Anilines as markers for mineral oils

A method of marking mineral oils, comprising:

• mixing, into a mineral oil, a marker aniline compound of formula I:
• ##STR126## where R.sup.1 and R.sup.2 independently of one another are each hydrogen, C.sub.1 -C.sub.18 -alkyl which is unsubstituted or substituted and may be interrupted by 1 to 3 oxygen atoms as ether functional groups or from 1 to 3 C.sub.1 -C.sub.4 -alkylimino groups, or C.sub.3 -C.sub.18 -alkenyl or unsubstituted or substituted phenyl, or R.sup.1 and R.sup.2, together with the nitrogen atom which links them, may be a 5-membered or 6-membered saturated heterocyclic radical which may have a further hetero atom, or R.sup.1 may furthermore be a radical of the formula OL.sup.1 or NL.sup.1 L.sup.2, where L.sup.1 and L.sup.2 independently of one another are each hydrogen, unsubstituted or substituted C.sub.1 -C.sub.18 -alkyl, C.sub.3 -C.sub.18 -alkenyl or unsubstituted or substituted phenyl,
• R.sup.3 and R.sup.7 independently of one another are each hydrogen, unsubstituted or substituted C.sub.1 -C.sub.18 -alkyl, C.sub.2 -C.sub.18 -alkenyl, cyano, nitro, formyl, unsubstituted or substituted C.sub.2 -C.sub.4 -alkanoyl, formylamino, unsubstituted or substituted C.sub.2 -C.sub.4 -alkanoylamino, benzoylamino or a radical of the formula OL.sup.1, CH.sub.2 COOL.sup.1, NL.sup.1 L.sup.2, SL.sup.1 or SO.sub.2 NL.sup.1 L.sup.2, where L.sup.1 and L.sup.2 each have the above-mentioned meanings, or together with R.sup.2 are C.sub.2 - or C.sub.3 -alkylene which is unsubstituted or monosubstituted to trisubstituted by methyl or are unsubstituted or phenyl-substituted C.sub.2 - or C.sub.3 -alkenylene,
• R.sup.4 is hydrogen, unsubstituted or substituted C.sub.1 -C.sub.18 -alkyl, C.sub.2 -C.sub.18 -alkenyl, nitro or a radical of the formula OL.sup.1, NL.sup.1 L.sup.2, COOL.sup.1 or SO.sub.2 L.sup.1 L.sup.2, where L.sup.1 and L.sup.2 each have the above-mentioned meanings, and
• R.sup.5 and R.sup.6 independently of one another are each hydrogen, unsubstituted or substituted C.sub.1 -C.sub.18 -alkyl, C.sub.2 -C.sub.18 -alkenyl, unsubstituted or substituted phenyl, nitro, formylamino, unsubstituted or substituted C.sub.2 -C.sub.4 -alkanoylamino, benzoylamino or a radical of the formula OL.sup.1, NL.sup.1 L.sup.2, SO.sub.2 NL.sup.1 L.sup.2, SO.sub.2 L.sup.3, COL.sup.1 or COOL.sup.1, where L.sup.1 and L.sup.2 each have the above-mentioned meanings and L.sup.3 is unsubstituted or substituted C.sub.1 --C.sub.18 -alkyl, C.sub.3 -C.sub.18 -alkenyl or unsubstituted or substituted phenyl,
• with the proviso that at least one of R.sup.3, R.sup.5 or R.sup.7 is hydrogen and with the proviso that aniline and all toluidine isomers are excluded.