Résumé Structural analysis of the solid-liquid interface topography in relation to the reaction of the sulfonium salt considered and furfural allows definition of the nature of the acid-base interactions that result predominately in formation of the 2-furyl oxiran. Moreover the study made with KOH H 2 O; Ba (OH) 2 0, 8 H 2 O and K 2 CO 3 1, 5 H 2 O in the solid state pointed out that compatibility between the crystalline lattice of the solid phase and the ...