Straylight error in a spectrophotometer.

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 lution of benzoic acid was 1.6 per cent lower at an absorbancy of than at 0.4. Errors of this magnitude are far greater than the ding error. In deriving a correction formula to cover the entire range of abrbancies, a constant blank reading on the transmission scale, olv), and a constant amount of unabsorbed stray radiant energy ching the photo cell were assumed (I, 2). The constant stray iant energy is introduced as the ratio of the stray radiant energy ding to the blank reading and denoted . Thus, the true abrbancy is given by