EXPLANATION
In the United States, high-sulfur content distillate products and diesel fuel used for off-road purposes, other than aviation turbine fuel are required to contain red dye. A similar dye requirement exists for tax-free distillates. Contamination of aviation turbine fuel by small quantities of red dye has occurred. Such contamination presents major problems because airframe and engine manufacturers have severely limited operation on aviation turbine fuel containing red dye. An alternate methodology for the determination of the presence of the red dye in aviation turbine fuel is the observation of the color of the fuel when placed in a white bucket. The presence of the dye can be masked in the aviation turbine fuels having dark Saybolt color. This test method provides an objective means of quickly measuring red dye concentration, but to avoid confusion with trace levels of other materials which will be indicated by the instrument, the method requires that the instrument readings below 0.026 mg/L be reported as No Dye Present. The color of the base fuel is masked by the presence of the red dye. This test method provides a means of estimating the base color of aviation turbine fuel and kerosene in the presence of red dye. This test method covers the determination of the red dye concentration of aviation turbine fuel and kerosene and the estimation of the Saybolt color of undyed and red dyed (<0.750 mg/L of Solvent Red 26 equivalent) aviation turbine fuel and kerosene. The method is appropriate for use with aviation turbine fuel and kerosene described in Specifications ASTM D1655 and ASTM D3699. Red dye concentrations are determined at levels equivalent to 0.026 to 0.750 mg/L of Solvent Red 26 in samples with Saybolt colors ranging from +30 to -16. The Saybolt color of base fuel for samples dyed red with concentration levels equivalent to 0.026 to 0.750 mg/L of Solvent Red 26 is estimated in the Saybolt color range +30 to -16. The Saybolt color for undyed samples is estimated in the Saybolt color range from +30 to -16.
TEST SUMMARY
Comparing with Test Method ASTM D6756, the only difference is that in D6756 ASTM color equivalent is measured; in Test Method ASTM D7058, Saybolt color equivalent is measured.
INTERFERENCES - The presence of colorants resulting from the refining process or crude oil or the presence of red dye other than the quantified types (alkyl derivatives of azobenzene-4-azo-2-naphthol) can interfere with the accurate determination of the red dye concentration reported as Solvent Red 26 equivalent, or the accurate estimation of the base fuel color. If there is controversy over whether the indicated dye concentration is from the alkyl derivatives of azobenzene-4-azo-2-naphthol, the procedure described in the Annex of this test method shall be used to confirm the presence of a red dye.
TEST PRECISION
Since there is no accepted reference material suitable for determining the bias of the procedure in this test method, bias has not been determined.