Metal Mouth


Concepts Shown:

galvanism, electrode, potential, electrolyte


Galvanism: The generation of electrical currents resulting from dissimilar metals placed in an electrolyte. Electrolyte: A liquid containing ions.

Case 1: General Anyone with fillings can relate directly with this example. Most fillings are made of amalgam. Amalgam contains mercury and silver, copper, and/or tin. A galvanic reaction occurs when a person touches a fork, (silver, aluminum, stainless steel) to one of his/her fillings. The dissimilar metals form an electric cell with your saliva acting as the electrolyte. The person experiences a shock (current flow) because of the potential difference. The person will have a metal taste in his/her mouth because some metal ions from the anode have gone into solution. [eq].

Case 2: Detailed Aluminum as a strong tendency to go into solution. Aluminum has an electrode potential of +1.33 volts. Anode. Gold does not go easily into solution. Gold has an electrode potential of -1.36 volts. Cathode. Oral fluids act like an electrolyte. This system acts like an electric cell. When the two crowns touch, the potential difference is 2.60 volts. A current flows and some aluminum (anode) will go into solution. Al � Al 3+ + 3e- Anode Au3+ + 3e- � Au Cathode [eq].

Case 3: For the extremely brave or stupid. To experience a galvanic reaction at home or in a restaurant do the following: Obtain a piece of aluminum foil (from the kitchen drawer or from the baked potato if you are at a restaurant). Imagine that you are eating your favorite food. Take foil and chew!




Marcia Muller

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