Dyestuff laser consisting of a reservoir, with a laser dyestuff solution contained therein, and a pumped light source associated therewith, which is capable of exciting the dyestuff solution to produce an emission, characterized in that the dyestuff solution contains, in a solvent which does not interfere with the emission, a dyestuff which, in the form of the free acid, corresponds to the general formula ##STR1## wherein R.sub.1 to R.sub.4 independently of one another represent hydrogen, alkyl, trifluormethyl, alkoxy, aralkoxy, alkenyloxy, halogen or the carboxyl, cyano, alkylsulphone, aryl-sulphone, carboxamide, sulphonamide or carboxylic acid ester group, R.sub.1 and R.sub.4 can additionally denote a fused-on benzene ring, n represents a number 2 to 6 and o, p, q and r independently of one another represent 0, 1 or 2, in a concentration, preferably of 10.sup.-2 to 10.sup.-5 mol/1, which emits laser radiation.

Process for the preparation of sulfonated bis-[benzofuranyl-(2)] compounds by treating the corresponding unsulfonated bis-[benzofuranyl-(3)] compounds with sulfuric acid having a content of from 90 to 100% and isolating the mono- and polysulfonic acids formed as such or after conversion into their salts.

Novel benzofuranylbiphenyl compounds of the formula ##STR1## which are unsubstituted or polysubstituted by radicals R=hydrogen, C.sub.1 -C.sub.4 alkyl, C.sub.1 -C.sub.4 alkoxy, halogen, phenoxy and benzyloxy and in which M is hydrogen and/or one equivalent of a non-chromophoric cation and n is the number zero, 1 or 2 and m is the number zero or 1, subject to the condition that n and m are not both zero, and the preparation and use thereof as fluorescent brighteners, for example for textiles and paper. The novel benzofuranylbiphenyl compounds are distinguished by their very good stability associated with excellent whitening properties.

Benzodifuran compounds of the formula ##SPC1## Wherein R represents alkoxy, aralkoxy, aryloxy, cycloalkoxy, hydroxyl, an oxygen atom linked to the radical Ar, or the group ##EQU1## R.sub.1 and R.sub.2 independently of one another denote hydrogen, alkyl, aralkyl or aryl, or together denote a saturated carbocyclic or heterocyclic ring and Ar denotes an aromatic-carbocyclic or aromatic-heterocyclic radical, with the proviso that Ar denotes a substituted benzene radical if R represents C.sub.1 -C.sub.2 -alkyl, Are suitable as optical brightening agents and UV-absorber for organic materials.

Furanyl-(2)-1,2,4-oxadiazoles of the formula ##STR1## wherein A represents an aromatic mononuclear or binuclear ring system which with two adjacent carbon atoms is fused with the furan nucleus in the manner indicated, R represents hydrogen, a lower alkyl group, an optionally substituted phenyl group, as well as an optionally functionally modified carboxy group, X represents a direct bond, as well as the following divalent radicals ##STR2## B represents a straight-chained or branched, optionally substituted alkyl group or an optionally substituted aryl or heteroaryl group. These compounds are suitable for the optical brightening of high molecular weight organic substances, especially for textile materials of synthetic polymers.