“It is general knowledge that naphtha or petroleum, also known as crude oil or rock oil, is a natural product that occurs underground in both gas and liquid form and is obtained on a large scale via deep drilling. Chemically speaking, it is a compound of carbon and hydrogen, i.e. it is a hydrocarbon of varied composition, according to where it is found and what its geological age is. Crude naphtha of the kind that is obtained underground represents a blend of different volatilities, which in the overall product is, however, a viscous oil with a greenish-black colour and a specific weight of about 0.81 to 0.88 and a flash point of approximately 24 to 35°C. Crude naphtha cannot therefore be used directly either as lamp oil (due to its consistency) or as a fuel (because of its flammability), except – for instance – at the locations where it is obtained. It needs to be processed in order to be used.
“Naphtha als Brennmaterial für Dampfkesselheizung”, Hoh. Winkel. Polytechnisches Journal, Volume 316 (1901), 782 – 786