Epson salt ISNT sodium, its magnesium sulfate. I actually wonder how an epson or other magnesium salt bar might work as there's a lot of talk in the last couple years about magnesium deficiency and transdermal magnesium supplementation. There is no accurate test for magnesium deficiency because so little of the body's magnesium is carried in the blood. People with gastrointestinal problems are more likely to be magensium deficient, and less likely to be able to absorb magnesium from an oral supplement. Epson baths are a type of transdermal magnesium supplementation. Magnesium chloride is supposed to be better for a direct transdermal supplementation such as mag oil or lotion but epson which is magnesium sulfate is fine for baths. So if it would physically work in a soap bar, its interesting. Now did I just give away a great idea? haha. I think I might try it..