On Mon, 06 Jun 2005 17:44:57 GMT, PaPaPeng wrote:

On Fri, 3 Jun 2005 23:39:26 +0100, "Mike" wrote:

Probably because it's a little less volatile and so doesn't evaporate before
you've wiped it off.

For the same reason it is used in industry because less of the vapour
escapes the containment or extraction system.



That would be my guesstimate although I can't give a good explanation
why this should be so. I'm no chemist. It is only one carbon atom
higher and that shouldn't affect the evaporation that much. Home use
solvent alcohols are mainly ethyl alcohol because they are cheap to
manufacture from fermentation or from raw stock (CO, H2).

Its not just the molecular weight that changes and effects the
evaporatoin, especially in small chain alcohols. There are both
molecular shape factors and hydrogen bonding changes that also
influence the evaporation/heat capacity.

The adulteration by methyl alcohol is from historical times when wood
alcohol was used to make grain alcohol undrinkable. Grain alcohol was
too useful a solvent to use for just drinks alone. But drinks alcohol
was one of the few staples the lord could depend on for taxes (salt
and grain harvests being some of the others.) By adding wood alcohol
(from charcoal manufacturing distillates?) even the dumbest village
yokel knew that adulterated alcohol would make him blind, make him
lose his bodily functions or more likely kill him.

Wood alcohol in the test tube oxidizes into formaldehyde, then to
formic acid and finally CO2 and water. In the body oxidation stops
at formaldehyde the stuff used in biology class to preserve
specimens. Nerves being the most sensitive get "preserved" first,
thus blindness and ataxia. By the time there is enough to kill you
the result will be a well pre-preserved corpse. Ethyl alcohol on the
other hand oxidizes to acetaldehyde, acetic acid then to CO2 and
water.

Gary Dyrkacz

Radio Control Aircraft/Paintball Physics/Paintball for 40+
http://home.comcast.net/~dyrgcmn/