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 advance.

David

_________________________________________________________________________

David A. Katz
Chemist, Educator, Expert Demonstrator, Science Communicator, and Consultant
Programs and workshops for teachers, schools, museums, and the public
133 N. Desert Stream Dr. * Tucson, AZ 85745-2277 * USA
voice/fax: (520) 624-2207 * email: dakatz45**At_Symbol_Here**msn.com
Visit my web site: http://www.chymist.com
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----- Original Message -----

From: Samantha D

To: DCHAS-L**At_Symbol_Here**MED.CORNELL.EDU

Sent: Thursday, September 12, 2013 8:09 AM

Subject: Re: [DCHAS-L] 4L filter flasks

Hi all,

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?

Thank you,

Sam

On Thu, Sep 12, 2013 at 10:56 AM, Samantha D <samantha.dannenberg**At_Symbol_Here**gmail.com> wrote:

Hi all,

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?

Thank you,

Sam