Usage of Magnesium Sulphate
Good question. I don't have good experience with using sulfates. There's a lot of differences in sulfates, sulfites, nitrates, peroxide, carbonates, oxide, etc. The one advantage that magnesium chloride is that it is antibacterial, antiviral and it also increases your stomach acids as well as having a therapeutic effect.
The actions of sulfates is still an unknown. I have also bad experience with many kinds of sulfates, such as zinc sulfates which causes vomiting. Sulfates did not have much medicinal properties when it comes to having a bad back, weakness, tiredness, etc.
Nitrates and nitrites are toxic, while carbonates have varying absorbability. Oxides are poorly absorbed. Chlorides are completely soluble and make it ideal for bioavailability.
Therefore, based on trial and error (and a painful one at that), magnesium chloride do in fact have medicinal properties.
Of course, you can challenge me on that. But French doctors in the beginning of the century found magnesium chloride were valuable in treating many diseases.