Silicon, determination

Phosphorus and Silicon in Waters, Effluents and Sludges [e.g. Phosphorus in Waters, Effluents and Sludges by Spectrophotometry-phosphomolybdenum blue method. Phosphorus in Waters and Acidic Digests by Spectrophotometry-phosphovanadomolybdate method. Ion Chromatographic Methods for the Determination of Phosphorus Compound, Pretreatment Methods for Phosphorus Determinations, Determination of silicon by Spectrophotometric Determination of Molybdate Reactive Silicon-1 -amino-2-naphthol-4, sulphonic acid (ANSA) or Metol reduction methods or ascorbic acid reduction method. Pretreatment Methods to Convert Other Eorms of Silicon to Soluble Molybdate Reactive Silicon, Determination of Phosphorus and Silicon Emission Spectrophotometry], 1992... 

Figure 6.7 Part of a mass spectrum for silicon determination at m/z = 28 in high purity GaAs measured by rf GDMS (Element, Thermo with rf glow discharge ion source constructed in our lab). The interfering polyatomic ions 12CuO+ and UN2+ are well separated at mass resolution m/Am of 3000. (J. S. Becker et ai, Int. J. Mass Spectrom. 164, 81 (1995). Reproduced by permission of Elsevier.)...

The increased stability of a carbocation p to silicon determines the regioselectivity of the reactions between electrophiles and both allylsilanes and vinylsilanes (see p. 84 and p. 76 respectively). 

Secondary amines give the aminosilane, with the more hindered amines requiring heating under pressure. With primary amines, the aminosilane is formed initially, but the size of the substituents at nitrogen and silicon determines whether deamination subsequently occurs. Prolonged heating under reflux in the presence of ammonium sulfate, or the precipitated amine hydrochloride as acid catalyst yields the disilazane in good yield. 

P. Bermejo Barrera, M. C. Barciela Alonso, R. Dominguez Gonzalez, A. Bermejo Barrera, J. A. Cocho de Juan, J. M. Fraga Bermudez, Silicon determination in milk by electrothermal atomic absorption spectrometry using Pd as chemical modifier, Anal. Bioanal. Chem., 374 (2002), 1290-1293. 

Plot of 4/n, where n is the average nuiriber of A1 neighbors per silicon determined by Si NMR, as a function of composition. For frameworks subject to Loewenstein s rule 4/n = R. 

D. Hydrofluoric acid—boric acid attack for silicon determination in rock, soil, or sediment... 

This method is useful when silicon determinations are required on samples which are not decomposed by hydrofluoric—boric acids at 95°C. The finely ground sample is fused with lithium metaborate in a graphite crucible and the melt is dissolved in dilute nitric acid [12]. 

Al, Si Digestion with concentrated sulphuric acid-chromic acid in current of oxygen. Silicon determined volumetrically as Na2SiF6. Aluminium determined by titrimetric EDTA method. 

Al, Si, P Digestion with diethyl ether-concentrated sulphuric acid-potassium persulphate. Silicon determined gravimetrically. Aluminium determined by titrimetric EDTA method. Phosphorus determined by spectrophotometric molybdenum blue method. 

The corresponding explanation for silicon, advanced by Ottaviani et al. [325], is that the specific reactive interface (i.e. silicide—silicon) determines the barrier height, but again it is the result of a metal—semiconductor interaction. 

Huang Z, D Haese PC, Lamberts LV, Van Landeghem GF and De Broe ME (1993) Silicon determination in biologicalfluids by Zeeman atomic absorption spectrometry. In Anke M, Meissner D, Mills CP, eds. Trace Elements in man and animals - TEMA 8, pp. 98-99. Verlag Mediatou-ristik, Gersdorf... 

Lugowski SJ, Smith DC, Lugowski JZ, Peters W and Semple J (1998) A review of silicon and silicone determination in tissue and body fluids - a need for standard reference materials. Fresenius J Anal Chem 360 486-488. 

P. Ganesh and M. Widom, Liquid-liquid transition in supercooled silicon determined by first-principles simulation, Phys. Rev. Lett. 102, 075701 (2009). 

The liquid is a fluorinated oil called PFAS (polyfluoromethylalkylsilox-ane). Since the dewetting kinetics of water is far too rapid to be observable with a regular camera, PFAS is a much better choice. It dewets much more slowly and does not dissolve PDMS. The number of monomers of this fluoro-silicone determines its viscosity, which is 100 to 1,000 times higher than that of water. Experiments with a fast camera show that water obeys the same laws. 

Silicon, which occurs in nature as Si02, is the material from which most computer chips are made. If Si02 is heated until it melts into a liquid, it reacts with solid carbon to form liquid silicon and carbon monoxide gas. In an industrial preparation of silicon, 52.8 kg of Si02 reacts with 25.8 kg of carbon to produce 22.4 kg of silicon. Determine the limiting reactant, theoretical yield, and percent )deld for the reaction. 

They used a Varian 2440 gas chromatograph equipped with a flame ionization detector (FID). Stainless steel chromatographic columns were used. These were a 3 ft x in. o.d. column of 5% OV-17 on 100/120 mesh Chromosorb 750 (adapted for on-column injection) which was used for the mercury evaluation, a 3 ft x g in. o.d. column of 3% QF-1 on 100/120 mesh Varaport 30 (adapted for on-column injection) for the phosphorous evaluation, a 6 ft x in. o.d. column of 6% Carbowax 20M on 100/120 mesh Chromosorb P for the silicon determination, and a 6 ft x in o.d. column of 2.5% Dexsil 300 on 100/120 mesh Chromosorb 750 for the remainder of the elements investigated. Helium carrier gas flow rates were 50 ml/min. The injector, detector, transfer line and interface oven were maintained at 170 0 for lead. 

The determination of silicon has been reviewed in detail [663, 664]. The element can be determined as Si02 or Si02 + 12 MoOj by gravimetric analysis. Fig. 5.6 shows a simple apparatus for pyrametric silicon determination [665]. 

Other methods of gravimetric silicon determination are fusion with fuming sulphuric acid [667] or with a mixture of fuming sulphuric and nitric acids [668,669], and fusion with sodium peroxide, followed by determination as SiOj -1-12 M0O3 [670]. 

Figure 5.6 Apparatus for silicon determination as silicon dioxide [665].

Jellison Jr., G. E. (1992) Optical functions of silicon determined by two-channel polarization modulation ellipsometry. Opt. Mater, 1, 41-47. 

Carry out the silicon determination as described in Section F, above (paragraphs 1-3) using 25.0 ml of the dilute silicon standard instead of a seawater sample. Determine the extinction of four such standards and of two blanks made with synthetic sea water. A reagent blank is unnecessary. Measure the extinction in a 1-cm cell after allowing 3 hr for full colour development (see Note /). 

Radeglia and co-workers consider that not only the charge on the silicon determines the shielding but also its distribution. This is due to the paramagnetic contribution to the shielding constant. They define a reduced shielding constant a" on the basis of the... 

Tuma, J., 1962. Colorimetric microdetermination of silicon. Determination of silicon in biological material and minerals. Mikrochim. Acta 513. 

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