MaterialsSodium carbonate and castor oil are sold at many stores. Sodium carbonate is used in cooking and as a water softener. Castor oil usually is sold in the pharmacy section.
Perform the TrickThis is a terrific chemistry demonstration because the materials are common and inexpensive and it's extremely quick and easy to perform:
- In a dry test tube or small beaker, add a scoop of sodium carbonate and 3 drops of castor oil.
- Heat the container in a burner flame or on a hot plate until a cloud of white vapor rises from the chemicals.
- Walk around the room with the glassware to allow the fragrance to dissipate. The odor of violets is evident.
How It WorksWhen sodium carbonate and castor oil are heated together, one of the products is ionone. Although it is a simple demonstration, this is a fairly complicated reaction, in which citral and acetone with calcium oxide catalyze an aldol condensation followed by a rearrangement reaction. A mixture of alpha and beta ionone is responsible for the characteristic odor of violets. Beta ionone is a component of the fragrance responsible for the scent of roses, too. Natural or synthetic ionone is used in many perfumes and flavorings. In flowers, ionones derive from the degradation of carotenoids, which are pigment molecules.
An interesting property of violets is that they are responsible for another type of chemical magic. Violets temporarily steal your sense of smell! Initially, ionone binds to scent receptors and stimulates them, so you smell the odor of violets. Then, for a few moments, the receptors are unable to receive further stimulus. You lose awareness of the fragrance, only to regain it when it registers as a new smell. Whether you like the scent of violets or not, it's a scent that can't become overpowering or fade with time.
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