1. n. [Drilling Fluids]
A test to evaluate base oils that are used in oil mud. The test indicates if an oil is likely to damage elastomers (rubber compounds) that come in contact with the oil. The aniline point is called the "aniline point temperature," which is the lowest temperature at which equal volumes of aniline (C6H5NH2) and the oil form a single phase. The aniline point (AP) correlates roughly with the amount and type of aromatic hydrocarbons in an oil sample. A low AP is indicative of higher aromatics, while a high AP is indicative of lower aromatics content. Diesel oil with AP below 120 degF [49 degC] is probably risky to use in oil-based mud. The API has developed test procedures that are the standard for the industry.