Silicon tetrachloride determination

These three frameworks and the framework for glycine in Figure 9 illustrate an important point about Lewis structures. Although Lewis structures show how atoms are connected to one another, a Lewis structure is not intended to show the actual shape of a molecule. Silicon tetrachloride is not flat and square, SO2 is not linear, and the fluorine atoms in CIF3 are not all equivalent. We describe how to use Lewis structures to determine the shapes of molecules later in this chapter. 

In an engineering analysis, the solubility parameter and liquid volume are needed for silicon tetrachloride (SiCI4). Determine the solubility parameter and liquid volume for silicon tetrachloride. 

The method with ECR was applied for the determination of aluminium in biological materials [12,97], natural waters [31,98], plants and soils [99,100], steel samples [29], lead-and tin alloys [101], and silicon tetrachloride [102]. The FIA technique was used for determination of aluminium, in the presence of a surfactant, in natural waters [32]. 

The bathophenanthroline method was used for determining iron in blood plasma [157], in plant materials [158], in waters [159], in niobium, tantalum, molybdenum, and tungsten [42,160], in molybdenum compounds [161], in cobalt [162], in cadmium and cadmium telluride [5], platinum [163], synthetic rubies and sapphires [164], silicon tetrachloride [165], and in boiler water [166]. 

In the determination of traces of P in silicon tetrachloride, shaking the sample with concentrated sulphuric acid causes the phosphorus to pass into the acid layer [7]. ... 

The method involving the Mo-V-P acid has been used in determinations of phosphorus in biological tissues [127], plant material [128], fruits [129], fish products [130], foodstuffs [131], phosphate minerals [132], cast iron and steel [133,134], niobium, zirconium and its alloys, titanium and tungsten, aluminium, copper, and white metal [135], nickel alloys [134,135], metallurgy products [136], molybdenum concentrates [137], silicon tetrachloride [7], cement [138], and lubricants[139]. The flow injection technique has been applied for determining phosphate in minerals [140] and in plant materials [141]. 

Intramolecular chlorine isotope effects have been determined in metastable ion decompositions induced by El of carbon tetrachloride, silicon tetrachloride, hexachloroethane and hexachlorosilane [687]. In all cases, the isotope effects were normal, i.e. losses involving the lighter isotope Cl were favoured. The loss of a chlorine atom from (CCl3) and from (SiCl4) showed isotope effects greater than 1.50. Other... 

Spectrophotometric methods have been described for the determination of copper, iron, cobalt and manganese in trichlorosilanes and in silicon tetrachloride186 boron in silicon tetrachloride and in hexachlorosilane187 and iron and aluminium in silicone polymers189. 

Down to 0.0001%, benzene in silicon tetrachloride could be determined in a column containing petroleum jelly on firebrick with flame ionisation detector and hydrogen as the carrier gas. The minimum determinable amount of benzene is 10 5 mg, with a relative error of 7.2%. The method was also applied to the determination of benzene in trichlorosilane. 

The following technique for the analysis of easily hydrolysable compounds is particularly valuable and sufficiently universal. In trace analysis and calibration of chromatographs by means of easily hydrolysable compounds one can suppress the hydrolysis of the trace component by preparing it in a substance which can be hydrolysed more easily. For example, in the determination of trace amounts of silicon tetrachloride its solutions in boron trichloride are used for calibration [98]. 

Pure silica end-members may be considered as special cases of aluminosilicate zeolites. They may be prepared directly from hydrothermal synthesis and in some cases from aluminosilicates by post-synthetic treatment. For example, the pure silica analogue of ZSM-5 (Silicalite-1) is readily prepared by direct synthesis, whereas purely siliceous zeolite Y can only be obtained by postsynthetic treatment (Chapter 6). The microstructures present in these solids depend on the way in which they are prepared. For direct preparation routes the presence or absence of fluoride as a mineraliser in the preparation (see Chapter 5) determines whether the framework is prepared defect-free or with high concentrations of terminal silanol (SiOH) hydroxyls, where silicon is attached to three bridging oxygen atoms and a hydroxyl group. Post-crystallisation preparation of pure silica zeolites can be achieved by treatment of appropriate starting materials with silicon tetrachloride or by removal of aluminium from the aluminosilicate framework by heating the ammonium form in steam (Chapter 6). 

Summary The treatment of silicon tetrachloride with two equivalents of 2-dimethyl-aminomethylferrocenyllithium (1), (FcN)Li, affords (FcN)2SiCl2 (2). The structure of 2 has been determined by X-ray diffraction analysis. It was used as starting chlorosilyl compound for reaction with Na[(ri -C5Me4Et)Mo(CO)3]. The reaction of 1 with 1,6-dichloro-dodecamethylhexasilane yields the novel (FcN)(SiMe2)6(FcN) (4). 

This is normally a slow process, carried out on a 60 lb and a 200 lb scale, over a period of several days, the progress being followed by determination of the loss in weight owing to evolution of chlorine. However, the rate might be considerably increased by the use of a catalyst. A final distillation from the same vessel removes the vanadium oxytrichloride and other volatile impurities such as silicon tetrachloride (b.p. S6°C) and titanium tetrachloride (b.p. 136°C), which may have remained with the product up to this point. This is performed firstly at atmospheric pressure and finally under reduced pressure. The quantity of oxytrichloride removed may be as much as 20 per cent of the total volume, and represents a loss of vanadium. 

Determine the molecular and empirical formulas of the following (a) The organic solvent benzene, which has six carbon atoms and six hydrogen atoms, (b) The compound silicon tetrachloride, which has a silicon atom and four chlorine atoms and is used in the manufacture of computer chips. 

Tius compound was discovered by Heae but its exact composition was determined by Ftiedel and ladenbutg. In order to prepare this substance a mixture of sulphuretted hydrogen and the vapour of silicon tetrachloride is peased t ngh a reddiot poroehdn tube... 

Brazhnikov and Sakodynskii determined the retention time of boron trichloride on various supports and stationary phases and compared its behaviour to that of boronalkyls, Zelyaev et al used a molybdenum glass column packed with poly (methylsiloxane) on Spherchrom 1 to separate in amounts down to O.lppm of various trace impurities in boron trichloride, such as chlorine, phosgene, silicon tetrachloride, chloroform, carbon tetrachloride and dichloroethane. They used a column temperature of 60°C with nitrogen as carrier gas and employed thermionic and flame ionization detectors,... 

Impurities such as methane, ethane, propane, isobutane, butane, chloromethane, chloroethane, hydrogen chloride, silicon tetrachloride and methyltrichlorosilane can be determined in trichlorosilane by separation on a glass column (4.5 metres x 4mm) packed with silanized silica gel operated at 50 C using nitrogen as carrier gas and flame ionization or thermal conductivity detectors. 

Friedrich separated six silanes including trimethylchloro-silane and silicon tetrachloride using nitrobenzene on infusorial earth as the stationary phase. The gas stream was passed into 0.02 N potassium chloride and changes in acidity are determined by conductivity measurements,... 

Burson and Kenner determined the purity of trichlorosilane and silicon tetrachloride with the SF-96 column. DC-LSX-3-0295 tri-fluoropropyl silicone gum was found to be the best for analysing samples of the methylchlorosilanes. Figure 57 shows a chromatogram of a sample of methyltrichlorosilane containing as impurities 0.02% silicon tetrachloride, 0.03% methyldichlorosilane, 0.04% trimethyl-chlorosilane, 0.12% dimethyldichlorosilane, and 0.07% 1,1,3,3,-tetra-chloro-1,3-dimethyldisiloxane. The concentrations of these impurities were determined by comparison of peak areas with standards prepared by adding known amounts of these impurities to methyltrichlorosilane of 99.99% purity. 

Namba et al. [171,172] subjected H-ZSM-5 to silicon tetrachloride vapor at temperatures between 450 and 650 °C and observed only a slight increase in the bulk Si/Al ratio from 19 to 24, while the surface Si/Al ratio determined by XPS increased, depending on the reaction temperature, from 18 to 39. Thus, the external crystal shell was preferentially dealuminated upon contact with SiCl4, obviously due to diffusion restrictions. In this way the contribution of the surface layer to the catalytic activity of ZSM-5 zeolite could be diminished and the shape-selectivity effect enhanced. In contrast, Thomas et al. [173] reported that aluminum could be removed from the lattice of ZSM-5 by treatment with SiCl4 at540°C. 

A rapid procedure has been described10 based on sodium peroxide bomb fusion, for the determination of silicon and halogen in fluorine-containing organosilicon compounds and resins. The silicon is separated from the decomposition product as zinc silicate and estimated gravimetrically as silica. The filtrate is concentrated, acidified and, when necessary, reduced with sulphur dioxide. Chloride, bromide or iodide is then determined by the usual methods. Fluoride can be determined in neutral solution either gravimetrically as calcium fluoride, or volumetrically with zirconium tetrachloride or thorium nitrate, or directly in the decomposition solution by titration with zirconium tetrachloride. 

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