HE PRINCIPAL SUBJECT MATTER of this paper is the description of a thod of obtaining a calibration curve relating apparent absorbancy 81) and concentration (x). It is frequently observed that the orbancy index decreases with increasing concentration in cases in ich one would expect Beer’s law, A = log(10/I) = KX, to hold. For ample, with our instrument, the absorbancy index at 273.5 m of a lutio...