Preparation, typical aqueous

Typical gels are prepared from aqueous solutions of reactants such as sodium aluminate, NaOH, and sodium siUcate other reactants include alumina trihydrate (AI2O2 3H2O), coUoidal siUca, and siUcic acid. Some synthetic 2eohtes prepared from sodium aluminosihcate gels are given in Table 3. 

The quality of magnesium oxychloride cements is highly dependent on the reactivity of the magnesium oxide used in their preparation. Typically, such oxides are prepared by calcination of the basic carbonate (Eubank, 1951 Harper, 1967), but their reactivity varies according to the conditions under which such calcination is carried out. As the reactivity alters so does the amount of oxide that can be incorporated into a cement relative to the amount of aqueous MgClj (Harper, 1967). 

In summary, the use of RPLC is ideal for pharmaceutical analyses because of the broad range of commercially available stationary phases because the most common RPLC mobile phases (buffers with acetonitrile or methanol) have low UV cut-off wavelengths, which facilitate high sensitivity detection for quantitation of low-level impurities and because selectivity can readily be controlled via mobile phase optimization. Additionally, the samples generated for selectivity screening (as detailed above) are typically aqueous based. In subsequent phases of pharmaceutical development, aqueous-based sample solvents are ideal for sample preparation and are, under limited constraints, compatible with MS detection required to identify impurities and degradation products. 

Preparation of Aqueous Extract of Cotton Dust. Cotton cardroom dust was collected from V-cell filters in a commercial textile mill. A typical extraction was carried out by manually kneading 50 g of dust with 500 ml of deionized water for 5 min at 25°c and removing the liquor by centrifugation. The process was repeated twice with 250 ml of deionized water each time. The combined supernatant was filtered through filter paper by gravity and the filtrate (of final pH 8.3 without addition of buffer) was freeze-dried to yield fraction 1 (f-1). The major portion of f-1... 

Several attempts to prepare typical alcohol derivatives of [Cr(HO-A)2]-were unsuccessful these include Schotten-Bauman conditions (acetyl chloride in chloroform shaken with cold, aqueous alkaline solution of complex), refluxing in acetyl chloride, in glacial acetic acid, acetyl chloride in hot dimethyl formamide, acetyl chloride and pyridine in acetonitrile, and acetic anhydride in acetonitrile. The failure of refluxing acetyl chloride to effect acetylation brings to mind the work of Keller and Edwards (4) the acetyl chloride system is completely heterogeneous and consequently not conducive to reaction. However, even the homogeneous reaction of [Cr(HO-A)2] — with acetyl chloride in acetonitrile failed to give a measurable quantity of the diester. 

Nebulizer systems are universally aqueous in nature and can be either solution or suspension based. Excipients that have been used in nebulizer formulations relate to typical aqueous formulations and the formulation issues common to this type of preparation (i.e., stability and sterility issues). Table 3 provides several examples of nebulizer formulations that are commonly marketed along with the excipients... 

Figure 16.37. Typical examples of fluorescence spectra of humic acids from Brazilian soil (Hapludox) under different tillage systems. The samples were prepared in aqueous solutions (20 mg liter-1, pH 8). (a) Fluorescence emission (Xexc = 240nm). (b) Fluorescence synchronous-scan excitation spectra (AX = 55 nm). (c) Fluorescence excitation spectra (Xem = 517 nm). (d) Fluorescence emission spectra (Xoxc = 465 nm).

The first step in the manufacture of fine powder resins is to prepare an aqueous colloidal dispersion by polymerization with initiator and emulsifier present.21 Although the polymerization mechanism is not a typical emulsion type, some of the principles of emulsion polymerization apply here. Both the process and the ingredients have significant effects on the product.22 The solids contents of such disper-... 

As the use of cocamidopropyl betaine increased as a secondary surfactant in anionic systems, the relatively low concentration of about 35% nonvolatiles at which it is normally sold became an issue. At this concentration, betaines are somewhat susceptible to bacterial growth so a preservative is often needed and the low concentration also increases freight costs so that several patented technologies were developed to address this [7]. Typically, the inclusion of about 2% of one of the patented additives allows the producers to prepare an aqueous solution of 45% nonvolatiles which is hostile to microbial growth without... 

Similar to the porosils, the dense, thermodynamically stable Si02 modification a-quartz is also prepared under hydrothermal conditions. However, in the industrial process for the production of quartz, the temperatures are rather high (around 400°C). In this process, NaOH is added as a mineralizer to the aqueous solution to promote dissolution of the silica precursor. The reaction mixtures for the preparation of porosils and other zeotype materials also generally contain a mineralizer, but the reaction conditions are much milder. Synthesis temperatures are below 200°C, typically between 140 and 180°C. Some zeolites can even be prepared from aqueous solutions under reflux at normal pressure. These mild synthesis conditions provide the kinetic control necessary to form metastable products [5-9]. 

The Fe-Au nanoparticles were reported to consist of metallic cores, having an average diameter of 6.1 nm, surrounded by an oxide shell, averaging 2.7 nm in thickness, for a total average particle diameter of 11.5 nm [101]. A surfactant solution is prepared with nonylphenol poly(ethoxylate) ethers. Au-coated Fe nanoparticles were also prepared in a reverse micelle formed by cetyltrimethylammonium bromide (CTAB), 1-butanol and octane as the surfactant, the co-surfactant and the oil phase, respectively [100]. The nanoparticles were prepared in aqueous solutions of micelles by reduction of Fe(II) and Au precursors with NaBH4. The typical size of the nanoparticles is about 20 nm. The existence of Fe and Au is again confirmed by energy dispersive X-ray microanalysis. 

Typical Aqueous Solution Preparation (70% non-volatile in 2-Bu-toxyethanol). A cold cut was made of 105 grams of the epoxy ester and 45 grams of 2-butoxyethanol. To this solution were added 8.41 grams triemylamine, 100% neutralization based on the pretitrated acidity. Wa-... 

Traditional polymeric antistats relying on ionic conductivity and comprising quaternary halide groups or acidic groups can be prepared as latexes. Electrically conducting polymers are also typically prepared as aqueous latexes. In dye-diffusion-transfer processes, especially for anionically charged dyes, mordent polymers are also prepared as latexes. 

Three main chemical systems (compounds) are normally used to test for SERS activity in metallic colloidal suspensions pyridine, adenine and 1,2-Bis (4-pyridyl)-ethane (BPE). These analytes were prepared in aqueous solutions in the 10" to 10 M concentration range, as well as the other analytes studied. The final concentration was 10 times lower. Figure 5 shows the intensity enhancement that is typically obtained. 

The generation of silica in situ, in the polymer matrix, has been performed by using the sol-gel process. The typical aqueous sol-gel process consists of the hydrolysis of metal alkoxides M(OR)x followed by condensation reaction. Reactions involved to prepare silica through the sol-gel process are reported as follows ... 

---