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Top tip for useful info.

Isn't it usually the hydrated form though? The crystalline one you buy in chemists as epsom salts is magnesium sulphate heptahydrate (MgSO4+7(H20)).
 
Hi all,
Magnesium sulphate is always the heptahydrate form (.7H20) unless it is stated to be "anhydrous" and has then been kept in a low moisture environment (a desiccator). This is because MgSO4 is hygroscopic, and will naturally pick up atmospheric moisture to form "Epsom Salts" - MgSO4.7H20. You can use the anhydrous form as a desiccant, re-charging it at in an a very hot oven (at about 450oF).

cheers Darrel
 
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