potash vs caustic potash

potash and caustic potash both are nouns.

Word	Noun	Adjective	Verb	Adverb
potash	Yes	No	No	No
caustic potash	Yes	No	No	No

As nouns, potash and caustic potash are synonyms defined as:

potash and caustic potash: a potassium compound often used in agriculture and industry

Other synonyms of potash include potassium hydroxide.

potash (noun)	caustic potash (noun)
a potassium compound often used in agriculture and industry	a potassium compound often used in agriculture and industry