Question

what is turpentine? and its refractive index?

Answer 1

Turpentine is a semifluid substance consisting of two principal components, spirits of turpentine (volatile portion also known as oil of turpentine or turps ) and a type of rosin (nonvolatile portion also known as colophony). Turpentine is exuded from coniferous trees. The crude turpentine is distilled through steam into commercial turpentine, oil of turpentine. The pure turpentine oil is a transparent oily liquid with a penetrating odor and a characteristic taste. Turpentine is not a pure substance but a complex mixture of terpenes, particularly large proportion of pinene (bicyclic monoterpenic hydrocarbon), a compound from which camphor is manufactured. Terpene is a class of naturally occurring unsaturated hydrocarbons whose carbon skeletons are composed exclusively of isoprene C5 units (CH2=C(CH3)-CH=CH2).

Answer 2

 Turpentine  is often used for thinning or removing paint (from brushes/etc.). It's a solvent.