Science Buddies: "Ask an Expert"

I am doing the Electrolyte Challenge using the Science Buddies Multimeter kit. I am doing my trials and today I tested Pedialyte. During the test, one of my copper wires attached to my conductance señor (the straw) started developing bubbles on the wire. I read that this is "electrolysis" that is occurring when bubbles form at the ends of the conductance sensor. I changed out the copper wires and tested the Pedialyte again. Electrolysis occurred again and as a result, during the (5) trials my readings from the multimeter fluctuated rapidly during all 5 trials. The multimeter was set at: 200 M and these were my readings: 97.3, 76.6,74.3,104.8 and 90.8 milliamps. The readings never stabled out (I kept the conductance sensor still and the copper wiring was very secure to the straw). I don't trust that these are accurate readings. I did not have this issue when I tested the Gatorade.

My question is, how do I stop the electrolysis from occurring? I assume that is what is causing the readings from fluctuating so much during my trials of the Pedilyte. I changed out the copper wires, rinsed the conductance sensor in tap water and changed out the Pedilyte, but still had electrolysis. What else should I do?

Thank you for your help.

Hello. Please post your question in only one forum so that our experts can best help you based on what has already been discussed. Please refer to your post in the Life and Earth Science section. Good luck, and thanks for using Science Buddies!

pfieffer - One problem with this experiment is that a higher conductance electrolyte will pass a significant current through the circuit that will cause 'micro-bubbles' to form on the wire electrodes. These bubbles greatly reduce the effective surface area of the electrodes in the solution, preventing accurate or stable readings The effect is that you will read a much higher current immediately after the electrodes are immersed (or the battery is connected). The current will continue to drop and getting a stable reading is impossible.

The best solution is to greatly reduce the current flow by adding a series resistance to the circuit and simply make your measurements in the range of hundreds of micro-amperes up to a few milliamps. Using the 9 volt battery on a highly conductive electrolyte could see currents approaching a hundred milliamps. You might also try using the voltmeter's resistance range (as an ohmmeter) as it will make the resistance measurements at a much lower current.

Rick Marz