As this is a health conscious site it is normal to promote the use of substances that are as pure as possible.
The Epsom Salts
you are looking for should be 100% pure. If you live in the States or the UK you shouldn't have any problems getting it. It should clearly state that it is 100% pure Magnesium Sulphate ( Epsom Salts
), that it is for internal use, a laxative or something similar.
Note: there is a spelling difference and sulphate can be spelt with "ph" or "f".
Something like this:
The contaminants that you find in less that 100% pure Epsom salts include arsenic and iron.