  Good optical transparency is a fundamental requirement of liquid scintillator
(LS) detectors. Characterizing the transparency of a liquid scintillator to its
own emitted light is a key parameter to determine the overall sensitivity of a
large-volume detector. The attenuation of light in an optical-pure LS is
dominated by Rayleigh scattering, which poses an intrinsic limit to the
transparency of LS. This work presents a spectrometric approach of measuring
the wavelength-dependent scattering length of liquids by applying the
Einstein-Smoluchowski theory to a measurement of scattered light intensity. The
scattering lengths of linear alkyl benzene (LAB) and EJ309-base
(Di-isopropylnaphthalene, DIN) were measured and are reported in the wavelength
range of 410 to 520 nm. The spectral peak of scintillation light emitted by a
nominal LS is around 430 nm at which the scattering length for LAB and
EJ-309-base was determined to be 27.9 +/- 2.3 m and 6.1 +/- 0.6 m respectively.
