Technology
The source of the heat for the self-heated can is an exothermic reaction that the user initiates by pressing on the bottom of the can. The can is manufactured as three containers. A container for the beverage surrounds a container of the heating agent separated from a container of water by a thin breakable membrane. When the user pushes on the bottom of the can, a rod pierces the membrane, allowing the water and heating agent to mix. The resulting reaction releases heat thus warms the beverage surrounding it.
The heating agent and responsible reaction vary from product to product. Calcium oxide is used in the following reaction:
- CaO(s)+ H2O(l) → Ca(OH)2(s)
Copper sulfate and powdered zinc can also be used, but to lesser effect:
- CuSO4(s) + Zn(s) → ZnSO4(s) + Cu(s)
Anhydrous calcium chloride is often used as well. In this case, no chemical reaction occurs, instead the heat of solution is generated.
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