Active silicates

Mono-, di- and triacylglycerols may all be measured by determination of the amount of glycerol released by hydrolysis. The lipid is first extracted into chloroform-methanol (2 1) and saponification is performed under conditions that will not affect any phosphate ester bonds, otherwise glycerol originating from phosphoglycerides would also be measured. Heating at 70°C for 30 min with alcoholic potassium hydroxide (0.5 mol l-1) has been shown to be satisfactory. However, the phospholipids may be removed prior to saponification either by extraction or by adsorption on activated silicic acid. 

Coagulants and coagulant aids iron and aluminum sulfates, activated silicates, alginates, synthetic polyelectrolytes and their impurities, silica, and aluminum electrolyte monomers. 

When fine powders of vitreous silica, quartz, tridymite, cristobalite, coesite, and stishovite of known particle-size distribution and specific surface area are investigated for their solubility in aqueous suspensions, final concentrations at and below the level of the saturated concentration of molybdate-active silicic acid are established. Experimental evidence indicates that all final concentrations are influenced by surface adsorption of silicic acid. Thus, the true solubility, in the sense of a saturated concentration of silicic acid in dynamic equilibrium with the suspended silica modification, is obscured. Regarding this solubility, the experimental final concentration represents a more or less supersaturated state. Through adsorption, the normally slow dissolution rates of silica decrease further with increasing silicic acid concentrations. Great differences exist between the dissolution rates of the individual samples. 

Tn 1950 Weitz et al. (23) developed a sensitive colorimetric method to measure small amounts of oligomeric silicic acid in the presence of polymeric forms. Oligomeric acid in this sense comprises molecules up to hexameric chains of hydrated SiC>4 tetrahedrons, which react readily with ammonium molybdate. Hence, this fraction of a sol is frequently referred to as molybdate-active silicic acid. 

NG from proplnts A process of selective adsorption is used ie, a benz soln of the various constituents of the compn are selectively adsorbed on mats such as Fullers earth, silicic acid, activated carbon, activated silicates, etc, followed by a desorption process 20... 

Kornilovich, Boris, Structure and Surface Properties of Mechanochemically Activated Silicates and Carbonates. Kiev Naukova Dumka, 1994. 

Temporal monitoring resulted in the first direct evidence for active silicate volcanism on lo, when a large increase in lo s infrared signal was detected one night in 1986 in multiple spectral bands. Analysis of this event suggested that material with a temperature of > 900 K is necessary to explain the infrared spectral signature, ruling out molten sulfur (Johnson et al., 1988). 

The separation medium is activated silicic acid with a particle size of 10-40/1, which is packed into the column by a dynamic introduction of a slurry. Unfortunately, a new column must be packed for each analysis. This is a weak point in the system, and it is an obvious area... 

Liquid Water Linde Type Linde Type Activated Silicic Acid... 

In another form of acid catalysis, the polymerization of cyclic and linear siloxanes is carried out on acidic solids such as ion exchange resins and acid-activated silicates (heterogeneous catalysis). This process also leads to an equilibrium mixture of linear polysiloxanes with a content... 

The solution-mediated transport mechanism has been extensively discussed in the literature. In the middle of the 1960s, according to their studies on the crystallization of zeolite A, Kerr and Ciric proposed the solution-mediated transport mechanism. They believed that the nucleation and growth of zeolite crystals happened in solution. The initial gel was partially or completely dissolved in the solution with the formation of active silicate and aluminate ions. These active silicate and aluminate ions could further form the structural units of zeolite crystal. 

Rassaei, L., Sillanpaa, M., Milson, E.V., Zhang, X., and Marken, F. 2008. Layer-by-layer assembly of Ru + and SigOjo " into electrochemically active silicate films. Journal of Solid State Electrochemistry 12, 747-755. 

Mechanism of Particle Growth. As shown in Scheme I, the silicic acid undergoes dehydrating condensation polymerization in the presence of alkali. The higher the temperature and the pH and the longer the reaction time, the faster the polymerization proceeds. As a result of polymerization, Na+OH- that was adsorbed onto the active silicic acid is released and increases the pH. 

Variations of Silica Sol Manufacturing Process. As shown in Figure 4, the four methods, A-l, A-2, B-l, and B-2, use different technical combinations of nucleation, particle growth, and concentration. In any of these methods the raw material aqueous water-glass solution is diluted, and sodium is removed with a cation-exchange resin to obtain an active silicic acid. The characteristics of these four processes are shown in Table I. 

Methods A-l and A-2. In Methods A-l and A-2, a small amount of an aqueous NaOH solution is added, while stirring, to the acidic active silicic... 

Scheme II. Polymerization of active silicic acid to form nuclei. ...

As indicated in Scheme IV, stable dilute sol is nucleated to obtain sols having a particle size of, for example, 20 nm, which is used as a heel. Then, in the next step, an active silicic acid or stable dilute sol is continuously charged onto the heel to allow the silica particles to grow to a diameter of 50 nm. Thus, the process consists of two separate steps. In either Method B nucleation is carried out in the initial stage of the process, and buildup occurs from the intermediate to the final stages. However, this method is not clearly separated into two steps. 

Figure 9, this new silica sol is elongated. For example, the particles have a diameter of about 10 nm and a length of 50-100 nm. To prepare such elongated silica sols, a calcium salt and an aqueous sodium hydroxide solution are added to an active silicic acid or an acidic silica sol, and the mixture is heated in an autoclave at 100-150 °C for several hours. Thus, particle polymerization takes place in nonuniform directions, and an elongated silica sol (31) can be formed. 

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