fluorine

Something interesting: a classical demonstration in fluorous chemistry: 3 non miscible layers (organic-aqueous -fluorous).

The upper layer is an organic solution: Sudan IV (a red colored azo dye) dissolved in toluene.

The middle layer is water and methanol.

The bottom layer is a fluorous solution: perfluoroalkylated cobalt phthalocyanine (a blue colored complex) dissolved in perfluoroperhydrophenanthrene.

Charoite

One of the world’s more unusual gemstone materials is the rare mineral Charoite, named after the river at the only locality in which it has been found in the Yakutia region of Russia’s far east. It is also one of the youngest gems in the jewellers arsenal, only first described in 1978 (though discovered some 30 years earlier). Popular with carvers and designers since it can be obtained in large blocks, its amazing white feldspar swirls in a deep purple background of charoite are powerfully attractive.

A complex hydrated potassium/sodium/calcium fluorosilicate, it occurs in an intrusive volcanic rock called a syenite, similar to granite but without the quartz. The syenite rose through the crust in a molten state until it reached its buoyancy point in the middle of a limestone, and some interesting chemical reactions happened. The rocks around it were baked, and the metamorphism produced hot supercritical fluids (a weird state between liquid and gas that occurs at high temperatures under pressure) that transformed the surrounding rocks, a process called metasomatism. 

It has an odd pearly lustre (surface reflection) that is unique and combined with its fibrous texture almost seems like a cat’s eye stone. There are no convincing imitations, and the stone is instantly recognisable. The Mohs hardness is around 6, a bit low for safe use in a ring, but fine for other jewellery uses, though it should not be steam or ultrasonically cleaned as this may affect the colour (whose source remains unknown). Some samples contain dark green to black crystals of pyroxene minerals, while others may have crystals of orange tinaksite. 

Loz

Image credit: G Minerals

http://webmineral.com/data/Charoite.shtml#.VL_GGi4mkkE
http://www.mindat.org/min-972.html
http://www.gemsociety.org/article/charoite-jewelry-and-gemstone-information/

Day 9: Interesting Facts About Fluorine
Atomic Symbol: F; Atomic Number: 9: Atomic Mass: 18.9984

  1. Fluorine does not exist in nature as a free element, but it can be isolated through complex electrolysis and in 1906, the French chemist Ferdinand Frederic Henri Moissan won the Nobel Prize for being the first to do so.
  2. Fluorine is the most chemically reactive element. It reacts, often very vigorously, with all of the other elements except oxygen, helium, neon and krypton.
  3. Fluorine is most useful for its compounds such as uranium hexafluoride which is used for processing nuclear fuel, fluorocarbon in the production of teflon, sodium fluoride in toothpaste, hydrofluoric acid for etching glass (since HF can dissolve glass), and formerly Chlorofluorocarbons, which were used as refrigerants in air conditioning and freezers, until they were banned for causing ozone depletion.
  4. The term fluorescence was coined as a response to how light emissions are induced in fluorite by radiating it with lesser wavelengths of ultraviolet light. Fluorescence microscopes widely used in drug tests and infectious disease diagnostics operate on the principles of fluorescence.

Image: Liquid fluorine at cryogenic temperatures.

Fifty Shades of Fluorine 2

“He’s just using you for … you know’” Argon said to a grinning Lithium.
“For what?” she asked.
“For your electron!” Argon said in a hushed voice. Lithium’s electron plummeted to her nucleus.
“Look, I don’t think Fluorine would do that!” she protested. “Besides, we have such great chemistry!”
“I’m just tying to warn you, ok? I don’t want you to get hurt!”

“Oh please, don’t be so noble!”

In yesterday’s post we learned that one of the most common types of terrestrial plasma can be found in fluorescent lighting.  The word fluorescent and fluorescence come to us from the Latin word fluor meaning to flow.  The element Fluorine (the thirteenth most common element in the Earth’s crust) is a highly reactive element that has been known in various forms (notably fluorite) to improve the flow of metals when added as ‘flux’ (another word derived from fluor).    Fluorine is so reactive that it took almost a century to separate fluorine from fluorine based compounds, and several scientists were killed or blinded in the attempt-known today as the 'fluorine martyrs’.  Fluorescence occurs when a substance absorbs light or other electro-magnetic spectrum energy and re-emits it as visible light. 

Don’t forget to find us on NPR’s outreach website for Science Friday:  www.talkingscience.org/category/parent/sciencedad

Image of fluorescent elements courtesy Hannes Grobe.  For a list of the elements and minerals, click the photo. 

A small cylinder of hydrogen fluoride with 340 g or 360 liter of HF in it. More than enough to kill someone. 

Hydrogen fluoride is a colorless gas what can be liquefied quite easily, with a little ice and water, since its boiling point is 19.5 °C. The gas or its solution in water (hydrofluoric acid) attacks glass, so it could be only stored in steel or plastic. The reaction with silicates (glass) produces silicon tetrafluoride what is a low boiling point ( 4 °C), highly reactive compound and hexafluorosilicic acid.

SiO2 + 4 HF → SiF4(g) + 2 H2O
SiO2 + 6 HF → H2SiF6 + 2 H2O

Hydrogen fluoride is the only hydrohalic acid that is not considered a strong acid, i.e. it does not fully ionize in dilute aqueous solutions. When the concentration of HF approaches 100% (like in the gas cylinder on the picture), the acidity increases dramatically because of homoassociation: 3 HF is in equilibrium with H2F+ +  FHF−

Once absorbed into blood through the skin, it reacts with blood calcium and may cause cardiac arrest. In the body, hydrofluoric acid reacts with the ubiquitous biologically important ions Ca2+ and Mg2+. Hydrofluoric acid exposure is often treated with calcium gluconate, a source of Ca2+ that sequesters the fluoride ions. So if anyone works with this, always have a lot calcium gluconate solution somewhere close.

Jeremjevite: The world’s rarest gemstone?

First discovered as colourless crystals in 1833 in Siberia and named after a Russian mineralogist, it is also one of the globe’s rarest minerals. Born in pegmatites, the last water rich stews that crystallise quickly into large crystals after the main body of a granite has cooled, it’s main constituents are aluminum and boron, with an occasional splash of fluorine. For many decades it was almost unknown, until the discovery of several pockets in the Erongo mountains of Namibia and a further small deposit in the Eifel region of Germany. It has also been reported from Tajikistan, but the source is obscure and poorly documented and nearly all the material on the market is Namibian.

Occasionally faceted into gems for collectors (with a Mohs hardness of 7, similar to quartz), these beautiful blue crystals (unlike most gems) are worth more as mineral specimens, and therefore often preserved from the usual fate of transparent and colourful crystals. Other hues include pale yellow and lavender, but the clear sparkly blues are the most prized. The Namibian crystal in the photo measures 2.6x1.4x1cm.

Loz

Image credit: Rob Lavinsky/iRocks.com
http://www.mindat.org/min-2090.html
http://www.vtreasures.ch/fr/actualites/entry/not-just-any-blue-gemstone

Fluorite ‘mesa’

A specimen of purple and yellow fluorite (see http://on.fb.me/1AMqoMj) has grown as the waters of the Earth interacted with the surrounding rocks to form a shape which echoes large scale erosional processes. Mined in Illinois in a unique pocket in 1992, the unusual piece measures 18 x 11.5 x 7 cm. The crystals have been etched by caustic fluids at some point in their trip through geological time, which seem to have attacked the yellow fluorite preferentially (probably due to a slight difference in chemical composition), creating a mineral landform.

Once again, this illustrates the fractal nature of geological processes, in which similar processes result in similar forms across different scales, from a mineral specimen to the spectacular landforms of the national parks in the western USA.

Loz

Image credit: Rob Lavinsky/iRocks.com