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Diffusion of Hydrogen



Summary:  Introduction of hydrogen gas into an inverted bell jar suspended over a porous cup forces colored water into a beaker.


Hydrogen gas is extremely flammable.

Chemicals and Solutions: 

Lecture bottle of compressed hydrogen gas with pressure regulator


Hydrogen diffusion apparatus (containing colored water)

Bell jar

250 ml beaker

piece of 1/4 inch amber tubing

Stands and clamps


Attach a piece of rubber tubing to hydrogen regulator.

Position the beaker beneath the side arm of hydrogen apparatus to capture displaced liquid.

Fill the bell jar with hydrogen gas and then place the bell jar over the porous clay cylinder.


The bell jar can be suspended over the porous cup, and hydrogen gas introduced via amber tube.


The hydrogen molecules effuse through the holes in the porous cylinder faster than the oxygen and nitrogen molecules inside effuse out, creating an excess pressure inside the flask.  The excess pressure forces the water out through the side arm.





To schedule a demonstration, please send an email to the demonstration lab.



Eric Camp

Lecture Demonstration Technician

Bagley Hall 171

(206) 543-1606


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