The old alchemical names for acids often described how they were made rather than their modern chemical identity. Hydrochloric acid was classically obtained by heating common salt (sodium chloride) with concentrated sulphuric acid, releasing hydrogen chloride gas that was absorbed in water, hence it earned the name "spirit of salt," with "spirit" being the old term for a distilled or volatile substance. Nitric acid's historical name was "aqua fortis," while boric acid and thioglycolic acid never carried this alchemical label at all, so none of the other three options fit.
Therefore, the correct answer is Hydrochloric acid.
Which is the correct order of acid strength from the following?
Amides are less basic than amines.
Why phenol does not undergo protonation readily?