Which of the following is known as oil of vitriol ?

Sulfuric acid is sometimes referred to as "oil of vitriol" or simply "vitriol." The term "vitriol" comes from the Latin word "vitreus," meaning "glassy," and was used to describe any glassy substance, including sulfuric acid.

The name "oil of vitriol" is derived from the oily texture of concentrated sulfuric acid. When sulfuric acid is highly concentrated, it becomes viscous and oily, hence the name "oil of vitriol." The term "vitriol" itself refers to the corrosive and caustic nature of the acid, which was historically used as a powerful industrial and laboratory reagent.