sulfurous vs caustic

sulfurous is not a noun while caustic is a noun.

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

As adjectives, sulfurous and caustic are synonyms defined as:

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

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

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