Re: Where does all the chlorine in salt water come from?

The chlorine in sea water is in ion form as a part of sodium chloride.  
This is a highly soluble chemical, also known as halite.   Because it is so 
soluble it dissolves readily and is transported to the sea in streams, 
rivers, and by groundwater.   A lot of information about the composition of 
sea water and its origin can be found at the following web site:
 http://www.geog.ouc.bc.ca/physgeog/contents/8p.html

Please explore that site and others for a lot of information about the 
various substances that make up sea water.