Congrats to -Fortress- for the FTF!
There was some confusion with the original Fluorine cache. It had been reported that it was muggled, and indeed, when I went to check on it, I couldn't find it either. Having seen two different caches disappear from the park, I decided to move it.
Imagine my surprise when people began finding it at the original site. I had already moved it, then archived it.
The original cache is back in it's original spot, but Fluorine is so darned interesting I moved the second cache and here it is with some more info on my second favourite element (gold being my first!)
First: The junior high chemistry lesson:
Pure fluorine (F2, since fluorine is diatomic) is a corrosive pale yellow gas that is a powerful oxidizing agent. It is the most reactive and electronegative of all the elements, and readily forms compounds with most other elements. Fluorine even combines with the noble gases, krypton, xenon, and radon. Even in dark, cool conditions, fluorine reacts explosively with hydrogen. It is so reactive that glass, metals, and even water, as well as other substances, burn with a bright flame in a jet of fluorine gas. It is far too reactive to be found in elemental form and has such an affinity for most elements, including silicon, that it can neither be prepared nor be kept in glass vessels. In moist air it reacts with water to form the equally dangerous hydrofluoric acid.
Atomic fluorine and molecular fluorine are used for plasma etching in semiconductor manufacturing, flat panel display production and MEMS fabrication. Other uses:
Hydrofluoric acid (chemical formula HF) is used to etch glass in light bulbs and other products.
Fluorine is indirectly used in the production of low friction plastics such as Teflon, and in halons such as Freon.
Along with some of its compounds, fluorine is used in the production of pure uranium from uranium hexafluoride and in the synthesis of numerous commercial fluorochemicals, including vitally important pharmaceuticals, agrochemical compounds, lubricants, and textiles.
Fluorochlorohydrocarbons are used extensively in air conditioning and in refrigeration.
Sulfur hexafluoride is an extremely inert and nontoxic gas, and a member of a class of compounds that are potent greenhouse gases.
Many important agents for general anaesthesia such as sevoflurane, desflurane, and isoflurane are fluorohydrocarbon derivatives.
Sodium hexafluoroaluminate (cryolite), is used in the electrolysis of aluminium.
Compounds of fluorine, including sodium fluoride, are used in toothpaste to prevent dental cavities. These compounds are also added to municipal water supplies, a process called water fluoridation, though a combination of health concerns and urban legends has sometimes led to controversy.
In much higher concentrations, sodium fluoride has been used as an insecticide, especially against cockroaches. Fluorides have been used in the past to help molten metal flow, hence the name.
18F, a radioactive isotope that emits positrons, is often used in positron emission tomography because of its half-life of 110 minutes.
Some researchers including US space scientists in the early 1960s have studied elemental fluorine gas as a possible rocket propellant due to its exceptionally high specific impulse. The experiments failed because fluorine was so hard to handle.
Fluorine is widely distributed in the earth's crust. Despite this, fluorine does not commonly occur in deposits sufficiently rich for commercial development and only three minerals are important, namely, cryolite (3NaFAlF3), fluorspar (CaF2) and fluorapatite (CaF2 3Ca3 (PO4)2 ). Cryolite or Greenland spar is not a common mineral and commercial deposits occur only in Greenland. Cryolite has numerous industrial applications, the most important being in the aluminum industry, and it is now manufactured synthetically from fluorspar. Fluorspar is the most important fluorine mineral in commerce. Its workable deposits are found in many such as the United States, Mexico, ex-URSS, China and Europe. The principal uses of fluorspar are in the steel industry, in the manufacture of hydrofluoric acid and cryolite, and in the ceramics industry.