[vesnicepraha]

Hello,
I've been trying to find an anwer for question why is BeSO4 not soluble in water while its hydrate BeSO4.4H2O is very easily soluble. Is there any explanation for this?
Thanks to everyone.

[Borek]

Is it? Do you have any source for that?

I can easily imagine anhydrous form to be slowly soluble, which doesn't mean it is insoluble.

[vesnicepraha]

Well, my textbook says that. But alright, let me rephrase my question. Why is BeSO4.4H2O more soluble in water than BeSO4?

[Enthalpy]

At least the
 Encyclopedia of the Alkaline Earth Compounds
 By Richard C. Ropp
states too that the tetrahydrate is more soluble in water than the anhydrous salt.

Maybe it doesn't imply that, if starting with the tetrahydrate form, the same final water amount contains more beryllium and sulphate.

It can be a matter of definition of the solubility:

• The four water molecules add mass to the amount of the dissolved solid;
• and the four water molecules increase the amount of water available to dissolve beryllium and sulphate;

so in the same initial amount of liquid water, a bigger mass of hydrate dissolves.