Re: IML: distilled or soft water for the cooling system?

[James <nyb@xxxxxxx>]

I'm curious about the basis for 'Skinned Knuckles' advice.  There may be 
some reason for using soft as opposed to distilled water hidden in 
there, but from a chemist's perspective, the explanation is poor. 
Properly distilled water should not have an 'abundance' of ions (for the 
record, ions can be positively charged, too!).  The only reason I can 
see distilled water having an abundance of ions would be if the 
distillation system used was dirty, or a poor choice of a condenser 
material was used.  Yes, distilled water is weakly acidic due to the 
uptake of CO2 from the atmosphere and the formation of carbonic acid, 
but this is again a weakly acidic system and in your cooling system will 
be offset by the ability of antifreeze to act as a corrosion inhibitor.

For your radiator, I think the author's of 'Skinned Knuckles' forget 
that although softened water contains fewer Ca++ and Mg+ ions, it can 
still be full of all sorts of dissolved solids.  Soft water only refers 
to the type of dissolved solids, not the amount.  Granted, the biggest 
enemy in terms of adding tap water to your radiator is calcium carbonate 
deposits, which obviously can't form as well with little Ca++ around. 
From a corrosion perspective, adding softened water is really adding an 
unknown quantity as its composition depends completely on the tap water 
you started with, and that varies a lot from area to area.  And, as I 
said in an earlier post, the chloride stuffed into softened water by ion 
exchange water softeners using sodium chloride is one of the worst 
things you could consider adding.

So, although I'd love to hear if there's some good science behind 
'Skinned Knuckles' recommendation, I'm going to stick to using a mixture 
of antifreeze and distilled water, with the usual residence time of two 
years in my cars.

James

Frederick Joslin wrote:
> Pure water is naturally ionized to exteny of 10-7 moles/L.
> In absolutely pure water at a pH of 7 there are 1x10-7 moles of H+ and 
> 1x10-7 moles of OH- ions per L.
>  
> One mole of water H+ is 1g; one mole of OH- is 17g.
>  
> Thus there are a total of 1x10-7 x 18g / L of ions in pure water = 
> 1.8x10-6g/L = 7.6x10-6g / gallon
> =.00000024 oz / gal ions.  
>
>     ----- Original Message -----
>     



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