1. Scope

This standard specifies the requirements, test methods, inspection rules, marking, labeling, packaging, transportation, and storage of Sodium Metabisulfite Industrial Grade.

This standard is applicable to Sodium Metabisulfite Industrial Grade, which is mainly used in industries such as printing and dyeing, organic synthesis, printing, tanning, pharmaceuticals, rare metal mining, and sewage treatment.

2. Referenced standards

The clauses in the following documents become the clauses of this standard through reference. For dated reference documents, all subsequent amendments (excluding corrected content) or revisions are not applicable to this standard. However, parties to agreements based on this standard are encouraged to study whether the latest versions of these documents can be used. For undated references, the latest version applies to this standard.

GB/T 191-2000 Packaging, Storage and Transportation Pictorial Symbols (eqv ISO 780:1997)

GB/T 610.1-88 Chemical reagent – General method for the determination of divine content (plaque method)

GB/T 1250 Representation and Judgment Methods for Limit Values

GB/T 3049-2006 General Method for the Determination of Iron Content in Industrial Chemical Products -1,10-Phenanthroline Spectrometric Method (idt ISO 6685:1982)

GB/T 6678 General rules for sampling chemical products

GB/T 6682-92 Specification and Test Methods for Analytical Laboratory Water (eqv ISO 3696:1987)

GB/T 8946-98 Plastic Woven Bags

GB/T 8947-98 Composite Plastic Woven Bags

HG/T 3696.1 Preparation of Standard Titration Solutions for Chemical Analysis of Inorganic Chemical Products

HG/T 3696.2 Preparation of impurity standard solutions for chemical analysis of inorganic chemical products

HG/T 3696.3 Preparation of formulations and products for chemical analysis of inorganic chemical products

3. Molecular formula and relative molecular weight

Molecular formula: Na2S2O5

Relative molecular weight: 190.10 (according to the 2005 international relative atomic mass)

Sodium Metabisulfite Chemical Industry Standard (2)

4. Requirements

4.1 Appearance: Sodium Metabisulfite Industrial Grade is a white or slightly yellow crystalline powder.

4.2 Sodium Metabisulfite Industrial Grade should meet the requirements of Table 1:

Table 1 requirements                             The unit to be a percentage (%)

Item Specification
Premium Grade First Grade
Main Content(Na2S2O5 96. 5 95. 0
Water Insoluble 0. 05 0.05
Iron (Fe) 0. 005 0. 010
Arsenic(As) 0.0001

5. Test methods

5.1 Safety tips

Some of the reagents used in this test method are toxic or corrosive, and operators must be cautious! If splashed onto the skin, rinse immediately with water, and in severe cases, seek immediate treatment. When using flammable materials, it is strictly prohibited to use open flames for heating.

5.2 General provisions

The reagents and water used in this standard, unless otherwise specified, refer to analytical pure reagents and Grade III water as specified in GB/T 6682-1992.

The standard solution, impurity standard solution, formulation, and product required in the experiment shall comply with HG/T 3696.1, HG/T 3696.2 and HG/T 3696.3 unless otherwise specified.

5.3 Appearance discrimination

Under natural light, visually distinguish the sample taken.

5.4 Determination of main content

5.4.1 Method Summary

Add an excess of iodine standard solution to a certain amount of sample solution, and in a weakly acidic solution, use metabisulfite to reduce iodine to iodine ions. Using starch as an indicator, titrate excess iodine with sodium thiosulfate standard titration solution.

5.4.2 Reagents

5.4.2.1 Iodine standard solution: c (1/2I2) is approximately 0.1 mol/L.

5.4.2.2 Sodium thiosulfate standard titration solution: c (Na2S2O3) is approximately 0.1 mol/L.

5.4.2.3 Acetic acid solution: 1+3.

5.4.2.4 Starch indicator solution; 5g/L.

5.4.3 Analysis steps

Quickly weigh approximately 0.2 g of the sample to the nearest 0.0002 g, was put into a 250 mL iodine measuring bottle that was added 50 mL of iodine standard solution and 30 mL of water with a pipette in advance, 5 mL of acetic acid solution was added, the bottle stopper was immediately covered, water sealed, slowly shaken to dissolve, and placed in a dark place for 5 minutes. Titrate with sodium thiosulfate standard titration solution, add approximately 2 mL of starch indicator solution near the endpoint, and continue titrating until the blue color of the solution disappears as the endpoint.

Use a pipette to take 50 mL of iodine standard solution, and carry out blank test under the same conditions.

5.4.4 Result calculation

The main content is calculated as the mass fraction ω1 of sodium metabisulfite (Na2S2O5), and the value is expressed in %, calculated according to formula (1):

sodium metabisulfite main content formula

V0— The numerical value of the volume of sodium thiosulfate standard titration solution consumed for titrating the blank test solution, in milliliters (mL);

V1— The numerical value of the volume of sodium thiosulfate standard titration solution consumed in the titration test solution, in milliliters (mL);

c— The actual concentration value of sodium thiosulfate standard titration solution, in moles per liter (mol/L);

m— The numerical value of the sample mass, in grams (g);

M— Molar mass value of sodium metabisulfite (1/4 Na2S2O5), in grams per mole (g/mol) (M=47.52).

Take the arithmetic mean of the parallel measurement results as the measurement results, and the absolute difference between the two parallel measurement results shall not be greater than 0.2%.

5.5 Determination of iron content

5.5.1 Principle

Same as Chapter 3 of GB/T 3049-2006.

5.5.2 Reagents and Solutions

Same as Chapter 4 of GB/T 3049-2006.

5.5.3 Instruments and Equipment

Same as Chapter 5 of GB/T 3049-2006.

5.5.4 Analysis steps

5.5.4.1 Drawing of standard curves

According to GB/T 3049-2006 Section 6 According to the regulations of 3, use a colorimetric dish with an optical path of 4cm or 5cm and the corresponding amount of iron standard solution to draw the working curve.

5.5.4.2 Preparation of test solution

Weigh approximately 3 g of the sample to the nearest 0.01 g. Place in a 250 mL tall beaker, dissolve with a small amount of water, add 25 mL of hydrochloric acid solution, and evaporate to dryness in a boiling water bath. Dissolve the residue with water, transfer all into a 250mL volumetric flask, dilute with water to the scale, and shake up.

5.5.4.3 Preparation of blank test solution

In a 250mL tall beaker, add a small amount of water, add 25mL hydrochloric acid, evaporate it in a boiling water bath, dissolve the residue with water, transfer all of it into a 250mL volumetric flask, dilute it with water to the scale, and shake it up.

5.5.4.4 Determination

Use a pipette to take 50 mL of test solution and blank test solution and place them in 100 mL volumetric flasks respectively. Follow 6.4.1 of GB/T 3049-2006. Start the operation by adding water to 60 mL if necessary.

5.5.5 Result calculation

The iron content is calculated as the mass fraction of iron (Fe) ω2, and the value is expressed in %, calculated according to formula (2):

iron content of sodium metabisulfite formula

m1— The numerical value of the mass of iron in the test solution obtained from the working curve, in milligrams (mg);

m2— The numerical value of the mass of iron in the blank test solution obtained from the working curve, in milligrams (mg);

m— The numerical value of the sample mass, in grams (g).

Take the arithmetic mean of the parallel determination results as the determination results. The absolute difference between the results of two parallel measurements shall not exceed 0.0005%.

5.6 Determination of water insoluble matter content

5.6 1. Instruments and equipment

5.6.1.1 Glass sand filter: The filter plate aperture is 5um~15um.

5.6.1.2 Electric drying oven: The temperature can be controlled between 105 ℃ and 110 ℃.

5.6.2 Analysis steps

Weigh approximately 20 g of the sample to the nearest 0.001g. Place in a 400 mL beaker and dissolve with approximately 100 mL of water. Filter with glass sand that has been dried to a constant mass at 105 ℃~110 ℃, wash the residue 4-5 times with water at 60 ℃~80 ℃, using approximately 30 mL of water each time. Dry the snail and residue at 105 ℃~110 ℃ until the mass remains constant.

5.6.3 Result calculation

The content of insoluble substances in water is calculated as a mass fraction of ω3, and the value is expressed in %, calculated according to formula (3):

sodium metabisulfite insoluble substances content formula

m1— The numerical value of the mass of the glass sand snail, in grams (g);

m2— The numerical value of the mass of water insoluble substances and glass sand tower collapse, in grams (g);

m— The numerical value of the sample mass, in grams (g).

Take the arithmetic mean of the parallel determination results as the determination results. The absolute difference between the results of two parallel measurements shall not exceed 0.005%.

5.7 Determination of arsenic content

5.7.1 Method Summary

Same as Chapter 3 of GB 610.1-88.

5.7.2 Reagents

5.7.2.1 Hydrochloric acid.

5.7.2.2 Nitric acid.

5.7.2.3 Sulfuric acid.

5.7.2.4 Potassium iodide.

5.7.2.5 Arsenic free zinc particles.

5.7.2.6 Stannous chloride solution: 400 g/L.

5.7 2.7 Lead acetate cotton.

5.7.2.8 Mercury bromide test paper.

5.7.2.9 Arsenic standard solution: Arsenic standard solution: 1 mL containing arsenic (As) l ug, prepared before use.

Use pipette to transfer 1mL according to HG/T 3696 Place the tablet standard solution specified in 2 in a 1000 mL volumetric flask, dilute with water to the scale, and shake up.

5.7.3 Instruments

Same as Chapter 5 of GB 610.1-88.

5.7.4 Analysis steps

Weigh (1.00±0.01) Place g of the sample in a 250 mL beaker, dissolve 10 mL of water in the beaker, 2 mL of nitric acid and 1 mL of sulfuric acid in the beaker, evaporate on an electric furnace until white smoke comes out, and cool. Dissolve in an appropriate amount of water, transfer all to a wide mouthed or ground conical flask in a tranquilizer, add water to a volume of approximately 25 mL, add 3 mL of hydrochloric acid, and shake well. According to Chapter 6 of GB 610.1-88. The color presented should not be darker than the standard.

Sodium Metabisulfite Chemical Industry Standard (3)

6. Inspection Rules

6.1 All items specified in this standard are factory inspection items and should be inspected batch by batch.

6.2 Production enterprises use the same materials and basically the same production conditions to continuously produce or produce the same level of Sodium Metabisulfite Industrial Grade in the same team. Each batch of products does not exceed 50 tons.

6.3 Determine the number of sampling units in accordance with GB/T 6678. When sampling, insert the sampler vertically into the center of the packaging bag at 3/4 of the depth of the material layer for sampling. After mixing the collected samples, use the quartering method to reduce them to no less than 500 g, and pack them into two clean and dry wide mouth bottles with ground stoppers, sealed. Stick a label on the bottle, indicating the manufacturer’s name, product name, batch number, sampling date, and sampler’s name. One bottle is used as an experimental sample, and the other bottle is kept for future reference. The retention time is determined by the manufacturer according to actual needs.

6.4 Sodium Metabisulfite Industrial Grade should be inspected by the quality supervision and inspection department of the production plant in accordance with the requirements of this standard. The production plant should ensure that each batch of products leaving the factory meets the requirements of this standard.

6.5 If there are any indicators in the inspection results that do not meet the requirements of this standard, samples should be taken from twice the quantity of the packaging for retesting. Even if only one indicator does not meet the requirements of this standard, the entire batch of products will be considered unqualified.

6.6 Use the rounding comparison method specified in GB/T 1250 to determine whether the inspection results meet the standards.

7. Signs and labels

7.1 The packaging of Sodium Metabisulfite Industrial Grade should have firm and clear markings, including the manufacturer’s name, address, product name, net content, batch number or production date, this standard number, and the “rain proof” and “sun proof” markings specified in GB/T 191-2000.

7.2 Each batch of Sodium Metabisulfite Industrial Grade produced from the factory should be accompanied by a quality certificate, which includes: sodium metabisulfite manufacturer name, address, product name, net content, batch number or production date, proof of product quality compliance with this standard, and the serial number of this standard.

8. Packaging, Transportation, and Storage

8.1 Sodium Metabisulfite Industrial Grade is packaged in double layers, with an inner packaging made of polyethylene plastic film bags with a thickness of not less than 0.07 mm. The outer packaging is made of plastic woven bags that comply with GB/T 8946-1998 or composite plastic woven bags that comply with GB/T 8947-1998. Its performance and inspection methods should comply with the provisions of GB/T 8946. When packaging, after the air in the inner bag is discharged, use nylon rope or other ropes of equivalent quality to manually tie the mouth, and use nylon rope or other ropes of equivalent quality to sew the mouth of the outer bag. Each bag contains 25 kg or 50 kg net.

8.2 Sodium Metabisulfite Industrial Grade should be covered during transportation to avoid direct sunlight, rain, and moisture. Do not mix with oxidizing or flammable materials for transportation.

8.3 Sodium Metabisulfite Industrial Grade should be stored in a ventilated and dry warehouse to prevent rain and moisture. It shall not be mixed with oxidizing or flammable materials for storage.

For more information, pls view:

Sodium Metabisulfite Industrial Grade TDS

Sodium Metabisulfite SDS