Science Buddies: "Ask an Expert"

Hello!

I have a quick question about my project and a certain portion which I do not understand.

My project: https://www.sciencebuddies.org/science- ... #procedure

If you scroll down to "Making the Salt Bridges", it says something about "Cover one end of the tube section from the compression fitting securely with aluminum foil".

My question is, what is the compression fitting? I understand it to be the tubing that links the two anode containers, is it something else?

My second and final question is in the same section and it says " Place all tubes, open end up, vertically on the petri dish and then set it aside".

How exactly do you place the tubes into the petri dish so they balance? I am using a flexible type of plastic tubing so would it not just tip over?

Thank you, please respond quickly because I need this ASAP!

Hi,

I think your case is different since you are using plastic tubing instead of the rigid plastic tube shown in the picture:

https://www.sciencebuddies.org/science- ... #procedure



You are right. The tubing is not going to stand up in a Petri dish. I would seal one end of the tubing with a piece of plastic wrap held in place by a small rubber band. You can then put all the tubes into a cup or small glass to hold them upright, prepare the agar and fill the tubes to make the salt bridges.

Did you check your tube and fittings by filling the containers with water to make sure it does not leak? The fittings have to compress the tube tightly to make a seal and the holes in the containers have to be exactly the right size otherwise liquid make leak out around the tubing. If this happens, your fuel cell can run dry and that's bad, so check your fittings before you pour the salt bridges. You can put a little vaseline on the tubing or fittings to make a better seal if necessary.

Hope this helps. If you have more questions, we'll be here.

Good luck!

Sybee

Sorry, I forgot your other question about what are the compression fittings. You can see them in the photo in the previous post. The compression fittings are the two larger pieces on either end of the tube that are glued to the containers. Did you not get these parts? They insure a tight seal between the tubing and the containers.

Let me know if you need more help.

Sybee