# Hydrate isomerism

My book specifically mentions in the solution to a question:

$$\ce{[CrBrCl2 (H2O) (NH3)2].H2O}$$ is not the hydrate isomer of $$\ce{[CrCl2 (H2O)2 (NH3)2]Br}$$

But the author hasn't provided any reason for it. I am unable to understand why the two are not hydrate isomers even though they differ in the number of water of crystallisation.

• Well, obviously the book has different definition of "hydrate isomerism". – Mithoron Oct 22 '18 at 18:47