Refractive index database

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Optical constants of C3H6(OH)2 (Propylene glycol)
Otanicar et al. 2009: n 0.434–0.656 µm, k 0.2–1.5 µm

Wavelength: µm

Complex refractive index (n+ik)[ i ]

n   k   LogX   LogY   eV

Derived optical constants


25 °C


1) T. P. Otanicar, P. E. Phelan J. S. Golden. Optical properties of liquids for direct absorption solar thermal energy systems, Solar Energy 83, 969-977 (2009) - extinction coefficient
2) C. Wohlfarth, B. Wohlfarth. Optical Constants. Springer-Verlag, New York (1996) (as cited in ref. 1) - refractive index


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Propylene glycol, C3H8O2

Propylene glycol (C3H8O2) is a synthetic organic compound that is a colorless, nearly odorless, clear, viscous liquid with a faintly sweet taste. Often regarded as a safer alternative to ethylene glycol, it is miscible with a broad range of solvents including water, acetone, and chloroform. In industrial settings, propylene glycol is used as a moisturizer in cosmetics, as a food additive, in the manufacture of hydraulic fluids and as a coolant in liquid cooling systems. Pharmacologically, it's employed to help retain the moisture content in medicines and as a solvent for oral, injectable, and topical drugs. In the realm of optics, its refractive properties can be significant, especially when used as a matching or immersion fluid.

Other names

  • Propane-1,2-diol
  • α-Propylene glycol
  • 1,2-Propanediol
  • 1,2-Dihydroxypropane
  • Methyl ethyl glycol (MEG)
  • Methylethylene glycol

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