Water testing silica content

Brombenztiazo (BBT) is known to be one of the best reagents for extraction-photometric determination of cadmium(II). The reagent also fonus complexes with Co(II), Cu(II), Fe(II), Ni(II), Zn(II). The aim of this work was to develop a solid-phase reagent on the base of BBT immobilized on silica gel for sorption-spectroscopic and visual test determination of Cadmium, and also for soi ption-atomic-adsoi ption determination of total heavy metals contents in natural waters. 

Increasing the molecular weight of a copolymer containing 5% methyl acrylate (MA) from 100,000 to 1,000,000 daltons had little effect on silica stabilization effectiveness (see Table IX). Increasing the methyl acrylate content from 5% to 30% had also little effect on silica fines stabilization effectiveness. Acidizing substantially reduced the effectiveness of this class of copolymer. Results for the injection of 10,000 pore volumes of water indicated that silica fines elution from the test column was substantially reduced on a long-term basis. 

Method. To the residue in a test-tube is added 1 ml of 5% sodium hydroxide followed by 30 pi of anisoyl chloride. The tube is shaken for 1 min and left to stand at room temperature for 20 min in order to complete the reaction. At this time, 9 ml of water are added and the contents of the tube are shaken for 2 min. The mixture is then shaken with three 10-ml volumes of hexane. After centrifugation, the hexane solution is transferred quantitatively to a clean test-tube and evaporated to dryness. 1.0 ml of n-butyl chloride is added in order to dissolve the residue. An aliquot portion of the resulting solution is injected into the liquid chromatograph. The chromatographic apparatus consists of a stainless-steel column (2 ft. X 2.3 mm I.D.) which is packed with silica (particle diameter, 36-40 pm). The mobile phase is hexane-n-butyl chloride (11 9) at a flow-rate of 0.7 ml/ min. UV detection is carried out at 254 nm. The absorption spectrum of the HCP dianisate... 

We believe that a similar water vapor solubility enhancement of alkali vapor transport is possible in soda-lime-silica glass systems, and work is in progress to verify this. Some of the disparities between various glass vaporization studies may well result from variations in water content and, hence, alkali activities. The common explanation for water vapor enhanced alkali vapor transport over silicates has revolved around formation of volatile NaOH (77) and KOH (53) species. However, no direct test for the presence of these species has been made, and the possibility of water vapor enhancement of atomic Na and K transport exists in these systems. 

Siliceous oozes are accumulations of opaline silica (opal-A, an amorphous phase of high water content and porosity) in the tests of diatoms, radiolarians, and/or silicoflagellates. Opal-A solubility at 25 °C is 60-130 ppm Si02(aq) (e.g., Williams etal., 1985), and solubility increases with increasing temperature and pressure (Walther and Helgeson, 1977). Adsorption of aluminum and iron on the surfaces of siliceous tests decreases their solubility (Her, 1955 Lewin, 1961). Opal-A is a metastable phase that with burial eventually recrystallizes to quartz, often with another metastable intermediary phase, opal-CT (e.g., Hein et ai, 1978 Williams et ah, 1985 Williams and Crerar, 1985). Opal-CT structurally resembles an inter-layering of the two silica phases, cristobalite... 

According to JIS R 5201 (Physical testing method for cement), cement pastes were prepared with the mix proportions in Table 5 (series 1) and Table 6 (series 2). Cement ratios to cement plus silica stone powder (cement content) were 30,40 and 50%, and water/cement ratios were constant at 50%. The scrap FRP powder was used as a filler, and the percentages of addition were 5, 10 and 15% in this study. 

Wittwer investigated the influence of the volatilization of amines in the mobile phase by testing the same solvent system, containing amnonia in various concentrations (without changing the water content of the mobile phase) in combination with a silica gel column. For the compounds tested, common adulterants or impurities of illicit heroin samples, only a few changes in the elution order were observed, particularly for the early eluting compounds, and furthermore an increase of retention time was observed upon decreasing ammonia concentration (Table 7.11). However, the relative retention varied little for most test compounds. The water content of the mobile phase was found to play an important role in the selectivity of the system. Retention times were reduced considerably on increase of the water content of the mobile phase but some compounds were more affected than others. Therefore, the water content of the mobile phase should be controlled... 

Porous silicas are usually mesoporous materials and they can be made with a variety of pore dimensions. In particular, silica glasses can be made with well-defined pore diameters, typically in the range 30-250 A, using sol-gel methods. Such a system provides a good model for testing the models of relaxation behaviour of fluids in porous solids. It is normally found that the two-site fast-exchange model for relaxation described above for macroporous systems is still valid. For instance, H and relaxation times have been measured during both adsorption and desorption of water in a porous silica. Despite hysteresis in the observed adsorption isotherms, it was found that the relaxation times depended solely on water content.For deuterated water in some porous silicas, multicomponent relaxation behaviour for T2 and Tip has been observed, and this has been attributed to the fractal nature of the pore structure. 

The equilibration with the mobile phase should be fast This means that we should choose an analyte as test marker, whose interaction with the stationary phase is simple and does not depend on the concentration of small impurities in the mobile phase. For example, we would choose an aromatic hydrocarbon as a test compound for reversed-phase packings. For silica columns, one should use a mobile phase with a controlled water content to speed up equilibration. 

Selectivity. The retention factors of test solutes were dependant on the Mw/aot molar ratio and the heptane content. Fig. 13.4 shows that the k variations were not monotonous. It was demonstrated that the hydration of the polar unbonded silica surface changed significantly in the 0water adsorbed on the silica surface forming a composite layer so thick that it changed the column permeability and dead volume [7]. The combined effect of stationary phase hydration and adsorbed layer was responsible for the observed retention factor variations (Figure 13.4). The Mw/aot ratio is directly related to the water droplet size so the retention factor of a test solute can be related to the structnre of the L2 microemulsion. 

Sokolowska [63, 64] detected and determined tritolyl phosphate in PVC by extracting the additive with diethyl ether for 16 hours, the solvent was evaporated off, and a solution of the residue in chloroform was applied to layers of Silica gel G. Chromatograms were developed with benzene - ethyl acetate (20 1) and the spots of tritolyl phosphate were located with 0.5 N ethanolic - potassium hydroxide and diazotised 4-nitroaniline solution. The contents of total phenols and o- and p-cresols were determined by mixing the test solution (20 ml) containing 0.25 to 2 mg of phenols per litre, with diazotised 4-nitroaniline solution (5 ml). Borate buffer solution (28.42 g of Na2B40y IOH2O and 13 g of sodium hydroxide per litre (20 ml) was added and these solutions were then diluted to 50 ml with water and after 15 to 30 minutes, the extinction was measured at 485 nm against a... 

---