vacuum filtration

[lada]

Our chem students are doing gravimetric analysis and I need to update our vacuum filtration. We have a little pump attached to a tap which works well with individual flasks but is very water wasting.
We have a large vacuum pump used with bell jars and I was wondering if any of you have anything that can attach to this pump and filter a number of flasks.
Lada

[Ross]

Lada,

You cannot use the vacuum pump for this purpose - the vacuum produced by the pump is to high and will suck what you are trying to filter into the flask (and maybe even the paper). Also you have to be very careful not to get water unto the pump.

I know the water pumps are water wasteful but they have about the right ammount of suction. The water tap does not really need to be turned full on, only needs some water flowing through the pump to get enough of a suction.

So, not an ideal answer but I cannot think of any better at the moment.

Cheers
Ross

[Sandra Curry]

We use hand operated vacuum pumps (originally bought for E coli determination). They are in the current Science Supply catalogue on page 89. They aren't cheap, but ours have lasted twenty years and are still going strong.

[Sandra Curry]

And they're entirely portable!

[lada]

Thanks, that is exactly what we need.
Karma is coming your way
lada

[Krysia Lee]

Hi
I've a teacher who wants to do this and is asking for scintered glass crucibles. Any ideas on what they are and where I'll find them?
Cheers Krysia

[rae]

They are called Gooch crucibles and you can get them from science supply.
Cat No; 25 85134 and the cost about $40 each. There are cheaper models but I have the schott duran ones and they seem very good. If you have the catalogue see page 22 thet are listed under crucibles.

[ellice]

Sintered glass crucibles are used with filtration flasks to filter very fine particles. The filtration flasks are connected to venturi pumps that use water as the source of suction. I think a lot of us are doing the prac at the moment . ie Sulfate in Fertiliser.
I purchased some sintered glass crucibles in '07 from Science Supply Australia at around $25. Cheapest price, as these things can get quite expensive. You have to buy the Guko rubber gasket as well. These fit into the flask, and then the crucible sits in that.
Lada, I've just run through the prac that was on here somewhere that uses agar as a coagulating agent and it gave good results. I just filtered with filter paper (No 42) and a filter funnel. No need for pumps. (I was a bit concerned as well about the water wasted) I've suggested we try this method next year.

[RosalieL]

Does anyone have a photo of this set-up?

[bigmack]

This sort of thing Rosalie.
There is a Buchner funnel here but you can swap that out for the Sintered glass crucible when doing the phosphate prac .

The key things are the side arm conical flask and the vacuum pump which works when water is flowing through it .
If your school is old , you may well have a metal version of the vacuum unit .
The ones here are labeled as one way valves .

IMG_1243.jpeg

[RosalieL]

Yes this is it. Thanks. I can't work out what the sintered glass crucible is supposed to look like though. I'm pretty sure I saw some here the other day when I was looking for something else (this place needs a good clean out and it is happening soon!) but they didn't have any rubber around them to seal them to the side-arm flask.

[bigmack]

The sintered glass crucibles look like this

IMG_1246.jpeg

IMG_1248.jpeg

To seal the crucible to the Conical flask , you use a Gooch rubber or ring .

Google Gooch Rubber will get you hits to familiar Science Supply outlets
It looks like these .

IMG_1244.jpeg

IMG_1245.jpeg

Sometimes it is hard to follow the logic of the Lab assistant that proceeds you .
But I would have thought that they would have grouped the Sintered glass crucibles with the rubber seals ….. iff’n they had any idea what they were for .

If not , think where might they put a rubber seal …


Hopefully , it’s not in the Aquatics area

[RosalieL]

My predecessor and I have VERY different brains! I think hers was better in a lot of ways. Unfortunately they moved out of labs into temporary labs in order to upgrade/rebuild (before my time) but the rebuild never happened so I was left with the "temporary arrangement" and I've been here 4 years now. I am trying to make it more suitable for "permanent" use... The current temporary labs are being re-done over the Christmas break so I am doing a complete move out as there will be only enough under-bench storage for the bunsens and "everyday" type stuff. The rest will go in my prep room and another room I've asked to take over for science storage for the stuff that only comes out for a couple of weeks at a time, or even once or twice a year. I am looking forward to a few discoveries as I have cardboard boxes full of stuff I haven't touched yet!

[bigmack]

That sounds horrible Rosalie .Four years of living out of random boxes would have done my head in.
I hope your well deserved upgrade goes ahead and it makes things more functional .

On a side note .
Wondering if anyone has tips for cleaning Sintered glass Crucibles ?
When they do the fertilizer /phosphate prac , the crucibles come back all yellow .I've tried all manner of things to clean them out . Even flipping them upside down and running water through them under vacuum to try and reverse flush the crap back out of them . It helps but they are still stained

[Anna Z]

Have you tried some dilute HCl or NaOH...... soak and chuck them in an ultrasonic bath for a bit.

[RosalieL]

Napisan is what I usually try first for glassware...

[Labbie]

My go to Napisan

[bigmack]

Thanks
Never tried Napisan before .Might be worth a go

Ultrasonic cleaner sounds nice Anna. Remember my Father was a watchmaker and there wasn't much that couldn't be removed .Hmmmmm.Maybe next years budget .

[Anna Z]

Thanks
Never tried Napisan before .Might be worth a go

Ultrasonic cleaner sounds nice Anna. Remember my Father was a watchmaker and there wasn't much that couldn't be removed .Hmmmmm.Maybe next years budget .

Yes a little jewelry one is perfect, time to start watching the home shopping channel

[RosalieL]

How do I make this work????? I am going insane. Every year I have to search for videos and every year I fail... We have the buchner funnels and side arm flasks and the metal vacuum thing with the three tubes. I have set it all up, even re-did the tubes in case they were getting old and not as secure, tried the connections in both directions, I cannot for the life of me get a vacuum, or any suction at all.... Suggestions please!! We are resorting to old-school slow filtering in multiple flasks and funnels (thankfully it is a class of 2 students and one is away today) so nobody is stressing out, (except me getting frustrated because WHY DOES THIS NEVER WORK???)