To make the adapted graduated cylinders, I was lucky enough to have the help of a student intern from MIT. At one time, the 25 mL cylinders were available in adapted form from the Lawrence Hall of Science, but they are not actively marketing them now. Those cylinders were very lightweight plastic with a separate base, and fell over very easily. We adapt cylinders in a variety of volumes, using heavy duty plastic or glass ones (But those do break!).
For the plungers, we use a strip of styrene or other waterproof material, cut to the length and width of the cylinder.
The float that is attached to the plunger is made of insulation grade StyrofoamTM. Regular Styrofoam did not work! There may be other materials that work better. One problem is the absorbency of the foam. We plan to experiment additionally this fall.
- Cut the Styrofoam into a circle slightly smaller than the diameter of the cylinder. Roll this piece of foam to make it as round and smooth as possible. Then insert the plunger into the center of the foam. You may need to add Styrofoam or make a thicker piece. The MIT intern increased the accuracy and decreased the absorption by rolling the Styrofoam piece in acetone. (Not nail polish remover). Be sure to work with good ventilation or under a fume hood!
- Calibrate the cylinder visually. Decide the intervals you want. On the smaller cylinder we use 5 mL on the larger ones 25. (While usually accurate enough for HS labs, the cylinders are not as accurate as using pre-marked syringes, which can be calibrated to a much greater precision.)
- Measure the water for each interval, 5, 10, etc. So, for example, pour the measured 5 mL water into the adapted cylinder. Add the plunger, and let it float, mark the plunger, remove and then make a notch at that level. Repeat by adding 10 mL next, mark and notch, until you have reached to capacity of the cylinder. Again I use the larger cylinders most often as the smaller amounts can easily be done by the syringes. Syringes are also better for liquids that you do not want spilled or touched!
- To use the cylinder the student slowly adds the water while keeping a fingertip on the edge of the cylinder.
- To make the cylinders more universally accessible, I put a colorful piece of Wikki StixTM on the desired notch and on the cylinder at the desired measurement.