when I say "vitriol" do you think...?

my first though was acid, but I am a chemist by training. I knew the word vitriol as nasty, hateful or corrosive speech well before I knew it as sulfuric acid. I used the word for that meaning well before I knew its origin, basically.

Sulfuric acid is correct, but "oil of vitriol" is better.

In phraseology, vitriol is hate filled words, not necessarily a criticism. When I opine that you are a ****** or a ***** or even an actual *******, I am not offering a criticism.

Both.

I read a lot of Victorian texts: there was a major moral panic about "vitriol throwing" in the mid-1800s. http://www.victorianlondon.org/crime/vitriol.htm

Vitriol is not always criticism. It can be just plain mean mouthing.