Por lo que leí en el texto que pasaban bajo la pantalla simplemente ha mezclado yodato y bisulfito con almidón.
El bisulfito se oxida a sulfato y el yodato se reduce a yodo. El yodo reacciona con almidón dando una coloración violeta característica. Como casi todos los colores si tienes demasiado acaba siendo negro.
Vale cualquier variante que quieras inventarte siempre que acabes mezclando yodo con almidón.
No es demasiado espectacular, me parece más entretenido lo del azul de metileno y la glucosa, no creo que tarden mucho en hacerlo
"Starch solution is used to test for elemental iodine. A blue/black color indicates the presence of iodine in starch solution. The details of this reaction are not yet fully known, but it is thought that the iodine (I3− and I5− ions) fits inside the coils of amylose, the charge transfers between the iodine and the starch, and the energy level spacings in the resulting complex correspond to the absorption spectrum in the visible light region. A 0.3% w/w solution is the standard concentration for a dilute starch indicator solution. It is made by adding 4 grams of soluble starch to 1 litre of heated water; the solution is cooled before use (starch-iodine complex becomes unstable at temperatures above 35°C). This complex is often used in redox titrations: in presence of an oxidizing agent the solution turns blue, in presence of reducing agent blue color disappears because I5− ions break up into iodine and iodide"
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