Some standard content:
Chemical Industry Standard of the People's Republic of China
HG/T2822—1996
Lithium bromide solution for refrigerator
Published on December 25, 1996
Ministry of Chemical Industry of the People's Republic of China
Implementation on April 1, 1997
WHG/T2822—1996
Since there are no advanced foreign standards to adopt, this industry standard is based on the standards of major domestic enterprises and is determined according to actual production conditions and user requirements.
The differences from the existing enterprise standards are as follows:
1 The category of solution without lithium chromate that is no longer used has been cancelled. 2 According to the actual domestic situation, only one grade is stipulated, and its indicators are better than the current enterprise standard level. The two indicators of copper and lock content stipulated in some enterprise standards have been cancelled, and the carbonate indicator has been added according to user requirements. 5
The chloride content is deducted from the calculation of lithium bromide content. 4
This standard is proposed by the Technical Supervision Department of the Ministry of Chemical Industry of the People's Republic of China. This standard is under the jurisdiction of Tianjin Chemical Research Institute of the Ministry of Chemical Industry. The drafting units of this standard are: Tianjin Chemical Research Institute of the Ministry of Chemical Industry, Hunan Xiangtan Moore Chemical Co., Ltd., Shanghai Reagent Factory No. 2, Jiangsu Lianyungang Lithium Bromide Joint Venture Factory, Tianjin Chemical Reagent Factory No. 3, and Changshu Organic Chemical Research Institute of Jiangsu Province. The main drafters of this standard are: Wang Qi, Bao Hongda, Li Zhensheng, Yang Lairu, Xu Shanquan, and Wang Lin. This standard is entrusted to the technical unit responsible for the standardization of inorganic salt products of the Ministry of Chemical Industry for interpretation. I
W.1 Scope
Chemical Industry Standard of the People's Republic of China
Lithium Bromide Solution for Refrigerator
HG/T2822—1996
This standard specifies the requirements, sampling, test methods, marking, packaging, transportation and storage of lithium bromide solution for refrigerator. This standard applies to lithium bromide solution for refrigerator. This product is mainly used as an absorbent for absorption refrigerators. Molecular formula: LiBr
Relative molecular mass: 86.84 (according to the 1993 international relative atomic mass) 2 Reference standards
The provisions contained in the following standards constitute the provisions of this standard through reference in this standard. When this standard is published, the versions shown are valid. All standards will be revised, and the parties using this standard should explore the possibility of using the latest versions of the following standards. GB191—90 Pictorial symbols for packaging, storage and transportation
GB/T601-88 Preparation of standard solutions for titration analysis (volumetric analysis) of chemical reagents GB/T602—88
Preparation of standard solutions for determination of impurities in chemical reagents (neqISO6353/1:1982) Preparation of preparations and products used in test methods (neqISO6353/1:1982) GB/T603—88 Chemical reagents
GB/T1250—89
9 Methods for expressing and determining limit values GB/T6678—86 General rules for sampling of chemical products GB/T6682—92 Specifications and test methods for water for analytical laboratories (eqvISO3696:1987) GB/T 9724—88www.bzxz.net
8 General rules for determination of pH value of chemical reagents
3 Requirements
3.1 Appearance: yellow transparent liquid.
3.2 Lithium bromide solution for refrigerators shall meet the requirements of Table 1: Table 1 Requirements
Lithium bromide (LIBr) content, %
pH value (100g/L solution)
Lithium chromate (Li2Cro) content, %
Chloride (as C1) content, %
Sulfate (as SO) content, %
Bromoate (as BrO:) content, %
Approved by the Ministry of Chemical Industry of the People's Republic of China on December 25, 1996>|| tt||0.20~0.30
1997-04-01 implementation
W.bzsoso.coD item
Ammonium salt (NH3) content, %
Total content of potassium (K) and sodium (Na), %
Calcium (Ca) content, %
Magnesium (Mg) content, %
Iron (Fe) content, %
Carbonate (CO3) content, %
4 Sampling
4.1 Each batch of products shall not exceed 3t.
HG/T2822—1996
Continued Table 1
4.2 Determine the number of sampling units in accordance with the provisions of 6.6 of GB/T6678. When sampling, mix the product in the barrel, insert the glass sampling tube to 3/4 of the barrel, and seal the upper end after the sample is full, and take it out. The sample shall not be less than 500g. After mixing the collected samples, divide them into two clean and dry polyethylene plastic bottles and seal them. Stick labels on the bottles, indicating the manufacturer name, product name, batch number, sampling date and name of the sampler. One bottle is used as a laboratory sample, and the other bottle is kept away from light for three months for future reference. 4.3 If one of the indicators in the test results does not meet the requirements of this standard, re-sample from twice the amount of packaging for verification. If even one of the indicators in the verification results does not meet the requirements of this standard, the entire batch of products is unqualified. 5 Test method
5.1 The rounded value comparison method specified in 5.2 of GB/T1250 is used to determine whether the test results meet the standard. 5.2 The reagents and water used in this standard, unless otherwise specified, refer to analytical pure reagents and grade 3 water specified in GB/T6682.
The standard titration solutions, preparations and products used in the test, unless otherwise specified, shall be prepared in accordance with the provisions of GB/T601, GB/T602 and GB/T603.
5.3 Determination of lithium bromide content
5.3.1 Summary of the method
Under acetic acidic conditions, titrate with standard silver nitrate titration solution using sodium eosin as the indicator. 5.3.2 Reagents and materials
5.3.2.1 Acetic acid solution: 1+19;
5.3.2.2 Standard silver nitrate titration solution: c (AgNOs) about 0.1 mol/L; 5.3.2.3 Sodium eosin indicator solution: 5 g/L. 5.3.3 Analysis steps
Weigh about 0.5 g of the sample (accurate to 0.0002 g). Place in a 250mL conical flask, add water to 100mL, add 10mL acetic acid solution and 3 drops of sodium eosin indicator solution, and titrate with silver nitrate standard titration solution until it turns red. 5.3.4 Expression of analysis results
The lithium bromide (LiBr) content X1 expressed as mass percentage is calculated according to formula (1):2
WHG/T2822—1996
V ·cX0. 086 84×100Xs X2. 450Xi
V·cX8.684
-XsX2.450
Wherein: V——the volume of the standard silver nitrate solution consumed by the titration test solution, mL; the actual concentration of the standard silver nitrate solution, mol/L; (1)
0.08684——the mass of lithium bromide in grams equivalent to 1.00mL of the standard silver nitrate solution [c(AgNOs)=1.000mol/L];
——the mass of the sample, g;
——the chloride content in mass percentage measured according to 5.6; Xs
2.450——the coefficient for converting chlorine to lithium bromide. 5.3.5 Allowable difference
The arithmetic mean of the parallel determination results shall be taken as the determination result. The absolute difference of the parallel determination results shall not exceed 0.2%. 5.4 Determination of pH value
Weigh 10.0±0.1g of sample, add carbon dioxide-free water to 100mL, and determine according to the provisions of GB/T9724. 5.5 Determination of lithium chromate content
5.5.1 Summary of method
Under acidic conditions, chromate is converted into dichromate, potassium iodide is oxidized into iodine, and starch is used as an indicator liquid, and titrated with sodium thiosulfate standard titration solution.
5.5.2 Reagents and materials
5.5.2.1 Potassium iodide;
5.5.2.2 Sulfuric acid solution: 1+4;
5.5.2.3 Sodium thiosulfate standard titration solution: c (Na2S20s) about 0.1mol/L; 5.5.2.4 Starch indicator solution: 10g/L.
5.5.3 Instruments and equipment
5.5.3.1 Microburette: graduation value is 0.02 or 0.05mL. 5.5.4 Analysis steps
Weigh about 15g of sample (accurate to 0.01g), placed in a 250mL sulfuric acid volumetric flask. Add 25mL water, 2g potassium iodide and 10mL sulfuric acid solution, immediately cover with a stopper, seal with water, and shake well. Place in a dark place for 10min, add 100mL water not exceeding 10℃, and titrate with sodium thiosulfate standard titration solution. When approaching the end point, add 2mL starch indicator solution and continue titrating until the blue color turns bright green. At the same time, perform a blank test.
5.5.5 Expression of analysis results
The lithium chromate (LizCrO,) content X2 expressed as mass percentage is calculated according to formula (2): _(VV)·oX0. 043 29×100
(V-Vo)·cX4.329
Where: V is the volume of sodium thiosulfate standard titration solution consumed by the titration test solution, mL; V. ——The volume of sodium thiosulfate standard titration solution consumed in the titration of the blank test solution, mL, (2)
WHG/T2822—1996
c——The actual concentration of sodium thiosulfate standard titration solution, mol/L; 0.04329——The mass of lithium chromate in grams equivalent to 1.00mL of sodium thiosulfate standard titration solution (c(Na2S20s)=1.000mol/L);
m—The mass of the sample, g.
5.5.6 Allowable difference
The arithmetic mean of the parallel determination results shall be taken as the determination result. The absolute difference of the parallel determination results shall not exceed 0.02%. 5.6 Determination of chloride content
5.6.1 Method summary
Use nitric acid to oxidize bromide ions to bromine, heat and evaporate, add a known amount of excess silver nitrate standard titration solution, use ammonium ferric sulfate as indicator solution, and back titrate with sodium thiocyanate standard titration solution. 5.6.2 Reagents and materials
5.6.2.1 Nitrobenzene;
5.6.2.2 Nitric acid solution: 2+3;
5.6.2.3 Silver nitrate standard titration solution: c (AgNOa) about 0.1 mol/L; 5.6.2.4 Sodium thiocyanate standard titration solution: c (NaSCN) about 0.1 mol/L; 5.6.2.5 Ammonium ferric sulfate indicator solution: 80 g/L. 5.6.3 Instruments and equipment
5.6.3.1 Microburette: graduation value is 0.02 or 0.05mL. 5.6.4 Analysis steps
Weigh about 4g of sample (accurate to 0.01g) and place it in a 250mL flask. Add 50mL of nitric acid solution. Heat on a water bath until the yellow color of the solution disappears, rinse the bottle wall with a small amount of water, continue heating for 15min, cool, and add water to about 50mL. Use a pipette to add 10mL of silver nitrate standard titration solution, then add 5 drops of nitrobenzene and shake for 1min. Add 1mL of ammonium ferric sulfate indicator solution and titrate with sodium thiocyanate standard titration solution until the solution turns red.
5.6.5 Expression of analysis results
The chloride content (in terms of CI) X expressed as mass percentage is calculated according to formula (3): (ViCi-V2C2)X0.03545
2×100
(V1Ci—V2C2)X3.545
Wherein: V, the volume of the standard silver nitrate titration solution added, mL; Ci—the actual concentration of the standard silver nitrate titration solution concentration, mol/L; V, the volume of sodium thiocyanate standard titration solution consumed in titration, mL; c2——the actual concentration of sodium thiocyanate standard titration solution, mol/L; m
——the mass of the sample, g;
(3)
the mass of 0.03545-
of chlorine in grams equivalent to 1.00mL of silver nitrate standard titration solution [c(AgNO3)=1.000mol/L].
5.6.6 Allowable difference
The arithmetic mean of the parallel determination results shall be taken as the determination result. The absolute difference of the parallel determination results shall not exceed 0.01%. 5.7 Determination of sulfate content
5.7.1 Reagents and materials
5.7.1.1 95% ethanol;
5.7.1.2 Hydrochloric acid solution: 1+3;
5.7.1.3 Stannous chloride solution: 400g/L
5.7.1.4 Stannous chloride solution: 250g/L;
HG/T2822—1996
5.7.1.5 Sulfate standard solution: 1mL solution contains 0.1mgS04. 5.7.2 Analysis steps
Weigh 1.00±0.01g of sample, place it in a 50mL beaker, add 1mL of hydrochloric acid solution, add stannous chloride solution dropwise until the solution is colorless, transfer to a 50mL volumetric flask, add water to the scale, and shake well. Take 10mL with a pipette, place it in a 25mL colorimetric tube, add 5mL ethanol and 1mL hydrochloric acid solution. Under continuous shaking, add 3mL barium chloride solution, add water to the scale, and shake well. Let it stand for 10 minutes, and the turbidity must not be greater than the standard turbidimetric solution. The standard turbidimetric solution is 0.80mL sulfate standard solution, placed in a 25mL colorimetric tube, add water to 10mL, and treat it in the same way as the test solution of the same volume.
5.8 Determination of bromate content
5.8.1 Reagents and materials
5.8.1.1 Carbon tetrachloride;
5.8.1.2 Sulfuric acid solution: 1+9;
5.8.1.3 Bromate standard solution: 1mL solution contains 0.1mgBrOs. 5.8.2 Analysis steps
Weigh 20.00±0.01g of sample and place it in a 150mL separatory funnel. Add water to 50mL, add 10 drops of sulfuric acid solution, shake well, and let it stand for 10min. Add 5mL of carbon tetrachloride, shake for 1min, let it stand for 5min, and repeat shaking and standing for three times. After standing and stratifying, place the carbon tetrachloride layer in a 25mL colorimetric tube. Add 5mL of carbon tetrachloride to the separatory funnel, shake for 1min, let it stand for 5min, and repeat shaking and standing for three times. After standing and stratifying, place the carbon tetrachloride layer in the same colorimetric tube. The yellow color of the carbon tetrachloride layer shall not be darker than that of the standard colorimetric solution.
The standard colorimetric solution is made by weighing 10.00±0.01g of sample, adding 5.00mL of bromate standard solution, and treating it in the same way as the sample.
5.9 Determination of ammonium salt content
5.9.1 Reagents and materials
5.9.1.1 Hydrochloric acid;
5.9.1.2 Ammonia-free water;
5.9.1.3 Ammonia-free sodium hydroxide solution: 100g/L, 5.9.1.4 Nessler's reagent;
5.9.1.5 Ammonium standard solution: 1mL of solution contains 0.01mgNH4. Take 10.0mL of the ammonium standard solution prepared according to GB/T602, place it in a 100mL volumetric flask, dilute it to the mark with water, and shake it well. This solution is prepared before use.
5.9.2 Instruments and equipment
W.bzsoso.coIHG/T2822—1996
1—Distillation flask (250mL); 2—Gas-liquid separation ball; 3—Conduit; 4—Ammonia absorption tube with buffer ball (there is a small hole with a diameter of 1mm at the end of the tube inserted into the bottom of the colorimetric tube, and the distribution of the holes is shown in the figure); 5—Colorimetric tube (100mL)
Figure 1 Diagram of the device for determining the content of ammonium salt
5.9.3 Analysis steps
Weigh 1.00±0.01g of sample, add 50mL of ammonia-free water and 20mL of ammonia-free sodium hydroxide solution, immediately connect the device, and heat for distillation. Use a 100mL colorimetric tube filled with 1 drop of hydrochloric acid and 50mL of water to receive about 50mL of distillate. Add 2mL of ammonia-free sodium hydroxide solution and 2mL of Nessler's reagent to the receiving liquid and shake well. The yellow color should not be darker than the standard colorimetric solution. The standard colorimetric solution is 1.00 mL of ammonium standard solution, which is treated in the same way as the test sample. 5.10 Determination of total potassium and sodium content
5.10.1 Method summary
On an atomic absorption spectrophotometer, with air-acetylene flame, the standard addition method is used to determine the sodium and potassium contents using wavelengths of 589.0 nm and 766.5 nm.
5.10.2 Reagents and materials
5.10.2.1 Hydrochloric acid solution: 1+1;
5.10.2.2 Sodium and potassium standard solutions: 1 mL of solution contains 0.01 mg Na and 0.01 mg K. Take 10.0 mL of sodium standard solution and potassium standard solution prepared according to GB/T602 respectively. Place in a 100 mL volumetric flask, dilute to the mark with water, and shake well. The solution is prepared before use. The solution should be stored in a polyethylene plastic bottle. 5.10.3 Apparatus and equipment
Atomic absorption spectrophotometer: equipped with sodium and potassium hollow cathode lamps. 5.10.4 Analysis steps
5.10.4.1 Preparation of test solution A
Weigh about 10 g of sample (accurate to 0.01g), place it in a 250mL volumetric flask, add water to the mark, and shake well. 5.10.4.2 Determination
W.bzsoso.coIHG/T2822—1996
Use a pipette to transfer 4 portions of 2.5mL of test solution A, place them in 4 100mL volumetric flasks, add 0.5mL of hydrochloric acid solution respectively, and then add 0, 1.00, 3.00, 5.00mL of sodium and potassium standard solutions respectively, dilute with water to the mark, and shake well. On an atomic absorption spectrophotometer, use an air-acetylene flame, adjust to zero with water at wavelengths of 589.0nm and 766.5nm, and measure the absorbance of the above solutions.
Use the concentration of the added standard solution as the abscissa and the corresponding absorbance as the ordinate to draw curves respectively. Extend the curve in the opposite direction to intersect with the abscissa. The intersection is the amount of sodium and potassium in the tested test solution. 5.10.5 Expression of analysis results
The total content of sodium (Na) and potassium (K) X4 expressed as mass percentage is calculated according to formula (4): m+m2
mi+m2×10
-the amount of sodium in the test solution obtained by the graphic epitaxy method, mg; where: m
m2-the amount of potassium in the test solution obtained by the graphic epitaxy method, mg; m-the mass of the sample taken in 5.10.4.1, g. 5.10.6 Allowable difference
The arithmetic mean of the parallel determination results is taken as the determination result, and the absolute difference of the parallel determination results shall not exceed 0.005%. 5.11 Determination of calcium content
5.11.1 Summary of method
The determination is carried out on an atomic absorption spectrophotometer using a wavelength of 422.7nm and an air-acetylene flame using the standard addition method. 5.11.2 Reagents and materials
5.11.2.1 Hydrochloric acid solution: 1+1;
5.11.2.2 Calcium standard solution: 1mL solution contains 0.01mgCa. Take 10.0mL of calcium standard solution prepared according to GB/T602, place it in a 100mL volumetric flask, dilute it to the mark with water, and shake it well. This solution should be prepared just before use.
5.11.3 Instruments and equipment
5.11.3.1 Atomic absorption spectrophotometer: equipped with a calcium hollow cathode lamp. 5.11.4 Analysis steps
Use a pipette to take 4 portions of 5mL of test solution A (5.10.4.1), place them in 4 100mL volumetric flasks, add 2mL of hydrochloric acid solution to each, and then add 0, 1.00, 2.00, and 3.00mL of calcium standard solution to each, dilute it to the mark with water, and shake it well. On an atomic absorption spectrophotometer, use an air-acetylene flame at a wavelength of 422.7 nm and adjust to zero with water to measure the absorbance of the above solution.
Use the concentration of the added standard solution as the abscissa and the corresponding absorbance as the ordinate to draw a curve. Extend the curve in the opposite direction to intersect with the abscissa. The intersection is the amount of calcium in the tested solution. 5.11.5 Expression of analysis results
Calcium (Ca) content X expressed as mass percentage is calculated according to formula (5): 7
HG/T2822—1996
m×20×1000
Where: m1——the amount of calcium in the test solution obtained by the graphical epitaxy method, mg; m-
—the mass of the sample taken in 5.10.4.1, g. 5.11.6 Allowable difference
The arithmetic mean of the parallel determination results shall be taken as the determination result. The absolute difference of the parallel determination results shall not exceed 0.0002%. 5.12 Determination of magnesium content
5.12.1 Method summary
On an atomic absorption spectrophotometer, use a wavelength of 285.2nm and an air-acetylene flame to determine by the standard addition method. 5.12.2 Reagents and materials
5.12.2.1 Hydrochloric acid solution: 1+1;
5.12.2.2 Magnesium standard solution: 1mL of solution contains 0.01mgMg. (5)
Take 10.0mL of the magnesium standard solution prepared according to GB/T602, place it in a 100mL volumetric flask, dilute to the mark with water, and shake well. This solution is prepared before use.
5.12.3 Instruments and equipment
Atomic absorption spectrophotometer: equipped with a magnesium hollow cathode lamp. 5.12.4 Analysis steps
Use a pipette to transfer 4 portions of 25 mL of test solution A (5.10.4.1) and place them in 4 100 mL volumetric flasks. Add 2 mL of hydrochloric acid solution to each flask, and then add 0, 1.00, 2.00, and 3.00 mL of magnesium standard solution to each flask. Dilute to the mark with water and shake well. On the atomic absorption spectrophotometer, use an air-acetylene flame and adjust to zero with water at a wavelength of 285.2 nm to measure the absorbance of the above solution.
Use the concentration of the added standard solution as the abscissa and the corresponding absorbance as the ordinate to draw a curve. Extend the curve in the opposite direction to intersect with the abscissa. The intersection is the amount of magnesium in the tested test solution. 5.12.5 Expression of analysis results
The magnesium (Mg) content X expressed as mass percentage. Calculate according to formula (6): Xg
251000
m×250
-the amount of magnesium in the test solution obtained by the graphic epitaxy method, mg; where: ml
-the mass of the sample taken in 5.10.4.1, g. m
5.12.6 Allowable difference
The arithmetic mean of the parallel determination results is taken as the determination result. The absolute difference of the parallel determination results shall not exceed 0.0002%. 5.13 Determination of iron content
5.13.1 Reagents and materials
5.13.1.195% ethanol;
(6)
W.bzsoso.coI5.13.1.2 Hydrogen peroxide;
5.13.1.3 Ammonium persulfate;
5.13.1.4 n-Butanol;
5.13.1.5 Hydrochloric acid solution: 1+3;
5.13.1.6 Ammonium thiocyanate solution: 250g/L; HG/T2822—1996
5.13.1.7 Iron standard solution: 1mL solution contains 0.1mgFe. 5.13.2 Analysis steps
Weigh 2.00±0.01g of the sample, place it in a 100mL beaker, add 2mL of hydrochloric acid solution, 50mL of ethanol and 1mL of hydrogen peroxide, place it in a water bath, and evaporate to dryness. Dissolve the residue in 10mL of water, filter, and wash with a small amount of water. Collect the filtrate and washing liquid in a 50mL colorimetric tube. Add 1mL of hydrochloric acid, 30mg of ammonium persulfate, 2mL of ammonium thiocyanate solution, add water to 25mL, and shake well. Extract with 10mL of n-butanol, and the red color of the organic layer shall not be darker than that of the standard colorimetric solution. The standard colorimetric solution is 0.20mL of iron standard solution, which is treated in the same way as the sample. 5.14 Determination of carbonate content
5.14.1 Reagents and materials
5.14.1.1 95% ethanol;
5.14.1.2 No carbon dioxide and water;
5.14.1.3 Hydrochloric acid solution: 1+3;
5.14.1.4 Barium hydroxide solution: 10g/L; 5.14.1.5 Carbonate standard solution: 1mL solution contains 0.1mgcOs. 5.14.2 Instruments and equipment
1-Three-necked distillation flask (250mL);
2-Dropping funnel (50mL);
3-Condenser;
4-Ammonia absorption tube with buffer ball (the end of the tube inserted into the bottom of the colorimetric tube has a small hole with a diameter of 1mm, and the distribution of the holes is shown in the figure); 5-Colorimetric tube (25mL)
Figure 2 Diagram of carbonate content determination device
W.bzsoso.coD5.14.3 Analysis steps
HG/T2822-1996
Weigh 2.00±0.01g of sample and place it in a three-necked distillation flask. Add 50mL of carbon dioxide-free water and heat and boil for 1min to drive out the air in the system. Add 5mL of hydrochloric acid solution to the dropping funnel, open the stopcock, and close it immediately after the hydrochloric acid solution is drained. Use a 25mL colorimetric tube containing 10mL of clear barium hydroxide solution and 2mL of ethanol to absorb the distillate until it is close to the scale. Add water to dilute to the scale. Shake well. The turbidity should not be greater than that of the standard turbidimetric solution. The standard turbidimetric solution is to weigh 1.00±0.01g of the sample, add 4mL of carbonate standard solution, and treat it in the same way as the sample. 6 Marking, packaging, transportation, storage
6.1 The packaging of lithium bromide solution for refrigerators should have firm and clear markings, including the manufacturer's name, address, product name, trademark, net weight, batch number or production date, this standard number and the "heat-afraid" mark specified in 4 of GB191. 6.2 Each batch of lithium bromide solution for refrigerators shipped out of the factory should be accompanied by a quality certificate. The content includes the manufacturer's name, address, product name, trademark, net weight, batch number or production date, proof that the product quality complies with this standard and the standard number. 6.3 Lithium bromide solution for refrigerators is packaged in plastic barrels. Net weight of each barrel is 25kg or 30kg. 6.4 The inner cover of the lithium bromide solution barrel for refrigerators should be tightly closed and the outer cover should be screwed tight. 6.5 Lithium bromide solution for refrigerators should be covered during transportation to avoid direct sunlight. 6.6 Lithium bromide solution for refrigerators should be stored in a cool and dry place, away from light, sealed, and not in contact with air. 6.7 The shelf life of the product is half a year from the date of leaving the factory. If the shelf life is exceeded, it should be retested. 10
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