Re: How is coolant oil based!?!

[Robert Myers <rmyers@inetone.net>]

Apologies for the bandwidth to those who are totally uninterested.

The "oily feeling" is due to the ethylene glycol, not additives.  Have you
ever had glycerol (glycerine) on your hands.  It has an extremely "oily
feel".  (Glycerol is a major component of many hand lotion products.)
Ethylene glycol is, structurally, approximately half way between ethanol
(ordinary ethyl alcohol - drinking alcohol) and glycerol.  

Ethanol=             CH3-CH2-OH
Ethylene glycol = HO-CH2-CH2-OH
Glycerol =        HO-CH2-CH(OH)-CH2-OH
Propylene glycol =   CH3-CH(OH)-CH2-OH

(The glycols are diols.  Glycerol is a triol.  In general, they are polyols.)

Ethanol is much more like water in the way it feels on clean intact skin.
This intermediate position results in physical properties which are also
intermediate between these substances.  The "oily feeling" is the result.

You are correct about the smell.  Ethylene glycol is similar in structure
to sugars and has a corresponding sweet taste.  It is also rather toxic.
This is the primary reason why you should never allow antifreeze (used or
fresh) to be in the reach of animals or young children.

Propylene glycol is used as a substitute for ethylene glycol in some of the
"green" antifreezes.  It is somewhat less toxic than ethylene glycol.  I
still would not recommend it as a beverage for your kids or your pets.

An "Oily feel" is only part of what makes a substance an oil.  Primary
property of what are commonly considered as oils includes solubility in
water (common oils such as motor oil or diesel fuel aren't water soluble -
these polyols are water highly soluble).

At 10:41 PM 7/17/98 -0500, you wrote:
>Coolant is primarily ethylene glycol, actually an alcohol, the oily texture
>prob. comes from the additives to prevent corrosion, and the like. The
>ethylene glycol is what gives coolant that sickeningly sweet odor you smell
>when you blow a hose, or have some other leak in the system.
>
>Richard Haroutunian wrote:
>
>> well, i don't know -- i'm just going by what someone told me.. i don;t
>> think he meant it'
>> s 'oil-based' i think he meant that coolant has an oily texture because
>> it's made up of some 'ethyl' something-or-other that gives it an oily
>> texture.
>
>
>
>
>
___
   Bob
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