German version
Supermarket products:
| hartshorn salt
| red cabbage juice | |
Miscellaneous materials:
| balloon
| white coffee filter paper | |
Apparatus and glass wares:
| tripod stand with mesh screen
| Bunsen burher
| Erlenmeyer flask 50 mL
| Petri dish d = 9 cm | |
Experimental procedure:
Two spatulas full of hartshorn salt (1.5 g) are placed in an Erlenmeyer flask. A balloon is securely placed over the top of the flask. Using a bunsen burner the hartshorn salt is heated. The produced gas fills the flask and the balloon. The gas escaping from the balloon is directed to the surface of a coffee filter paper soaked with red cabbage juice.
| Result:
The purple color of the filter paper turns green. |
  Videoclip (Download RealPlayer .rm file)
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Discussion and background:
Hartshorn salt consists mainly of ammonium bicarbonate (NH4HCO3), ammonium carbonate (NH4)2CO3 and ammonium carbamate. Hartshorn salt is made by heating and subliming a mixture of ammonia chloride, calcium carbonate and char.
The salt is used as a leavening agent in baking powder. It aerates the dough and imparts a distinctive crispness to flat pastries such as gingerbread and speculaas (speculatius) cookie.
Upon heating (60 °C) ammonia bicarbonate and ammonium carbonate decompose to form ammonia, carbon dioxide and water all of which are sources of leavening in baked goods.
