Fluoride silicates

Table V.12 Separation of cations into groups (Anions of organic acids, borates, fluorides, silicates, and phosphates being present). Add a few drops of dilute HC1 to the cold solution. If a ppt. forms, continue adding dilute HC1 until no further precipitation takes place. Filter. (1)...

Separation of cations into groups can be carried out according to the instructions of Table VI. 11. Note, that this method is suitable only if anions of organic acids, borate, fluoride, silicate, and phosphate are absent. Modifications of the separation scheme in the presence of these anions are described in Section VI. 17. 

Table VI.ll Separation of cations into Groups on the semimicro scale (anions of organic adds, borate, fluoride, silicate, and phosphate being absent) Add 2 drops (1) of dilute HC1 to 1 ml of the clear solution in a 3 ml centrifuge tube (or a 4 ml test-tube). If a ppt. forms, stir and add a further 1-2 drops to ensure complete precipitation. Centrifuge (2) wash the ppt. with a few drops of cold water (3) and add washings to centrifugate.

VI.17 MODIFICATIONS OF SEPARATION PROCEDURES IN THE PRESENCE OF INTERFERING ANIONS The separation of cations, as described in Sections VI.9 to VI.16, is interfered with if anions of certain organic acids, borate, fluoride, silicate, and phosphate are present. During the course of... 

SYNS BARIUM FLUOROSIUCATE BARIUM FLUOSILICATE BARIUM HEXAFLUOROSIUCATE O BARIUM HEXAFLUOROSILICATE(2-) BARIUMSILICOFLUORID BARIUM SIUCON FLUORIDE SILICATE(2-), HEXAFLUORO-, BARIUM SILICATE(2-), HEXAFLUORO-. BARIUM (1 1) (9CI) SILICON FLUORIDE BARIUM SALT... 

Silicon tetrafluoride is formed when hydrogen fluoride reacts with silica or a silicate ... 

Aqueous hydrogen fluoride is a weak acid (see above) and dissolves silica and silicates to form hexafluorosilicic acid hence glass is etched by the acid, which must be kept in polythene bottles. 

The action of concentrated sulphuric acid liberates hydrogen fluoride, which attacks glass, forming silicon tetrafluoride the latter is hydrolysed to silicic acid by water, which therefore becomes turbid,... 

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—)... 

Hydrogen fluoride Catalyst in some petroleum refining, etching glass, silicate extraction by-product in electrolytic production of aluminum Petroleum, primary metals, aluminum Strong irritant and corrosive action on all body tissue damage to citrus plants, effect on teeth and bones of cattle from eating plants... 

Hydrogen fluoride reacts witlr metal carbonates, oxides, and hydroxides. Accumulation of these fluoride compounds can render valves and other close-fitting moving parts inoperable in a process system, causing possible equipment or process failures. Hydrogen fluoride also attacks glass, silicate ceramics, leather, natural rubber, and wood, but does not promote their combustion. 

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. 

Sodium silicate and silico fluoride solutions as concrete surface hardeners 9/104... 

Both sodium silicate and silico fluoride solutions are applied to clean, dry, sound concrete floors as dilute aqueous solutions (10-15 per cent solids) in two to three applications, taking care to ensure that all material penetrates and is absorbed into the concrete surface. The silicate or silico fluoride reacts with the small amount of free lime in the cement to form glassy inert materials in the surface, and the successful application of both materials depends upon filling the micropores in the surface of good-quality concrete, leaving its surface appearance and non-skid characteristics virtually unchanged. 

The main difference between the two types are that the reaction products of the silico fluoride types are less soluble in water and are also harder, which may give better in-service performance but at a slightly higher material cost. However, with recent developments in floor-laying techniques, the concrete substrates for industrial floors are laid with much more dense low-porosity surfaces, so that neither silicate nor silico fluoride treatments are as effective as they used to be, when the concrete used had a slightly more open finish and hence was more receptive to these treatments. With modern concrete floors, it is imperative to wash any material not absorbed into the surface within a short period. Otherwise, unpleasant white alkaline deposits, which are difficult to remove, may occur. 

It is important to stress that neither sodium silicate nor silico fluoride will improve the performance of a poor, low-strength, dusty concrete floor and if the surface is too porous, there is no way that all the material applied can react with the relatively small quantity of free lime in the concrete surface. All that will happen is that the pores will be filled with non-reacted powder, producing a most unpleasant alkaline dust, which can be very irritating to the skin and eyes when the floor is put into service. 

Finally, it is important to note that sodium silicate or siT ico fluoride treatments properly applied to clean and sound concrete floors can improve their performance, wear resistance and resistance to mild aqueous chemicals and oils, at a relatively low cost. However, they are not the answer to... 

Beryllium is extracted from the main source mineral, the alumino-silicate beryl, by conversion to the hydroxide and then through either the fluoride or the chloride to the final metal. If the fluoride is used, it is reduced to beryllium by magnesium by a Kroll-type reaction. The raw metal takes the form of pebble and contains much residual halides and magnesium. With the chloride on the other hand, the pure metal is extracted by electrolysis of a mixture of fused beryllium chloride and sodium chloride. The raw beryllium is now dendritic in character, but still contains residual chloride. 

A large number of electrolytic treatments of magnesium, anodic or a.c., have been developed, in which adherent white or grey films consisting of fluoride, oxide, hydroxide, aluminate or basic carbonate are deposited from alkaline solutions containing caustic alkali, alkali carbonates, phosphates, pyrophosphates, cyanides, aluminates, oxalates, silicates, borates, etc. Some films are thin, and some are relatively thick. All are more or less absorbent and act as good bases for paint, though none contributes appreciable inhibition. All can, however, absorb chromates with consequent improvement of protective efficiency. 

Discussion. The determination of this anion is of little practical importance. The methods available for its determination will, however, be outlined. Alkali fluorosilicates are decomposed by heating with sodium carbonate solution into a fluoride and silicic acid ... 

Insoluble fluorosilicates are brought into solution by fusion with four times the bulk of fusion mixture, and extracting the melt with water. In either case, the solution is treated with a considerable excess of ammonium carbonate, warmed to 40 °C, and, after standing for 12 hours, the precipitated silicic acid is filtered off, and washed with 2 per cent ammonium carbonate solution. The filtrate contains a little silicic acid, which may be removed by shaking with a little freshly precipitated cadmium oxide. The fluoride in the filtrate is determined as described in Section 11.59. 

If an acid solution of a fluorosilicate is rendered faintly alkaline with aqueous sodium hydroxide and then shaken with freshly precipitated cadmium oxide, all the silicic acid is adsorbed by the suspension. The alkali fluoride is then determined in the filtrate. 

Allylic transposition is observed in fluoride-induced reactions of allyl(trifluoro)silanes50 and allyl(trichloro)- and allyl(trialkoxy)silanes in the presence of hydroxylic promoters, e.g., 1,2-benzenediol51,52. Pentacoordinated silicates are believed to be involved53. 

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 ... 

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). 

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