English translation of a Russian article from 1928. Translator's abstract: The article presents general considerations on the validity of the superposition principle for light in vacuo from out a quantum theoretic point of view. It contains a report on an optical experiment designed to detect the phenomenon of photon-photon scattering. To understand the negative result of the performed experiment, a consideration of the solar corona is undertaken in order to derive an empirical upper limit on the photon-photon scattering rate. Source details: S. I. Vavilov: Zamechaniya ob empiricheskoi tochnosti opticheskogo printsipa superpozitsii. Zhurnal Russkogo Fiziko-Khimicheskogo Obshchestva pri Leningradskom Universitete, Chast' Fizicheskaya [Journal of the Russian Physico-Chemical Society at Leningrad University, Physical Part], Vol. LX (1928) No. 6, pp. 555-563.