ABSTRACT
Color measurements involve that part of the electromagnetic spectrum that is visible or sensed by the human eye. Color can be measured as an indication of a concentration or as a signal that a reaction end point has been reached, such as in the case of colorimetric titration. Precise and accurate color measurements require multidimensional or coordinate systems using the tristimulus method. Several one-dimensional color standards are used in the process industries, including the American Public Health Association color standards, and the Saybolt and the American Society for Testing and Materials (ASTM) color scales. The ASTM color scale is based on ASTM method D–1500, in which there is a general correlation between the "lightness" of oil and the extent of refining. Reflectance color measurements utilize the reflected light from a sample to monitor the surface color of the sample. Some UV colorimeter designs are capable of monitoring between 150 and 1000 mµ and are frequently called photometric analyzers.
