Chemical Traffic Light

Reagents and supplies:

• glu­cose (6 g);
• in­di­go carmine (0.01 g);
• 1 M so­lu­tion of sodi­um hy­drox­ide (40 ml);
• beakers (3);
• dis­tilled wa­ter.

Instructions:

Dis­solve ap­prox­i­mate­ly 6 ml of glucose in 200 ml of warm dis­tilled wa­ter.

Add 40 ml of sodi­um hy­drox­ide so­lu­tion.

In an­oth­er beaker, dis­solve the in­di­go carmine, cre­at­ing a blue so­lu­tion.

Pour the al­ka­line so­lu­tion of glu­cose and the in­di­go carmine so­lu­tion into a large beaker and cover it.

Ob­serve the change in col­or.

Once it’s finished changing colour, shake again and observe!

Ini­tial­ly, the so­lu­tion col­ored by the in­di­go carmine (blue) is ox­i­dized by the oxy­gen in the air to a green col­or – this is the col­or of its ox­i­dized form. When the green so­lu­tion is left to stand, the glu­cose be­gins to re­duce the in­di­go carmine, first to red, and then to yel­low. If you shake the solution or de­cant it, it mix­es with air, and the oxy­gen once more ox­i­dizes it to green.

SAFETY PRECAUTIONS

When work­ing with sodi­um hy­drox­ide, wear rub­ber gloves and pro­tec­tive glass­es, as it caus­es burns if it gets on the skin or in the eyes.Warn­ing! Sub­stances of this ex­per­i­ment are tox­ic and high­ly dan­ger­ous for your health.