A spectrophotometer is particularly recommended where a wide variety of determinations is made. Its versatility allows the best wavelength of light to be used at all times. The optimum wavelength can be determined at any time by establishing a spectral transmission curve. This is an essential part of research aimed at developing new methods of colorimetric analysis. The curve is established by making a series of observations of light transmission at several different wavelengths of light while using a typical colored solution in the cell. The results when plotted on linear coordinate paper yield a curve like that shown in Fig. 11.7 for nitrite. The wavelength that is absorbed to the greatest extent, in the case of nitrite 525 nanometers (nm), is the optimum wavelength to use.