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Salty water showing a voltage?

  1. Aug 24, 2011 #1
    Hello. Today, I have observed something which I do not understand. I have a glass of water with some table salt in it. I stuck the probes of my digital multimeter into the water. Strangely, I am getting a reading.

    If there is any current, it is less than a tenth of a mA. Still, the voltage has been as much as 300 mV. Though, unsteady.

    It went up and down, perhaps as low as half the peak value. Then, it would recover. Sometimes, it would hang around one value with little change. Then suddenly, it would begin to quickly change, before slowing again.

    Even after hours, I still see about 30 mV. Though, it is a lot more steady now.

    Just a moment ago, I repeated what I did earlier in the day. Similar results.

    My analog multimeter does not show any voltage. Then again, the smallest of its ranges is 10 volts. Such small millivolt readings are difficult to make.

    Anyway, does this have to do with the dissolution of the table salt? That is the only answer I can come up with...

    I had never heard of this before...
  2. jcsd
  3. Aug 25, 2011 #2


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    Staff: Mentor

    What are your electrodes made of?
  4. Aug 25, 2011 #3
    Wet coffee filters.

    Then later, just whatever my multimeter's probes were made of.
  5. Aug 25, 2011 #4


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    Gold Member

    Here is a video of a bioengineering professor who is making some interesting experiments with water. With water, hydrophylic surfaces and sunlight he is achieving charge separation, making batteries and doing other neat stuff.

    Respectfully submitted,
    Last edited by a moderator: Sep 25, 2014
  6. Aug 25, 2011 #5


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    Staff: Mentor

    My bet would be that you observe your probes reacting with the solution.
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