Strontium chloride is a metallic salt that is composed of the elements strontium and chloride in the chemical formula SrCl2, and it has a variety of limited, specific uses. In the past, it was the most common ingredient in certain toothpastes where it is often in the chemical form of strontium chloride hexahydrate, or SrCl2 6H2O. These toothpastes are marketed to people with sensitive teeth, where it serves to block nerve transmission signals in the dentine layer below tooth enamel. Potassium nitrate has replaced strontium chloride in toothpaste in some formulations, however, due to health concerns. As an additive in cosmetics, it is also found in some skin conditioning and soothing agents.
Strontium salts are considered rather stable chemicals that have a level of toxicity somewhat above that of calcium chloride. Strontium chloride has a high boiling point of 2,282° Fahrenheit (1,250° Celsius) and is soluble in water. Preparation and storage of the compound is as a white crystalline powder, and one of its risks is that it decomposes in the presence of water, which can result in the production of hydrogen chloride and caustic hydrochloric acid vapor.
A radioactive version of the compound, 89strontium chloride, is injected intravenously into cancer patients who are suffering from bone cancer or prostate cancer as a form of pain reliever. Since 89strontium chloride has a half life of 50.5 days, after which half of it decays into 89yttrium, injections into the body suppress pain for about three months before they need to be repeated. The compound is believed to relieve pain by interfering with cancer growth or metastasis of tumors in bone tissue. A related form of the compound called strontium ranelate is being studied for the effect on human bone in patients with osteoporosis, where it may also stimulate new bone growth, as well as the growth of collagen and cartilage that support joint function.
In the industrial sector, strontium chloride is uses as a precursor chemical to produce other types of strontium compounds used as brazing fluxes and phosphor coatings. It is also used as a corrosion inhibitor in aluminum alloys as the compound strontium chromate, and, since it burns with a bright red color, strontium and fireworks go hand in hand. The same compound used in toothpaste, strontium chloride hexahydrate, is used as well in the manufacture of magnetic materials. Both metallurgy and glass-production processes as well as the natural life cycles of ocean plankton all require the use of small quantities of the chemical.