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Name: Scott
Status: other
Grade: other
Location:  OR
Country: N/A
Date: January 2007

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.



Replies:
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.

Van Hoeck


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



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