Figure 12. Absorption spectra prior to (green line) and after (blue line) the addition of sodium dithionite to the aqueous dye solution from the green Herlitz pen

From

Color-Changing Markers – An Exiting Topic for Inquiry-Based Chemistry Education

M. Ducci

World Journal of Chemical Education. 2018, 6(1), 24-28 doi:10.12691/wjce-6-1-5