Talk:Anhydrate

I changed from the Greek word án(h)ydros meaning "water loss" to from the Greek word án(h)ydros meaning "without water". But I don't speak Greek, have I mis-stated the intent of the original word by substituting the English meaning? RJFJR 01:36, 9 October 2005 (UTC)

Anhydrate=anhydride

In my 10 years as a practicing chemist, I've never heard of an anhydrate. This group of compounds is properly referred to (perhaps counterintuitively, given hydrates are called what they are) as anhydrides.

Their relationship to hydrates is tenuous at best. e.g. sulfur trioxide is indeed the anhydride of sulfuric acid, and copper(II) sulfate hexahydrate is a hydrated form of copper(II) sulfate, but in the former pair the difference is that the water is covalently bound to the anhydride, whereas in the latter the water is loosely held in the crystal lattice, held in there only by noncovalent interations. What I'm trying to say is that nobody thinks of sulfuric acid as a hydrate, nor do they think of sodium hydroxide as the hydrate of sodium oxide, whereas magnesium sulfate decahydrate is indeed thought of as a hydrate. Is that clear?

While I'm at it, a chemist would call copper(II) sulfate without any water in there 'anhydrous copper(II) sulfate'. It's not an anhydride in any sense of the word. The word ahydride implies that there is a corresponding ionic or covalent compound that has the formula anhydride + water, not one with loosely-bound water. It's not a suitable example for this article. 66.65.37.68 03:17, 18 May 2006 (UTC)