'Oil of vitriol' is the common name of:

In medieval times, sulphuric acid was made by heating "green vitriol" (iron(II) sulphate crystals) or "blue vitriol" (copper sulphate). The oily liquid obtained was called "oil of vitriol". The word "vitriol" comes from the Latin word vitreus, meaning "glassy", because the sulphate salts look like glass.

Sulphuric acid is a dense, colourless, oily liquid. It is a strong acid and is highly corrosive. It is called the "king of chemicals" because it is used in making so many other chemicals, and the amount of sulphuric acid a country uses is sometimes taken as a measure of its industrial development.

Today, sulphuric acid is made by the Contact process. Sulphur is burnt to form sulphur dioxide. Sulphur dioxide is then oxidised to sulphur trioxide in the presence of a vanadium pentoxide (V2O5) catalyst. Sulphur trioxide is dissolved in concentrated sulphuric acid to form oleum, which is diluted with water to give sulphuric acid.

Uses of sulphuric acid:

• Making fertilisers, such as ammonium sulphate and superphosphate of lime (its biggest use).
• In lead-acid storage batteries, as in cars.
• Refining petroleum and making detergents, dyes, paints, drugs and explosives.
• As a dehydrating (drying) agent; it removes water from sugar, turning it into black carbon.
• Safety rule: when diluting concentrated sulphuric acid, the acid must always be added slowly to water, never water to acid, because the mixing releases a great deal of heat and can make the mixture splash and boil.

Why not the other options?

• ✗Nitric acid was called "aqua fortis" ("strong water").
• ✗Hydrochloric acid was called "muriatic acid" or "spirit of salt".
• ✗Acetic acid is the acid in vinegar.