STRUCTURAL TRANSFORMATIONS IN FOAM

Recent observations have suggested a revision of the prevailing view t hat monodisperse foams are generally disordered. Among the ordered str uctures which are possible, b.c.c. (the Kelvin structure) should preva il at low liquid fractions, and f.c.c. (or other close-packed structur e) at high liquid fractions. The instabilities of both structures are discussed, and it is argued that structures of the clathrate type shou ld intervene in the intermediate range. This scenario offers an intere sting challenge to further experiment (including emulsions) and comput ation.