# So what are epsom salts, anyway?
**URL:** https://boards.straightdope.com/t/so-what-are-epsom-salts-anyway/404985
**Category:** Factual Questions
**Created:** [May 21, 2007, 9:38pm UTC](https://boards.straightdope.com/t/so-what-are-epsom-salts-anyway/404985 "2007-05-21T21:38:39Z")
**Posts on this page:** 3
**Page:** 1
### Author:  [@Northern\_Piper](https://boards.straightdope.com/u/Northern_Piper)
#### Post date: [May 21, 2007, 9:38pm UTC](https://boards.straightdope.com/t/so-what-are-epsom-salts-anyway/404985/1 "2007-05-21T21:38:39Z")
**Arnold’s** question about the hole in his leg reminded me of a question I’ve been meaning to ask: what are epsom salts, anyway? what makes them different from regular salt? and how are epsom salts used for medical treatments? (not asking about any partiuclar medial case or anything - just curious.)
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### Author:  [@Squink](https://boards.straightdope.com/u/Squink)
#### Post date: [May 21, 2007, 10:01pm UTC](https://boards.straightdope.com/t/so-what-are-epsom-salts-anyway/404985/2 "2007-05-21T22:01:10Z")
[Magnesium sulphate](http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=6085985&dopt=Abstract)
> [@](#):
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> The purgative effect of the waters of Epsom, in southern England, was first discovered in the early seventeenth century. Epsom subsequently developed as one of the great English spas where high society flocked to take the medicinal waters. The extraction of the Epsom Salts from the spa waters and their chemical analysis, the essential feature of which was magnesium sulphate, were first successfully carried out by Doctor Nehemiah Grew, distinguished as a physician, botanist and an early Fellow of the Royal Society. His attempt to patent the production and sale of the Epsom Salts precipitated a dispute with two unscrupulous…
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### Author:  [@David\_Simmons](https://boards.straightdope.com/u/David_Simmons)
#### Post date: [May 22, 2007, 2:11am UTC](https://boards.straightdope.com/t/so-what-are-epsom-salts-anyway/404985/3 "2007-05-22T02:11:10Z")
[QUOTE=Northern Piper]
what are epsom salts, anyway? what makes them different from regular salt?
[/QUOTE]
A “salt” is a chemical consisting of a molecule with metal (or a group acting like a metal) replacing the hydrogen in an acid. For example, HCl (one atom of H and one of Cl) is the chemical formula for hydrocloric acit. When the hyrogen, H, is replaced by sodium, Na, the result is NaCl, common table salt.
Sulphuric acid’s chemical formula is H[sub]2[/sub]SO[sub]4[/sub]. When the H’s are replaced by magnesium, Mg, the result is magnesium sulphate, MgSO[sub]4[/sub]. When this moleculte is hydrated, that is water molecules are attached to the magnesium sulphate molecule, the result is Epsom Salt, MgSO[sub]4[/sub]∙7H[sub]2[/sub]O. The water of hydration can be removed, such as by heating, without affecting the basic subtance of the magnesium sulphate.
There. I have just exhausted what’s left of two years of college chemistry. If you have further questions you will have to wait for a chemist to come along. 🙂