Make a Microbial Fuel Cell (MFC) - Part 1

Step 2 Preparing the electrolyte

Okay so here's the first tricky bit. We're going to make an algar/salt solution and use it to fill the salt bridge. Now the really clever bit is figuring out how to keep the salt bridge upright while the agar cools.

Agar can be obtained from health food stores and high end supermarkets with health food departments. The clerks will be able to help you if you ask if they carry 'the dietary supplement agar and calcium supplements with calcium carbonate because a friend recommended them" instead "Hey, you guys got any stuff for a microbial reactor salt bridge?"

Preparing Tablet or Powdered Agar:

Dissolve 1 bar, 10 tablets or 7 grams of powdered agar in 1/2 quart of the soilwater we prepared in the last step. Warm the agar in a hot water bath by placing it in a glass bottle. Heat water on the stove until just about boiling, remove from heat and place the agar bottle in the water. The microwave is another good way. Simply heat up a bowl of water and place the bottle with agar in the center.

As it warms the agar will begin to melt, warm the agar until it becomes liquid. Add the salt and mix well to dissolve the salt in the agar. Remove from the heat

Dissolving salt:

• Finely ground salt such as canners salt or table salt dissolves much faster than coarsely ground salt (rock salt).
• It is not clear that all salt added must be dissolved if a solution is to obtain maximum electron exchange
• Salt dissolves much faster in hot water than in cold water.
• Salt dissolves much slower as the salt concentration increases. The last bit of salt may take a long ime to dissolve.
• Agitation greatly increases the rate at which salt dissolves
• A layer of salt on the bottom may take days to dissolve if left undisturbed

Comments

[knexfreak32]

Ok thanks.

[knexfreak32]

Do you have to use agar.

[egbertfitzwilly]

No, if you you look at my other instructables I've substituted Knox unflavored gelatin.