silica is a colorless transparent crystal or amorphous powder and is tasteless. The melting point is 1710 ° C. (cristobalite),1670 ° C. (titrimetric quartz), and the boiling point is 2230 ° C. Almost insoluble in water, common acid, can be dissolved in hydrofluoric acid to generate silicon fluoride gas, slowly with the heat of concentrated phosphoric acid. The amorphous powder can function with a base. The physical and chemical properties are stable, easy to form, inert, the melt is layered, and the expansion coefficient is small when heated

This strain reacts sodium silicate with acid (such as hydrochloric acid, sulfuric acid, phosphoric acid, etc.) or with salt (such as ammonium chloride, ammonium sulfate, ammonium bicarbonate, etc.), silicic acid precipitates (I. E., hydrated silica) are produced by washing with water, removing impurities, and drying. The content & 0 2 shall not be less than 99.0% based on the calculation of the ignition product.

using tetraethyl orthosilicate as a raw material, tetraethyl orthosilicate was first subjected to high-efficiency rectification, and a fraction at 160-168 ° C. Was collected. Then, the tetraethyl orthosilicate and ammonia are mixed and heated in a certain proportion, and the reaction mixture is sufficiently stirred, and the reactant will change from turbid to viscous until the solution is boiled, the stirring is stopped, and the solution is left to settle, after centrifugation, it was dried at low temperature for a certain period of time, then burned at 900 ° C. And cooled naturally.

A masking film and a protective layer for impurity diffusion in transistors and integrated circuits. As a filler used in epoxy casting, optical fibers, coatings and other fields. It can also be used in the manufacture of glass, emission spectrum analysis reagent, and the control of antimony concentration in the production of antimony in solid state circuit.

take about 5mg of this product, put it in a platinum crucible, add 200mg of potassium carbonate, mix well, burn it at 600~700°C for 1 0 min, cool it, add 2M l of water to dissolve it with slight heat, slowly add human ammonium molybdate test solution (take molybdic acid 6. 5G, add 14ml of water and ammonia water 1 4 .5 m l, shake to dissolve, cool, slowly add a cooled mixture of 32ml nitric acid and 40ml water under stirring, let stand for 48 hours, filter, and take the filtrate, 2ml, the solution was dark yellow.

stored in a dry warehouse.

Take 10g of this product, according to the particle size and particle size distribution determination method [general principles 0982 second method (1 ) ] inspection, through the seven sieve (125Mm) of the test quantity should not be less than 85%.

take l g of this product, add water 20 m l, shake, filter, take the filtrate, according to the law (General 0631),p H value should be 5 .0 to 7. 5. Nitride take 0801g of this product, add water 50ml, heat reflux for 2 hours, cool, add water to make up to 50ml, shake, filter, take the filtrate 10ml, check according to law (general rule), with standard sodium chloride solution 10. Compared with the control solution made of 0M l, it should not be deeper (0.1%).

Take 10ml of the filtrate under the chloride item, check according to law (General Rule 0 8 0 1 ) , and standard potassium sulfate solution 5. Compared with the control solution made of 0M l, it should not be deeper (0. 5%).

take this product, dry at 145°C for 2 hours, weight loss shall not be '5 .0% (General rule 0831).

The Test product l left under the item of loss of drying is taken. O g, precision weighing, in the lOOtTC ignition for 1 hour, loss of weight should not exceed the dry product weight 8. 5%.

take this product 0. 2G, add water 25ml, hydrochloric acid 2M l and nitric acid 5 drops, boil for 5 minutes, let cool, filter, wash the filter with a small amount of water, combine the filtrate and wash, add ammonium persulfate 50mg, add water to dilute to 35ml, check according to law (General 0807), and standard iron solution 3. Compared with the control solution made of 0M l, it should not be deeper (0.015%).

take this product 3. 3G, add 40ml of water and 5ml of hydrochloric acid, slowly heat and boil for 15 minutes, let cool, filter, the filtrate is placed in a 100ml measuring flask, wash the filter with an appropriate amount of water, wash the washing solution into the measuring flask, add water to dilute to the scale, shake well, take 20ml, add 1 drop of phenolphthalein indicator solution, add ammonia solution Dropwise to light red color, add 2M l acetate buffer (pH 3.5) and appropriate amount of water to make 25ml, inspection according to law (General Principles 0821, Law 1), containing heavy metals shall not exceed 30 parts per million.

Take 20ml of the solution under the heavy metal item, and add hydrochloric acid to check according to law (General rule 0822 first law), which shall comply with the regulations (0.0003%).

Take lg of this product, weigh it accurately, place it in a platinum crucible that has been burned to constant weight at 1000°C, burn it at 1000°C for 1 hour, take it out, cool it, the residue was wetted with water, hydrofluoric acid (10ml) was added dropwise, evaporated to dryness on a water bath, allowed to cool, and then human hydrofluoric acid (10ml) and sulfuric acid (0ml) were added. 5ml, evaporated to near dryness on a water bath, transferred to an electric furnace, slowly heated until the acid vapor was removed, burned to constant weight at 1000°C, let go cold, accurately weighed, lost weight, that is, the weight of the test amount containing 0 2.

pharmaceutical excipients, glidants and suspending agents.

sealed storage.