Patent ID: 6274381
Filing Date: 2001-08-14
Classification: C09B,C10L,G01N,Y10T

Abstract:
A method for identifying an invisibly tagged liquid petroleum hydrocarbon, comprising:exposing a petroleum hydrocarbon to visible radiation having wavelengths of about 500 to about 700 nm, wherein said petroleum hydrocarbon has incorporated therein dyes consisting essentially of at least one anthraquinone dye and at least one diazo dye, each at a level below 1 ppm, wherein the dyes are hydrocarbon-soluble, and wherein the dyes have their absorption maximum in the visible spectrum over wavelengths from about 500 to about 700 nm; and,detecting the presence of the dyes from their absorption in a wavelength region from about 500 to about 700 nm without performing any chemical manipulation of the petroleum hydrocarbon.