This method is a spectrophotometric determination of thecarbonyl number, present as ketone or aldehyde carbonyl, anddefined as "milligrams of carbonyl function per liter of sampleusing acetophenone as the standard." The color intensity of thereaction product is determined both by concentration and the typeof R-group presenting the carbonyl function. This method applies toaqueous solutions, and hydrocarbons and alcohols in theC₅ to C₁₇ range. The typical analysis rangefor carbonyl number is 0.1 to 100 mg/L carbonyl. Results of thisanalysis are primarily used as an indication of the oxygen exposureof UOP Parex and Molex feedstocks.