Marclio Dos Santos Tavares*, Antonio de Souza Arajo and Valter Jose Fernandes Jnior Department of Chemistry – Federal University of the Rio Grande of the North – Department of Chemistry? CEP: 59078 – 970 – Native – RN, Brazil. INTRODUCTION colorimtrica Analysis is based on the change in the intensity of the color of a solution with variations in the concentration. Colorimtricos methods represent the form simplest of analysis of absoro1-3. The human eye is used to compare the color of the solution of the sample with a set of norms until a correspondence is found. An increase in the result of sensitivity and precision when one espectrofotmetro is used to measure the intensity of the color. Basically, it measures the fraction of an incident beam of light that is transmitted by a sample in one determined length of onda4-6. In this experiment one was used espectrofotmetro of mark SHIMADZU model UV-1650. It has two ways to measure the difference in the intensity of the light beam. One of them is percentile transmitncia, %T, what it is defined as: %T = Io/I = log 1/T = – log T (01) For any composed determining, the amount of absorbed light depends on the (a) concentration, (b) of the length of the way, (c) of the wave length and (d) of the solvent. Absorbncia is related in the concentration in accordance with the law of Beer-Lambert7: = bc (02) Where is the extinguishing coefficient (M-1cm-1), b is the length of the way of solution (cm) and c is the concentration (mol liter-1).