1. n. [Enhanced Oil Recovery]

The change in the Gibbs free energy (G) of a system when an infinitesimally small amount of a component is added under constant pressure (P) and temperature (T) while keeping the mass of the other components of the system unchanged. Concentration variation within a system tends to drive a particle along a gradient from higher to lower chemical potential (μ). Chemical potential can also be defined in terms of Helmholtz free energy (A) under conditions of constant volume (V) and temperature.

Chemical potential equation:
μ_i = (∂G / ∂N_i)_{T, P, Nj ≠ i},

alternatively:
μ_i = (∂A / ∂N_i)_{T, V, Nj ≠ i},

where

• μ_i = chemical potential of component i
• G = Gibbs free energy
• A = Helmholtz free energy
• N_i = number of particles or moles of component i
• T = temperature
• P = pressure
• V = volume
• ∂ = differential operator
• i, j = chemical components.