The vial is a fruit fly vial, but you can use any container that you can stopper, even larger test tubes. I use #7 rubber stoppers on the vials. You just need a one-hole stopper (to fit whatever vial you use) with a short piece of glass tubing sticking out of the hole. Then attach a length of flexible plastic tubing to that and this will serve as the conduit for the escaping gas bubbles. I got my flexible plastic tubing at the pet store. I use 100mL graduated cylinders to collect the O₂.

To make the catalase solution, use 1 package (7g) yeast in 200-250mL warm water (do NOT add sugar so that bubbling is kept at a minimum before use). Since the procedure requires 100%, then 75%, 50%, 25% of enzyme, I make it easy by starting with 1.0ml of yeast catalase. Then we go from 1.0 to 0.75 to 0.5 to 0.25ml. We use 20ml of peroxide as our starting amount of substrate.

After an initial practice, the students had the whole system ready. Then they put the peroxide in the vial first and then added the catalase (yeast solution) to the vial with a pipette. They can plug the vial and slip the tubing into the inverted graduated cyliner well before any bubbles escape. All the other variables are run off of this protocol.

This is so smooth and easy!

Thank you to Dot Gillespie of Nashua High School for introducing this idea to me!