ISO 13759 Petroleum products - Determination of alkyl nitrate in diesel fuels - Spectrometric method
WARNING - The use of this International Standard may involve hazardous materials, operations and equipment. This standard does not purport to address all of the safety problems associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use.
1 Scope
This International Standard specifies a procedure for the determination of alkyl nitrate in diesel fuel in the concentration range 0.03 % (WV) to 0.30 % (VW) (volume fraction 0.03 % to 0.30 %).
A knowledge of the specific alkyl nitrate present in the diesel fuel is required for accurate determinations, as the calibration of instrumentation is reliant on reference solutions containing the nitrate to be analysed. When the specific alkyl nitrate is not known, a result comparative to a reference alkyl nitrate (4.2) gives indicative information.
NOTE - The addition of certain alkyl nitrates to diesel fuel enhances the cetane number as measured by the engine test described in ISO 5165. It has no effect on the cetane index value as described in ISO 4264. See annex A.
The presence of nitrate esters, inorganic nitrate ions and nitrogen oxides will interfere with this determination.
2 Normative references
The following standards contain provisions which, through reference in this text, constitute provisions of this International Standard. At the time of publication, the editions indicated were valid. All standards are subject to revision, and parties to agreements based on this International Standard are encouraged to investigate the possibility of applying the most recent editions of the standards indicated below. Members of IEC and ISO maintain registers of currently valid International Standards.
ISO 385-1:1984, Laboratory g/assware - Burettes - Part 7: General requirements.
ISO 835-1:1981, Laboratory glassware - Graduated pipettes - Part 1: General requirements.
ISO 1042:1983, Laboratory glassware - One-mark volumetric f/asks.
ISO 3696:1987, Water for analytical laboratory use - Specification and test methods.
3 Principle
The alkyl nitrate is hydrolysed in strong sulfuric acid solution and the nitric acid released is reacted with 2,4-dimethylphenol. The nitroxylenol is extracted from the reaction mixture and treated with sodium hydroxide to form a solution of the yellow salt. The colour intensity is measured spectrometrically at 452 nm, and the concentration of alkyl nitrate is determined by reference to the calibration curve.
