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.
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.
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.
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.