Silicate, determination

Angstrom unit (A), definition, 307 Antimony, determination by x-ray emission spectrography, 328 in silicate, determination by absorption-edge method, 140 in solution, determination by absorption-edge method, 140 Aperture, relative, of x-ray optical system, 113... 

The percentage of dicalcium silicate determines the final strength of the cement, whereas the amount of tricalcium silicate is related to the early strength (7 to 8 days) required of the cement. Tricalcium aluminate relates to the set in the cement, and tetracalcium aluminoferrite reduces the heat necessary in manufacture. 

A portion (150 pi) of 0.1 mol/1 ammonium molybdate in 0.4 mol/1 HCl was aspirated into a reaction coil followed by a portion (800 pi) of the sample, after which the flow was stopped for 10 s. Next, 75 pi 5.6% oxalic acid in 0.18 mol/1 HCl, a further portion (1200 pi) of sample and 75 pi 0.035 mol/1 ammonium molybdate/3 mmol/1 ammonium vanadate in 0.65 mol/1 HCl were sequentially aspirated into the reaction coil. The flow was then reversed and the entire content of the reaction coil was propelled by a carrier stream of 0.05 mol/1 HCl toward the detector. A flow rate of 4 ml/min was used for both aspiration and propelling purposes. The absorbance was measured at 400 nm for both phosphate and silicate determinations. Phosphate was determined from the first peak and silicate from the second. Calibration graphs were linear up to 12 and 36 mg/1, phosphate and silicate, respectively. 

Fig. 10-3. Determination of the salt-effect (a) and correction factor (b) for silicate determination 0-100 /rmol/L, salinities 15-35 and zero water salinity of 25. The salinity correction factor (F au) is 0.0045 (b).

Sulphuric acid, 0.45 mol/L Dilute 10 mL of the 4.5mol/L sulphuric add (reagent 1 of the silicate determination, see Section 10.2.11) to lOOmL with pure water. Store in a polyethylene bottle. 

Salah, M.S. and Magnus, U.L., A kinetic sequential injection analysis method for silicate determination in water samples containing phosphates, JFIA (2005), 22(1), 25-29. 

Hydroxyl Coverage of a Variety of High-Surface-Area Silicates Determined by Different methods. 

Silicates are covalent atomic sohds (see Section 11.12) that contain silicon, oxygen, and various metal atoms. Rocks, clays, and soils contain silicates. Their great diversity illustrates a theme that we have encountered since Chapter 1 of this book the properties of substances are determined by their atomic and molecular structures. The structures of silicates determine their properties—and since these structures are varied, their properties are also varied. Some silicates form strong three-dimensional materials, while others break into sheets, and still others are highly fibrous. Let s examine more closely several of these structures. 

Sewage effluents, determination of, organic compounds 135-137,194, 207,226,261,262,353-362,462, 463 organometallic compounds 265, 266 Silicate, determination of 213 Silver, determination of 205, 206 Size exclusion high performance liquid chromatography, applications of 216-221 determination of, anions 218-220 cations 217, 218 organic compounds 216,217 Sodium, determination of 205, 206,... 

Brunauer and co-workers [129, 130] found values of of 1310, 1180, and 386 ergs/cm for CaO, Ca(OH)2 and tobermorite (a calcium silicate hydrate). Jura and Garland [131] reported a value of 1040 ergs/cm for magnesium oxide. Patterson and coworkers [132] used fractionated sodium chloride particles prepared by a volatilization method to find that the surface contribution to the low-temperature heat capacity varied approximately in proportion to the area determined by gas adsorption. Questions of equilibrium arise in these and adsorption studies on finely divided surfaces as discussed in Section X-3. 

Table XI-1 (from Ref. 166) lists the potential-determining ion and its concentration giving zero charge on the mineral. There is a large family of minerals for which hydrogen (or hydroxide) ion is potential determining—oxides, silicates, phosphates, carbonates, and so on. For these, adsorption of surfactant ions is highly pH-dependent. An example is shown in Fig. XI-14. This type of behavior has important applications in flotation and is discussed further in Section XIII-4.

B2O3 577 Ft For silicates and oxides when alkalis are to be determined... 

CaC03 plus NH3CI Ni For decomposing silicates in the determination of alkali element... 

It is a consequence of the action of different pH values in the aeration cell that these cells do not arise in well-buffered media [4] and in fast-flowing waters [5-7]. The enforced uniform corrosion leads to the formation of homogeneous surface films in solutions containing Oj [7-9]. This process is encouraged by film-forming inhibitors (HCOj, phosphate, silicate, Ca and AP ) and disrupted by peptizing anions (CP, SO ") [10]. In pure salt water, no protective films are formed. In this case the corrosion rate is determined by oxygen diffusion [6,7,10]... 

The ratio Db/Da is a so-called relative sensitivity factor D. This ratio is mostly determined by one element, e. g. the element for insulating samples, silicon, which is one of the main components of glasses. By use of the equation that the sum of the concentrations of all elements is equal to unity, the bulk concentrations can be determined directly from the measured intensities and the known D-factors, if all components of the sample are known. The linearity of the detected intensity and the flux of the sputtered neutrals in IBSCA and SNMS has been demonstrated for silicate glasses [4.253]. For SNMS the lower matrix dependence has been shown for a variety of samples [4.263]. Comparison of normalized SNMS and IBSCA signals for Na and Pb as prominent components of optical glasses shows that a fairly good linear dependence exists (Fig. 4.49). 

Determination of titanium with tannic acid and phenazone Discussion. This method affords a separation from iron, aluminium, chromium, manganese, nickel, cobalt, and zinc, and is applicable in the presence of phosphates and silicates. Small quantities of titanium (2-50 mg) may be readily determined. 

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. 

A. Determination of silica in a soluble silicate Discussion. Most of the silicates which come within the classification of soluble silicates are the orthosilicates formed from SiO units in combination with just one or two cations. More highly condensed silicate structures give rise to the insoluble silicates. 

Notes. (1) For practice in this determination, powdered, fused sodium silicate may be used. 

Discussion. Small quantities of dissolved silicic acid react with a solution of a molybdate in an acid medium to give an intense yellow coloration, due probably to the complex molybdosilicic acid H4[SiMo12O40]. The latter may be employed as a basis for the colorimetric determination of silicate (absorbance measurements at 400 nm). It is usually better to reduce the complex acid to molybdenum blue (the composition is uncertain) a solution of a mixture of l-amino-2-naphthol-4-sulphonic acid and sodium hydrogensulphite solution is a satisfactory reducing agent. 

Glocker and Frohnmayer determined the characteristic constant c for nine elements (Reference 2, Table 4) ranging in atomic numbers from 42 (molybdenum) to 90 (thorium). They proved that identical results could be obtained with the sample in the primary (polychromatic) or in the diffracted (monochromatic) beam. The method was applied with good results to the determination of barium in glass of antimony in a silicate of hafnium in the mineral alvite and of molybdenum, antimony, barium, and lanthanum in a solution of their salts—for example, 5.45% barium was found on 90-minute exposure by the x-ray method for a glass that yielded 5.8% on being analyzed chemically. 

A further resolution of the higher oxidation states in aquatic systems occurred in 1978 when scientists at Argonne National Laboratory(20) and Oak Ridge National Laboratory(21) independently established the capability to identify Pu(V) as the oxidized form that exists in natural waters. Both methods are based upon preferential adsorption on finely divided solids. In the Argonne procedure, adapted from a Japanese method for determining Np(V)(22), Pu(IV) and Pu(VI) adsorb onto silicic acid while Pu(V) does not. The Argonne scientists also have shown that the oxidized form of plutonium in natural waters carries on CaC03 when it is formed by... 

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