Instead of purchasing a large filter flask at a high price, just use a
video camera to project the live demonstration, in a 250-mL or 500-mL
filter flask, on a large screen in the lecture hall. Check the filter
flask, before use, for scratches or chips and use proper clamping and safety
shielding of the apparatus.
As an alternative, use a bell jar and vacuum apparatus to do this
demonstration in a beaker. Again, project the demonstration on a large
screen. Safety shields are still recommended. Protect your vacuum
pump from the water vapors with a trap.
You probably want to use room temperature water for the demonstration, but
you can get reasonable results with warm water in the filter flask using a
good water aspirator.
I also use large 140-mL or 100-mL plastic syringes (never glass) with
end caps, containing a small amount of water, which can be passed around the
room so students can repeat the demonstration at their seats.
Occasionally, a student will pull the plunger completely out of the syringe
splashing the water, but you can minimize that by cautioning the students in
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----- Original Message -----
Sent: Thursday, September 12, 2013 8:09
Subject: Re: [DCHAS-L] 4L filter
I'm looking for a 4L filter flask for a demo but
they all seem to be $150-$250. We are creating a vacuum in order to boil
water. It needs to be that big because of the size of the lecture hall. Does
anyone have a good website to turn to for glassware like this?