Silicate standard

Figure 2 shows a typical set of kxS curves determined from a suite of silicate standards including olivine, pyroxene, and amphibole which have been characterised by bulk techniques such as electron microprobe and x-ray fluoresence analysis. These minerals were chosen so as to provide a wide concentration range of many elements within the one set of standards and because beam degradation effects were negligible. In a plot of Cx/Cg versus Ix ISi/ kxSi determined from the slope of the best fit line and the intercept should be close to zero, since the (0,0) point itself can be considered a data point. 

High selectivities are also obtained by combining ion-exclusion chromatography with photometric detection after derivatization of the column effluent with suitable reagents. As a typical example, Fig. 4-6 shows the chromatogram of a 20-ppm silicate standard obtained by derivatization with sodium molybdate in acid solution and subsequent photometric detection at 410 nm. Orthophosphate may also be detected under these conditions. Because of its different acid strength it elutes prior to silicate, so that this method is very selective for the determination of both anions. 

B. P. Fabbi, A refined fusion x-ray fluorescence technique and determination of major and minor elements in silicate standards, Amer. Mineral, 57 237-245 (1972). 

FIGURE 43.10 Well-defined calibration line H7SL versus H atoms/Si atoms specific for medium-silica, low-H silicate standards. Amphiboles MHl and DH. Basaltic glasses CY-1 (short for CY82-29-1V) and CLDR (short for CLDR01-5V). 

Note The bottle holding the dilute standard must be plastic. All the above standards must be prepared afresh each day but they are mutually compatible, i.e., a mbced nitrate, ammonia, phosphate, and silicate standard can be used as one solution. 

Many catalysts have been used but the standard catalysts are generally mixtures of silica and alumina or natural or synthetic aluminium silicate zeolites. 

A number of cement materials are used with brick. Standard are phenolic and furan resins, polyesters, sulfur, silicate, and epoxy-based materials. Carbon-filled polyesters and furanes are good against nonoxidizing acids, salts, and solvents. Silica-filled resins should not be used against hydrofluoric or fluosihcic acids. Sulfur-based cements are limited to 93°C (200°F), while resins can be used to about 180°C (350°F). The sodium silicate-based cements are good against acids to 400°C (750°F). 

Table 11.1 Standard heats of formation of some metal silicates at room temperature (from metal oxides)...

Zinc silicate This material has good corrosion resistance and can withstand temperatures up to 540°C, particularly when over-coated with silicone-based aluminum. The zinc silicate requires a high standard of surface preparation before application. 

Sodium-silicate glass, 151 Sol-gel films, 120, 173 Solid electrodes, 110 Solid state devices, 160 Solvents, 102 Speciation, 84 Spectroelectrochenristry, 40 Spherical electrode, 6, 8, 9, 61 Square-wave voltammetry, 72, 92 Staircase voltammetry, 74 Standard potential, 3 Standard rate constant, 12, 18 Stripping analysis, 75, 79, 110 Supporting electrolyte, 102 Surface-active agents, 79... 

Values of are obtained partly by previous calibration using a series of standard light scatterers whose Rayleigh ratios have been precisely determined. Typical standards used in practice are poly(methyl methacrylate) blocks, colloidal silica suspensions, or tungsto-silicic acid, H4SiW 2O40-... 

Paffenbarger, G. C. (1937). Dental silicate cements. In Judd, D. B. Optical specifications of light scattering materials. Rep>ort No. 1026. Journal of the National Bureau of Standards, 19, 314-16. 

Paffenbarger, G. C. (1940). Silicate cements an investigation by a group of practising dentists under the direction of the ADA Research Fellowship at the National Bureau of Standards. Journal of the American Dental Association,... 

Abbey S (1980) Studies in Standard Samples for use in the general analysis of Silicate Rocks and Minerals, Part 6 1979 Edition of Usable Values. Pap - Geol Surv Can Paper 80-14. 

If the standard free energy change associated with the metal silicate chlorination reaction is given by AG , then... 

If AG has a value which is more negative than that of AG, then AG° becomes more negative than the standard free energy change for the metal oxide chlorination reaction (AG ). An oxide which is difficult to chlorinate in the free state may, therefore, be chlorinated more easily when compounded into a silicate. 

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