Slugs and Osmosis

name        Scott
status       other
grade        other
location     OR

Question -   My father is a very intelligent man and is well
respected in the community, and I too work a very technical job.
One day however my father was presented with a question that was
actually able to stump him. This simple question was brought up
last night over dinner, I was certain that I could provide an
answer but have been having no luck whatsoever. I am certain I am
just missing something simple here as chemistry is not my forte

The question was "Why does salt melt slugs?"

I am quite certain that what is occurring is the salt is absorbing
with the water contained in a slugs body and from this point
creating a Salt-water-slug protein solution. From this I got to
thinking, why is it exactly that salt seems to absorb water, what
are the chemical equations for this? Am I missing something in the
manner of which salt crystals are formed? I will continue conducting
my own research but would also love to hear your views on the
subject as well.
---------------------------------------
Scott,

Slugs use slime for many things like moving, breathing and reproduction.  I
won't go into a long detailed explanation of why slugs need slime, but the
link below is very good if you are interested.  When you pour salt onto a
slug, the slug appears to melt.  What is actually happening is the liquids
and "blood" inside of the slug are sent to dilute the salt and maintain the
mucus layer.  Too much salt will effectively dehydrate the slug's body and
kill it by making all of the liquid inside go to the outside.  Think about
this if it could happen to you!

Salt is hygroscopic (not hyDROscopic--there is no such word).  This means
that it will pick up water from the surrounding environment.  This is a slow
process and not what is happening with a slug, but when the liquids that the
slug secretes gets to the outside of its body the salt might readily
dissolve in the mucus/liquid.  This would probably end up speeding up the
process--think of it as osmosis from the outside in.

Matt Voss
====================================================================
This is due to osmosis.  The skin of the slug acts as a semi-permeable
membrane where there are different concentrations of salt and water on each
side.  Remember that water will move from an area where there is more water
to an area where there is less water.  The salt that you sprinkle on
the slug mixes with water in the slime on the outside of the slug to make a
salty solution.  In any solution there is only so much room, so if there is
a lot of salt, there is not a lot of water.  There is more water, less salt
on the inside of the slug, so water leaves the slug to mix with the salt
outside the slug in order to equalize (or "more equalize") the water on both
sides of the membrane.  There is a net loss of water from the slug and it
dehydrates to death.

vanhoeck
====================================================================
Scott,

Slugs use slime for many things like moving, breathing and reproduction.  I
won't go into a long detailed explaination of why slugs need slime, but the
link below is very good if you are interested.  When you pour salt onto a
slug, the slug appears to melt.  What is actually happening is the liquids
and "blood" inside of the slug are sent to dilute the salt and maintain the
mucus layer.  Too much salt will effectively dehydrate the slug's body and
kill it by making all of the liquid inside go to the outside.  Think about
this if it could happen to you!

Salt is hygroscopic (not hyDROscopic--there is no such word).  This means
that it will pick up water from the surrounding environment.  This is a slow
process and not what is happening with a slug, but when the liquids that the
slug secretes gets to the outside of its body the salt might readily
dissolve in the mucus/liquid.  This would probably end up speeding up the
process--think of it as osmosis from the outside in.

Matt Voss
====================================================================