ASTM D4046 Test Method for Alkyl Nitrate in Diesel Fuels by Spectrophotometry
3. Summary of Test Method
3.1 The determination is based on the simultaneous hydrolysis of the ester in 65 % sulfuric acid solution and nitration of m-xylenol by the nitric acid liberated. The nitroxylenol is extracted from the reaction mixture and reacted with sodium hydroxide to form the yellow salt. The color is measured spectrophotometrically at 452 nm, and the concentration of alkyl nitrate is determined by reference to the slope of the calibration curve.
4. Significance and Use
4.1 This test method can be used to determine the amount of alkyl nitrate that has been added to diesel fuel to improve Cetane Number. The test method is applicable as a basis for judging compliance with specifications covering any alkyl nitrate.
5. Interferences
5.1 Other nitrate esters, inorganic nitrate ions, and nitrogen oxides will interfere.
