Polysilicates

Coagulation and precipitation programs These programs are extremely widely used and employ various types of phosphates as a precipitant to provide control over the unwelcome deposition of hardness scales. Carbonate and polysilicates were once commonly used, although less so today. 

Orthosilicates are not suitable for corrosion inhibitor purposes, and metasilicates are not generally used because they tend to increase the caustic alkalinity too much, leading to the potential for caustic-induced problems. However, glassy polysilicates are widely used. They have inhibition properties similar to those of polyphosphates and also have an indefinite crystalline structure. 

Polysilicates are effective in potable HW systems and provide threshold effect protection against hardness destabilization and red water. They also function by laying down a protective calcium silicate film. Polysilicates used for this type of application typically require a dose rate of 8 to 15 ppm Si02 above that of the natural orthosilicate found in the MU water. Where polysilicates are employed for dualtemperature and LPHW systems, however, the silicate reserve required is higher and ranges from 50 to 150 ppm. 

Commercially, the selection of a suitable polysilicate treatment depends to some extent on the pH level of the water but also on the temperatures involved. (The polysilicate NajCkSiOj ratio required tends to be around 1 2 at pH 7.0, rising to 1 4 at a pH level of 9.0.)... 

Both sodium and potassium polysilicates are used in formulations of these types, and it is critical that products containing two (or slightly more) molecules of silica to every one molecule of sodium oxide are obtained to ensure adequate long-term inhibitor effectiveness. 

The permeability of subterranean oil-bearing formations can be controlled by injection of an organic polysilicate ester [851]. Polysilicate esters may be... 

D. H. Hoskin and L. D. Rollmann. Polysilicate esters for oil reservoir permeability control. Patent EP 283602,1988. 

The product of the fusion of silica with sodium carbonate, sodium silicate (strictly called sodium poly trioxosilicate but usually metasilicate), dissolves in water to give a clear, viscous solution known as waterglass . It hydrolyses slowly and silica is precipitated. Besides the metasilicate, other silicates of sodium are known, e.g. the poly-tetroxosilicate (orthosilicate), Na4Si04. Only the silicates of the alkali metals are soluble in water. Other silicates, many of which occur naturally, are insoluble, and in these substances the polysilicate anions can have highly complicated structures, all of which are constructed from a unit of one silicon and four oxygen atoms arranged tetrahedrally (cf. the structure of silica). Some of these contain aluminium (the aluminatesilicates) and some have import ant properties and uses. 

Alcohols and ketones, arylnaphthalenes Whelk-O 1 and poly Whelk-O (= its polysil-oxane borne analog) Subcritical carbon dioxide-based mobile phase at cryogenic temperatures 166... 

K. (1993) Synthesis of highly ordered mesoporous materials from a layered polysilicate./. Chem. Soc. Chem. 

In mineralogy, monosilicates are called nesosilicates and all other oligosili-cates are called sorosilicates moreover, the term polysilicates is replaced by inosilicates. ... 

Polysilicates monopolysilicates, dipolysilicates, tripolysilicates, tetrapolysilicates, pentapolysilicates... 

Magnesium forms an array of silicates having varying structures. Such a wide variety of silicates include metasilicate, orthosilicate, pyrosilicate, polysilicates, and a number of complex silicates, such as asbestos and talc in combination with other metal ions. Many such silicates occur in nature either as complex silicates or as discrete magnesium silicate. Some important magnesium silicates are listed below ... 

It may appear rather strange to measure a strictly inorganic compound. However, there is one important correlation to biopolymers. In proteins the polypeptide chain imposes considerable strain on metal-sulphur binding centres which may lead to sulphur radical species. Such species have been discussed for cytochrome c oxidase and plastocyanin Likewise the polysilicates could take over the same role. They are capable to polarize the sulphur species and the existence of sulphur radicals are debated. 

Several polysilabicyclosilirenes (79) have been obtained in the reactions of polysil-acyclooctynes (78) with dimesitylsilylene generated from the photolysis of 2,2-dimesityl-l,l,l,3,3,3-hexamethyltrisilane (Eq. 8). Thermolysis of bis(silacyclo-propane) (80) in the presence of bis(trimethylsilyl)acetylene at 60 °C affords bis-(silacyclopropene) (81) in 61% yield (Scheme 14.41). ... 

Other PDMS—silica-based hybrids have been reported (16,17) and related to the ceramer hybrids (10—12,17). Using differential scanning calorimetry, dynamic mechanical analysis, and saxs, the microstructure of these PDMS hybrids was determined to be microphase-separated, in that the polysilicate domains (of ca 3 nm in diameter) behave as network cross-link junctions dispersed within the PDMS oligomer-rich phase. The distance between these... 

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