Potassium fluosilicate

Gay Lussac and Thenard in 1809 obtained very impure amorphous silicon by passing silicon tetrafluoride over heated potassium. Berzelius in 1823 prepared elemental silicon in high purity by the same method. He also obtained silicon by heating potassium fluosilicate with potassium metal. Deville produced crystalline silicon in 1854 by electrolysis of a molten mixture of impure sodium aluminum chloride containing 10% silicon and a small quantity of aluminum. 

In his other method Berzelius heated the potassium fluosilicate with excess potassium. The resulting potassium silicide was easily decomposed with water, the amorphous silicon settling to the bottom. 

G. S. Serullas treated potassium chlorate with an excess of hydrofluosilicic acid the clear liquid was decanted from the sparingly soluble potassium fluosilicate, the soln. evaporated below 30°, and filtered through glass powder J. J. Berzelius evaporated the acid liquid mixed with finely divided silica below 30° in air, or over cone, sulphuric acid and potassium hydroxide in vacuo. The excess of hydrofluoric acid was volatilized as silicon fluoride, and the clear liquid was then filtered from the excess of silica. R. Bottger treated sodium chlorate with oxalic acid whereby sparingly soluble sodium oxalate was formed J. L. Wheeler, and T. B. Munroe treated sodium chlorate with hydrofluosilicic acid and M. Brandau treated potassium chlorate with aluminium sulphate and sulphuric acid and precipitated the alum so formed with alcohol. Chloric acid is formed in many reactions with hypochlorous and chlorous acid for example, it is formed when an aq. soln. of chlorine or hypochlorous or chlorous acid decomposes in light. It is also formed when an aq. soln. of chlorine dioxide stands in darkness or in light. A mixture of alkali chlorate and chlorite is formed when an aq. soln. of an alkali hydroxide is treated with chlorine dioxide. 

Heat a portion of the solution to boiling and neutralize it with potassium carbonate. On cooling, the potassium fluosilicate separates as a very transparent crystalline product, which should be filtered off and preserved. It will serve just as well to add potassium chloride, since potassium fluosilicate is not decomposed by hydrochloric acid. 

Phosphate rock contains about 3.5 percent fluorine, some of which is recovered as a byproduct in manufacturing wet process phosphoric acid. During acidulation, the fluorine is released as hydrofluoric acid, HF, which reacts with the silica present as an impurity in the rock to form fluosilicic acid, H2SiF6. Some of the fluorine is lost with the gypsum as sodium or potassium fluosilicates, and some remains dissolved in the filter acid. When the acid is concentrated, much of the fluorine in the feed is boiled off, appearing as HF and silicon tetrafluoride, SiF4, in the vapors. 

Potassium fluosilicate, K2SiF6.—The fluosilicate is precipitated in the form of microscopic crystals of slight solubility by the action of fluosilicic acid on solutions of potassium salts ... 

Fhiosilicate fusion has been used in the Soviet Union [SI] to produce feed for separation of hafnium from zirconium by fractional crystallization of KjMF . Zircon is ground to pass 200 medi and mixed with potassium fluosilicate and potassium chloride (to act as promoter). The mixture is sintered in a rotary furnace at 650 to 700°C. The following reaction takes place ... 

Also known as silicium occurs in three allotropic forms Amorphous silicon, formed when silicon ehlorid is passed over heated K or Na, is a dark brown powder, heavier than water. When heated in air, it bums with a bright flame to tiie dioxid. It dissolves in potash and in hydrofluoric acid, but is not attacked by other acids. Graphitoid silicon is obtained by fusing potassium fluosilicate with aluminium. It forms hexagonal plates, of sp. gr. 2.49, which do not burn when heated to whiteness in 0, but may be oxidized at that temperature, by a mixture of iiotassium chlorate and nitrate. It dissolves slowly in alkaline solutions, but not in acids. Crystallized silicon, corresponding to the diamond, forms crystalline needles, which are only attacked by a mixture of nitric and hydrofluoric acids. 

Potassium azide + fluosilicic acid Potassium fluosilicate 0.2 0... 

Potassium fluorozirconate. See Zirconium potassium hexafluoride Potassium fluosilicate CAS 16871-90-2... 

Silicate, hexafluoro-, dipotassium. See Potassium fluosilicate Silicate, hexafluoro-, disodium. See Sodium silicofluoride... 

Fluosilicic acid aluminum metallurgy Potassium fluosilicate aluminum mfg. 

Ammonium biborate Calcium fluoride Copper oxide (ic) Potassium chromate Zinc fluoride enamel ingredient, specialty Potassium fluosilicate enamel mfg. 

Potassium fluosilicate Potassium N-methyldithiocarbamate Potassium thiocyanate Silica gel Silica, hydrated... 

Calcium fluoride Calcium glycerophosphate Calcium monocarbonate Calcium monofluorophosphate Calcium phosphate monobasic anhydrous Calcium phosphate tribasic Calcium saccharin Cetylamine hydrofluoride Chlorothymol Hydroxyapatite Magnesium fluoride Magnesium silicofluoride 6-Methylcoumarin Nicomethanol hydrofluoride Olaflur Phenolphthalein Potassium fluoride Potassium fluosilicate Potassium monofluorophosphate Saccharin Saccharin sodium anhydrous Sodium fluorophosphate (Na2P03p) Sodium metaphosphate Sodium silicofluoride Stannous fluoride... 

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