Sol preparation

Fig. 8. Gelation behavior of alumina sols prepared from hydrolysis of aluminum isopropoxide at ( ) 90°C and (-) room temperature (49).

Transparent monoliths can be prepared by drying high density gels (49,50). Control of initial conditions of sol preparation is essential to achieve success during the drying step. 

Roark D, Yphantis DA (1969) Ann New York Acad Sci 164 245 Rinde H (1928) The Distribuhon of the Sizes of Particles in Gold Sols Prepared According to the Nuclear Method. PhD Thesis, University of Uppsala, Uppsala, Sweden Harding SE (1988) Gums and Stabilisers for the Food Industry 4 15 http //www.wyatt.com/... 

One percent Au/C catalysts were prepared according to the following general procedure the fresh sol, prepared as... 

In this paper, suitable gold sol preparations designed for catal5fiic pru poses that fulfil the above-reported prerequisites have been reported. 

After few minutes of gold sol preparation, metal particles have to be immobilized on a suitable support for practical purpose. Normally this step is simply performed by dipping the support in the sol. The metal particles are... 

Hanefeld and coworkers developed a straightforward process for the encapsulation of 7/iHNL under low methanol conditions. By adding a sol, prepared by hydrolysis of tetra-methoxysilane-methyltrimethoxysilane at pH 2.8 with continuous removal of methanol, to a stirred solution of the enzyme in a buffer at pH 6.5, at least 65% of the activity of the free enzyme could be recovered after the encapsulation. The aquagels were successfully used in the synthesis of (5)-cyanohydrins [54]. 

Any of the particle sols prepared above may be used to adsorb macromolecules to create gold probes. To concentrate the suspensions, the solutions may be filtered through a small-pore... 

Sol Preparation. Microcrystalline cellulose (Avicel PH 105) was supplied by the FMC Corporation, Philadelphia, PA., as a white powder. Twenty grams of Avicel PH 105 were mixed with 180 ml of water in a Waring blender for 5 minutes. The thick slurry was then transferred to a Lt. volumetric flask and gradually diluted to It. under constant stirring. The diluted suspension was left undisturbed for 3 days. The supernatant with a volume of about 650 ml was removed. This constituted the microcrystalline cellulose (MCC) stock sol. The solids concentration of the sols were determined by oven dry weighing and was about (1.2g/l). The unadjusted pH was 5.6. All the salts, hydrochloric acid and sodium hydroxide used were certified A.C.S. grade from Fisher Scientific. 

A more careful investigation was made by Perry et al. (14). In their experiments, a buffered silver sol prepared by dextrose reduction of ammoniacal silver nitrate was mixed with a solution of hydroquinone in a hydrogen atmosphere. Both solutions were deaerated before mixing. The mixed solution was stirred with hydrogen for one-half hour, then pressed through an ultrafilter under hydrogen pressure. The filtrate was analyzed for hydroquinone, and correction was made for retention of hydroquinone by the filter membrane. A small amount of... 

Fig. 1.1.9 Particle size distribution curves obtained by light scattering for two different aluminum hydrous oxide sols prepared by aging at 98°C for 30 h solutions containing 5 X I0-4 and I X 10" mol dm--1 Al2(S04)j, respectively (solid lines). Dashed lines show the corresponding size distributions of the same sols after all sulfate ions in the particles had been exchanged for hydroxyl groups.

Fig. 1.1.10 Tile electrophoretic mobilities of aluminum hydrous oxide sols prepared by aging at 98°C for 24 h a 1 X 10-3 mol dm-3 solution of Al2(S04)t and treated as follows A, original sol at room temperature , sol freed of the original electrolyte by centrifugation and redispersed in dilute NaOH solutions O, pH of the sol adjusted to 9.7 by NaOH, followed by deionization, and redispersion at various pH values.

Copper Dissolution in Alcohol. Copper is believed to be stable to alcohol, at least in bulk, because copper still is used in distillation processes for the production of whisky. However, it was found that the color of copper sols prepared by the gas flow-solution trap method changed from the initial wine red to yellow within 30... 

To prepare solids using the sol-gel method, a sol of reactants is first prepared in a suitable liquid. Sol preparation can be either simply the dispersal of an insoluble solid or addition of a precursor which reacts with the solvent to form a colloidal product. A typical example of the first is the dispersal of oxides or hydroxides in water with the pH adjusted so that the solid particles remain in suspension rather than precipitate out. A typical example of the second method is the addition of metal alkoxides to water the alkoxides are hydrolysed giving the oxide as a colloidal product. 

Air lock (personnel entrance and exit to sol. preparation) (room no. ) Class 10,000... 

Preparation of a Sulphur Sol. Prepare a saturated solution of sulphur in ethanol in a test tube. Take 2-3 g of sulphur and 10 ml of ethanol for this purpose. The solution will become saturated after vigorous shaking during 15 min. Filter off the undissolved sulphur, measure off 5 ml of the solution, and carefully pour it dropwise into 20 ml of distilled water. Pour part of the colloidal solution into two test tubes in equal portions. Add 1 ml of water to the first tube and 1 ml of a barium chloride solution to the second one, and heat both tubes. What happens How does the electrolyte affect the stability of the solution Define a gel and a sol. 

Carbonyl double bonds can also be photoelectrochemically reduced ZnS sols prepared from cold oxygen-free aqueous solutions ofZnSO4 and NajS induce efficient photodisproportionation of aldehydes, i.e., a photo-Canizzaro reaction Thus, acetaldehyde produces ethanol and acetic acid, together with smaller quantities of biacetyl and acetoin, Eq. (37). 

With selenium sols prepared by means of hydrazine hydrate at the ordinary temperature, by pouring into a large volume of water it has been shown that the stability of the colloid depends mainly on the degree of dispersion. An optimum concentration of electrolyte is necessary for the stability of the hydrosols. In the absence of electrolytes the system is quite unstable towards freezing. 

Any of the particle sols prepared above may be used to adsorb macromolecules to create gold probes. To concentrate the suspensions, the solutions may be filtered through a small-pore filter. Centrifugation also may be done. Each protein-gold complexation should be optimized for the proper amount of protein to add to maintain stability of the colloid. This can be done according to the method described in Section 1. 

Figure 7.4 Zeta potentials for silver iodide sols prepared by simple mixing90, ( calculated from Smoiuchowski equation (By courtesy of Elsevier Publishing Company)...

In an interesting illustration of the first strategy, Sakaguchi and coworkers covalently attached hemoglobin to an aminopropyl silica particle and then polymerized organoalkoxysilanes on the surface of the hemoglobin-modified silica particle.85 The template was removed via treatment with oxalic acid.85 In more recent work, Zhang and coworkers utilized a similar approach. In their case, the sphere was made from the functionalized biopolymer, chitosan.86 The model template protein, bovine serum albumin, was covalently attached to the chitosan microsphere and then coated with a composite sol prepared from TEOS and an aminosilane.86... 

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