[Determination of free chlorine with spectrophotometric method using N,N-diethyl-1,4-phenylenediamine].

In this paper, the absorption spectra of free chlorine in the visible region has been measured after free chlorine in the solution had reacted with N,N-diethyl-1,4-phenylenediamine (DPD). The relation between the absorption spectra and peak wavelength has been discussed. From the experiment of liquor with different concentration, the error of spectral measurement is less than 0.04%. By nonlinear data fitting, the relation between the concentration of free chlorine and the transmittivity has been given.