Experiment "Chemical cocktail" (three-layered solution)

How to make a striped liquid

Who should you in­vite to a par­ty? A chemist, of course! Only chemists know how to make a three-col­or, three-lay­ered chem­i­cal “cock­tail”. The se­cret of this chem­i­cal “trick” lies in the dif­fer­ent den­si­ty of liq­uids and sol­u­bil­i­ty of sub­stances.

Reagents and equip­ment:

  • chlo­ro­form (150 ml);
  • dis­tilled wa­ter (150 ml);
  • ethyl ac­etate (150 ml);
  • cop­per sul­fate(II) (1 g);
  • crys­tal io­dine (1 g);
  • a mea­sur­ing cylin­der of 500 ml;
  • a long chem­i­cal spoon.

Step-by-step in­struc­tions

Pour the three trans­par­ent liq­uids with dif­fer­ent den­si­ty (from bot­tom to top): chlo­ro­form, wa­ter and ethyl ac­etate. Ob­serve the lay­er­ing of the so­lu­tions. Then add 1 g of cop­per sul­fate (II) to the mea­sur­ing cylin­der. The wa­ter lay­er turns blue. Then add crys­tal io­dine. In the lay­ers with ethyl ac­etate and chlo­ro­form, the io­dine dis­solves, and they turn or­ange and pur­ple re­spec­tive­ly.

Pro­cess­es de­scrip­tion

In the course of the ex­per­i­ment, a three-lay­ered so­lu­tion forms, as we add liq­uids with dif­fer­ent den­si­ty: chlo­ro­form has a den­si­ty of 1.483 g/cm³, wa­ter 0.998 g/cm³ and ethyl ac­etate 0.902 g/cm³. Thus, the chlo­ro­form will be the “heav­i­est”, so it forms the low­est lay­er. Then comes the lay­er of wa­ter, and then the “light­est” liq­uid by den­si­ty, ethyl ac­etate. Our so­lu­tion turns three dif­fer­ent col­ors be­cause of the dif­fer­ent sol­u­bil­i­ty of sub­stances in dif­fer­ent sol­vents. The gen­er­al con­cept that de­scribes the abil­i­ty of sub­stances to dis­solve in a cer­tain sol­vent can be for­mu­lat­ed as “like dis­solves in like”. Cop­per sul­fate (II) is an ion­ic com­pound, and a po­lar sol­vent will dis­solve it best. In this ex­per­i­ment we took wa­ter, as it is a po­lar sol­vent, Or­gan­ic sol­vents are not po­lar and can­not dis­solve cop­per sul­fate. The io­dine molec­u­lar has a non-ion­ic struc­ture. It does not dis­solve in wa­ter, but dis­solves in the lay­er with a non-po­lar sol­vent, such as chlo­ro­form and ethyl ac­etate. In chlo­ro­form, io­dine col­ors the so­lu­tion pur­ple, and in ethyl ac­etate it col­ors it or­ange.

Safe­ty pre­cau­tions

Be­fore start­ing the ex­per­i­ment, put on rub­ber gloves and pro­tec­tive glass­es, as the sub­stances used may cause burns if they get in your eyes or on your skin. The ex­per­i­ment must be car­ried out in a well-ven­ti­lat­ed room or in a fume hood. Ethyl ac­etate fumes ir­ri­tate the mu­cus mem­branes of the eyes and res­pi­ra­to­ry tract, cause der­mati­tis and eczema on the skin, and chlo­ro­form fumes can dam­age the cen­tral ner­vous sys­tem.

Warn­ing! Sub­stances of this ex­per­i­ment are tox­ic and high­ly dan­ger­ous for your health. Do not try this at home. Only un­der pro­fes­sion­al su­per­vi­sion.