The filtered set of species S f iltered is then used to populate buckets that are each defined by a unique composition (Figure ). Buckets are populated by members containing either one or two species where the total composition of each member matches the composition of the bucket. This means that any pair of members in a given bucket define the reactants and products of a stoichiometrically balanced chemical reaction containing one or two reactants and one or two products. In order to reduce the number of possible reactions, we do not presently allow ternary reactions. While some elementary reactions with three products are possible, we expect them to be rare, and we do not generally believe that elementary reactions with three reactants are meaningful in electrochemistry. For each bucket, all combinations of two unique . . .