Use of a Simple Conductivity Meter

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Use of a Simple Conductivity Meter

Conductivity measurements will tell you a lot about the state of the ions in your solutions. While expensive conductivity devices are available in catalogs, the one shown here costs about $1 and a bit of shopping and construction time. For an alternative device you might want to use a horizontal electrophoresis chamber.

ITEMS NEEDED

After you place solution to be tested into the container, attach one lead of your ohm meter to the alligator clip. Then with your fingers you will pinch the other ohm-meter lead to the bare circular wire of the probe. It will take a couple of seconds for the meter to get within range of the value you are measuring. It is at this 2-second point* that you take your reading. (You will notice that if you continue to pinch the wires together, the meter will continue to rise and rise. The reason for this is that electrolysis of the water is occurring and bubbles are forming on the probe's electrodes increasing the resistance as bubbles continue to buildup. You might find that stirring the probe may help. In more advanced labs in physical chemistry there are expensive ways of overcoming this problem.

Remember that you are measuring the relative resistance of the various solutions. The relative conductance is the reciprocal of the resistance.


* How to have fun in the lab counting two seconds duration: certainly don't mumble "one thousand, two thousand," but rather say "one elephant, two elephants." Imagine a class all mumbling this at times - smiles and laughter. You've heard of "Fun with Chemistry!" haven't you?


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