FED-STD-791D
Method 6050.1
September 30, 1986
NITRATE-TYPE IGNITION IMPROVERS IN DIESEL FUEL
1. SCOPE
1.1 This method of test covers the determination of organic nitrate ester-type
cetane improver additives used in diesel fuel. It is intended as a screening test for those
diesel fuel inspection test procedures that are affected by the presence of cetane
improvers; namely, ASTM D 524 Standard Method of Test for Ramsbottom Carbon
Residue of Petroleum Products and D 976 Standard Methods for Calculated Cetane Index
of Distillate Fuels.
2. SUMMARY
2.1 A diesel fuel sample is saponified in a potassium hydroxide-1-butanol
mixture and then filtered through a glass fiber filter disk. The material remaining on the
disc is treated with diphenylamine reagent after drying. The presence of a nitrate ester
cetane improver is revealed by the formation of a blue ring or blue-black spot due to
oxidation of diplenylamine to intense blue quinoidal compounds by the nitrate salt. No
color change confirms the absence of a cetane improver.
3. SAMPLE SIZE
3.1 A 10-mL sample of diesel fuel is required.
4. REFERENCES, STANDARDS, AND APPARATUS.
4.1 Reaction bottle - screw-cap bottle, 29.6 mL (l fl oz) capacity, wide mouth,
flint glass, with screw-cap lined with tin or tetrafluoroethylene (TFE) resin.
4.2 Glass fiber filter paper - 3.7 cm diameter, Grade 934 AH (H. Reeve Angel,
Inc., Clifton, NJ, or equivalent).
4.3 Pipette - 10 mL capacity, fitted with pipetting bulb. Several types and makes
of pipetting bulbs and assemblies are available. One of the following is suggested:
Fisher Cat. No. 13-681, Safety Pipet Filler, or equal; Fisher Cat. No. 13-681-50, Pipet
Filler, or equal.
4.4 Graduated cylinders - 10 and 25 mL capacity.
4.5 Suction flask with a suitable holder to accommodate a 60-mL glass-fritted
crucible.
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