"Chemical traffic light" experiment

Сan a solution change its color by itself?

Can a liq­uid change col­ors by it­self? Check out “Chem­i­cal traf­fic light” – a breath­tak­ing­ly col­or­ful re­ac­tion!

Safe­ty pre­cau­tions

Wear pro­tec­tive gloves and eye­wear when work­ing with sodi­um hy­drox­ide, as it caus­es burns upon con­tact with the eyes and skin.

Reagents and equip­ment:

  • 40 mL 10% glu­cose so­lu­tion;
  • 25 mL 10% in­di­go carmine so­lu­tion;
  • 150 mL 1 M sodi­um hy­drox­ide so­lu­tion;
  • 3 beakers.

Step-by-step in­struc­tions

Com­bine 150 mL 1 M sodi­um hy­drox­ide so­lu­tion, 40 mL 10% glu­cose so­lu­tion, and 25 mL 10% in­di­go carmine so­lu­tion in the flask. Watch as the so­lu­tion grad­u­al­ly shifts from dark green to red, and then to yel­low.

Pro­cess­es de­scrip­tion

In an al­ka­line medi­um, blue in­di­go carmine turns green as it is ox­i­dized by the oxy­gen in the air. Glu­cose then grad­u­al­ly re­duces the in­di­go carmine, chang­ing its col­or first to red, then to yel­low. If the flask is shak­en, the oxy­gen con­tained in the air ox­i­dizes the in­di­go carmine, turn­ing it back to green. The so­lu­tion will con­tin­ue to change col­ors un­til all of the glu­cose has been ox­i­dized!

Try it