carboxylic acids (usually monobasic) of the alicyclic series, containing one or more five-member (less frequently, six-member) hydrocarbon rings—for example,
Naphthenic acids are the main oxygen-containing components or petroleum (content in petroleum, 0.5–3.0 percent), from which they are extracted in the form of salts (naphthenates) by means of an aqueous solution of an alkali. Naphthenic acids are viscous, colorless liquids that turn yellowish upon standing. Boiling point, 220°-300°C; pour point, < 80°C. They are virtually insoluble in water but dissolve readily in petroleum products and other organic solvents. They have all the properties characteristic of carboxylic acids.
Naphthenic acids are used to a limited extent for demulsification of petroleum and impregnation of crossties, and also as solvents for resins and gums. Salts of naphthenic acids are most widely used. Salts of alkali metals (alkaline naphthenates) are used to wash wool and as emulsifiers and disinfectants; salts of lead, manganese, cobalt, and zinc serve as desiccants in the preparation of oil paints; copper salts are used in the impregnation of wood, cables, and fabrics to prevent rotting; and lead and aluminum salts serve as special additives in the preparation of lubricating oils and fuels.