Liquid measurement cell having a transparent partition therein

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. The flow cell has a liquid supply passage and a liquid removal passage formed therein. A plurality of spacer elements may be disposed in the air cavity to maintain the spaced relationship between the partition and the window. Alternatively a pressurized fluid, such as pressurized air, fills the air cavity such that the spaced relationship between the partition and the window is maintained by pressurized fluid in the air cavity. The pressure of the pressurizedfluid in the air cavity i