Calcium silicate fluorides

Another calcium silicate fluoride, cuspidine [Ca4(Si207)F2], exists but is not formed under conditions relevant to clinker formation. Systems containing fluorosilicate ions [SiF ] and the possible use of calcium fluorosilicate as a flux have been investigated (S16). 

Modem production of elemental phosphoras uses a technique similar to the metallurgical processes described in Chapter 20. Apatite is mixed with silica and coke and then heated strongly in the absence of oxygen. Under these conditions, coke reduces phosphate to elemental phosphoms, the silica forms liquid calcium silicate, and the fluoride ions in apatite dissolve In the liquid calcium silicate. The reactions are not fully understood, but the stoichiometry for the calcium phosphate part of apatite is as follows ... 

Figure 6.13 Electron micrograph of a single-stage replica of a dental silicate cement glass, showing phase-separated droplets rich in calcium and fluoride large droplets 400 nm in diameter and small droplets 20 to 30 nm in diameter (Wilson et at., 1972).

Mold fluxes are routinely used in both continuous casting and bottom pouring of steel. These fluxes are generally calcium silicate based compositions with alkali oxides [(Li, Na, K)20] and fluorides [CaF2, NaF] added as fluidizers. The compositions frequently use fly ash as the base material because it provides a significant concentration of silica in a prefused form easily dissolved as the powder melts on the liquid steel. 

Calcium is found in rocks as the carbonate, fluoride, oxide, phosphate, and sulfate. In purified forms, each of these minerals has practical applications. Limestone, calcite, and marble occur in the form of calcium carbonate (CaC03) and are used as building materials. In addition, marble is carved to make statues. Portland cement—derived mainly from calcium carbonate and calcium silicates—is a staple of the building industry. Calcium carbonate is taken to relieve heartburn antacids like... 

It is convenient to regard calcium silicate, CaSiOg, as a compound of calcium oxide and silicon dioxide (Ca0,Si02), for thus it is evident why hydrofluoric acid acts on calcium silicate to form the fluorides of both calcium and silicon, together with the second product of double decomposition, water. Glass is a mixture of silicates and silicon dioxide, and when it is exposed to hydrofluoric acid it is acted upon in accordance with the reactions just described. As the action takes place unevenly on a polished surface of glass, the surface becomes pitted and produces a frosted or etched appearance. 

Calcium Carbonate Calcium Phosphate Calcium Silicate Calcium Sulfate Copper(II) Sulfate Magnesium Chloride Magnesium Silicate Hydroxide Magnesium Sulfate Mercury(II) Sulfide Monosodium Glutamate Perchlorates Potassium Bicarbonate Potassium Bisulfate Potassium Bitartrate Potassium Carbonate Potassium Chloride Potassium Fluoride Potassium Iodide Potassium Nitrate Potassium Sulfate Silver Iodide Silver Nitrate Silver(I) Sulfide Sodium Acetate... 

Elementary phosphorus is manufactured by reduction of apatite with coke in electric furnaces at a temperature of 1400-1500°C. Quartz is also present in the charge. It reacts with the calcium in apatite and forms a slag of liquid calcium silicate. If the apatite contains fluorine, SiF gas is formed that is passed into water containing soda. The compound formed, sodium hexafluorosilicate Na SiF, is used for fluoridating drinking water. In the process described, white phosphorus is the product. In the world about 1 million tonnes per year are produced. White phosphorus is used to some extent for smoke bombs and incendiary bombs, but most of it is used for the manufacture of phosphoric acid and other chemicals and for preparing red phosphorus for the match industry. 

There are several publications [4—16] on admixtures of barium sulfate, aluminium fluoride, aluminium borate, aluminium titanate, calcium silicate (woUastonite), aluminium nitride, and silicon carbide and its combinations in alumina silica refractories for decreasing the wetting ability of Al in these refractories. 

Ejima A, Shimoji M (1970) Effect of alkali and alkaline-earth fluorides on surface tension of molten calcium silicates. Trans Faraday Soc 66 99-106... 

Tran, T. T., D. Herfort, H. J. Jakobsen and J. Skibsted. 2009. Site preferences of fluoride guest ions in the calcium silicate phases of Portland cement from Si F) CP-REDOR NMR spectroscopy. J.Am. Chem. Soc. 131,14170-14171. 

Valentinite, see Antimony(III) oxide Verdigris, see Copper acetate hydrate Vermillion, see Mercury(II) sulflde Villiaumite, see Sodium fluoride Vitamin B3, see Calcium (+)pantothenate Washing soda, see Sodium carbonate 10-water Whitlockite, see Calcium phosphate Willemite, see Zinc silicate(4—)... 

Fluor-jod, n. iodine fluoride, -kalium, n. potassium fluoride, -kalzium, n. calcium fluoride, -kiesel, m. silicon fluoride, -kie-selsaure,/. fluosilicic acid, -kohlenstoff, m. carbon fluoride, -lithium, n. lithium fluoride. -metall, n. metallic fluoride, -natrium, n. sodium fluoride, -phosphat, n. fluophosphate. -phosphor, m. phosphorus fluoride, -salz, n. fluoride, -schwefel, m. sulfur fluoride, -selen, n. selenium fluoride, -silber, n. silver fluoride, -silikat, n. fluo-silicate. -silizium, n. silicon fluoride, -sili-ziumverbindung, /. fluosilicate. -tantal-sMure, /. fluotantalic acid, -tellur, n. tellurium fluoride, -titan, n. titanium fluoride, -toluol, n. fluorotoluene, fluotoluene. 

On mixing the cement paste, the calcium aluminosilicate glass is attacked by hydrogen ions from the poly(alkenoic acid) and decomposes with liberation of metal ions (aluminium and calcium), fluoride (if present) and silicic acid (which later condenses to form a silica gel). 

Poetschke (1925) patented a dental silicate powder prepared by fusing zinc silicate with calcium fluoride. This is a kind of silicophosphate cement (Section 6.6). Thomsen (1931) attempted to formulate a water-setting dental cement. Heynemann (1931) included lithium salts in the flux and Brill (1935) included them in the liquid. 

Silicate analysis is not without problems. If measurement of silicon is not required, it may be volatilized off as silicon tetrafluoride, using hydrofluoric acid, although some calcium may be lost as calcium fluoride. Alternatively, sodium carbonate-boric acid fusions may be employed. Where possible, final solutions are made up in hydrochloric acid. 

Compound Name Oil Mineral Seal Ethyl Silicate Trichlorosilane Fluosilicic Acid Silicon Tetrachloride Dimethyl Polysiloxahe Silicon Tetrachloride Silver Acetate Silver Carbonate Silver Fluoride Silver Iodate Silver Fluoride Silver Nitrate Silver Oxide Silver Sulfate Cacodylic Acid Calcium Hydroxide Oil Road Sodium Amide Sodium... 

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