Fluorides are the salts of hydrofluoric acid (HF), which is also known as hydrofluoric acid. They contain in their ionic lattice as a negative lattice components (anions) fluoride ions ( F- ). In addition, covalent, non- ionic compounds of non-metals, and organic fluorine compounds such as fluorinated hydrocarbons or carboxylic acid derivatives are known as fluoride obsolete.
Fluorides are added to foods and cosmetics ( toothpaste ) was added and applied by means of highly concentrated preparations for the purpose of preventing tooth decay on the teeth. This is known as fluoridation.
- 4.1 Physical methods of analysis
- 4.2 Wet Chemical
Fluorides occur in nature in the form of many minerals. The most important representative of fluorite ( CaF2), also Yttrofluorit, an addition mixed crystal with YF3, and Cerfluorit (also Yttrocerit ), which still contains cerium, erbium and yttrium addition to hydration. Other fluorides are Frankdicksonit ( BaF2 ), Gagarinit ( NaCaYF6 ) tysonite (also Fluocerit, (Ce, La, Se) F3) and Neighborit ( NaMgF3 ). Complex fluoride containing another element within a complex anion, such as boron, aluminum or silicon, and then forming, for example, hexafluorosilicates and tetrafluoroborates. Representatives are here Ferruccit ( NaBF4 ) Avogadrit ( (K, Cs) BF4), Malladrit ( Na2SiF6 ) Hieratit ( K2SiF6 ) Kryolithionit ( Na3Al2Li3F12 ), cryolite ( Na3AlF6 ) elpasolite ( K2Na [ AlF6 ] ), Jarlit ( NaSr2 [ AlF6 ] 2 ), Usovit ( Ba2Mg [ AlF6 ] 2 ) and Weberit ( Na2MgAlF7 ).
See also: Category fluorine minerals
Important salt-like fluorides
Some important fluorides are:
- Aluminum fluoride ( AlF3 )
- Ammonium fluoride ( NH4F ),
- Sodium fluoride (NaF ) mainly for plaque prophylaxis
- Stannous fluoride ( SnF ) mainly for plaque prophylaxis
In addition to the simple fluorides also HYDROGENDIFLUORIDES the composition Me [ HF2 ] exist - such as sodium hydrogen ( NaHF2 ) and potassium hydrogen difluoride ( KHF2 ). These include the linear [ FHF ] - anion. Display is possible from aqueous solutions of fluorides in the presence of an excess of hydrogen fluoride ( HF). On heating, the HYDROGENDIFLUORIDES split the hydrogen fluoride from again.
Decomposition by heating:
Molecularly structured inorganic fluorine compounds such as hexafluoride platinum (VI ) fluoride, uranium (VI ) fluoride or plutonium (VI ) fluoride are often referred to as fluorides.
In most organic fluoride, the fluorine atom is covalently bonded Examples:
- Sarin ( C4H10FO2P )
- Tetrafluoride (CF4 )
- Trifluoromethane ( CHF3 )
- Chlorodifluoromethane ( CHClF2 )
However, there are organic fluorine compounds in which the fluorine atom is present as a salt-like fluoride anion. Examples:
- Amine fluorides
Physical methods of analysis
Professionally fluorides are determined in minerals and solids with X-ray fluorescence analysis, X-ray diffraction or mass spectrometry today. Liquids in with fluoride electrodes, IR or NMR methods
In wet chemical
With simple laboratory methods can prove fluoride by the lead pot test or the etching sample. Is treated with sulfuric acid, forming hydrogen fluoride, which etches the glass container.
Are you the sample in a lead crucible with powdered silica or sodium silicate and then overlayed sulfuric acid, then silicon tetrafluoride gas forms:
The crucible is closed again and moisturizes the cover with water. The Siliciumtetrafluoid reacts with the water again to silicate which cratered settles in the water drops.
Fluorides are used above all as a flux in metallurgy, for the synthesis of organic fluorochemicals and for gas-tight sealing of fuel tanks; The plastic tanks, for example, PA (polyamide) are vapor-deposited with the dissolved fluoride, characterized diffuses 3-4 microns into the surface.
When fluoridation is defined as the addition of fluorides in particular to table salt, water, milk, tablets and toothpastes for preventing dental caries.
The toxicology of fluorides is dependent on numerous factors such as the type of fluoride, its solubility, the Resorptionsgeschwindigkteit in the stomach, the acid -base balance and the pH value of the acquired fluoride. The safe toxic dose ( Certainly Toxic Dose - CTD) is 32 - 64mg of fluoride per kilogram of body weight. In infants, the probable toxic dose ( Probably Toxic Dose - PTD) is 5 mg of fluoride per kilogram of body weight.
By comparison, in a tube of toothpaste ( 100g or 75ml ) with a fluoride content of 1000 ppm (parts per million - one million parts ) are 100mg fluoride. A child weighing 15kg would have exceeded the probable toxic dose so that the consumption of the entire tube of toothpaste.
Water-soluble fluorides are classified as toxic. The toxic effect is based partly on the precipitation of calcium as required by the metabolism of calcium fluoride, partly from the effect of protoplasm and cell poison that inhibits certain enzyme systems and protein synthesis.
When ingested, there is rapid and almost complete absorption of soluble fluoride on the gastric mucosa, because the salts formed by the hydrochloric acid of the stomach hydrogen fluoride. Acute symptoms include severe pain in the stomach and intestine, behind the breastbone, convulsions, unconsciousness, and severe metabolic disturbances. Hydrogen fluoride also causes severe burns to the destruction of cells.
A chronic recording even in low concentrations can lead to poisoning ( fluorosis ), which manifests itself in lesions of the skeleton, teeth, lung function, skin and metabolic disorders.
Water-insoluble or sparingly soluble fluorides as calcium fluoride and aluminum fluoride have a much lower toxicity. However, there is always the danger of the formation of the also highly toxic hydrogen fluoride in contact with strong acids.
As an antidote for fluoride poisoning Calcium gluconate is used. As a first aid measure, other calcium-containing agents are effective; For example, it may help to drink milk in order to inhibit the absorption of fluoride ions.