On 21 Mar 2006 12:07:56 -0800, Aidan wrote:

......... by swapping the carbonate ion for the chloride ion.

Close. It swaps the calcium &/or magnesium base ions for sodium, but
who cares if they work. Which they do.

Same thing. Turns Sodium Chloride and Calcium Carbonate into Sodium
Carbonate and Calcium Chloride.

--
Nigel M