Re: How does temperature+different types of salts effect the buoyancy of water?

The hydrated water won't be released when the hydrate is dissolved. 
Exactly the opposite - if you dissolve dry (non-hydrated) magnesium 
sulphate, then it will form hydrate taking some of the water from the 
solution. In my oppinion it is not important whether the hydrated water is 
included in the calculations or not, as long as it is explicitly mentioned 
in the report of the experiment i.e. if you like to regard the liquid as a 
solution of MgSO4 in water, then you should exclude the hydrated water, 
but if you regard it as a solution of MgSO4.7H2O (epsom salt) in water 
then there's no need to exclude the mass of the hydrated water and to add 
it to the mass of the solvent. What concerns the bouyant force is solely 
the density of the liquid and it doesn't matter which way you choose to 
express the concentration.

Finally I would like to mention that in my country 'table salt' and 'sea 
salt' are two names for one and the same thing - Sodium Chloride (NaCl)