Where a2 is a constant for the particular solution and c is the concentration of the solution. If light is absorbed exponentially with concentration over a reasonable and practical range of concentration, the colored material is said to complex obeys Beer’s law is to prepare a series of samples in the desired range of concentration and submit them to test on a photoelectric colorimeter or spectrophotometer. If the observations of percent light transmission plot along a straight line on a semilog graph, the material can be considered to obey Beer’s law. Many colored systems do not conform to Beer’s law, and therefore development of any new colorimetric method should involve such a test procedure.