“Egyptian Night at home” experiment

How to do a classical experiment with starch and iodine

The most mys­ti­cal ex­per­i­ment of all is “Egyp­tian Night”. A trans­par­ent so­lu­tion turns dark af­ter a cer­tain time. In this ex­per­i­ment, we’ll show you how to con­duct the ex­per­i­ment at home.

Safe­ty pre­cau­tions

Wear pro­tec­tive gloves, a mask and glass­es.

Reagents and equip­ment:

  • med­i­cal io­dine (5% io­dine so­lu­tion in potas­si­um io­dide);
  • 9% acetic acid;
  • 3% hy­dro­gen per­ox­ide;
  • 1% starch so­lu­tion;
  • 5% Vi­ta­min C so­lu­tion (ascor­bic acid);
  • beaker.

Step-by-step in­struc­tions

Pour the so­lu­tions into the beaker in turn: acetic acid, then med­i­cal io­dine, ascor­bic acid un­til the mix­ture be­comes col­or­less, then starch and hy­dro­gen per­ox­ide. Ob­serve the so­lu­tion in the beaker turn dark.

Pro­cess­es de­scrip­tion

Vi­ta­min C (ascor­bic acid) is a strong re­duc­er, so it re­duces io­dide to col­or­less io­dide ions. Then the io­dide ions re­duce the hy­dro­gen per­ox­ide, and io­dide forms again, which re­acts with starch, form­ing a dark blue io­dine-starch com­plex.