Which Metal Flourides Are Insoluble?

Metal Fluorides

• Metal fluorides are compounds of fluorine and elements that are of a metallic nature. Some common metal fluorides are: lithium fluoride, calcium fluoride, sodium fluoride, potassium fluoride and rubidium fluoride. While lithium fluoride, potassium fluoride and sodium fluoride are somewhat soluble in water, many are insoluble due to fluorine bonding strongly with other elements. Once in a compound, fluorine does not easily release its connection with another element.

Calcium Fluoride

• Calcium fluoride is an insoluble fluoride compound that occurs naturally in the form of fluorite. Fluorite is considered a rare gemstone. It is found in purple, blue, yellow and green varieties. Calcium fluoride is used in industry to lower the melting temperature during the production of enamel, glass and steel. Fluorite is used in specialty optical lenses and as a flux in the iron smelting process. Because fluoride does not occur naturally, fluorite is often used to extract fluoride.

Strontium Fluoride and Barium Fluoride

• Strontium fluoride, also known as strontium difluoride, is almost insoluble in water. It is used primarily in optical applications, such as eyeglasses, as a coating material. Barium fluoride is a transparent material used in standard optics, spectroscopy, lasers and telescopes. It is almost completely insoluble in water.

Yttrium Fluoride and Scandium Fluoride

• Another fluoride compound that is insoluble in water is yttrium fluoride. It is used primarily in glass making, electronics, ceramics and metallurgy. Scandium fluoride is an ionic fluoride compound that is insoluble in water or mineral acids. It is often used in laser industry, electronic ceramics and as an optical coating. It is also used as a catalyst and in producing scandium alloys.

Thorium Tetrafluoride and Uranium Tetrafluoride

• Also known as thorium fluoride, thorium tetrafluoride is an insoluble metal fluoride compound. It is used primarily as an anti-reflective coating material in optical lenses. Uranium tetrafluoride is a green crystalline solid metal fluoride that is almost completely insoluble in water. This compound is an intermediate step in the process of converting uranium hexafluoride to uranium metal or uranium oxides.

Lanthanides

• Lanthanides are a group of rare earth elements that have their own section on the periodic table. These are the elements with atomic numbers 57 through 71: lanthanum, cerium, praseodymium, neodymium, promethium, samarium, europium, gadolinium, terbium, dysprosium, holmium, erbium, thulium, ytterbium, and lutetium. When these elements are combined with fluorine, the resulting compounds are highly insoluble. As these elements are rare, their compounds with fluorine are also rare outside of a laboratory setting.