This applies especially to oximes of the general formula: ##STR4## in which R' is an oxygen atom, a further oxime group or a positively charged amino group, the amino group optionally being substituted once or twice by lower alkyl radicals and the lower alkyl radicals can, in turn, be substituted by a hydroxyl group, an amino group substituted one or more times by lower alkyl, PO3 H2, COOH or SO3