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.
4-Methylcyclohexanemethanol carboxylic acids, which in the case of MCHM is 4-methylcyclohexanecarboxylic acid (CAS 13064-83-0), a naphthenic acid. The toxicity and environmental properties of these naphthenic acids have been well studied recently due to their occurrence as a major contaminant in water used for extraction of oil from tar sands. Naphthenic acids have both acute and chronic toxicity to fish and other organisms. The methyl ester of this acid is also listed as one of the major impurities in the "crude MCHM" as supplied by Eastman. The closely related compound cyclohexanedimethanol (CAS 105-08-8) exhibits low toxicity (3.5 g/kg) when fed orally to