“…In these methods, the structure of a molecule is represented by a two-dimensional(2-D) graph, with vertices (atoms) and edges (bonds). The numerical values resulting from the operation of a given descriptor on a graph are related to a physical property, for example, the activity coefficient at infinite dilution (Faulon et al, 2003;He and Zhong, 2003). Because the method has little theoretical basis, the type and the number of descriptors needed is property-dependent, that is, the method is specific for each thermodynamic property.…”