A flow cell for measuring the color properties of a liquid flowing through
the flow cell using interrogating radiation at a predetermined wavelength
has a thin partition mounted in spaced relationship between both a window
and a base of the cell. The partition has a predetermined index of
refraction and has a thickness dimension that is less than that of the
window. The spacing between the partition and the window is such that
evanescent coupling of radiation reflected from the liquid into the
material of the window is prevented. Typically, this spacing is a
distance not less than three (3) times the predetermined maximum
wavelength in the wavelength range of interrogating radiation. A
plurality of spacer elements may be disposed in the air cavity to
maintain the spaced relationship between the partition and the window.
The flow cell has a liquid supply passage and a liquid removal passage
formed therein. The liquid supply passage, the sample chamber and the
liquid removal passage cooperate to define a liquid flow path through the
flow cell. The liquid supply passage, the sample chamber and the liquid
removal passage are configured such that any cross section taken in a
plane substantially perpendicular to the liquid flow path at any location
therealong exhibits substantially the same cross-sectional area.