Hydrate dissolving in it's own waters

[flatmaster]

I remember a demonstration you can do when determining the waters of hydration of a perticular hydrate. As temperature increases, the compound actually becomes soluble in it's own waters of hydration and becomes a solution. As it is heated further, the waters of hydration are driven off.

Anyone know what hydrate will do this?

 

[Borek]

Sodium thiosulfate pentahydrate and sodium sulfate decahydrate come to mind.