Na(2) eosinate, erythrosine and fluorescein Na were converted with Me(3)RNCl (R = coconut-, C(12)H(25)-, tallow- or soya-) ammonium salts in H(2)O at 80 degrees C for 30 min to resp. ammonium 6-hydroxy-3-oxo-3H-xanthenyl-9-benzoates (yield 70-90%). The ionic liqs. produced were analyzed for chem. structure (NMR), purity, color, thermal stability, decompn. with O(3) and UV irradn., biolog. activity against bacteria (rods and cocci) and fungi as well as for interaction towards higher mammals. The products were stable up to 265-317 degrees C, showed microbicide activity and were inert against warm-blooded animals. The products were recommended for dying polymers and greases as well as wood and cellulose protection.