Hartshorn Salt - Leavening Ingredient in Baking Powder

Demonstration Experiment on Video

Hartshorn Salt - Leavening Ingredient in Baking Powder

Ojective: Decomposition of Ammonia Bicarbonate, Test for Ammonia

Peter Keusch

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)

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.

Hartshorn salt is used in cookies, which are flat enough to allow all of the ammonia odor to dissipate during baking.

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