Sciencemadness Discussion Board - Those rubber ring things for hirsh/buchner funnels - How to improvise one

Those rubber ring things for hirsh/buchner funnels - How to improvise one

mycotheologist - 7-12-2012 at 15:51

These things:

Are there any commonly available items that can be easily adapted for use as one of these filter adapters? If not, how would you go about making one?

smaerd - 7-12-2012 at 15:52

Rubber stoppers can be bought at home-brew stores(beer brewing stores) and online very cheaply. A hole can be drilled through them when they are frozen with any kind of drill as long as they are clamped down. A little soap and on goes the buchner.

Lambda-Eyde - 7-12-2012 at 17:05

Quote: Originally posted by smaerd

Rubber stoppers can be bought at home-brew stores(beer brewing stores) and online very cheaply. A hole can be drilled through them when they are frozen with any kind of drill as long as they are clamped down. A little soap and on goes the buchner.

Ugh... Forcing buchner funnels (especially glass ones) through stoppers are a recipe for disaster and bad lab practice.

I find that blue-tac makes a good seal. OR: just buy a damn guko rubber gasket for 3$

chemrox - 7-12-2012 at 17:56

"Those things" don't work after a couple of years and you have to pay profession prices. I don't know what they're called but they are flat, black rubber washers and come in several sizes. They cost $3 or $4. You can carve out a rubber stopper as the man says and don't use them on anything but Coors porcelain.

Funkerman23 - 7-12-2012 at 18:50

The flat filter aids or pluro-stoppers? I'll admit the filter aid I bought from Elemental is a bit stiff. It works well but I don't see how anything made of rubber will be a long-term thing given our line of work. as for improvising short of a notched stopper anything that won't contaminate the batch should help..

mycotheologist - 8-12-2012 at 05:31

Quote: Originally posted by Lambda-Eyde

I find that blue-tac makes a good seal. OR: just buy a damn guko rubber gasket for 3$

I thought of blu-tac but I wasn't sure it would work. If it works then no need to look any further for a solution. Thanks. Guko rubber gaskets, they're the things I was talking about aren't they?

EDIT: I just google imaged pluro-stoppers and the thing I have in mind came up:

Is that what they're called, pluro-stoppers? So far, I've seen them be called filter adapters, pluro-stoppers and if I'm not mistaken, Guko rubber gaskets.

[Edited on 8-12-2012 by mycotheologist]

garage chemist - 8-12-2012 at 05:44

When I didn't have any Gukos, I simply smeared a thick layer of bathroom silicone caulk on the conical outside section of my buchner funnels and sintered glass filters. After curing, this made a fairly good seal when placed on the filter flask.
Now I use Gukos made of silicone rubber. This is more resistant to solvents than natural rubber.

Lambda-Eyde - 8-12-2012 at 05:47

Quote: Originally posted by mycotheologist

I thought of blu-tac but I wasn't sure it would work. If it works then no need to look any further for a solution.

Yup. Here's a pic of it in action. And yes, I know that the funnel is overfilled, but it was only 20 grams of benzoic acid.

Quote: Originally posted by mycotheologist

Thanks. Guko rubber gaskets, they're the things I was talking about aren't they?

[pic]

EDIT: I just google imaged pluro-stoppers and the thing I have in mind came up:

[pic]

Is that what they're called, pluro-stoppers? So far, I've seen them be called filter adapters, pluro-stoppers and if I'm not mistaken, Guko rubber gaskets.

AFAIK all those names refer to the same thing, yes. I don't think it's worth it to invest in a whole set, but if you've got the money, why not? It might come in handy one day, but so far I'm doing fine with just two sizes.

mycotheologist - 8-12-2012 at 08:06

Lambda-Eyde: Nice. Right now I'm trying to get a vacuum source, I've been looking into converting fridge compressors and tyre pumps but that water aspirator you have looks like it may be just what I need. How much did it cost? What are those specific types of water aspirators (small and simple) called? Is that 1/4" braided hose? Do you have to have the tap on full blast to get decent pressure? Sorry for the flurry of questions lol.

garage chemist: Caulk, I thought of that too but I assumed it would stick to the funnel and be difficult to get off.

[Edited on 8-12-2012 by mycotheologist]

smaerd - 8-12-2012 at 08:53

The pressure is related to the flow of water from a faucet. It works based on the venturi effect. I got a 'nalgene' aspirator for I think 20$ on e-bay or maybe it was agile-fx.com I forget? If you only need it for filtration and basic evacuation purposes an aspirator is great. Though for vacuum distillation I get guilty for wasting all the water, even though I use a well system and don't pay for water. Usually I don't use full-blast for the water, but when things are going too slow I tend to turn the sink all the way.

As far as the tubing, the size will depend on the barb on the aspirator and the barb on the vacuum flask or the barb on the in-let/out-let being used. I use the cheap flexible tubing from hard-ware stores. I forget what kind of plastic it is but it works just fine. I do use a in-line plastic adapter to increase and decrease the size of the tubing. I think I got these from USPlastics.com for 50 cent's a piece as well as a plastic 'needle-valve' which isn't good for high-vacuum, but it works for breaking vacuums on vacuum filtrations. Plastic adapters are a lot more affordable then buying brass nozzles and such at hard-ware stores and in general serves the same use. If you do choose to use this company be warned they will send you really annoying pamphlets in the mail trying to encourage you to buy more things from them.

--
Also in relation to my first post in this thread I wasn't anticipating the OP to be improvising a filter-aid for a glass buchner funnel. A rubber stopper is just something I've seen done in under budget labs, and I agree it isn't a good solution in regards to the longevity of the funnel and shouldn't be used on glass. I just forked over the what was it, 5 USD for a proper one.

mycotheologist - 8-12-2012 at 09:22

Thanks for the explanation. I wanna be able to do vacuum distillations in the future. I know what you mean about wasting water, I'm trying to think of a way to recycle it. For condensers, I use an aquarium pump in a bucket of water which works perfectly but for an aspirator, you'd need a way more powerful pump.

Vacuum flask barbs are all the same diameter aren't they? I measured a 250mL one just now and its about 1/4". Do you mean the clear plastic tubing? That seems pretty rigid so I don't think its very likely to collapse under pressure. I'm gonna get a wide selection of those cheap plastic adapters cuz with little bits and pieces like that, its better to have them and not need them than to need them and not have them. I'm in Europe so I don't order from America but I found a real good plasticware site for Europeans:
http://www.justplastics.co.uk
they sell cheap aspirators as well as various adapters. They sell cheap (way cheaper than porcelaine anyway) plastic Buchner funnels which is pretty cool.

Endimion17 - 8-12-2012 at 18:00

Take a piece of rubber sheet and make an annulus. Works great.
If you don't have a rubber sheet, carve one out of a hollow rubber ball because it doesn't have to be a planar annulus.
Problem solved.

ziqquratu - 8-12-2012 at 21:44

No need to buy anything... I wear rubber kitchen gloves for handling hot stuff and for washing my glassware. When a pair eventually gets a hole, I cut them into squares (about 2.5 inches wide), then cut a small hole in the middle of each square. Two of these on your funnel makes an excellent seal (one isn't always good enough). They then last just about forever (I've got a small stack that I've been using for at least 3 years now)

Dr.Bob - 9-12-2012 at 20:46

I have some of the Guko rubber gaskets in larger sizes that work well in 2L and larger filter flasks. I have tried to throw them in with the larger filter flasks I sell. I had some smaller ones, but have sold most of those. You can buy kits with one of every size from VWR, but of course, you only use about 4 sizes for most chemistry and the most common sized Buchners and filter flasks, which is why the larger ones are always left. Few people use 2 - 4 L filter flasks daily.

I also just found some solid rubber stoppers in natural and black, I thought I had seen some, but finally found a bag of them. I have a fe of each size from 0 to about 10 sized rubber stoppers, including a few with one or two holes already in them. I would agree that it is harder to safely use them with Buchner funnels.