dosing can only somewhat accurately be determined by colorimetry spec, using the Beer-Lambert law to determine the concentration in solution.
http://sciencemag.org/content/83/2146/166.extractsee Fig. 1 for wavelength of max abs, and log e.
"Nothing is true, everything is permitted." ~ hassan i sabbah
"Experiments are the only means of attaining knowledge at our disposal. The rest is poetry, imagination." -Max Planck