Calcium Hypochlorite - chemical formula Ca(OCl)2.

This chemical is made in a similar manner to sodium hypochlorite. A solution of calcium hydroxide (calcium hydrate, hydrated lime or caustic lime - CaOH) is charged with chlorine gas (Cl2) and then the solution is evaporated and milled to a granule. The solution of caustic lime is usually about 50 percent. One pound of calcium hypopchlorite would contain about 32.5 percent chlorine, about 50.2 percent caustic lime, with the balance of 17.3 percent being water, salt(NaCl) and calcium chloride.

In pool industry terms of a label stating "provides XX percent available chlorine," the 32.5 percent would give an available chlorine of 65 percent.

This also means that if you add 1 pound of cal hypo to 10,000 gallons of water you will be adding about 5.6 oz of calcium from the CaOH and about 2.8 oz of calcium from Ca(OCl)2 and CaCl2. Total is about 8.4 oz of calcium per pound. This is 4.25 ppm of calcium added to a 10,000 gallon pool for each pound of 65% cal hypo added.

Cal hypo dissolves better in cold water than in hot. The saturation index shows this. However, the high pH 11.3 of cal hypo allows most of the calcium to dissolve in the bucket of water.

The "crud" on the bottom when you dissolve cal hypo in a bucket of water is a mixture of insoluble calcium and sodium salts. But if it weighs only an ounce or two then that is a small part of the 8.4 oz of calcium that is in there.