potash alum vs potassium alum

potash alum and potassium alum both are nouns.

Word	Noun	Adjective	Verb	Adverb
potash alum	Yes	No	No	No
potassium alum	Yes	No	No	No

As nouns, potash alum and potassium alum are synonyms defined as:

potash alum and potassium alum: a white crystalline double sulfate of aluminum: the potassium double sulfate of aluminum

Other synonyms of potash alum include alum.

potash alum (noun)	potassium alum (noun)
a white crystalline double sulfate of aluminum: the potassium double sulfate of aluminum	a white crystalline double sulfate of aluminum: the potassium double sulfate of aluminum