A very simple but effective accessory, based on a couple of large area silicon photodiodes, is presented. It allows the analysis, by a conventional double-beam ultraviolet-visible spectro- photometer, of scattering samples. The accessory, very low in cost, can be installed and removed quickly and can be easily constructed by the users to match different commercial models. The layout and the wiring diagram of the unit are described and the performances are tested. ©1997 American Institute of Physics.