refractive index increment

in polymer chemistry
The change of the solution refractive index, n, with solute concentration, C, i.e. ∂n/∂C.
  1. The solute concentration is most frequently expressed in terms of mass concentration, molality or @V06643@. If expressed in terms of mass concentration or molality, the corresponding @R05240@ increments are referred to as specific or @M03969@ @R05240@ increments, respectively.
  2. Following use of the full name, the abbreviated name refractive increment may be used.
Purple Book, 1st ed., p. 65 (