 12:43
A porcelain Buchner funnel with filter paper and a heavy Erlenmeyer with side arm was my first thought
... classic from my 70s school chemistry
but this set is cheaper,
I have not used a sintered glass filter before so I'm hoping for an update to my 70s chemistry knowledge,
I imagine cleaning may be a problem - so is it economical vs. using filter papers ?
aga - 27-9-2015 at 15:54
Start with the Basics : Vacuum.
Personally i got a cheap itailian vac pump off ebay (single stage)
It pulls some sort of vacuum.
What vacuum it pulls i do not know as i have no accurate vac guage handy, and the guage is likely just a rough guide.
Works wonderfully with a buchner setup, greatly reducing the Time required to filter/wash precipitates.
In my first ever (recent) vac distillation it worked fine.
Excellent Tools are well worth spending the extra $ on - even if it's 20x more $ - Provided that you know how to use them and take care of them.
My logic is that the few $ i spent on this cheap pump will help me train myself in the use of vacuum, and what the limitations are of having a cheap
tool like this one.
It would be a shame to ruin a Good device simply because i had no idea how to use or care for it.
j_sum1 - 27-9-2015 at 15:57
You and i think similarly, aga. Must be the same lizard alien.
Sulaiman - 28-9-2015 at 01:03
Vacuum: per line three of my original post, I have two vacuum pumps for chemistry;
a cheap 12 Vdc piston/diaphragm pump, 20 lit/min -80 kpa (20 kpa abs = c152 mm Hg) . (I will probably use this one)
a shiny new HVAC dual stage oil sealed rotary vane pump, 3 cfm 0.3 pa (2.25 um Hg) . (overkill)
Although I was asking for an opinion on the particular bit of kit that I'm considering buying
what I really should have asked was:
I have only used filter paper before, never sintered glass, so could someone advise me on
. the relative benefits of perforated porcelain with a range of filter 'papers'
vs. a sintered glass filter not requiring consumables
. the 'best' general purpose porosity to buy, e.g. the kit above has a choice of grade/pore size in microns
#1 80 - 120
#2 40 - 80
#3 15 - 40 (I think that this is the 'standard' offering)
#4 5 - 15
#5 2 - 5
#6 <2
which ONE to choose?
is it just a trade off between efficiency and speed?
which are easier to clean?
which gives best recovery of residue?
any obvious/critical considerations that I've missed?
[Edited on 28-9-2015 by Sulaiman]
Dr.Bob - 29-9-2015 at 06:08
Buchner funnels are not very expensive, so I would just buy a few sizes and the matching filter paper, and a few sizes of filter flasks (I like 250 ml
a lot, that will handle most normal cases). You can find them on Ebay or similar places for a good price if you look around some. But pick the
volume of the reaction, add some, then get a bigger filter flask, and pick a Buchner that fits it well. Using a large Buchner on a small flask or
visa-vera is a mess. The funnel diameter should not be more than about twice the flasks diameter at the largest point, and that only works well if
the flask is clamped securely.
chemrox - 29-9-2015 at 17:34
What is your rotary setup? Vacuum source? and these filters are rarely more than $30 on ebay. I have around 5 or 6 of them. The sytem I like is the
frit funnel separate from the vacuum adapter which is connected to a flask by st. That way I can use several different volume funnels with different
frit. I like paper on the frit most fo the time but with my setup I can use a porcelain funnel as well.
Sulaiman - 30-9-2015 at 06:14
that would be nice,
but just over one year as a hobby now and I need to minimise costs
I can not afford all of the lovely chemistry 'toys' available,
(my wife is already 'hinting' at hobby costs 
so I was hoping to buy just one, just one cheap one that
is a fast flowing filter with pore size to catch viruses,
is easy to recover all of the residue,
is inert to all known chemicals,
is rugged and easy to clean,
did I mention ... cheap to buy and run.
that's all
so which would likely serve me best, all glass or porcelain/paper ?
or other ?
Praxichys - 30-9-2015 at 06:27
I would recommend the porcelain funnel. You don't have to use paper all the time. If you're filtering something that eats paper, go to the
hardware/craft store and get some felted polypropylene fabric (weed block or similar) and cut circles from it. It's dirt cheap, disposable, reusable,
and there isn't much you can't filter with either that stuff or paper. I have many fritted funnels and I still prefer the weed block!
The porcelain funnel is much easier to clean, less fragile, and less expensive for its capacity than fritted funnels. You can get a half-liter
porcelain buchner for like $15, compared to something like $50 for a chinese fritted one. You can even get plastic funnels that pop open for cleaning,
and those are even cheaper, almost disposable.
If it were up to me, I'd put my money into the filter flask. Anything less than 1 liter is kind of a joke for multi-step preparative stuff.
http://www.amazon.com/Polypropylene-Buchner-Funnel-Designed-...
https://drive.google.com/open?id=0B_16NzkNoL75bksyejZjZzQ3bE...
(weed-block filter cakes of calcium cyanurate)
Sulaiman - 30-9-2015 at 08:09
Thank You