Silicic acid Silicon dioxide

POLYDIMETHYLSILOXANE. A silicone polymer developed for use as a dielectric coolant and in solar energy installations, It also may have a number of other uses. It is stated to be highly resistant to oxidation and biodegradation by microorganisms. It is degradable when exposed to a soil environment by chemical reaction with clays and water, by which it is decomposed to silicic acid, carbon dioxide, and water. 

Aerosil Cab-O-Sil Cab-O-Sil MSP-, colloidal silica fumed silica light anhydrous silicic acid silicic anhydride silicon dioxide fumed Wacker HDK. 

It is convenient to regard calcium silicate, CaSiOg, as a compound of calcium oxide and silicon dioxide (Ca0,Si02), for thus it is evident why hydrofluoric acid acts on calcium silicate to form the fluorides of both calcium and silicon, together with the second product of double decomposition, water. Glass is a mixture of silicates and silicon dioxide, and when it is exposed to hydrofluoric acid it is acted upon in accordance with the reactions just described. As the action takes place unevenly on a polished surface of glass, the surface becomes pitted and produces a frosted or etched appearance. 

Silicon is the second most abundant element in the earth s crust. It occurs in sand as the dioxide Si02 and as complex silicate derivatives arising from combinations of the acidic oxide Si02 with various basic oxides such as CaO, MgO, and K20. The clays, micas, and granite, which make up most soils and rocks, are silicates. All have low solubility in water and they are difficult to dissolve, even in strong acids. Silicon is not found in the elemental state in nature. 

Silicic acid silica gel amorphous silicon dioxide... 

There are some exceptions. The diatoms are unicellular microorganisms that protect themselves with a filigree skeleton of silicon dioxide (silicic acid). The sometimes major fossil deposits of kieselguhr (diatomaceous earth or diatomite)... 

Table 5.1 summarizes the uses of lime. Lime is used as a basic flux in the manufacture of steel. Silicon dioxide is a common impurity in iron ore that cannot be melted unless it combines with another substance first to convert it to a more fluid lava called slag. Silicon dioxide is a Lewis acid and therefore it reacts with the Lewis base lime. The molten silicate slag is less dense than the molten iron and collects at the top of the reactor, where it can be drawn off. Over 100 lb of lime must be used to manufacture a ton of steel. 

Sulfur-containing chemicals Ditiocarbamates Stearic acid Hindered phenols Silicon oil Ahunnum silicates (clays) Titanium dioxide... 

Silicon is found in nature in combination with oxygen (mostly the dioxide, SiOs) and in different silicates (salts of various silicic acids). 

PLACE SOME OF THE GEL ON A METAL JAR LID. HEAT.THE SILICIC ACID (H2SiO,) GIVES UP WATER (H20) AND TURNS INTO A GRAYISH-WHITE POWDER OF SILICON DIOXIDE (SiOz). 

The mineral quartz is crystallized silicon dioxide. Sea sand consists mostly of rounded grains of broken quartz. If finely ground quartz or sand is fused for a long time with sodium carbonate, the weaker, but non-volatile, acid anhydride displaces the carbon dioxide, and sodium silicate is obtained. This is a glass-like substance, which, however, can slowly be dissolved by water heated under pressure. The solution so obtained is evaporated to a sirup-like consistency and is sold on the market under... 

Silicon Dioxide and Silicic Acid, (a) Wet a little silicon dioxide (very finely powdered quartz, or better the product of Preparation 41), test with litmus, and note that litmus is not... 

Silica (also called silicon dioxide), along with other silicates, makes up about 95% of Earth s crust—the outermost layer of rocks and soil. Silicon dioxide is also used to manufacture transistors. Silica reacts with hydrofluoric acid to produce silicon tetrafluoride and water vapour. 

Magnesium Silicate occurs as a very fine, white powder free from grittiness. It is a synthetic, usually amorphous form of magnesium silicate in which the molar ratio of magnesium oxide (MgO) to silicon dioxide (Si02) is approximately 2 5. It is insoluble in water and in alcohol, but is readily decomposed by mineral acids. The pH of a 1 10 slurry is between 7.0 and 10.8. 

Discussion of Experiment 140. — When silicon dioxide is fused with alkaline carbonates, an alkaline silicate is formed. The alkaline silicates are soluble in water, and when hydrochloric acid is added to such a solution, the gelatinous precipitate formed is a silicic acid having the formula H2Si03 (probably). This acid is decomposed by heat into silicon dioxide and water, thus —... 

Figure 6.13 Synthetic route of siliconates to polysiloxanes (a) reaction of siliconate with acid to give a methyl silanol, followed by further decomposition in the presence of atmospheric carbon dioxide to methyl silicic acid and alkali carbonate (b) formation of polysiloxanes from methyl silicic acid via intermolecular condensation. X = Na, K...

The most important industrially utilized silicon compounds include chlorosilanes, methylchlorosilanes, silicones, silicon dioxide and silicic acids in different forms, silicates in the form of glass, water glass, enamel frits, silicate fillers, zeolites, silicon carbide and silicon nitride. 

Silicon dioxide and Silicic acids Manufacture and applications in the filler sector, see Sections 5.8.3.1 and 5.8.4.I. 

---