bitter salts vs Epsom salts

bitter salts and Epsom salts both are nouns.

Word	Noun	Adjective	Verb	Adverb
bitter salts	Yes	No	No	No
Epsom salts	Yes	No	No	No

As nouns, bitter salts and Epsom salts are synonyms defined as:

bitter salts and Epsom salts: hydrated magnesium sulfate that is taken orally to treat heartburn and constipation and injected to prevent seizures

bitter salts (noun)	Epsom salts (noun)
hydrated magnesium sulfate that is taken orally to treat heartburn and constipation and injected to prevent seizures	(used with a singular noun) hydrated magnesium sulfate used as a laxative
	hydrated magnesium sulfate that is taken orally to treat heartburn and constipation and injected to prevent seizures