GB/T 5400-1998 Determination of copper value of pulp

This standard specifies the method for determining the copper value. This standard applies to bleached chemical pulp and dissolving pulp, but not to mechanical pulp or unbleached pulp. GB/T 5400-1998 Determination of copper value of pulp GB/T5400-1998 Standard download decompression password: www.bzxz.net

GB/T54001998
This standard is consistent with the original standard in terms of technical content, with only some textual modifications. This standard will replace GB5400-85 from the date of entry into force. This standard is proposed by the China Light Industry General Association.
This standard is under the jurisdiction of the National Technical Committee for Standardization of Paper Industry. The drafting unit of this standard is China Pulp and Paper Industry Research Institute. The main drafters of this standard are Lei Jinxuan and Chen Xi. This standard was first issued in 1985.
1 Scope
National Standard of the People's Republic of China
Determination of copper value of pulp
Pulp--Method for determination of copper numnber This standard specifies the method for determination of copper value. This standard is applicable to bleached chemical pulp and dissolving pulp, but not to mechanical pulp or unbleached pulp. GB/T 5400--1998
Replaces GB5400-85
Note: Copper value can determine the ability of hydrolyzed cellulose or oxidized cellulose to reduce certain metal ions to a low-valent state. At the same time, this type of reaction can be used to check the degree of degradation and deterioration of cellulose and to estimate the amount of reducing groups. In fact, copper value can be regarded as an indicator of certain reducing substances in pulp (for example, oxidized cellulose, hydrolyzed cellulose, lignin and sugar, etc.). 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 parties using this standard should explore the possibility of using the latest versions of the following standards. GB740-89 Taking pulp samples
GB741--89 Determination of moisture content of pulp analysis samples 3 Definitions
This standard adopts the following definitions.
Copper number of pulp
The number of grams of copper sulfate (CuSO,) reduced to cuprous oxide (CuzO) by 100g of absolutely dry pulp fiber in an alkaline medium at 100℃. 4 ApparatusbzxZ.net
4.1 Dry pulp mill
4.2 300mL or 500mL iodine volume flask.
4.3 25mL conical flask.
Note: 4.2 and 4.3 can be replaced by 300~~500mL conical flasks with ground glass stoppers and air condensers. 4.4 Constant temperature water bath.
5 Reagents
The drugs used in the preparation of reagents are analytically pure except for soluble starch which is chemically pure. 5.1 Sulfuric acid (GB625-89): 2mol/L solution, pour 108mL concentrated sulfuric acid (specific gravity 1.84) into about 800mL distilled water, and dilute to 1L with distilled water after cooling.
5.2 Sodium thiosulfate (GB637-88): 0.1mol/L standard solution (15.81g/L). Weigh 25g sodium thiosulfate (NazSO:·5H20) and 0.2g anhydrous sodium carbonate (Na2CO3) and dissolve them in 1000mL distilled water, and slowly boil for 10min. After cooling, store the solution in a stoppered glass reagent bottle, and filter it after several days. The filtrate is calibrated with the standard substance potassium dichromate (K,Cr2O,) or potassium iodate (KIO.) to obtain the accurate molar concentration of this sodium thiosulfate standard solution. Approved by the State Administration of Quality and Technical Supervision on May 19, 1998 386
Implemented on February 1, 1999
GB/T5400---1998
5.3 Sodium thiosulfate standard solution: 0.01 mol/L standard solution (1.581 g/L). Accurately transfer 100 ml of 0.1 mol/L sodium thiosulfate standard solution (5.2) into a 1000 mL volumetric flask and dilute to the mark with freshly boiled and cooled distilled water. 5.4 Starch indicator solution: 5 g/L solution. Weigh 0.5 g of soluble starch and add 10 mL of distilled water. Add to 90 ml of boiling distilled water under constant stirring, boil for another 2 min, cool and store in a glass reagent bottle. 5.5 Sodium hydroxide (GB629-81): 1 mol/L solution. Dissolve 4g sodium hydroxide in 80mL of distilled water without carbon dioxide, and then dilute to 100mL with the same distilled water. 5.6 Copper sulfate (GB665-88): 100g/L solution. Dissolve 10g copper sulfate in 50mL of distilled water, and then dilute to 100mL with distilled water.
5.7 Potassium iodide (GB1272-88): 100g/L solution. Dissolve 10g potassium iodide in 100mL of distilled water. 5.8 Potassium iodate (GB651-93): 0.1667mol/L solution. Dissolve 35.67g potassium iodate in 1000mL of distilled water. 5.9 Sabraud's reagent
5.9.1 Preparation method
Dissolve 30g potassium sodium tartrate (GB1288-92) and 30g anhydrous sodium carbonate in about 200mL of hot distilled water, and add 40mL of 1mol/L sodium hydroxide solution. Add 80mL of 100g/L copper sulfate solution under constant stirring, and boil to remove air from the solution. Dissolve 180g of anhydrous sodium sulfate in about 300mL of distilled water in another beaker, and boil to remove air from the solution. Then combine it with the solution containing copper sulfate, transfer it to a 1000mL volumetric flask after cooling, and add 80mL of 100g/L potassium iodide solution. After shaking well, add 4mL of 0.1667mol/L potassium iodate solution, and finally dilute to the scale with distilled water, shake well and let it stand for 1 to 2 days. If the solution becomes turbid, filter it with a glass sand core filter and store it in a reagent bottle for use. Note
The order of preparing this reagent cannot be reversed.
2 When using this reagent, if crystals precipitate due to low storage temperature, the reagent and the reagent bottle can be placed in water at about 35°C before use, and the crystals can be dissolved. The solution can be used only after it becomes clear. 6 Sampling and treatment
6.1 Sampling
Perform in accordance with the provisions of GB740.
6.2 Sample treatment
6.2.1 Air-dried pulp
Put the pulp in a dry pulp crusher and crush it to make it look like cotton wool. Store the sample in a wide-mouth bottle with a ground glass stopper and leave it overnight to allow the moisture to reach equilibrium for analysis. 6.2.2 Slurry coagulation
Add distilled water to the wet pulp in a wet pulp dissociator (or other discrete equipment) to disperse it (no pulp lumps or fiber bundles should be left), and place a filter cloth on the Buchner funnel to filter the pulp sample, absorb it dry, and finally air dry it. Then treat the air-dried pulp sample in accordance with the provisions of 6.2.1. 7 Test steps and result calculation
7.1 Test steps
7.1.1 Accurately weigh 0.5g (accurately weigh to 0.0001g) of the prepared sample and place it in a 300mL or 500mL dry iodine volume flask. Use a pipette to add 50mL of Sabouraud's reagent and shake while adding. After shaking well, place a 25mL conical flask upside down on the bottle mouth (or place a glass air condenser tube), place it in a boiling water bath (the liquid level in the bottle should be slightly lower than the boiling water surface) and heat for 1h. The time difference should not exceed 3min. During the heating process, the iodine volume flask should be shaken frequently (once every 10 to 15 minutes). After heating, take out the iodine volume flask and place it in running cold water to cool to room temperature. Remove the conical flask covering the bottle mouth and immediately wash the conical flask with a small amount of distilled water. The washing water should be washed into the iodine volume flask without damage. Add 50mL of distilled water and 30mL of sulfuric acid solution and shake it thoroughly for about 30min. After the bubbles have basically stopped, cover the original iodine volume bottle with the cap, shake it further and place it in a dark place for 5 minutes, remove the cap, purge it with distilled water and dilute it to a solution volume of about 200mL. Then titrate with sodium thiosulfate standard solution, and add 2~～3mL of starch indicator solution when it is close to the end point. While shaking thoroughly, continue to titrate until the blue color just disappears. 7.1.2 In another iodine volume bottle, add 50mL of Sabouraud's reagent and perform a blank test in the same way as above. 7.1.3 According to the provisions of GB741, weigh the sample to determine the moisture content. 7.2 Calculation of results
7.2.1 The copper price (in grams) is calculated according to formula (1): (V, - Vz) × c × 0. 063 55 × 100Copper price-
Wherein: V——the volume of sodium thiosulfate standard solution consumed in the blank test, mL; V2—the volume of sodium thiosulfate standard solution consumed in the titration of the sample, mL;-the molar concentration of sodium thiosulfate standard solution, mol/L; C
the mass of the absolute dry sample,.
7.2.2 Carry out two determinations at the same time, and take the arithmetic mean as the determination result, and round the figures to the second decimal place. The relative error between the calculated values ​​of the two determinations should not exceed 10%.
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