GB 25576-2020National food safety standard - Food additives - Silicon dioxide (English PDF)

Foreword

This Standard replaces GB 25576-2010, "Food Additives - Silicon dioxide".

Compared with GB 25576-2010, the major changes of this Standard are as

follows.

-- Modify the indicator of loss on drying for Type-III products to not more than

7.0%;

-- Modify the drying time for the inspection method of loss on drying;

-- Modify the ignition time for the inspection method of loss on ignition;

-- Modify the reference method of lead content determination;

-- Modify the reference method of arsenic content determination.

National food safety standard - Food additive - Silicon

dioxide

1 Scope

This Standard applies to fumed silica that is produced by the gas phase method

(chlorosilane is hydrolyzed in the oxygen-hydrogen flame), silica gel and

hydrated silica gel that are produced by the gel method (reaction of sodium

silicate solution and acid), and precipitated silicon dioxide that is produced by

the precipitation method (reaction of sodium silicate solution and acid).

2 Molecular formula and relative molecular mass

3 Technical requirements

600 °C; cool; add 2 mL of water to dissolve. If necessary, heat up; then, slowly

add 2 mL of ammonium molybdate solution, to produce a dark yellow color.

A.3.2.2 Drop 1 drop of the dissolved sample in A.3.2.1 onto the filter paper;

evaporate the solution; add 1 drop of o-tolidine glacial acetic acid saturated

solution; then, put the filter paper on the ammonia; there shall be green spots.

A.4 Determination of silicon dioxide content

A.4.1 Method summary

After the sample is burned at 950 °C +/- 50 °C, heat excess hydrofluoric acid to

decompose the silicon dioxide, to react and produce fluorosilicic acid, which

escapes. Weigh after ignition; the lost mass is the silicon dioxide content.

A.4.2 Reagents and materials

A.4.3 Instruments and apparatuses

A.4.3.1 High temperature furnace. Control the temperature at 950 °C +/- 50 °C.

A.4.3.2 Platinum crucible. 50 mL.

A.4.4 Analysis steps

Use a platinum crucible that is fired to a constant mass at 950 °C +/- 50 °C to

weigh about 1 g of sample B (see A.6.2), accurate to 0.0002 g. Use an

appropriate amount of ethanol (about 2 mL) to wet the sample; add 5 ~ 6 drops

of sulfuric acid; add 10 mL of hydrofluoric acid to submerge the sample. Place

it on an electric furnace to evaporate until a large amount of white smoke

appears; cool it; add 5 mL of hydrofluoric acid; carefully reverberate the crucible

to rinse the inner wall; then, evaporate to dryness. Burn at 950 °C +/- 50 °C for

60 min +/- 5 min. Take it out; cool it in a desiccator; weigh it.

A.5 Determination of loss on drying

A.5.1 Instruments and apparatuses

A.5.1.1 Electrothermal constant-temperature drying oven. Control the

temperature at 105 °C +/- 2 °C.

A.5.1.2 Weighing bottle. dia. 60 mm x 30 mm.

A.5.2 Analysis steps

Use a weighing bottle that is dried at 105 °C +/- 2 °C to weigh 2 g ~ 3 g of the

sample (for Type-II, weigh 8 g ~ 10 g), accurate to 0.000 2 g. Transfer it into the

electrothermal constant-temperature drying oven; dry at 105 °C +/- 2 °C for 120

min +/- 5 min; cool in a desiccator; weigh. Keep this dried sample as sample A,

for use in the determination of loss on ignition in A.6.

A.5.3 Result calculation

Calculate the mass fraction w2 of loss on drying according to Formula (A.2).

Where.

A.6 Determination of loss on ignition

A.6.1 Instruments and apparatuses

A.6.2 Analysis steps

Weigh 1 g ~ 2 g of sample A (see A.5.2), accurate to 0.000 2 g; place it in a

porcelain crucible that is fired to a constant mass at 950 °C +/- 50 °C; burn it at

950 °C +/- 50 °C for 60 min +/- 5 min; cool in a desiccator; weigh. Keep this burnt

sample as sample B, for use in the determination of silicon dioxide content in

A.4.

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