
The present invention relates to the use of diureides of dicarboxylic acids of the formula I ##STR1## in which R is hydrogen or SO.sub.2 OM.sup..sym., M is lithium, sodium, potassium, cesium, ammonium, copper, silver, 0.5 iron, 0.5 calcium, 0.5 magnesium, 0.5 manganese, 0.5 zinc or 0.5 cobalt and X is a saturated or monounsaturated, straight-chain or branched C.sub.1 -to C.sub.8 -alkyl which may be interrupted by oxygen or NH and which may have attached to it C.sub.1 -to C.sub.4 -alkoxy, hydroxy...











