Abstract: Mixture of alkyl phenyl sulfonates of alkaline earth metals having: (a) from 20% to 70% by weight of a linear mono alkyl phenyl sulfonate in which the linear mono alkyl substituent contains from 14 to 40 carbon atoms, preferably from 20 to 24 carbon atoms, and the mole % of the phenyl sulfonate radical fixed on position 1 or 2 of the linear alkyl chain is between 10% and 25%, preferably between 13% and 20%, and (b) from 30% to 80% by weight of a branched mono alkyl phenyl sulfonate in which the branched mono alkyl substituent contains from 14 to 18 carbon atoms.