| 摘要 |
Method for detecting marked mineral oils by treating the marked mineral oil with an extractant comprising water, a solvent and a base comprises using as marker an azo dye of the formula <IMAGE> where ring A may be benzofused, m is from 1 to 4, X1 is hydrogen, C1-C4-alkyl, cyano or nitro, X2 is hydrogen, C1-C4-alkyl, cyano, nitro, C1-C4-alkoxy or C1-C16-alkoxycarbonyl, X3 is hydrogen, C1-C4-alkyl, cyano or C1-C16-alkoxycarbonyl, and X4 is hydrogen, hydroxyl, substituted or unsubstituted C1-C8-alkyl, C1-C4-alkoxy, amino, C1-C4-dialkylamino or substituted or unsubstituted C1-C16-monoalkylamino, as solvent a partially or completely water-miscible organic solvent, and as base an alkali or alkaline earth metal hydroxide, an alkali metal carbonate or a quaternary ammonium hydroxide, the use of azo dyes as markers for mineral oils, and novel azo dyes.
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