Some standard content:
National Standard of the People's Republic of China
Sulphur for industrial use
and its testing methods
1 Subject content and scope of application
GB 2449-92
GB 2449~2458—81
GB 7683~7685-87
This standard specifies the technical requirements, test methods, inspection rules, and requirements for marking, packaging, transportation, storage and safety of industrial sulfur.
This standard applies to industrial sulfur obtained from pyrite and recovered from natural gas, oil refinery gas, etc. Industrial sulfur is used to manufacture sulfuric acid, dyes and rubber products, and is also used in industrial sectors such as medicine and pesticides. Chemical symbol: S
Relative atomic mass: 32.066 (according to the international relative atomic mass in 1987) Reference standards
GB 190
GB 601
Dangerous goods packaging mark
Chemical reagents Preparation of standard solution for titration analysis (volume analysis) Preparation of standard solution for impurity determination
Chemical reagents
GB 603
Chemical reagents
Preparation of preparations and products used in test methods GB6682 Laboratory water specifications
Technical requirements
Industrial sulfur is in the form of blocks, powders, granules and flakes, and its superior and first-class products should be yellow or pale yellow. 3.1
Industrial sulfur should not contain any mechanical impurities. 3.3 Industrial sulfur shall meet the requirements of Table 1: Table 1
Indicator Name
Sulfur (S)
Acidity (in H,SO)
Organic matter
Arsenic (As)
Iron (Fe)
Superior product
Approved by the State Bureau of Technical Supervision on July 9, 1992
%(m/m）
Qualified product
Implemented on June 1, 1993
Indicator Name
Sieve residue:
Aperture 150μm
Aperture 75μm
Superior product
Note: The sieve residue index in Table 1 is only used for powdered sulfur. 4 Test methods
GB2449—92
Continued Table 1
First-class products
%(m/m)
Qualified products
Unless otherwise specified, the reagents and water used in this standard are analytically pure reagents and grade 3 water that conforms to the provisions of GB6682. 4.1 Determination of sulfur content
4.1.1 Summary of methods
This standard uses the method of deducting the sum of the impurities (ash, acidity, organic matter and arsenic) to calculate the sulfur content in industrial sulfur. 4.1.2 Expression of analysis results
Sulfur content (w) is expressed as mass percentage and is calculated according to formula (1): w100 --- (w+w+ws+ws)
Wherein: w3 is the ash content measured according to 4.3, % (m/m); w4
is the acidity measured according to 4.4, % (m/m); ws is the organic matter content measured according to 4.5, % (m/m); w, is the argon content measured according to 4.6, % (m/m). The result should be expressed to two decimal places.
4.2 Determination of moisture
The determination of moisture is equivalent to the international standard ISO3426-1976 "Industrial sulfur - 4.2.1 Summary of the method
The sample is dried in an oven at 80℃, and the weight lost is the moisture. 4.2.2 Instruments and equipment
Ordinary laboratory instruments and
4.2.2.1 Weighing bottle, diameter 70 mm, height 35 mm. 4.2.2.2 Electric oven, temperature controllable at 80 ± 2°C. 4.2.3 Analytical steps
Determination of weight loss at -80°C.
(1)
Place the weighing bottle in an oven at 80 ± 2°C and dry for 2 h. Take it out, cool it, and weigh it to an accuracy of 0.001 g. Weigh about 25 g of the sample (5.3.4) in this weighing bottle to an accuracy of 0.001 g. Place the weighing bottle containing the sample in an electric oven at 80 ± 2°C and dry it for 3 h. Then take out the weighing bottle and place it in a desiccator, cool it, and weigh it to an accuracy of 0.001 g. Repeat the above steps until the difference between two consecutive weighings does not exceed 0.002 g. If the total drying time exceeds 16 h and the weight is still not constant, record the last soft weighing result. 4.2.4 Expression of analysis results
Water content (wz) is expressed as mass percentage and calculated according to formula (2): m×100
Wherein: m. -
mass of the sample before drying, g;
m--mass lost by the sample after drying, area. The result should be expressed to two decimal places
4.2.5 Allowable difference
GB 2449-92
Take the arithmetic mean of the two parallel determinations as the analysis result. The difference between the two parallel determination results shall not be greater than the provisions of Table 2. Table 2
Permanent content, %
>0.10~40.50
4.3 Determination of ash content
Allowable difference between two parallel determinations, %
The determination of ash content refers to the international standard ISO3425-~1975 "Industrial sulfur ~--Determination of ash content at 850~900℃". 4.3.1 Summary of the method
The sample is slowly burned in the air, then burned in a high-temperature electric furnace at a temperature of 800~850℃, cooled and weighed. 4.3.2 Instruments and equipment
Ordinary laboratory instruments and
4.3.2.1 Porcelain: 50mL.
4.3.2.2 Electric heating plate.
4.3.2.3 High-temperature electric furnace: the temperature can be controlled at 850±50℃. 4.3.3 Analysis steps
The porcelain is burned in a high-temperature furnace at 800~850℃ for 40min, taken out and placed in a desiccator, cooled to room temperature, and weighed until the difference between two consecutive weighings is no more than 0.0005g.
In this constant-weight porcelain crucible, weigh about 25g of the sample (5.3.4) to the nearest 0.05g. On an electric hot plate (or a clay triangle on a gas lamp), let the sulfur burn slowly. After the combustion is completed, move it to a high-temperature furnace and burn it at 800-850℃ for 40min. Take out the porcelain crucible, place it in a desiccator, cool it to room temperature, and weigh it until the difference between two consecutive weighings is no more than 0.0005g. 4.3.4 Expression of analysis results
Ash content (W:) is expressed as mass percentage and is calculated according to formula (3): W
Where; m. Sample mass, gt
Aash mass after ignition, 8,
A-moisture correction value, calculated by
4.3.5 allowable difference
100 wz
?AX 100
(h2 is the mass percentage of moisture). . (3)
Take the arithmetic mean of the two parallel determinations as the analysis result. The difference between the two parallel determination results shall not be greater than the provisions of Table 3. Table 3
>0. 007~≤0. 03
>0. 03~≤0. 07
>0. 07~≤0. 10
>0. 10~<0. 30
>0.30~≤0. 40
4.4 Determination of acidity
The determination of acidity is equivalent to the international standard ISO3704-1976 "Industrial sulfur 4.4.1 Method summary
Allowable error of two parallel determinations
Determination of acidity
%(m/m )
Titration method".
GB 2449--92
The acidic substances in sulfur are extracted with a water-isopropanol mixture and titrated with a sodium hydroxide standard titration solution using phenolphthalein as an indicator. 4.4.2 Reagents and materials
In addition to complying with the requirements of GB6682, the water used in the test should be boiled and cooled before use. 4.4.2.1 Isopropyl alcohol (HG1167).
4.4.2.2 Standard titration solution of sodium hydroxide (GB629): c (NaOH) = 0.05000mol/L. Prepare a solution of 0.5000mol/L in accordance with GB 601, dilute 10 times, and calibrate according to the method specified in the standard.
4.4.2.3 Ethanol solution of phenol butter (GB10729): 10g/L, prepared in accordance with GB603. 4.4.3 Instruments and equipment
General laboratory instruments and
4.4.3.1 Test sieve GB6003,R40/3 Series 4.4.4 Analysis Steps
4.4. 4. 1 Weigh about 25g of the sample that has passed the 250 μm test sieve, accurate to 0.1g, and place it in a 250 mL conical flask with a ground stopper. Add 25mL of isopropanol (4.4.2.1), cover the bottle stopper to completely wet the flask, then add 50mL of water, cover the bottle stopper, shake for 2min, leave it for 20min, shake it from time to time, add three drops of phenolic acid indicator solution, and use sodium hydroxide standard titration solution (4.4.2.2) to drop until it turns pink and keep it for 30s without fading.
4.4.4.2 Blank Test
At the same time as the determination, perform a blank test using the same amount of reagents in the same steps as the determination to correct the determination results. 4.4.5 Expression of analytical results
Acidity (w, in H2SO4) is expressed as mass percentage and calculated according to formula (4): (V - Vo) :c × 0.049.A × 100mol
-mass of sample weighed during determination, 8,
where: m. -
actual concentration of sodium hydroxide standard titration solution, mol/L, V——volume of sodium hydroxide standard titration solution consumed during determination, mL; V.
volume of sodium hydroxide standard titration solution consumed during blank test, mL, (4)
mass of sulfuric acid equivalent to 1.00mL sodium hydroxide standard titration solution [c(NaOH)=1.000mol/L>, expressed in grams, g$
-calculation (w is the mass percentage of water). A—Moisture correction value, with
1100-w2
4.4.6 Allowable difference
Take the arithmetic mean of two parallel determinations as the analysis result, and the difference between the two parallel determination results shall not be greater than the provisions of Table 4. Table 4
≤0.0020
>0. 002 0~≤0. 006 0
>0. 006 0~≤0. 020
4.5 Determination of organic matter content
Allowable difference of two parallel determinations
The determination of organic matter content refers to the international standard ISO2866-74 "Industrial Sulfur-4.5.1 Method Summary
Determination of total carbon content
The sample is burned in an oxygen stream to generate sulfur dioxide and sulfur trioxide, which are oxidized and absorbed in chromic acid and sulfuric acid solutions. 78
%(m/m)
titration method".
GB2449-92
The organic matter in the sample burns to generate carbon dioxide, which is absorbed by barium hydroxide solution and then titrated with phenolic acid and methyl red-methylene blue as indicators.
4.5.2 Reagents and materials
4.5.2.1 Chromium trioxide (HG 3-934) 500 g/L bath solution. 4.5.2.2 Sulfuric acid (GB 625); density about 1.84 g/cm2, concentration about 96% (m/m) solution. 4. 5. 2.3 Hydrogen peroxide (GB 6684) solution, analytical grade, about 60 g/L. 4.5.2.4 Barium hydroxide (GB630) solution: c[indicator.
This solution needs to be isolated from the carbon dioxide in the air by a trap tube filled with alkali asbestos. 4.5.2.5 Hydrochloric acid (GB622) standard titration solution: C(HCI)=0.05000mol/L, prepared according to GB601 to prepare a solution of c(HCI)=0.5000 mol/L, then diluted 10 times to obtain, and calibrated according to the method specified in the standard. 4.5.2.6 Sodium hydroxide (GB629) standard titration solution: c(NaOH)=0.05000mol/L, prepared according to GB601 to prepare a solution of c(NaOH)0.5000 mol/L, then diluted 10 times to obtain, and calibrated according to the method specified in the standard. 4.5.2.7 Methyl red-methylene blue mixed indicator: prepared according to GB603. 4.5.2.8 Phenolic acid indicator: 10g/L ethanol solution, prepared according to GB603. 4.5.2.9 Platinum asbestos: containing 5%~10% platinum.
4.5.2.10 Alkali asbestos.
4.5.2.11 Pure oxygen (without CO2), stored in a cylinder with a pressure reducing valve. 4.5.3 Instruments and equipment
Ordinary laboratory instruments and:
4.5.3.1 Combustion and absorption device
This device is used to make the sample burn completely, as shown in Figure 1. It includes:
A mercury seal (A), with an inner tube inserted 1 cm below the mercury surface. Three U-shaped tubes (Br, Bz, Bs), with two side tubes and ground plugs, the side tube diameter is 15 mm; the U-shaped tube height is 150 mm. Flowmeter (C), suitable for measuring oxygen flow of 20~~200 mL/min. Combustion tube (D), transparent quartz tube with an outer diameter of 15 mm and a length of 700 mm, a section of the tube with a length of 15 mm is reduced to a tubular furnace (E), the temperature can be controlled to 800~~900℃ during the combustion process. Tubular furnace (F), the temperature can be controlled to 400~500℃ during the combustion process. There are 6 gas washing bottles (G~G.), each with a capacity of 250mL. E
800~900°C400~5000
Electric cylinder to
Sealing valve
Figure 1 Combustion and absorption device
4.5.3.2 Porcelain boat: 88mm×12mm.
GB2449—92
4.5.3.3 Burette: 10mL, graduation value is 0.05mL4.5.4 Analysis steps
4.5.4.1 Preparation of combustion device
In the dry U-tubes B, and B: (4.5.3.1b), put alkali asbestos (4.5.2.10), and put a layer of glass wool on the alkali asbestos. Loosely fill the U-tube B2 (4.5.3.1b) with glass wool to capture the acid vapor generated during the measurement. If there is too much acid vapor, causing the barium hydroxide to be completely neutralized, replace the U-tube Bz with a sintered glass filter with a pore size of 15~40um, and re-measure. Unless it is necessary to open, the pores of the U-tubes B,, Bz and B: should be closed. Fill the scrubber Gz with at least 50 mL of chromium trioxide solution (4.5.2.1), and each of the scrubbers G: and G, with at least 50 mL of sulfuric acid solution (4.5.2.2).
Fill the combustion tube D with platinum asbestos (4.5.2.9), the length of which is slightly less than the length of the heating section of the tube furnace F. Connect the entire apparatus with a short rubber tube as shown in Figure 1. 4.5.4.2 Blank test
Raise the temperature of the tube furnace F and allow oxygen to flow through the apparatus at a flow rate of about 100 mL/min. About 30 minutes after the temperature of the tube furnace F reaches 400-450℃, remove the scrubbers Gs and G, add 20 mL of barium hydroxide solution, 40 mL of water and 5 mL of hydrogen peroxide solution to each, and then connect them back to the apparatus. These operations should be performed as quickly as possible to avoid absorbing carbon dioxide from the air.
While continuing to pass oxygen through the device at a flow rate of about 100mL/min, power on tube furnace E, raise the temperature to 400~~450℃, and maintain this temperature for about 10min, then continue to raise the temperature to 800~~900℃, and maintain this temperature for about 30min. Cut off the power supply of tube furnace E, continue to pass oxygen for about 30min, and then cut off the power supply of tube furnace F. Remove the washing bottles G and G, open the bottle caps, rinse with a small amount of water, add the washing liquid to the absorption liquid, and then perform blank titrations according to the following steps.
Use phenol anhydride solution (4.5.2.8) as an indicator and titrate the absorption solution with hydrochloric acid standard titration solution (4.5.2.5), stirring vigorously, and do not exceed the end point.
Then add two or three drops of methyl red-methylene blue mixed indicator to each washing bottle, accurately add a certain volume (generally 10.0 mL) of excess hydrochloric acid standard titration solution (4.5.2.5), spread evenly, and back titrate with sodium hydroxide standard titration solution (4.5.2.6). The hydrochloric acid standard titration solution consumed in the blank test should generally be less than 0.2 mL. Volume:
According to formula (5), calculate the volume V of the hydrochloric acid standard titration solution consumed in the two washing bottles G5 and G6 respectively. Vi-V2
Where: V. —The volume of the hydrochloric acid standard titration solution consumed in the blank test, mL; V, —The volume of the hydrochloric acid standard titration solution accurately added, mL; V2 —The volume of the sodium hydroxide standard titration solution consumed in the back titration, mL. (5)
Note: If the actual concentrations of the hydrochloric acid and sodium hydroxide standard titration solutions used are not exactly the same as those specified in 4.5.2,Corrections should be made during calculations. 4.5.4.3 Weighing and Combustion
Weigh 1-1.5 g of sample that has not been dried and has passed through a 250 μm test sieve to the nearest 0.01 g in a porcelain boat. Heat up tube furnace F and allow oxygen to flow through the device at a rate of about 100 mL/min. About 30 minutes after the temperature of tube furnace F reaches 400-450°C, remove gas washing bottles Gs and G and add 20 mL of barium hydroxide solution, 40 mL of water and 5 mL of hydrogen peroxide solution to oxidize any sulfites that may be generated. Then connect gas washing bottles Gs and G. back to the device. These operations should be performed as quickly as possible to avoid absorbing carbon dioxide from the air. Send the porcelain boat containing the sample to the unheated part of the combustion tube D before entering the tube furnace E. Immediately pass oxygen at a rate of 100 mL/min and heat up the tube furnace E. When the temperature of tube furnace E reaches 450℃, maintain this temperature and do not rise any more. Move tube furnace E slowly toward the porcelain boat to make the sulfur burn, and a small amount of carbonaceous matter will remain in the porcelain boat and combustion tube D. If the combustion is too intense, the chromium trioxide solution in the absorption bottle G may be withdrawn, and the oxygen flow rate should be increased to prevent it. If the sulfur sublimates outside the porcelain boat and condenses between the porcelain boat and platinum asbestos, move tube furnace E to make the sulfur burn completely. After the sulfur slowly burns, move tube furnace E to the position of heating the porcelain boat, raise the temperature to 800-900℃, heat the combustion tube D and the porcelain boat for about 30 minutes, so that the residual carbon burns and the carbonate decomposes. Cut off the power supply of tube furnace E, continue to pass oxygen for about 30 minutes, blow the device clean, and then cut off the power supply of tube furnace F.
4.5.4.4 Determination of released carbon dioxide
When all carbon dioxide is absorbed (by observing whether the precipitation in the washing bottle Gs.G: is complete), remove the washing bottles G, and G. Open the bottle cap, rinse with a small amount of water, and add the washing liquid into the absorption liquid. Then determine the carbon dioxide absorbed in the two washing bottles according to the following steps. Use the phenolic acid solution (4.5.2.8) as an indicator and titrate the absorption solution with the hydrochloric acid standard titration solution (4.5.2.5). Stir vigorously and do not drop past the end point.
Then add two or three drops of methyl red-methylene blue mixed indicator to each washing bottle, accurately add a certain volume (generally 10.0mL) of excess hydrochloric acid standard titration solution (4.5.2.5), shake well, and back-titrate and neutralize Gs, G with the sodium hydroxide standard titration solution (4.5.2.6). The volume of the hydrochloric acid standard titration solution (4 5. 2.5) consumed by the CO~ in the two scrubbing bottles is calculated according to formula (6): V3 V- Vs - V.
Wherein: V, the volume of the standard titration solution of beneficial acid consumed by ~ to neutralize CO-, mL, V, the volume of the standard titration solution of beneficial acid accurately added, mLV, the volume of the standard titration solution of sodium hydroxide consumed in the back titration, mLV. —The volume of the standard titration solution of hydrochloric acid consumed in the blank test obtained by formula (5), mL. +*.( 6 )
Note: If the actual concentrations of the hydrochloric acid and sodium hydroxide standard titration solutions used are not exactly the same as those specified in 4.5.2, corrections should be made during calculation. 4.5.5 Expression of analysis results
Organic matter content (ws) is expressed as mass percentage and calculated according to formula (7): 0. 000 3 · V
*A X.1. 25 × 100.bZxz.net
Wherein: 0.0003 — mass of carbon equivalent to 1.00mL hydrochloric acid standard titration solution [c(HC1)0.05000mol/L], expressed in grams, g1
V — total volume of hydrochloric acid standard titration solution consumed by the sample [i.e. the sum of V in formula (6)], mL; - amount of sample weighed, g;
A — moisture correction value, calculated based on 100 wz
(mass percentage of water);
1.25 — coefficient for converting carbon to organic matter. 4.5.6 Allowable difference
The arithmetic mean of the two parallel determinations shall be taken as the analysis result. The difference between the two parallel determination results shall not be greater than the provisions of Table 5. Table 5
Organic matter content
>0. 005 ~≤0. 030
>0.030~≤0.060
>0. 06~≤0. 20
0. 20~≤0. 50
4.6 Determination of arsenic content Diethyl dithiocarbamate silver photometric method The determination of arsenic content is equivalent to the international standard ISO3705-1976 "Industrial sulfosulfuric acid silver photometric method".
Allowable integral of two parallel determinations
Determination of arsenic content
%(m/m)
Dimethyl dithiocarbamate
GB 2449—92
This method is an arbitration method for the determination of arsenic content in industrial sulfur. 4.6.1 Summary of the method
The sample is dissolved in carbon tetrachloride and oxidized with bromine and nitric acid. In a sulfuric acid medium, arsenic is reduced to arsine with metallic zinc, and a pyridine solution of silver diethyldithiocarbamate absorbs arsine to generate a purple-red colloidal silver solution, which is then photometrically determined. The reaction formula is as follows:
AsH; + 6Ag(DDTC) 6Ag+ 3H(DDTC) +As(DDTC):4.6.2 Reagents and materials
4.6.2.1 Arsenic-free metallic zinc (GB2304): particle size 0.5~1mm or 5mm. Treat with 1+1 hydrochloric acid before use, then wash with distilled water.
4.6.2.2 Nitric acid (GB626): density 1.40 g/cm2. 4.6.2.3 Sulfuric acid (GB625) solution: 1+1 solution. 4.6.2.4 Sodium hydroxide (GB629) solution: 50 g/L. 4.6.2.5 Potassium iodide (GB1272) solution: 150-g/L. 4.6.2.6 Stannous chloride (GB638) solution: 400 g/L. Dissolve 40 g of stannous chloride dihydrate in 100 mL of hydrochloric acid with a concentration of c (HC1) = 9 mol/L.
4.6.2.7 Lead acetate (HG3--974) solution: 200 g/L. 4.6.2.8 Lead acetate cotton: soak the absorbent cotton with lead acetate solution (4.6.2.7), take it out and drain it, dry it at room temperature, and store it in a sealed container.
4.6.2.9 Azuronic acid-carbon tetrafluoride solution: the volume ratio of azuronic acid (GB1281) to carbon tetrafluoride (GB688) is 2:3. 4.6.2.10 Silver diethyldithiocarbamate pyridine solution (referred to as AgDDTC pyridine solution): 5 g/L pyridine solution. This solution should be stored in a sealed brown glass bottle and is valid for two weeks. 4.6.2.11 Arsenic standard solution: 0.100 g/L. Weigh 0.1320 g of arsenic trioxide (GB673) dried to constant weight in a sulfuric acid dryer, and refine boron to 0.0001 g. Place it in a 100 mL beaker and dissolve it with about 2 mL of sodium hydroxide solution (4.6.2.4). Quantitatively transfer this solution to a 1000mL volumetric flask, wash the beaker with water several times, add the washing solution to the volumetric flask, dilute with water to the mark, and shake well. 1 mL of this standard solution contains 100 μg of arsenic. 4.6. 2.12 Arsenic standard solution: 2.5 mg/L. Pipette 25.0mL of arsenic standard solution (4.6.2.11), place it in a 1000mL volumetric flask, dilute with water to the mark, and shake well. Prepare this solution when using it.
1mL of this solution contains 2.5μg of arsenic.
4.6.3 Instruments and equipment
The glassware used for arsenic determination must be washed with chromic acid cleaning solution. When washing, be careful not to splash the chromic acid cleaning solution on the eyes, skin and clothes. Then wash it thoroughly with water and dry it flat. Ordinary laboratory instruments and
4.6.3.1 Spectrophotometer. ：
4.6.3.2 Arsenic determination instrument, as shown in Figure 2, its components are: conical flask: volume 100mL, used to generate arsine, connecting tube: for capturing hydrogen sulfide
15 ball absorber: for absorbing arsine.
4.6.4 Analysis steps
GB 2449-92
Figure 2 Arsenic determination instrument
A—conical flask, B-connecting tube; C-15 ball absorber tube Based on the pyridine's properties and unpleasant odor, it must be operated with caution and should be carried out in a well-ventilated kitchen. Medical gloves should be worn when dissolving the sample.
4.6.4.1 Preparation of test solution
Weigh about 5g of sample (5.3.4), accurate to 0.1g, and place the sample in a 400mL beaker. In a well-ventilated hood, add 20 mL of bromine-carbon tetrachloride (4.6.2.9) to the beaker, let it stand for 45 min, and then add 25 mL of nitric acid (4.6.2.2) It can also be added several times to prevent the nitrous acid from escaping too quickly. For the first time, add about 5mL of nitric acid, cover with a watch glass, and shake well. Observe carefully, and when a little brown smoke comes out of the beaker, immediately place the beaker in ice water and shake it continuously until no obvious brown smoke comes out. Then add nitric acid again, and observe and operate in the same way until the nitric acid is completely dissolved and a small amount of bromine remains in the beaker. If the sulfur is not completely dissolved, use a few milliliters of bromine-carbon tetrachloride and nitric acid solution to continue dissolving. In order to remove excess bromine, carbon tetrachloride and nitric acid, place the beaker in a boiling water bath and heat until the solution is colorless and transparent. If the solution is turbid, add some nitric acid solution after cooling, and evaporate until no nitrous acid smoke escapes and the solution is colorless and transparent. Rinse the beaker with a small amount of water, place the beaker in a sand bath and evaporate until white sulfuric acid smoke escapes, and cool. Repeat this process three times to remove trace amounts of nitrite compounds. After cooling, dilute with water to about 80 mL and cool to room temperature. When the arsenic content in the sample is greater than 0.001% (m/m), transfer the test solution quantitatively to a 500 mL volumetric flask, dilute with water to the mark, and shake well. Accurately pipette 20.0 mL of the solution, place it in a conical flask for arsenic determination, add 10 mL of sulfuric acid solution (4.6.2.3) and 10 mL of water. When the arsenic content in the sample is between 0.00 1% and 0.000 1% (m/m), transfer the test solution quantitatively to a 100 mL volumetric flask, dilute with water to the mark, and shake well. Accurately pipette 20.0 mL of the solution, place it in a conical flask for arsenic determination, add 10 mL of sulfuric acid solution (4.6.2.3) and 10 mL of water.
When the arsenic content in the sample is less than 0.0001% (m/m), dilution is not required. Transfer all the test solution to the conical flask for arsenic determination, heat and concentrate to a volume of 40 mL, and no longer add sulfuric acid solution. 4.6.4.2: Blank test
At the same time as the determination, follow the same steps as the determination and use the same amount of all reagents to perform a blank test. 4.6.4.3 Drawing of the working curve
A working curve must be drawn every time a batch of metallic zinc is changed or a new AgDDTC pyridine solution is prepared. In 6 conical flasks for arsenic determination, add a certain volume of arsenic standard solution shown in Table 6 (4.6.2.12. Table 6
Volume of arsenic standard solution, mL
Note: 1) blank solution.
Corresponding monument mass, μg
Add 10mL sulfuric acid solution (4.6.2.3) to each conical flask for arsenic determination, add water to a volume of about 40mL, add 2mL potassium iodide solution (4.6.2.5) and 2mL stannous chloride solution (4.6.2.6), shake well, and let stand for 15 minutes. Insert a small amount of lead acetate cotton in each connecting tube to absorb the hydrogen sulfide that escapes with hydrogen sulfide. Apply a thin layer of vacuum grease on the ground glass joint. Absorb 5.0mL AgDDTC pyridine solution (4.6.2.10) into a 15-ball absorber.
After standing for 15 minutes, add 5g of metal zinc particles to the conical flask for arsenic determination with the help of a funnel, quickly connect the instrument as shown in Figure 2, and let it stand for 45 minutes to complete the reaction.
Disassemble the 15-ball absorber and shake it to dissolve the red precipitate formed in the lower part and mix the solution completely. This colored solution can be stable in the dark for about 2 hours, so the determination must be completed within 2 hours. At a wavelength of 540nm, use a 1cm absorption cell and a blank solution as a reference. After adjusting the absorbance of the spectrophotometer to zero, measure the absorbance of each standard solution. Draw a working curve with the mass of arsenic (ug) in the standard colorimetric solution as the horizontal axis and the corresponding absorbance as the vertical axis.
4.6.4.4 Determination
In the conical flask for arsenic determination containing 40mL of solution prepared according to step 4.6.4.1, add 2mL of potassium iodide solution (4.6.2.5) and 2mL of stannous chloride (4.6.2.6), spread evenly, and let it stand for 15 minutes. Then follow the steps in 4.6.4.3 from "insert a small amount of lead acetate cotton into each connecting tube" to "adjust the absorbance of the spectrophotometer to zero and measure the absorbance of the solution". 4.6.5 Expression of analysis results
According to the measured absorbance of the solution, find the corresponding arsenic mass (μg) from the working curve. 84
GB 2449-92
The content (w.) is expressed as mass percentage and calculated according to formula (8): W
-weighed sample mass + 8 +
Where: mo
n × 10-
the arsenic mass found from the working curve, ug-dilution multiple;
-water correction value, calculated according to
4.6.6 allowable difference
?K:AX 100
(w is the mass percentage of water).
Take the arithmetic mean of two parallel determinations as the analysis result. The difference between the two parallel determination results shall not be greater than the provisions of Table 7. Table 7
Arsenic content
>0. 001~≤0. 005
>0. 005~≤0. 010
>0. 01~≤0. 05
4.7 Determination of monument content
4.7.1 Summary of method
Gourd method
Allowed difference between two parallel determinations
%(m/m )
The sample is dissolved in carbon tetrachloride and oxidized with bromine and nitric acid. In sulfuric acid medium, use metallic zinc to reduce arsenic to arsenic hydrogen. Arsenic hydrogen forms red-brown spots on mercuric bromide test paper. Compare with the standard color scale to determine the arsenic content. 4.7.2 Reagents and materials
4.7.2.1 Arsenic standard solution: 1.00 mg/L. Accurately draw 5.0 mL of arsenic standard solution (4.6.2.11), place it in a 500 mL volumetric flask, dilute it to the scale with water, and shake it well. This solution is prepared when used.
1 mL of this standard solution contains 1 μg.
4.7.3 Instruments and equipment
Ordinary laboratory instruments and
4.7.3.1 Arsenic determination device: as shown in Figure 3.
4.7.4 Analysis steps
4.7.4.1 Preparation of test solution
GB 2449-92
Figure 3 Fixing device
A—Wide-mouth bottle; B—Rubber stopper; C—Glass tube, D—Upper end of glass tube; E—Glass phase The operation steps are the same as those specified in 4.6.4.1: only the phrase "placed in a conical flask for fixing the monument" in 4.6.4.1 is changed to "placed in a wide flask for fixing the monument".
4.7.4.2 Preparation of standard color scale
Pipette 0, 1.0, 2.0, 4.0.6.0, 8.0, 10.0mL of arsenic standard solution (4.7.2.1) respectively, place in the wide-mouth bottle of the arsenic analyzer, add 10mL of sulfuric acid solution (4.6.2.3), add water to the volume of about 40mL, then add 2mL of potassium iodide solution (4.6.2.5) and 2mL of stannous nitride solution (4.6.2.6), spread evenly, and let stand for 15min. Cut the mercuric bromide test paper (4.7.2.2) into a circle with a diameter of about 20mm in advance, place it between the upper port D and the glass cap E of the glass tube of the arsenic analyzer, and fix it with a rubber ring. Then add 5 more metal zinc to the wide-mouth bottle of the arsenic analyzer, quickly connect the instrument according to Figure 3, and let the reaction proceed for 45min. Take out the mercuric bromide test paper, mark the corresponding mass, permeate it with molten paraffin, and store it in a desiccator. 4.7.4.3 Determination
Add 2 mL potassium chloride solution (4.6.2.5) and 2 mL chlorinated chloride solution (4.6.2.6) to the wide-mouth bottle containing the test solution, shake well, and let it stand for 15 minutes. Then follow the steps in 4.7.4.2. "Pre-cut the mercuric bromide test paper (4.7.2.2) into a circle. ·\. Compare the obtained color spot with the standard color scale to measure the arsenic mass. 4.7.5 Expression of analysis results
Arsenic content (w,) is expressed as mass percentage and calculated according to formula (9): w
Weigh the mass of the sample, name,
In the formula; m. —-
-Measure the arsenic content in the test solution, μg
m X 10-6
K·AX 100It can also be added several times to prevent the nitrous acid from escaping too quickly. For the first time, add about 5mL of nitric acid, cover with a watch glass, and shake well. Observe carefully, and when a little brown smoke comes out of the beaker, immediately place the beaker in ice water and shake it continuously until no obvious brown smoke comes out. Then add nitric acid again, and observe and operate in the same way until the nitric acid is completely dissolved and a small amount of bromine remains in the beaker. If the sulfur is not completely dissolved, use a few milliliters of bromine-carbon tetrachloride and nitric acid solution to continue dissolving. In order to remove excess bromine, carbon tetrachloride and nitric acid, place the beaker in a boiling water bath and heat until the solution is colorless and transparent. If the solution is turbid, add some nitric acid solution after cooling, and evaporate until no nitrous acid smoke escapes and the solution is colorless and transparent. Rinse the beaker with a small amount of water, place the beaker in a sand bath and evaporate until white sulfuric acid smoke escapes, and cool. Repeat this three times to remove trace amounts of nitrous acid compounds. After cooling, dilute with water to about 80mL and cool to room temperature. When the arsenic content in the sample is greater than 0.001% (m/m), transfer the test solution quantitatively to a 500mL volumetric flask, dilute with water to the mark, and shake. Accurately pipette 20.0mL of the solution, place it in a conical flask for arsenic determination, add 10mL of sulfuric acid solution (4.6.2.3) and 10mL of water. When the arsenic content in the sample is between 0.00 1% and 0.000 1% (m/m), transfer the test solution quantitatively to a 100mL volumetric flask, dilute with water to the mark, and shake. Accurately pipette 20.0mL of the solution, place it in a conical flask for arsenic determination, add 10mL of sulfuric acid solution (4.6.2.3) and 10mL of water.
When the arsenic content in the sample is less than 0.0001% (m/m), dilution is not required. Transfer all the test solution to the conical flask for arsenic determination, heat and concentrate to a volume of 40 mL, and no longer add sulfuric acid solution. 4.6.4.2: Blank test
At the same time as the determination, follow the same steps as the determination and use the same amount of all reagents to perform a blank test. 4.6.4.3 Drawing of the working curve
A working curve must be drawn every time a batch of metallic zinc is changed or a new AgDDTC pyridine solution is prepared. In 6 conical flasks for arsenic determination, add a certain volume of arsenic standard solution shown in Table 6 (4.6.2.12. Table 6
Volume of arsenic standard solution, mL
Note: 1) blank solution.
Corresponding monument mass, μg
Add 10mL sulfuric acid solution (4.6.2.3) to each conical flask for arsenic determination, add water to a volume of about 40mL, add 2mL potassium iodide solution (4.6.2.5) and 2mL stannous chloride solution (4.6.2.6), shake well, and let stand for 15 minutes. Insert a small amount of lead acetate cotton in each connecting tube to absorb the hydrogen sulfide that escapes with hydrogen sulfide. Apply a thin layer of vacuum grease on the ground glass joint. Absorb 5.0mL AgDDTC pyridine solution (4.6.2.10) into a 15-ball absorber.
After standing for 15 minutes, add 5g of metal zinc particles to the conical flask for arsenic determination with the help of a funnel, quickly connect the instrument as shown in Figure 2, and let it stand for 45 minutes to complete the reaction.
Disassemble the 15-ball absorber and shake it to dissolve the red precipitate formed in the lower part and mix the solution completely. This colored solution can be stable in the dark for about 2 hours, so the determination must be completed within 2 hours. At a wavelength of 540nm, use a 1cm absorption cell and a blank solution as a reference. After adjusting the absorbance of the spectrophotometer to zero, measure the absorbance of each standard solution. Draw a working curve with the mass of arsenic (ug) in the standard colorimetric solution as the horizontal axis and the corresponding absorbance as the vertical axis.
4.6.4.4 Determination
In the conical flask for arsenic determination containing 40mL of solution prepared according to step 4.6.4.1, add 2mL of potassium iodide solution (4.6.2.5) and 2mL of stannous chloride (4.6.2.6), spread evenly, and let it stand for 15 minutes. Then follow the steps in 4.6.4.3 from "insert a small amount of lead acetate cotton into each connecting tube" to "adjust the absorbance of the spectrophotometer to zero and measure the absorbance of the solution". 4.6.5 Expression of analysis results
According to the measured absorbance of the solution, find the corresponding arsenic mass (μg) from the working curve. 84
GB 2449-92
The content (w.) is expressed as mass percentage and calculated according to formula (8): W
-weighed sample mass + 8 +
Where: mo
n × 10-
the arsenic mass found from the working curve, ug-dilution multiple;
-water correction value, calculated according to
4.6.6 allowable difference
?K:AX 100
(w is the mass percentage of water).
Take the arithmetic mean of two parallel determinations as the analysis result. The difference between the two parallel determination results shall not be greater than the provisions of Table 7. Table 7
Arsenic content
>0. 001~≤0. 005
>0. 005~≤0. 010
>0. 01~≤0. 05
4.7 Determination of monument content
4.7.1 Summary of method
Gourdun method
Allowed difference between two parallel determinations
%(m/m )
The sample is dissolved in carbon tetrachloride and oxidized with bromine and nitric acid. In sulfuric acid medium, use metallic zinc to reduce arsenic to arsenic hydrogen. Arsenic hydrogen forms red-brown spots on mercuric bromide test paper. Compare with the standard color scale to determine the arsenic content. 4.7.2 Reagents and materials
4.7.2.1 Arsenic standard solution: 1.00 mg/L. Accurately draw 5.0 mL of arsenic standard solution (4.6.2.11), place it in a 500 mL volumetric flask, dilute it to the scale with water, and shake it well. This solution is prepared when used.
1 mL of this standard solution contains 1 μg.
4.7.3 Instruments and equipment
Ordinary laboratory instruments and
4.7.3.1 Arsenic determination device: as shown in Figure 3.
4.7.4 Analysis steps
4.7.4.1 Preparation of test solution
GB 2449-92
Figure 3 Fixing device
A—Wide-mouth bottle; B—Rubber stopper; C—Glass tube, D—Upper end of glass tube; E—Glass phase The operation steps are the same as those specified in 4.6.4.1: only the phrase "placed in a conical flask for fixing the monument" in 4.6.4.1 is changed to "placed in a wide flask for fixing the monument".
4.7.4.2 Preparation of standard color scale
Pipette 0, 1.0, 2.0, 4.0.6.0, 8.0, 10.0mL of arsenic standard solution (4.7.2.1) respectively, place in the wide-mouth bottle of the arsenic analyzer, add 10mL of sulfuric acid solution (4.6.2.3), add water to the volume of about 40mL, then add 2mL of potassium iodide solution (4.6.2.5) and 2mL of stannous nitride solution (4.6.2.6), spread evenly, and let stand for 15min. Cut the mercuric bromide test paper (4.7.2.2) into a circle with a diameter of about 20mm in advance, place it between the upper port D and the glass cap E of the glass tube of the arsenic analyzer, and fix it with a rubber ring. Then add 5 more metal zinc to the wide-mouth bottle of the arsenic analyzer, quickly connect the instrument according to Figure 3, and let the reaction proceed for 45min. Take out the mercuric bromide test paper, mark the corresponding mass, permeate it with molten paraffin, and store it in a desiccator. 4.7.4.3 Determination
Add 2 mL potassium chloride solution (4.6.2.5) and 2 mL chlorinated chloride solution (4.6.2.6) to the wide-mouth bottle containing the test solution, shake well, and let it stand for 15 minutes. Then follow the steps in 4.7.4.2. "Pre-cut the mercuric bromide test paper (4.7.2.2) into a circle. ·\. Compare the obtained color spot with the standard color scale to measure the arsenic mass. 4.7.5 Expression of analysis results
Arsenic content (w,) is expressed as mass percentage and calculated according to formula (9): w
Weigh the mass of the sample, name,
In the formula; m. —-
-Measure the arsenic content in the test solution, μg
m X 10-6
K·AX 100It can also be added several times to prevent the nitrous acid from escaping too quickly. For the first time, add about 5mL of nitric acid, cover with a watch glass, and shake well. Observe carefully, and when a little brown smoke comes out of the beaker, immediately place the beaker in ice water and shake it continuously until no obvious brown smoke comes out. Then add nitric acid again, and observe and operate in the same way until the nitric acid is completely dissolved and a small amount of bromine remains in the beaker. If the sulfur is not completely dissolved, use a few milliliters of bromine-carbon tetrachloride and nitric acid solution to continue dissolving. In order to remove excess bromine, carbon tetrachloride and nitric acid, place the beaker in a boiling water bath and heat until the solution is colorless and transparent. If the solution is turbid, add some nitric acid solution after cooling, and evaporate until no nitrous acid smoke escapes and the solution is colorless and transparent. Rinse the beaker with a small amount of water, place the beaker in a sand bath and evaporate until white sulfuric acid smoke escapes, and cool. Repeat this three times to remove trace amounts of nitrous acid compounds. After cooling, dilute with water to about 80mL and cool to room temperature. When the arsenic content in the sample is greater than 0.001% (m/m), transfer the test solution quantitatively to a 500mL volumetric flask, dilute with water to the mark, and shake. Accurately pipette 20.0mL of the solution, place it in a conical flask for arsenic determination, add 10mL of sulfuric acid solution (4.6.2.3) and 10mL of water. When the arsenic content in the sample is between 0.00 1% and 0.000 1% (m/m), transfer the test solution quantitatively to a 100mL volumetric flask, dilute with water to the mark, and shake. Accurately pipette 20.0mL of the solution, place it in a conical flask for arsenic determination, add 10mL of sulfuric acid solution (4.6.2.3) and 10mL of water.
When the arsenic content in the sample is less than 0.0001% (m/m), dilution is not required. Transfer all the test solution to the conical flask for arsenic determination, heat and concentrate to a volume of 40 mL, and no longer add sulfuric acid solution. 4.6.4.2: Blank test
At the same time as the determination, follow the same steps as the determination and use the same amount of all reagents to perform a blank test. 4.6.4.3 Drawing of the working curve
A working curve must be drawn every time a batch of metallic zinc is changed or a new AgDDTC pyridine solution is prepared. In 6 conical flasks for arsenic determination, add a certain volume of arsenic standard solution shown in Table 6 (4.6.2.12. Table 6
Volume of arsenic standard solution, mL
Note: 1) blank solution.
Corresponding monument mass, μg
Add 10mL sulfuric acid solution (4.6.2.3) to each conical flask for arsenic determination, add water to a volume of about 40mL, add 2mL potassium iodide solution (4.6.2.5) and 2mL stannous chloride solution (4.6.2.6), shake well, and let stand for 15 minutes. Insert a small amount of lead acetate cotton in each connecting tube to absorb the hydrogen sulfide that escapes with hydrogen sulfide. Apply a thin layer of vacuum grease on the ground glass joint. Absorb 5.0mL AgDDTC pyridine solution (4.6.2.10) into a 15-ball absorber.
After standing for 15 minutes, add 5g of metal zinc particles to the conical flask for arsenic determination with the help of a funnel, quickly connect the instrument as shown in Figure 2, and let it stand for 45 minutes to complete the reaction.
Disassemble the 15-ball absorber and shake it to dissolve the red precipitate formed in the lower part and mix the solution completely. This colored solution can be stable in the dark for about 2 hours, so the determination must be completed within 2 hours. At a wavelength of 540nm, use a 1cm absorption cell and a blank solution as a reference. After adjusting the absorbance of the spectrophotometer to zero, measure the absorbance of each standard solution. Draw a working curve with the mass of arsenic (ug) in the standard colorimetric solution as the horizontal axis and the corresponding absorbance as the vertical axis.
4.6.4.4 Determination
In the conical flask for arsenic determination containing 40mL of solution prepared according to step 4.6.4.1, add 2mL of potassium iodide solution (4.6.2.5) and 2mL of stannous chloride (4.6.2.6), spread evenly, and let it stand for 15 minutes. Then follow the steps in 4.6.4.3 from "insert a small amount of lead acetate cotton into each connecting tube" to "adjust the absorbance of the spectrophotometer to zero and measure the absorbance of the solution". 4.6.5 Expression of analysis results
According to the measured absorbance of the solution, find the corresponding arsenic mass (μg) from the working curve. 84
GB 2449-92
The content (w.) is expressed as mass percentage and calculated according to formula (8): W
-weighed sample mass + 8 +
Where: mo
n × 10-
the arsenic mass found from the working curve, ug-dilution multiple;
-water correction value, calculated according to
4.6.6 allowable difference
?K:AX 100
(w is the mass percentage of water).
Take the arithmetic mean of two parallel determinations as the analysis result. The difference between the two parallel determination results shall not be greater than the provisions of Table 7. Table 7
Arsenic content
>0. 001~≤0. 005
>0. 005~≤0. 010
>0. 01~≤0. 05
4.7 Determination of monument content
4.7.1 Summary of method
Gourd method
Allowed difference between two parallel determinations
%(m/m )
The sample is dissolved in carbon tetrachloride and oxidized with bromine and nitric acid. In sulfuric acid medium, use metallic zinc to reduce arsenic to arsenic hydrogen. Arsenic hydrogen forms red-brown spots on mercuric bromide test paper. Compare with the standard color scale to determine the arsenic content. 4.7.2 Reagents and materials
4.7.2.1 Arsenic standard solution: 1.00 mg/L. Accurately draw 5.0 mL of arsenic standard solution (4.6.2.11), place it in a 500 mL volumetric flask, dilute it to the scale with water, and shake it well. This solution is prepared when used.
1 mL of this standard solution contains 1 μg.
4.7.3 Instruments and equipment
Ordinary laboratory instruments and
4.7.3.1 Arsenic determination device: as shown in Figure 3.
4.7.4 Analysis steps
4.7.4.1 Preparation of test solution
GB 2449-92
Figure 3 Fixing device
A—Wide-mouth bottle; B—Rubber stopper; C—Glass tube, D—Upper end of glass tube; E—Glass phase The operation steps are the same as those specified in 4.6.4.1: only the phrase "placed in a conical flask for fixing the monument" in 4.6.4.1 is changed to "placed in a wide flask for fixing the monument".
4.7.4.2 Preparation of standard color scale
Pipette 0, 1.0, 2.0, 4.0.6.0, 8.0, 10.0mL of arsenic standard solution (4.7.2.1) respectively, place in the wide-mouth bottle of the arsenic analyzer, add 10mL of sulfuric acid solution (4.6.2.3), add water to the volume of about 40mL, then add 2mL of potassium iodide solution (4.6.2.5) and 2mL of stannous nitride solution (4.6.2.6), spread evenly, and let stand for 15min. Cut the mercuric bromide test paper (4.7.2.2) into a circle with a diameter of about 20mm in advance, place it between the upper port D and the glass cap E of the glass tube of the arsenic analyzer, and fix it with a rubber ring. Then add 5 more metal zinc to the wide-mouth bottle of the arsenic analyzer, quickly connect the instrument according to Figure 3, and let the reaction proceed for 45min. Take out the mercuric bromide test paper, mark the corresponding mass, permeate it with molten paraffin, and store it in a desiccator. 4.7.4.3 Determination
Add 2 mL potassium chloride solution (4.6.2.5) and 2 mL chlorinated chloride solution (4.6.2.6) to the wide-mouth bottle containing the test solution, shake well, and let it stand for 15 minutes. Then follow the steps in 4.7.4.2. "Pre-cut the mercuric bromide test paper (4.7.2.2) into a circle. ·\. Compare the obtained color spot with the standard color scale to measure the arsenic mass. 4.7.5 Expression of analysis results
Arsenic content (w,) is expressed as mass percentage and calculated according to formula (9): w
Weigh the mass of the sample, name,
In the formula; m. —-
-Measure the arsenic content in the test solution, μg
m X 10-6
K·AX 1003) and 10mL water. When the arsenic content in the sample is between 0.00 1% and 0.000 1% (m/m), transfer the test solution quantitatively into a 100mL volumetric flask, dilute to the mark with water, and shake well. Accurately pipette 20.0mL of the solution into a conical flask for arsenic determination, add 10mL sulfuric acid solution (4.6.2.3) and 10mL water.
When the arsenic content in the sample is less than 0.0001% (m/m), no dilution is required. Transfer all the test solution into a conical flask for arsenic determination, heat and concentrate to a volume of 40mL, and no more sulfuric acid solution is added. 4.6.4.2: Blank test
At the same time as the determination, perform a blank test using the same steps as the determination and the same amount of all reagents. 4.6.4.3 Drawing of the working curve
A working curve must be drawn every time a batch of metallic zinc is changed or a new AgDDTC pyridine solution is prepared. In 6 conical flasks for arsenic determination, add a certain volume of arsenic standard solution (4.6.2.12) shown in Table 6. Table 6
Volume of arsenic standard solution, mL
Note: 1) Blank solution.
Corresponding mass of the monument, μg
Add 10mL of sulfuric acid solution (4.6.2.3) to each conical flask for arsenic determination, add water to a volume of about 40mL, add 2mL of potassium iodide solution (4.6.2.5) and 2mL of stannous chloride solution (4.6.2.6), shake well, and let stand for 15min. Insert a small amount of lead acetate cotton in each connecting tube to absorb the hydrogen sulfide that escapes with hydrogen sulfide. Apply a thin layer of vacuum grease on the ground glass joint. Absorb 5.0mL of AgDDTC pyridine solution (4.6.2.10) into a 15-ball absorber.
After standing for 15 minutes, add 5g of metal zinc particles to the conical flask for arsenic determination with the help of a funnel, quickly connect the instrument as shown in Figure 2, and leave it for 45 minutes to allow the reaction to complete.
Disassemble the 15-ball absorber, shake the absorber to dissolve the red precipitate formed in the lower part, and mix the solution completely. This colored solution can be stable in the dark for about 2 hours, so the determination must be completed within 2 hours. At a wavelength of 540nm, use a 1cm absorption cell and a blank solution as a reference. After adjusting the absorbance of the spectrophotometer to zero, measure the absorbance of each standard solution. Use the mass of arsenic (ug) in the standard colorimetric solution as the horizontal coordinate and the corresponding absorbance as the vertical coordinate to draw a working curve.
4.6.4.4 Determination
In the conical flask for arsenic determination containing 40mL of solution prepared according to step 4.6.4.1, add 2mL of potassium iodide solution (4.6.2.5) and 2mL of stannous chloride (4.6.2.6), spread evenly, and let it stand for 15 minutes. Then follow the steps in 4.6.4.3 from "insert a small amount of lead acetate cotton into each connecting tube" to "adjust the absorbance of the spectrophotometer to zero and measure the absorbance of the solution". 4.6.5 Expression of analysis results
According to the measured absorbance of the solution, find the corresponding arsenic mass (μg) from the working curve. 84
GB 2449-92
The content of arsenic (w.) is expressed as mass percentage and calculated according to formula (8): W
-weighed sample mass + 8 +
wherein: mo
n × 10-
the mass of arsenic found from the working curve, ug-dilution multiple;
-water correction value, calculated according to
4.6.6 allowable difference
?K:AX 100
(w is the mass percentage of water).
Take the arithmetic mean of the two parallel determinations as the analysis result, and the difference between the two parallel determination results shall not be greater than the provisions of Table 7. Table 7
Arsenic content
>0. 001~≤0. 005
>0. 005~≤0. 010
>0. 01~≤0. 05
4.7 Determination of arsenic content
4.7.1 Summary of method
Gourmelin method
Allowance difference between two parallel determinations
%(m/m )
The sample is dissolved in carbon tetrachloride and oxidized with bromine and nitric acid. In sulfuric acid medium, arsenic is reduced to arsenic hydrogen with metallic zinc. Arsenic hydrogen forms red-brown arsenic spots on mercuric bromide test paper. Compared with the standard color scale, the arsenic content is determined. 4.7.2 Reagents and materials
4.7.2.1 Arsenic standard solution: 1.00 mg/L. Accurately pipette 5.0mL of arsenic standard solution (4.6.2.11), place it in a 500mL volumetric flask, dilute to the mark with water, and shake well. Prepare this solution when using it.
1 mL of this standard solution contains 1 μg of arsenic.
4.7.3 Instruments and equipment
Ordinary laboratory instruments and
4.7.3.1 Arsenic analyzer: as shown in Figure 3.
4.7.4 Analysis steps
4.7.4.1 Preparation of test solution
GB 2449-92
Figure 3 Assay instrument
A—Wide-mouth bottle; B—Rubber stopper; C Glass tube, D—Upper end of glass tube; E—Glass phase The operation steps are the same as those specified in 4.6.4.1: only change "placed in a conical flask for determination" in 4.6.4.1 to "placed in a wide bottle for determination".
4.7.4.2 Preparation of standard color scale
Pipette 0, 1.0, 2.0, 4.0.6.0, 8.0, 10.0mL of arsenic standard solution (4.7.2.1) respectively, place in the wide-mouth bottle of the arsenic analyzer, add 10mL of sulfuric acid solution (4.6.2.3), add water to the volume of about 40mL, then add 2mL of potassium iodide solution (4.6.2.5) and 2mL of stannous nitride solution (4.6.2.6), spread evenly, and let stand for 15min. Cut the mercuric bromide test paper (4.7.2.2) into a circle with a diameter of about 20mm in advance, place it between the upper port D and the glass cap E of the glass tube of the arsenic analyzer, and fix it with a rubber ring. Then add 5 more metal zinc to the wide-mouth bottle of the arsenic analyzer, quickly connect the instrument according to Figure 3, and let the reaction proceed for 45min. Take out the mercuric bromide test paper, mark the corresponding mass, permeate it with molten paraffin, and store it in a desiccator. 4.7.4.3 Determination
Add 2 mL potassium chloride solution (4.6.2.5) and 2 mL chlorinated chloride solution (4.6.2.6) to the wide-mouth bottle containing the test solution, shake well, and let it stand for 15 minutes. Then follow the steps in 4.7.4.2. "Pre-cut the mercuric bromide test paper (4.7.2.2) into a circle. ·\. Compare the obtained color spot with the standard color scale to measure the arsenic mass. 4.7.5 Expression of analysis results
Arsenic content (w,) is expressed as mass percentage and calculated according to formula (9): w
Weigh the mass of the sample, name,
Where; m. ---
-Measure the arsenic content in the test solution, μg
m X 10-6
K·AX 1003) and 10mL water. When the arsenic content in the sample is between 0.00 1% and 0.000 1% (m/m), transfer the test solution quantitatively into a 100mL volumetric flask, dilute to the mark with water, and shake well. Accurately pipette 20.0mL of the solution into a conical flask for arsenic determination, add 10mL sulfuric acid solution (4.6.2.3) and 10mL water.
When the arsenic content in the sample is less than 0.0001% (m/m), no dilution is required. Transfer all the test solution into a conical flask for arsenic determination, heat and concentrate to a volume of 40mL, and no more sulfuric acid solution is added. 4.6.4.2: Blank test
At the same time as the determination, perform a blank test using the same steps as the determination and the same amount of all reagents. 4.6.4.3 Drawing of the working curve
A working curve must be drawn every time a batch of metallic zinc is changed or a new AgDDTC pyridine solution is prepared. In 6 conical flasks for arsenic determination, add a certain volume of arsenic standard solution (4.6.2.12) shown in Table 6. Table 6
Volume of arsenic standard solution, mL
Note: 1) Blank solution.
Corresponding mass of the monument, μg
Add 10mL of sulfuric acid solution (4.6.2.3) to each conical flask for arsenic determination, add water to a volume of about 40mL, add 2mL of potassium iodide solution (4.6.2.5) and 2mL of stannous chloride solution (4.6.2.6), shake well, and let stand for 15min. Insert a small amount of lead acetate cotton in each connecting tube to absorb the hydrogen sulfide that escapes with hydrogen sulfide. Apply a thin layer of vacuum grease on the ground glass joint. Absorb 5.0mL of AgDDTC pyridine solution (4.6.2.10) into a 15-ball absorber.
After standing for 15 minutes, add 5g of metal zinc particles to the conical flask for arsenic determination with the help of a funnel, quickly connect the instrument as shown in Figure 2, and leave it for 45 minutes to allow the reaction to complete.
Disassemble the 15-ball absorber, shake the absorber to dissolve the red precipitate formed in the lower part, and mix the solution completely. This colored solution can be stable in the dark for about 2 hours, so the determination must be completed within 2 hours. At a wavelength of 540nm, use a 1cm absorption cell and a blank solution as a reference. After adjusting the absorbance of the spectrophotometer to zero, measure the absorbance of each standard solution. Use the mass of arsenic (ug) in the standard colorimetric solution as the horizontal coordinate and the corresponding absorbance as the vertical coordinate to draw a working curve.
4.6.4.4 Determination
In the conical flask for arsenic determination containing 40mL of solution prepared according to step 4.6.4.1, add 2mL of potassium iodide solution (4.6.2.5) and 2mL of stannous chloride (4.6.2.6), spread evenly, and let it stand for 15 minutes. Then follow the steps in 4.6.4.3 from "insert a small amount of lead acetate cotton into each connecting tube" to "adjust the absorbance of the spectrophotometer to zero and measure the absorbance of the solution". 4.6.5 Expression of analysis results
According to the measured absorbance of the solution, find the corresponding arsenic mass (μg) from the working curve. 84
GB 2449-92
The content of arsenic (w.) is expressed as mass percentage and calculated according to formula (8): W
-weighed sample mass + 8 +
wherein: mo
n × 10-
the mass of arsenic found from the working curve, ug-dilution multiple;
-water correction value, calculated according to
4.6.6 allowable difference
?K:AX 100
(w is the mass percentage of water).
Take the arithmetic mean of the two parallel determinations as the analysis result, and the difference between the two parallel determination results shall not be greater than the provisions of Table 7. Table 7
Arsenic content
>0. 001~≤0. 005
>0. 005~≤0. 010
>0. 01~≤0. 05
4.7 Determination of arsenic content
4.7.1 Summary of method
Gourmelin method
Allowance difference between two parallel determinations
%(m/m )
The sample is dissolved in carbon tetrachloride and oxidized with bromine and nitric acid. In sulfuric acid medium, arsenic is reduced to arsenic hydrogen with metallic zinc. Arsenic hydrogen forms red-brown arsenic spots on mercuric bromide test paper. Compared with the standard color scale, the arsenic content is determined. 4.7.2 Reagents and materials
4.7.2.1 Arsenic standard solution: 1.00 mg/L. Accurately pipette 5.0mL of arsenic standard solution (4.6.2.11), place it in a 500mL volumetric flask, dilute to the mark with water, and shake well. Prepare this solution when using it.
1 mL of this standard solution contains 1 μg of arsenic.
4.7.3 Instruments and equipment
Ordinary laboratory instruments and
4.7.3.1 Arsenic analyzer: as shown in Figure 3.
4.7.4 Analysis steps
4.7.4.1 Preparation of test solution
GB 2449-92
Figure 3 Assay instrument
A—Wide-mouth bottle; B—Rubber stopper; C Glass tube, D—Upper end of glass tube; E—Glass phase The operation steps are the same as those specified in 4.6.4.1: only change "placed in a conical flask for determination" in 4.6.4.1 to "placed in a wide bottle for determination".
4.7.4.2 Preparation of standard color scale
Pipette 0, 1.0, 2.0, 4.0.6.0, 8.0, 10.0mL of arsenic standard solution (4.7.2.1) respectively, place in the wide-mouth bottle of the arsenic analyzer, add 10mL of sulfuric acid solution (4.6.2.3), add water to the volume of about 40mL, then add 2mL of potassium iodide solution (4.6.2.5) and 2mL of stannous nitride solution (4.6.2.6), spread evenly, and let stand for 15min. Cut the mercuric bromide test paper (4.7.2.2) into a circle with a diameter of about 20mm in advance, place it between the upper port D and the glass cap E of the glass tube of the arsenic analyzer, and fix it with a rubber ring. Then add 5 more metal zinc to the wide-mouth bottle of the arsenic analyzer, quickly connect the instrument according to Figure 3, and let the reaction proceed for 45min. Take out the mercuric bromide test paper, mark the corresponding mass, permeate it with molten paraffin, and store it in a desiccator. 4.7.4.3 Determination
Add 2 mL potassium chloride solution (4.6.2.5) and 2 mL chlorinated chloride solution (4.6.2.6) to the wide-mouth bottle containing the test solution, shake well, and let it stand for 15 minutes. Then follow the steps in 4.7.4.2. "Pre-cut the mercuric bromide test paper (4.7.2.2) into a circle. ·\. Compare the obtained color spot with the standard color scale to measure the arsen
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