Chalk can be used in place of limestone. It takes longer to react than limestone, however it may provide purer calcium chloride, depending on the quality of limestone available.
Calcium chloride is a salt of calcium and chlorine. It is used for many things from aquariums to road salt. In aquariums it is used to add calcium to the water for the fish.
Place the limestone in the beaker. Use enough limestone the fill the beaker about 1/4 full. Put on the gloves.
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Add a 1/4 of a beaker of hydrochloric acid to the limestone.
The hydrochloric acid will start to bubble as it dissolves the limestone. Gently swirl the beaker to mix the contents and make sure the reaction goes to completion. If all of the limestone dissolves, add a little bit more.
Once the solution stops bubbling, filter off the solids by pouring the solution through the filter paper into the second beaker. The calcium chloride is dissolved in the filtered solution.
Use the hot plate to gently heat the second beaker containing the calcium chloride solution. The solid left after the water evaporates is solid calcium chloride.