What are the specifications and standards for silica?

The main indicators are: bet specific surface area.

pH, electrical conductivity.

Sulfate, median diameter, oil absorption value, sieve residue, moisture, burning! The specifications of the particles are powder, microbeads, and blocks, and the median diameter is used to see the particle size, and the unit is microns; The specific surface area is divided into the outer specific surface area and the inner specific surface area, and the unit is square meters per gram; The oil absorption value is per gram of silica.

How much oil can be absorbed, in milliliters per gram! The main indicator is bet, moisture! The others are all sub-indicators, and different customers and different uses have different requirements!

The requirements for each product are different... You can check it out at the library. to the chemical material piece.

Pure natural silica crystals, which are hard, brittle, insoluble, colorless and transparent solids.

Physical. Crystalline silica.

Density: g cm3

Melting Point: 1723

Boiling Point: 2230

Refractive index: Solubility: Insoluble in water.

Chemical properties. The chemical properties are relatively stable. Does not react with water.

It has high fire resistance, high temperature resistance, low coefficient of thermal expansion, high insulation, corrosion resistance, piezoelectric effect, resonance effect and its unique optical properties. It is an acidic oxide and does not react with ordinary acids. Hydrofluoric acid reacts with silica to form gaseous silicon tetrafluoride.

Silicates and water are formed by reacting with a hot, concentrated alkali solution or molten alkali. It reacts with a variety of metal oxides at high temperatures to form silicate. The nature of silica is not active, it does not interact with halogens other than fluorine and hydrogen fluoride, hydrogen halide, sulfuric acid, nitric acid, perchloric acid (except for hot concentrated phosphoric acid).

Common concentrated phosphoric acid (or pyrophosphoric acid) can corrode silica at high temperatures to form heteropolyacids, and molten borate or boric anhydride can also corrode silica at high temperatures, in view of this property, borate can be used as a flux in ceramic firing, in addition to hydrogen fluoride can also make silica dissolved acids to produce fluorosilicic acid that is easily soluble in water.

sio2+4hf=sif4↑+2h2o

6hf+sio2=h2sif6+2h2o

SiO2+2NaOH (concentrated) = Na2SiO3 + H2OSiO2 + Na2CO3 = Na2SiO3 + CO2 (high temperature) SiO2 + Cao = Casio3

sio2+2c=2co↑+si

The relative molecular mass of silica is, and the molar mass is.

The relative atomic mass of Si is 28, the relative atomic mass of O is 16, the relative molecular mass of SiO2 is 28+18 2=60, and the relative molecular mass of the substance The molar mass of the substance, the molar mass of SiO2 is 60g mol. Silica is made up of one silicon atom and two oxygen atoms (chemical formula: SIO) relative to the molecular mass.

The natural silica that exists on the earth accounts for about 12% of the mass of the earth's crust, and its existence forms are crystalline and amorphous, collectively referred to as silica and silica.

Silica Introduction:

Silica is an acidic oxide that corresponds to silicic acid (H Sio). Silica is one of the more important compounds of silicon. Silica on the earth accounts for about 12% of the mass of the earth's crust, and its existence forms are crystalline and amorphous, collectively referred to as silica.

Silica is an acidic oxide that is solid at room temperature and has the chemical formula SIO. Silica is insoluble in water and insoluble in acid, but soluble in hydrofluoric acid and hot concentrated phosphoric acid, and can work with molten alkalis.

Gaseous hydrogen fluoride reacts with silica to form gaseous silicon tetrafluoride. Silicates and water are formed by reacting with a hot, concentrated alkali solution or molten alkali. It reacts with a variety of metal oxides at high temperatures to form silicate.

It is used to make glass, water glass, pottery, enamel, etc. Pure natural silica crystal is a hard, brittle, insoluble colorless and transparent solid, which is often used in the manufacture of optical instruments.

The above content reference: Encyclopedia - Silica.

1.Physical properties: silica is also known as silica, chemical formula sio, there are two kinds of crystalline silica and amorphous silica in nature, crystalline silica is divided into quartz, lemosis quartz and cristobalite due to different crystal structures, pure quartz is a colorless crystal, large and transparent prismatic quartz is called crystal, if the crystal containing trace impurities has different colors, there are amethyst, citrine, ink crystal, etc.

Ordinary sand is a fine quartz crystal, there are yellow sand and white sand, in the silica crystal, the 4 valence electrons of the silicon atom and the 4 oxygen atoms form 4 covalent bonds, the silicon atom is located in the center of the regular tetrahedron, the 4 oxygen atoms are located on the 4 apex angles of the regular tetrahedron, sio is the simplest expression of the composition, only the ratio of the number of atoms of silicon and oxygen in the silica crystal, and the silicon dioxide is an atomic crystal.

2.Properties: The chemical properties are relatively stable, insoluble in water and do not react with water, it is an acidic oxide, does not react with general acid, gaseous hydrogen fluoride reacts with silicon dioxide to form gaseous silicon tetrafluoride, reacts with hot concentrated alkali solution or molten alkali to form silicate and water, and reacts with a variety of metal oxides at high temperature to form silicate.

Silica is also known as silica and has the chemical formula SIO. There are two types of silica in nature: crystalline silica and amorphous silica. Crystalline silica is divided into three types: quartz, lemostomatite and cristobalite due to different crystal structures.

Pure quartz is a colorless crystal, and a large and transparent prismatic quartz is called a crystal. If the crystal containing trace impurities has different colors, there are amethyst, citrine, ink quartz, etc. Ordinary sand is fine quartz crystals, with yellow sand (more iron impurities) and white sand (less impurities, purer).

In the silica crystal, the 4 valence electrons of the silicon atom and the 4 oxygen atoms form 4 covalent bonds, the silicon atom is located in the center of the regular tetrahedron, and the 4 oxygen atoms are located on the 4 apex angles of the regular tetrahedron, and many such tetrahedron are connected by the oxygen atoms of the apex angle, and each oxygen atom is common to two tetrahedrons, that is, each oxygen atom is combined with two silicon atoms. SIO is the simplest form of representation of composition, which simply represents the ratio of the number of atoms of silicon and oxygen in a silica crystal. Silica is an atomic crystal.

The bond energy of Si—O bond in Sio is very high, and the melting point and boiling point are high (melting point 1723, boiling point 2230). The refractive index is approximate.

The refractive index of various silica products is: quartz sand; Pink quartz is; Vein quartz is; Diatomaceous earth is; Vapor phase silica is; Precipitated silica for.

Diatomaceous earth existing in nature is amorphous silica, which is the remains of diatoms of lower aquatic plants, which is white solid or powdery, porous, light and soft solid, and has strong adsorption.

The hardness has a large melting point and the boiling point is high.

Solid, insoluble in water.

Colorless transparent crystal or white powder, high melting point, high hardness, insoluble in water.

It is an acidic oxide, an acid anhydride of silicic acid. The chemical properties are very stable. It is insoluble in water and does not react with water, and does not work with ordinary acids. It can react with hydrogen fluoride gas or hydrofluoric acid to form silicon tetrafluoride gas.

sio2+4hf sif4↑+2h2o

It has other common properties of acidic oxides, and can react with alkali (strong alkali solution or molten alkali) at high temperatures to form salt and water.

At room temperature, the strong alkali solution slowly interacts with SiO2 to form the corresponding silicate. If a glass stopper (glass contains SiO2) is used, a viscous sodium silicate will be generated, which will bond the glass stopper and the bottle mouth together. Do not store concentrated lye in the glass bottle for a long time.

At high temperatures, silica is co-melted with basic oxides or carbonates of certain metals to form silicates.

SiO2+cao Casio3 (iron slag making).

Quartz glass can be obtained by cooling and cooling the sodium silicate in a molten state at this high temperature, which has good ultraviolet transmission performance and can be used as mercury lampshades, high-temperature resistant chemical instruments, quartz crucibles and optical instruments.

The chemical properties are very stable. It is insoluble in water and does not react with water. It is an acidic oxide and does not react with ordinary acids.

Gaseous hydrogen fluoride or hydrofluoric acid reacts with silica to form gaseous silicon tetrafluoride. Silicates and water are formed by reacting with a hot solution of strong alkali or molten alkali. It reacts with a variety of metal oxides at high temperatures to form silicate.

It is used in the manufacture of quartz glass, optical instruments, chemical utensils, ordinary glass, refractory materials, optical fibers, ceramics, etc. The nature of silica is not active, it does not interact with halogens, hydrogen halide and hydrohalic acid other than fluorine, hydrogen fluoride and hydrofluoric acid, as well as sulfuric acid, nitric acid, perchloric acid. Hydrogen fluoride (hydrofluoric acid) is the only acid that dissolves silica, producing fluorosilicic acid, which is easily soluble in water

The specific surface area of its silica is measured. SiO +4HF = SIF4 +2H O Acid and oxygen universality: Silica and basic oxides SiO +CAO = (high temperature) Casio3 Silica is soluble in a strong alkaline solution in concentrated heat:

Sio +2NaOH = Na2SiO3 + H O (the reason why the reagent bottle containing alkali cannot be corked with glass and rubber stopper) At high temperatures, silica can be reduced by carbon, magnesium and aluminum: Sio +2C = (high temperature) Si + 2Co

The properties of silica should be examined. Silica reacts with quicklime, which is often used to remove silica from ores used to refine metals, and silica is also the main material for glass.

Add some SiO2 with high melting point and high hardness. Not easily soluble in water.

Silica vs. basic oxide: SiO2 + Cao == High temperature == Casio3

Silica is soluble in a strong alkaline solution with concentrated heat: SiO2 + 2 NaOH = Na2SiO3 + H2O

The reason why the reagent bottle containing alkali can not be corked with glass and rubber can be stored with rubber stopper) At high temperature, silica can be reduced by carbon, magnesium and aluminum: SiO2 + 2 C == High temperature == Si + 2 CO

If C is excessive, a reaction occurs: Si + C == High temperature == SiC (emery) silica does not react with water, that is, it does not form silicic acid in contact with water.

It does not interact with halogens, hydrogen halides, as well as sulfuric acid, nitric acid, perchloric acid other than fluorine, hydrogen fluoride can dissolve silica acid: 4 HF + SiO2 = SIF4 + 2 H2O

SiO2 is also known as silica. It is widely distributed in nature, such as quartz, quartz sand, etc. White or colorless, with a higher iron content being pale yellow.

Density: melting point 1670 (lemosmosilica); 1710 (cristobalt). Boiling Point: 2230Insoluble in water and acids (except hydrofluoric acid), it can work with melt and alkali when particles.

It is used in glass, water glass, pottery, enamel, refractory materials, ferrosilicon, molding sand, elemental silicon, etc.