EXPLANATION
In the United States, high sulfur content (as defined by the U.S. Environmental Protection Agency) middle distillate products and diesel fuel used for off-road purposes, other than aviation turbine fuels, are required by government agencies to contain red dye. The dye concentration required to be present in high-sulfur and off-road diesel products is regulated by USEPA, and the U.S. Internal Revenue Service, respectively.
Some fuels that are readily exchanged in the market have a color specification. 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 Number 1 and Number 2 diesel fuel and heating oil in presence of red dye. The test method provides a means to indicate conformance to contractual and legal requirements. The test method is appropriate for use with diesel fuel and heating oil of Grades 1 and 2 described in Specifications ASTM D396, ASTM D975, ASTM D2880, and ASTM D3699. Red dye concentrations are determined at levels equivalent to 0.1 - 20 mg/L of Solvent Red 26 in samples with ASTM color ranging from 0.5 - 5. The ASTM color of the base fuel red-dyed samples with concentration levels equivalent to 0.1 - 20 mg/L of Solvent Red 26 is estimated for the ASTM color range from 0.5 - 5. The ASTM color of the undyed samples is estimated over the color range of 0.5 - 5.
TEST SUMMARY
A sample is introduced into the liquid specimen cell which is then placed into the light path of the apparatus. A beam of visible light is imaged through the sample onto a detector, and the detector response is determined. Wavelengths of the spectrum, which correlate highly with the red dye concentration and the ASTM color, are selected for analysis using selective bandpass filters. A multivariate mathematical model converts the absorption values from the filters to the red dye concentration and the estimated ASTM color.
INTERFERENCES - The presence of colorants other than the hydrocarbons typical of Number 1 and 2 diesel fuel and heating oils, or the presence of the red dye other than the specified types, can interfere with the accurate determination of the red dye concentration reported as Solvent Red 26 equivalent or the base fuel ASTM color.
TEST PRECISION
Since there is no accepted reference material suitable for determining the bias for the procedure in this test method, bias has not been determined.