pippo Posted September 27, 2014 Share Posted September 27, 2014 People, I always figured that the 2 methods for purifying water were about the same when comparing the end result- 2 means to the same end product. I know DI can get down to 18 megaohms resistivity at the service point, and after even a few minutes, it jumps to say, 0.2-0.5 u Mhos conductivity, which is still pretty clean water. Someone is now telling me distilled is what I need because DI is too "corrosive". Distilled may be 1-10 micromhos of resistivity, where di is usually less than 0.5 or so. Anyone have experience in this arena? Link to comment Share on other sites More sharing options...
fiveworlds Posted September 27, 2014 Share Posted September 27, 2014 (edited) same end product Not at all. They are two completely different processes. Distilled is boiled. Deionized is run through an ion exchange resin. Neither is perfect Distillation will not remove liquids with a similar boiling point(This may sometimes occur between a range of pressures changing the pressure may effect the boiling points of both liquids differently http://lorien.ncl.ac.uk/ming/distil/distilpri.htm). Deionized will not remove non-ionic particles. Edited September 27, 2014 by fiveworlds Link to comment Share on other sites More sharing options...
pippo Posted September 28, 2014 Author Share Posted September 28, 2014 Not at all. They are two completely different processes. Distilled is boiled. Deionized is run through an ion exchange resin. Neither is perfect Distillation will not remove liquids with a similar boiling point(This may sometimes occur between a range of pressures changing the pressure may effect the boiling points of both liquids differently http://lorien.ncl.ac.uk/ming/distil/distilpri.htm). Deionized will not remove non-ionic particles. I am aware they are 2 different processes, as I stated (2 means to same end product), although, technically, they are not same end product as you stated. But, only insofar as one can measure the difference. Your link is informative. But real world, our tap water contains almost no dissolved "solvents" to worry about. Trace pesticide residues are in the parts per trillion, if even detectable. Even so, most solvents have different boiling point as water. So the solvent at the same distillation temp is not relevant. So, to my original point, what should one expect in conductivity between the 2? Link to comment Share on other sites More sharing options...
fiveworlds Posted September 28, 2014 Share Posted September 28, 2014 (edited) So, to my original point, what should one expect in conductivity between the 2? Pure Water is a bad conductor. It is dissolved particles within the water that cause it to be conductive. Electrical conductivity of ultra-pure water is 5.5 × 10−6 S·m−1 (18 MΩ cm in the reciprocal terms of Electrical Resistivity) and is due only to H+ and OH- ions produced in the water dissociation equilibrium. I would believe it would depend largely on the water you started with. Edited September 28, 2014 by fiveworlds Link to comment Share on other sites More sharing options...
John Cuthber Posted September 28, 2014 Share Posted September 28, 2014 It is difficult to distil water in such a way that you prevent CO2 from the air dissolving in it. That will significantly increase the conductivity. Link to comment Share on other sites More sharing options...
CharonY Posted September 28, 2014 Share Posted September 28, 2014 IIRC the conductivity at equilibrium with atmospheric CO2 is about 1 uS/cm (and slightly acidic pH, around 5-6). The some obviously applies to deionized water when in contact with the atmosphere. Link to comment Share on other sites More sharing options...
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