caustic vs sulphurous

caustic is a noun but sulphurous is not a noun.

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

As adjectives, caustic and sulphurous are synonyms defined as:

Other synonyms of caustic include acerb, acerbic, acid, acrid, bitter, blistering, sulfurous, virulent, vitriolic.

caustic (noun)	sulphurous (noun)
the envelope of light rays reflected or refracted by a curved surface or object
any chemical substance that burns or destroys living tissue

caustic (adjective)	sulphurous (adjective)
of a substance, especially a strong acid; capable of destroying or eating away by chemical action	of or related to or containing sulfur or derived from sulfur
harsh or corrosive in tone	characterized by oppressive heat and humidity
	harsh or corrosive in tone