Colloidal silic

Silica fouling is the accumulation of insoluble silica on anion resins. It is caused by improper regeneration which allows the silicate (ionic form) to hydrolyze to soluble silicic acid which in turn polymerizes to form colloidal silicic acid with the beads. Silica fouling occurs in weak-base anion resins when they are regenerated with silica-laden waste caustic from the strongbase anion resin unless intermediate partial dumping is done. 

Washing machines currently on the market are constructed almost exclusively with drums and laundry tubs of corrosion-resistant stainless steel or with an enameled finish that is inert to alkaline wash liquors. Nevertheless, various machine components are made of less detergent resistant metals or alloys. To prevent corrosion of these parts, modern detergents contain corrosion inhibitors in the form of sodium silicate. The colloidal silicate that is present, deposits as a thin, inert layer on metallic surfaces, thereby protecting them from attack by alkali. 

As pointed out by Sposito (1984) this equation initiated the surface chemistry of naturally occurring solids. Maarten van Bemmelen published this equation (now referred to as the Freundlich isotherm) more than 100 years ago and distilled from his results, that the adsorptive power of ordinary soils depends on the colloidal silicates, humus, silica, and iron oxides they contain. 

No foreign binder products may contain a different form of the adsorbent, e.g., colloidal or hydrated silica gel or colloidal silicic acid, to improve layer stability... 

Agrosil . [BASF AG] Colloidal silicate agricultural akl encourages intensive root develt ment improves irrigation effidoicy, improves soils. 

Silicates in Solutions. The distribution of silicate species in aqueous sodium silicate solutions has long been of interest because of the wide variations in properties that these solutions exhibit with different moduli (23—25). Early work led to a dual-nature description of silicates as solutions composed of hydroxide ions, sodium ions, colloidal silicic acid, and so-called crystalloidal silica (26). Crystalloidal silica was assumed to be analogous to the simple species then thought to be the components of crystalline silicate compounds. These include charged aggregates of unit silicate structures and silica... 

Somewhat less than the stoichiometric quantity of ZnO is dissolved in aqueous HsSiFg. Complete saturation is avoided because it produces hydrolysis with formation of colloidal silicic acid. The mixture is evaporated on a steam bath in a platinum or lead dish vuitil a film forms on the surface the film is redissolved with some water and the product is allowed to crystallize over H3SO4 in a desiccator. 

Herrera [6]... (following on the work of Moore and Evans [7] and Bastian [8])... concluded that colloidal silicates yield structures most like natural forms when produced from reaction-mixtures of very low concentration, when contact between precipitating agent is made slowly and when the viscosity of the reacting solution is great. 

Silica-based microparticles obtained by the sol-gel process also have limitations that must be known and, when possible, faced. One problem arises with the tendency to gel of the colloidal silica particles formed as a side product in the tetra-alkoxysilane polymerization reaction. In this case, the addition of a sequestering agent or the reduction in the amount of colloidal silicate particles in the suspension leads to aqueous suspensions of silica shell miaocapsules having improved storage stability. ... 

Polywater (also called anomalous water), which was first described in the 1960s in the Soviet Union and controversially discussed in the 1970s, does not exist, however, and was probably a mixture of colloidal silicic acid. 

The columns used were 20 m long, 300 pm ID. and were pretreated with colloidal silicic acid to stabilize the film of stationary phase. The columns were coated with 0.15% solution of the stationary phase in chloroform using the static method of coating (the different methods of coating capillary columns will be described later). Prior to use, each column was conditioned at 175°C in a stream of hydrogen. The... 

See aiso Silica , Silica, colloidal Silicic acid... 

Silica sol. See Silica, colloidal Silicate Cluster 102. See Tris (tributoxysiloxy) methylsilane... 

Moermans et al. (2000) prepared PDMS membranes filled with colloidal silicate-1 and applied these membranes in the PV of EtOH-water mixtures. The nano-sized zeolites showed much improved PV results compared with the micron-sized silicate m branes. Both the flux and the selectivity were drastically increased at the highest loading. The best results were obtained with the PDMS membrane containing 40 wt% of silycated nano-sized siUcate-1. 

Silicic acid hydrolysis and decomposition on site by addition of the water to a mixture of hydrofluoric acid and perchloric acid determine photometrically in the laboratory insoluble or colloidal silicates should first... 

Graham used the dialyser to separate colloids, which dialysed slowly, from crystalloids which dialysed rapidly. He prepared colloidal silicic acid, alumina (discovered by Crum)," ferric oxide (including the meta -form described by Pean de Saint-Gilles), etc. He thought colloids could be freed completely from crystalloids by dialysis, but probably traces of crystalloids remain. He says ... 

Silica gel is a partially dehydrated form of polymeric colloidal silicic acid. The chemical composition can be expressed as SiOj nH20. The water content, which is present mainly in the form of chemically bound hydroxyl groups, amounts typically to about 5 wt. %. The material appears first to have been developed during the First World War for use in gas masks although in this service it proved inferior to activated carbon. 

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