Fig 2. An example of composing two reactions in bond graphs.

Reactions 1 and 2 represent two separate reactions in which the species C is common. To compose the reactions, the common species (C) is merged and the conservation equation at its corresponding ‘0: u’ junction alters to account for the imposed changes in structure. The conservation equation at the ‘0: u’ junction connected to the species C is v_c = v₁ in Reaction 1 and in Reaction 2 is v_C = −v₂ and in the composed reaction it changes to v_C = v₁−v₂.