Calcium chloride

Each vial contains 1g of calcium chloride, which equates to approximately 6.8 mmol of calcium and 13.6 mmol of chloride. Thus, it contains 3 times as much calcium as the same ampoule of calcium gluconate, because each calcium ion is partnered up with two relatively lightweight chloride ions, instead of two huge gluconate ions.

Contents of a calcium chloride ampoule

Its various uses outside of medicine include prevention of leaching calcium ions from swimming pool concrete, and providing ionized calcium to the invertebrates of a salt-water aquarium, so better to build their shells with.

References

From MIMS online, via CIAP; and directly from the manufacturer propaganda.