quicksilver vs erratic

quicksilver is a noun but erratic is not a noun.

Word	Noun	Adjective	Verb	Adverb
quicksilver	Yes	Yes	No	No
erratic	No	Yes	No	No

As adjectives, quicksilver and erratic are synonyms defined as:

Other synonyms of quicksilver include fickle, mercurial.

quicksilver (noun)	erratic (noun)
a heavy silvery toxic univalent and bivalent metallic element; the only metal that is liquid at ordinary temperatures

quicksilver (adjective)	erratic (adjective)
liable to sudden unpredictable change	liable to sudden unpredictable change
	likely to perform unpredictably
	having no fixed course