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Q & A: water conducts

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Most recent answer: 10/22/2007
Q:
why is the maximum resistivity of DI water 18.31 Megaohm? Couldnít it go beyond this reading? Is it true that although DI water have a theoretical pH of 7.00 but they are in fact corrosive by nature? People have advised me not to use copper piping for DI flow because of corrosion issue.
Hope you could help me clarify this.
Thanks.
- Alvin C.
Singapore
A:
That maximum resistivity occurs because water can fall apart into ions (charged parts) H+ and OH-. These conduct electricity. Their concentration in pure water depends on temperature, but at about room temperature thereís 10-7 molar of each. (ps.- that resistivity is in megohm-cm, not megohm).

Iím actually not too sure about how much copper will dissolve in DI water.

Mike W.

(published on 10/22/2007)

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