Re: Molecules & Salts (was Calcium & Carbon source).

David B. Fenske (
Sun, 08 Feb 1998 22:48:03 -0800

>>First, calcium carbonate is a salt, not a molecule.
>OH you really didn't say that did you? Have you never heard the definition
>of a molecule?
Glenn, I hate to quibble, but I think they're right, and this is what I
learned in high school and university chemistry. A molecule is a
collection of atoms covalently bonded together. In a salt, you don't have
individual molecules, you have a collection of positive and negative ions
forming a crystal lattice structure, held together by ionic interactions.
When you dissolve a salt in water, you get positive and negative ions in
solution, individually hydrated by water, you don't get a CaCO3 molecule as
an individual entity.

That's why when you buy a bottle of an organic molecule from Sigma, it has
the MW (moleculear weight) on the label; when you buy a bottle of any salt,
it gives you the FW (formula weight), which may or may not include water of