Naphthenic acid by a general formula CH O, where "n" indicates the carbon number and "z" specifies a homologous series. The "z" is equal to 0 for saturated, acyclic acids and increases to 2 in monocyclic naphthenic acids, to 4 in bicyclic naphthenic acids, to 6 in tricyclic acids, and to 8 in tetracyclic acids. Salts of naphthenic acids, called naphthenates, are widely used as hydrophobic sources of metal ions in diverse applications.Aluminium salts of naphthenic acid and palmitic acid were combined during World War II to produce napalm. The word "napalm" is derived from the words naphthenic acid and palmitic acid.
Flail (weapon) derived from the agricultural tool of the same name, commonly used in threshing. It was primarily considered a peasant's weapon, and while not common, they were deployed in Germany and Central Europe in the later Late Middle Ages. The smaller, more spherical-headed flail appears to be even less common; it appears occasionally in artwork from the 15th century onward, but many historians have expressed doubts that it ever saw use as an actual military weapon. In the Late Middle Ages, a particular type of flail appears in several works being used as a weapon, which consists of a very long