ammonium alum vs ammonia alum

ammonium alum and ammonia alum both are nouns.

Word	Noun	Adjective	Verb	Adverb
ammonium alum	Yes	No	No	No
ammonia alum	Yes	No	No	No

As nouns, ammonium alum and ammonia alum are synonyms defined as:

ammonium alum and ammonia alum: a white crystalline double sulfate of aluminum: the ammonium double sulfate of aluminum

Other synonyms of ammonium alum include alum.

ammonium alum (noun)	ammonia alum (noun)
a white crystalline double sulfate of aluminum: the ammonium double sulfate of aluminum	a white crystalline double sulfate of aluminum: the ammonium double sulfate of aluminum