T&T: antifreeze

[Jerry Berndt]

Peg and all, a treatise from a chemist if I may,

Ethylene glycol solutions became available in 40's and were marketed
as "permanent antifreeze", since the higher boiling points provided
advantages for summertime use as well as during cold weather. They
are still used today. Ethylene glycol antifreezes are poisonous and
should be kept away from any person or animal (children and
especially dogs) that might be tempted by its sweet taste. They form
calcium oxalate crystals in the kidneys and can cause acute renal
failure and death. All spills should be cleaned, or else an area in
which it may be present should be kept inaccessible to those who
might ingest it.  In order to prevent ingestion, bittering agent
(denatonium benzoate) is usually added to engine coolant to make it
taste unpleasant.

Propylene glycol, on the other hand, is considerably less toxic and
may be labeled as "non-toxic antifreeze". It is used as antifreeze
where ethylene glycol would be inappropriate, such as in food-
processing systems or in pipes in homes, RV's as well as numerous
other settings. It is also used in food, medicines, and cosmetics,
often as a binding agent. Propylene glycol is "generally recognized
as safe" by the Food and Drug Administration (FDA) for use in food.
However, propylene glycol-based antifreeze in it's pure form should
not be considered safe for consumption. In the event of accidental
ingestion, emergency medical services should be contacted.

In the 80s a waterless coolant for engine use was developed. The
formulation is a mixture of ethylene glycol and propylene glycol.
This coolant has a high boiling point of 188 0C (370 0F) and is not
corrosive, solving many of water's problems including freezing. Thus
the confusion of there being 2 propylene glycol's, one safe and one not.

Long winded but may be helpful....