Dippel's oil (sometimes referred to as bone oil) is a nitrogenous by-product of the destructive distillation of bones. A dark, viscous, tar-like liquid with an unpleasant smell, it is named after its inventor, Johann Konrad Dippel. The oil consists of aliphatic chains, with nitrogen functional groups including  pyrroles, pyridines and nitriles, as well as other nitrogenous compounds.
Dippel's oil had a number of uses, which are mostly obsolete. Its primary use was as an animal and insect repellent. It saw limited use as a chemical warfare harassing agent during the desert campaign of World War II. The oil was used to render wells undrinkable and thus deny their use to the enemy. 
By not being lethal, the oil was claimed to not be in breach of the Geneva Protocol.