Apart from sequihydrate and hemihydrate (1.5 and 0.5 respectively), I can't find a way to write any other fractional hydrates. Wikipedia states:
The notation "hydrated compound⋅nH2O", where n is the number of water molecules per formula unit of the salt, is commonly used to show that a salt is hydrated. The n is usually a low integer, though it is possible for fractional values to occur. For example, in a monohydrate n = 1, and in a hexahydrate n = 6.
Wikipedia says that fractional values can occur, but it doesn't show how to write the hydrate's name if n is fractional. Is there a simple way of writing a hydrate where n is, for example, 3.5 or 4.333...?