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No such thing as de-ionized water...

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ILikeMy240sx

Member
Joined
Sep 28, 2003
Location
University of Michigan
While studying for chem final tomorrow... I ran across this passage in the text book

"Although pure water is often considered a nonelectrolyte (nonconductor of electricity), precise measurements do show a very small conduction. this conduction results from self-ionization, a reaction in which two like molecules react to give ions. In case of water, a proton from one H20 molecule is transferred to another H20 molecule, leaving behind an OH- ion forming a hydronium ion, H3O+(aq)

H2O(l) + H20(l) <=> H30+(aq) + OH-(aq)

So from this passage I guess its safe to assume that no water regardless of distillation or "de-ionization" is perfectly non-conductive....
 

nikhsub1

Unoriginal Macho Moderator
Joined
Oct 12, 2001
Location
Los Angeles
As soon as any water comes into contact with the air, the metals in your system, the tubing etc, It becomes more and more conductive. Water will kill your system if not careful, you don't use distilled/de-ionized water because you think it is non-conductive do you? Most use it because it is generally free of minerals (unlike drinking water). You ever seen bad lime or calcium buildup? Frightning...
 
OP
ILikeMy240sx

ILikeMy240sx

Member
Joined
Sep 28, 2003
Location
University of Michigan
nikhsub1 said:
You ever seen bad lime or calcium buildup? Frightning...

hahaha as a matter of fact... I worked as a pool cleaner guy over the summer and yes its very frieghtening.....

I just wanted to clear up the idea that using distilled water isn't the all-safe method to prevent disasters...
 

walkerIV

Member
Joined
Sep 25, 2002
Location
L5N 2C6
Deionized water means that there are no foreign ions present.
Self-dissociation of water does not result in foreign ions.
 

p1ssboy

New Member
Joined
Dec 15, 2003
ILikeMy240sx.. where I work it is one of my jobs to make "clean" water. The water we use is pretty much non conductive as we really dont want it to conduct :) . We first filter the water to .35 micron (normal home filters are in the 30 micron range). The next step is to pass the filtered water through bags of resin which removes the dissolved particles from the water.


"...the role of the DI resin is to control the resistivity of the machine's dielectric water, by removing the dissolved solids. It accomplishes this by removing the metal ions and exchanging them for Hydrogen and Oxygen, which combine to produce water."

http://www.ebbcoinc.com/edmtoday-97.htm


The water is then sent into a "clean" water tank where it overflows into the "dirty" tank and is recleaned. In the clean tank we also use an ozone generator to effectively kill off any organisms. We achieve resistivity levels nearing 20 MegaOhms/cm. Usually the resin is able to take us to the 18.50-19.00MOhm/cm range. The thing you mentioned though, which is very true, is that once there are foreign contaminents in the water, its resistivity drops. In order to calibrate our resistivity meters, we buy samples of clean water. The cleanest water we have been able to buy from a lab is 20Mohm/CM, and most of the labs I have spoken to dont want to bother as it is hard to achieve. As soon as we crack the top of the bottle open, the resistivity begins to drop.