Re: What is the meaning of an anhydrous crystal?

Anhydrous means without water it is a simple as that. In crystal 
structures there is room for small water molecules to be trapped. This 
water is called the water of crystallisation. Crystals with water in are 
still dry solids but when heated quickly lose the water as steam.
Cobalt Chloride is blue when it has no water but pink when hydrated and is 
often sold as a means of detecting atmospheric moisture.