Figure 4. Potassium permanganate solution (left), solution after the addition of Magic Pen fluid (middle), white precipitate after the addition of barium chloride solution (right)

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