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Method for measuring free silicon dioxide in air, such as dust, electric heating plate, silicon carbide heating plate
Date of publication：2021-05-05

Measurement method of free silica in the air of workplace, such as dust, limestone, ore, etc.~A good helper for adjustable electric heating plate and silicon carbide electric heating plate

Free silicon dioxide determination ~ a good helper for silicon carbide heating plate and electric heating plate ! !

Determination of Free Silica

D⒔1 Method Summary

Use the properties of pyrophosphoric acid that can dissolve various ores at a temperature of 245 to 250 ℃, but cannot dissolve quartz silica to determine the content of free silica.

D⒔2 Analysis step

Weigh 0.1g sample into a 50mL Erlenmeyer flask, add 15mL pyrophosphoric acid, use a glass rod until all the sample powder is soaked in acid, insert a thermometer into it and place it on a low electric furnace or electric hot plate, and heat To 250℃, in the heating process, stir with a glass rod at all times, and keep the temperature at 245～250℃ for 15min, remove and cool to 100～150℃, move it into the cooling tank and continue to cool to 50～60℃, take it out, and put the inside Pour the dissolved substance dropwise into a 250mL beaker containing 100mL of distilled water, and then wash the Erlenmeyer flask with water. At this time, the volume is 150～200mL, boil it, filter it with dense filter paper while it is hot, and wash it with 0.1mol/L hydrochloric acid for 3～ Times, and then washed with distilled water until there is no chloride ion reaction. Put the filter paper and the precipitate into a porcelain crucible with a known constant amount for ashing, burn and cool for weighing. For accurate measurement, wash with hot water until there is no phosphate ion (usually 20 times or use a solution of ammonium molybdate and ascorbic acid to check). Put the precipitate into a clean platinum crucible with a known constant amount, first ash on an electric furnace, then burn it in a high-temperature furnace at 900～950℃ for 30 minutes, cool, weigh, and then drop sulfuric acid (1+1) into the platinum crucible ), soak all the silica with sulfuric acid, then add 5-10mL of hydrogen acid, put it on the sand bath and heat it until it evaporates and no white smoke is emitted, then burn it in a high-temperature furnace at 900-950℃ for 20 minutes , Cooling and weighing, the secondary weight difference is the mass of free silica.

D⒔3 The mass percentage of free silica is calculated as follows:

m1 ×m2

XSiO2 =——————×100

m

Where: m1—weight of residue and platinum crucible before hydrogen acid treatment, g;

m2— weight of residue and platinum crucible after hydrogen acid treatment, g;

m—mass of sample, g.

D⒔4 Attention:

When preparing pyrophosphoric acid, heat 85% phosphoric acid (secondary product) to boiling and gradually evaporate part of the water to 250°C and no more bubbles. Let it cool for use. Note that the temperature should reach 250°C, not low. At 150°C, it should not be lower than 150°C, because it starts to lose crystal water and transform into pyrophosphate when it is higher than 150°C.

If the sample contains sulfide, you need to add several milligrams of ammonium nitrate crystals when the pyrophosphoric acid solution is heated to dissolve, and heat at 120～170℃. When the ammonium nitrate decomposes, it will oxidize the sulfide and emit a brown gas of nitrogen dioxide at the same time. Keep this temperature for a while, so that the sulfide is completely dissolved and then increase the temperature (note that the temperature should not be too high, otherwise it will cause an explosion).

If the sample contains carbonate, it must be heated from low temperature after adding acid, otherwise the sample will splash out if the effect is too strong, causing inaccurate analysis.

The temperature and time for dissolving pyrophosphoric acid is 15min at 245～250℃. When the temperature exceeds 252°C, a colloidal precipitate will form, and the sample must be redone.

When diluting, the speed should not be too fast or too slow, it should be poured drop by drop.

*Instrument in the experiment:

silicon carbide electric heating plate, adjustable electric heating plate, adjustable electric
heating plate

NanoHeat Silicon Carbide Heating Plate

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project equipment name and

model/parameters

Laboratory nano heating plate

HTL-400EXT


workbench size (material)

440*340 (high-density silicon carbide board )

400*300 (heating zone)

set temperature

RT-360℃

temperature

controller split temperature control system, intelligent program segmented PID control

temperature control accuracy

±0.1℃

time setting

1min~999hr

working voltage

AC220V/50Hz

technical parameters: model HTL-400EXT

★ heating fabric: high-density carbonization Silicon plate

★Heating method: Nano thermal energy technology (no mechanical heating components)

★Power requirement: 220-240V AC, 50/60 Hz

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★ Heating zone: 400 (length) x 300 (width) mm

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★ Temperature control accuracy: +/- 1 ℃

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Product features:

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(1) Technical indicators:

Project equipment name

HTL-400EXT

workbench size (material)

440*340 (high-density silicon carbide board)

400*300 (heating zone)

setting temperature

RT-360℃

temperature

controller split temperature control system, Intelligent PID program section control

temperature control accuracy

±0.1℃,

time setting

1min~999hr

working voltage

AC220V/50Hz

heating power

1.5KW

outline size

440*340*70
(three) after-sales service commitment
1) Quality assurance: manufacturer for sales The equipment undertakes quality assurance to protect the buyer's rights and interests from loss. If the equipment fails within the warranty period, the instrument will be provided with free warranty service (non-human factors), and the warranty period is one year.

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(4) After-sales service

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high temperature 500C° high temperature adjustable piezoelectric hot plate,

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1. The plate surface is made of German Schott microcrystalline ceramic or Silicon carbide board is resistant to various acids and alkalis and corrosion;

2. Nano thermal energy technology, fast heating, heating rate calculation of 5 degrees per second;

3. Nano ceramic heating element, super far-infrared heat radiation, strong penetrating power;

4. , a large heating area, uniform temperature; no mechanical heating element, no magnetic interference;

five, microcrystalline ceramic thermal shock heating panel 700 degrees, the expansion coefficient is equal to 0, and the length may be

continuously between dry;

a, the HTL series of laboratory Nano heating plate, adjustable piezoelectric heating plate,

natural marble casing, PTFE power cord and components, the whole machine is resistant to strong acid and alkali;

(1) Use:

laboratory nano heating plate is widely used in medical and health, agriculture, soil, and environmental protection , Food, scientific research institutes, universities and colleges and other experiments and laboratories. Can be used for sample heating, baking, digestion, acid removal, etc.

(2) Performance:

Adjustable electric heating plate HTL-400

Nano thermal energy technology, no mechanical heating components, dry burning, no electromagnetic field interference and hazards, rapid heating to 5 ℃, only 1 second, only 18 minutes to reach 500, greatly improving work efficiency;

technical parameters: model HTL-400

★ Heating fabric: glass ceramic (Schott, Germany) or silicon carbide board

★Heating method: Nano thermal technology (no mechanical heating components)

★Power demand: 220-240V AC, 50/60 Hz

★Output power: 3000W

★Product size ：440 (L) x340 (W) x 70 (H) mm

★Heating area: 400 (L ) x 300 ( W) mm

★Temperature control range: room temperature -500℃

★Control system: Infinite voltage regulator controller

Product features:

☆By Driven by NanoHeat technology, the temperature rises to 5°C at an extremely fast speed in 1 second, and it only takes 18 minutes to reach 500°C.

☆No mechanical components, no electromagnetic field interference and harm, especially suitable for medical and laboratory use.

☆Save energy, the power consumption in standby state is less than 1W.

☆Suitable for most utensils, glass, ceramics, metal, all.

☆Easy to use, stepless voltage regulator controller, convenient for users.

☆Fashionable and beautiful appearance, luxurious atmosphere.

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(1) Technical indicators:

Project name

HTL-400

workbench size (material)

440*340 (microcrystalline ceramics, silicon carbide plate)

400*300 (heating zone)

setting temperature

RT-500℃

temperature

controller stepless voltage regulation control

Temperature control accuracy Stepless

temperature adjustment
time setting

No
working voltage

AC220V/50Hz

Heating power

3.0KW

Dimensions

440*340*70mm






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