Fluorescence count rates depending on the In mass density measured in 12 experiments covering a variety of nebulizer settings and gas flows. Solution concentrations covered 50 (circles), 100 (squares) and 200 mmol L−1 (triangles). The data points confirm a linear dependence of the absorption on the mass density. The fit showed that a fluorescence signal of 293 Hz resulted per incremental 1 µg cm−3 of In density. This signal is about two times lower than the expected intensity, which is probably related to aerosol dispersion after leaving the feeding tube.