Calcium chloride

Calcium chloride is a salt of calcium and chlorine. It's mainly used in amateur chemistry as a desiccant, because it is extremely hygroscopic and doesn't decompose when heated to dryness.

Properties

Chemical

Calcium chloride serves as a source of calcium ions for reactions. Because calcium carbonate and sulfate are more or less insoluble, calcium chloride can be used to produce any metal chloride by introduction of a soluble sulfate or carbonate to its solutions.

Molten calcium chloride can be electrolyzed to yield calcium metal and chlorine gas:

CaCl_2(l) → Ca_(s) + Cl_2(g)

Physical

Calcium chloride is white, solid at room temperature. The anhydrous salt is very hygroscopic, it will quickly absorb water from the air to form a solution, a property known as deliquescence. Anhydrous calcium chloride must be stored in a very dry environment.

Availability

Calcium chloride can be cheaply purchased at hardware stores, stored in desiccator bags, that contain the anhydrous form. Some road salts are another source, and can be obtained in large quantities, though these products may also contain other chlorides or impurities. The anhydrous form can be produced by strongly heating the hydrate. Often, the dried calcium chloride will harden into a solid mass, that takes time to break, during which it will rapidly absorb water from air as it cools.

Preparation

Calcium chloride can be obtained by the reaction of calcium hydroxide or calcium carbonate and hydrochloric acid. If these compounds are hard to come by, clean white limestone, seashells, or well-cleaned egg shells can be dissolved in hydrochloric acid, and the solute filtered. Calcium carbonate is then reprecipitated by addition of sodium carbonate or sodium bicarbonate, and finally dissolved in hydrochloric acid and filtered again. It is highly recommended that it is prepared strictly from a pure calcium salt though, as this process is time-consuming, costly, and fails to remove magnesium or iron impurities.

Projects

• Electrolysis of molten, anhydrous calcium chloride to produce calcium metal.
• Make ammonium chloride
• Building a homemade dessicator
• Make a dry box

Handling

Safety

Anhydrous calcium chloride can be an irritant due to its strong desiccating properties. Otherwise, it is only minimally toxic.

Storage

Calcium chloride should be stored in sealed containers or bags, as it is extremely hygroscopic. Zipper bags are also good to store anhydrous CaCl₂.

Disposal

No special disposal is required. Calcium chloride is non-toxic to the environment, and it's even used as anti-icing during the winter.