Some standard content:
National Standard of the People's Republic of China
Determination of alkali solubility of pulp
PulpDetermination of alkali solubilityUDC 676. 1. 017
GB5401-85
This standard is to determine the alkali soluble components of pulp by volumetric method, mainly used for the study of bleached pulp and bleaching stage, and can also be used for the study of unbleached pulp.
This standard is equivalent to the international standard ISO692--1982 "Pulp-1 Definition
-Determination of alkali solubility".
1.1S value: Alkali solubility, the soluble part expressed as a percentage of the weight of the absolute dry pulp sample. 1.2S18, S1 or S: S value for specifying the concentration of alkali solution, footnote 18, 10 or c is the selected concentration, expressed in grams of sodium hydroxide in 100g of solution.
2 Instruments
General laboratory instruments and the following devices:
2.1 Stirring device: The outer shell is made of stainless steel or other corrosion-resistant materials. The angle of the stirring blade is adjusted so that the pulp suspension can roll well from top to bottom in the center during stirring, and prevent air from entering the pulp suspension. The stirring device is shown in the figure. The motor power is 15W and the speed is about 24-28r/s. Volume 200m
Stainless steel
Stirring device
National Bureau of Standards 1985-09-28 Issued
1986-05-01 Implementation
GB5401 85
2.2 Constant temperature water bath device: can maintain a temperature of 20±0.2℃. 2.3 Glass sand core filter 1G2: volume is 50ml. 2.4 Suction filter bottle.
2.5 Analytical balance: accurate to 1mg.
2.6 High-shaped reaction bottle: volume is 200ml. 3 Reagents
Analytical reagents and distilled water or water of equivalent purity should be used. 3.1 Sodium hydroxide (GB629-81): a solution of known concentration, the sodium carbonate content of which should be less than 1g/L (see note). 3.1.1 5.39mol/L solution (specific gravity 1.1972), each 100g solution contains 18.0±0.1g sodium hydroxide, equivalent to 215.5±1.0g sodium hydroxide per liter.
3.1.2 2.77mol/L solution (specific gravity 1.1089), each 100g solution contains 10.0±0.1g sodium hydroxide, equivalent to 110.9±1.0g sodium hydroxide per liter.
Note: Sodium hydroxide solution can be prepared as follows: dissolve a certain amount of solid sodium hydroxide in an equal amount of water, let it stand to allow the suspended sodium carbonate to sink, pour out the supernatant, dilute it with carbon dioxide-free water to an appropriate concentration, and calibrate its concentration with a standard acid solution. 3.2 Sulfuric acid (GB625--77): concentrated sulfuric acid (specific gravity 1.84). 3.3 Potassium dichromate (GB642-77): concentration is about 0.067 mol/L solution, each liter of solution contains 20g potassium dichromate and 150ml sulfuric acid (specific gravity 1.84).
3.4 Ammonium ferrous sulfate (GB661-77): The concentration is about 0.1mol/L solution (the concentration should be accurate to ±0.0002mol/L). Each liter of solution contains 40-41g of ammonium ferrous sulfate [CFeSO, (NH), SO·6H2O] and 10ml of sulfuric acid (specific gravity 1.84). The solution is unstable and its concentration must be calibrated every day. Potassium dichromate can be used as a reference for calibration. Note: In order to stabilize the ammonium ferrous sulfate solution, a reducing agent can be placed in the storage bottle. The preparation method of the reducing agent is as follows: Add 5g of aluminum chips or aluminum foil with a purity higher than 99.99% to every 10L of ammonium ferrous sulfate solution, and store it at room temperature below 20C (it can be stored in a refrigerator). The concentration of the ammonium ferrous sulfate solution can remain stable before the aluminum foil is completely dissolved. 1) 3.5 Ferrocyanate indicator solution: Each liter of solution contains 15g of o-phenanthroline hydrate [C12HgN2·H2O] or 16g of o-phenanthroline hydrochloride hydrate [C12H.N2·HCl·H2O} and 7g of ferrous sulfate [FeSO. 7H,O]. 4 Preparation of the sample
If the pulp is a pulp board, tear it into pieces of about 55mm. If the pulp is a liquid pulp, dehydrate it by suction filtration, then squeeze the sample between absorbent papers and dry it at a temperature below 60℃. Before weighing, place the sample in the atmosphere near the balance for at least 20min.
5 Test steps
5.1 Sample
Weigh a sample equivalent to about 1.5g of absolute dry pulp, accurate to 0.005g, and then immediately weigh two samples. Determine the moisture content in accordance with the provisions of GB741--79 "Determination of Moisture Content in Chemical Pulp Analysis Samples". 5.2 Determination
5.2.1 Use a pipette to draw 100.0±0.2ml of the selected sodium hydroxide solution (3.1) into the reaction bottle (2.6), place the reaction bottle in a constant temperature water bath (2.2), and adjust its temperature to 20±0.2℃. Instructions for use:
1) When the ammonium ferrous sulfate solution approaches 20℃, the aluminum foil used as a stabilizer dissolves slowly, so it is stipulated that "when stored at room temperature below 20℃... the concentration can remain stable".
GB5401—85
Note: The solubility of sodium hydroxide solution with lower concentration (such as 10% (m/m)) is greatly affected by temperature. Therefore, at lower concentration, the temperature must be maintained at 2℃±0.2℃. For sodium hydroxide solution with higher concentration (such as 18% (m/m), generally speaking, the solubility is not greatly affected by temperature change. Therefore, when processing at this concentration, the temperature can be maintained at 20±2℃. However, the temperature of unbleached wood pulp and straw pulp is greatly affected, and the temperature must also be maintained at 20±0.2℃.
5.2.2 Add the sample to the sodium hydroxide solution and allow it to swell for 2 minutes. Stir in the reaction bottle for 3 minutes or until the pulp is completely dispersed. Take out the stirrer from the reaction bottle and use a glass rod to push the fibers and sodium hydroxide attached to the stirrer into the reaction bottle as much as possible. The fine fibers and trace amounts of sodium hydroxide still remaining on the stirrer can be ignored. Keep the reaction mixture at 20 ± 0.2°C for 60 minutes (the time is calculated from the time when the pulp sample contacts the sodium hydroxide solution). Note: The thinner the sample is torn, the better the sample dispersion is. Increasing the stirring time does not significantly affect the alkali solubility. However, if the dispersion is incomplete, the measured value will be low, so the stirring time can be appropriately increased until the sample is completely dispersed. 5.2.3 After 60 minutes, stir the sample suspension with a glass rod and filter the suspension with a glass sand core filter under slight suction. Be careful to avoid air passing through the residue, discard the initial filtrate 10~~~20ml, and then collect 40~50ml of filtrate in a clean suction filter bottle. Note: The used glass sand core filter should be washed immediately with potassium dichromate sulfuric acid washing solution. 5.2.4 Use a pipette to draw 10.0 ml of the filtrate into a 250 ml conical flask, add 10.0 ml of potassium dichromate solution (3.3) with a pipette, and then carefully add 30 ml of concentrated sulfuric acid (3.2) under continuous shaking. Adjust the temperature to between 125 and 130 °C, and heat if necessary. 2) Note: When testing general dissolving pulp, it is appropriate to take 10 ml of the filtrate for titration. If the alkali solubility of the pulp sample is greater than 16% (m/m), 5 ml of the filtrate and 25 ml of concentrated sulfuric acid should be taken for titration. If the alkali solubility of the pulp is less than 5% (m/m), 20 ml of the filtrate and 45 ml of concentrated sulfuric acid should be taken. In the blank test, the corresponding volume of sodium hydroxide solution and sulfuric acid should be used. 5.2.5 Let this hot solution stand at above 120 °C for 10 minutes to allow complete oxidation, and then cool the conical flask to room temperature. 5.2.6 Add 50 ml of water to the cold solution, cool it again, add 2 drops of ferrocyanide indicator solution (3.5), and titrate with newly standardized ammonium ferrous sulfate solution until it turns purple.
Note: In an excess of acidic potassium dichromate solution, the indicator will be partially oxidized, changing its original color and affecting the consumption of potassium dichromate. Since the oxidation is related to the relative amount and concentration of potassium dichromate and the indicator, the excess potassium dichromate should be reduced as soon as possible. After about 90% of the excess potassium dichromate is reduced, add the indicator immediately and titrate quickly to the end point to reduce the error of the indicator to a negligible level. 5.2.7 Replace the sample filtrate with 10 ml of the selected sodium hydroxide solution and perform a blank test at exactly the same temperature and time. Note: The iodine titration method can also be used, but it should be explained in the experimental report. After oxidation, transfer the cold solution to a 1000ml conical flask with 500ml of water, add 2g of potassium iodide, keep the temperature below 10℃, stir until dissolved and mixed evenly, then let it stand for 5min, and use 0.Titrate with 1 mol/L sodium thiosulfate standard solution, and add powdered starch indicator when the yellow color of iodine is about to disappear. The end point of titration is when the color of the solution changes from dark blue to light green. Perform a blank test by replacing the sample filtrate with 10 ml of sodium hydroxide solution. Calculate the results according to the method in 6.1, where V1 and V2 are replaced by the volume of the corresponding sodium thiosulfate standard solution and V2 by the concentration of the sodium thiosulfate standard solution.
Each sample is measured twice.
6 Expression of results
6.1 Calculation method and formula
Alkali solubility S. Expressed as weight percentage, calculated as follows: S. = 6 85V):X100×100_ 68. 5(VV) ·c1000Xm:V
Wherein: V is the volume of the filtrate used for oxidation, ml; Vl is the volume of the ammonium ferrous sulfate solution consumed by the titration sample, ml; Instructions for use: wwW.bzxz.Net
1) When the content of hemicellulose and other alkali-soluble substances in the pulp is high, the effect of temperature on alkali solubility is significant, so the provision of "the treatment temperature of unbleached wood pulp and grass pulp must be maintained at 20 ± 0.2℃" is added. 2) In order to ensure the reaction temperature, "heating can be performed when necessary" is added. 391
GB5401—85
The volume of ammonium ferrous sulfate solution consumed in the blank test, ml, the concentration of ammonium ferrous sulfate solution, mol/L; the weight of the absolutely dry sample, g;
6.85-empirical factor, indicating the amount of cellulose equivalent to 1/6mmol potassium dichromate, mg. Note: Theoretically, 1/6mmol potassium dichromate is equivalent to 6.75mg of cellulose or other polyhexose and 6.60mg of pentose. --Generally, since the alkali-soluble components of pulp contain oxidized cellulose, the consumption of oxidant is smaller than the theoretical amount. Therefore, in this method, a slightly higher number of 6.85mg is used. 6.2 Precision and expression of results
Two determinations are carried out at the same time, and the arithmetic mean is taken as the determination result. The figures are rounded to the first decimal place and marked with symbols such as S10, S18, etc. The error between the calculated values of the two determinations should not exceed 0.3%. 6.3 Calculation example
Weight of air-dried sample: 1.735g
Dead matter content of another sample: 92.4%;Dead sample weight (m): 1.604g;
Volume of ammonium ferrous sulfate solution consumed in blank test (V): 41.1ml;Volume of ammonium ferrous sulfate solution consumed in sample titration (V,): 15.5ml;Concentration of ammonium ferrous sulfate solution (c): 0.1005mol/L;Volume of filtrate used for oxidation (V): 10ml;Then the solubility in sodium hydroxide solution is: S. 68. 5x(41: 1=15:)×0.100511. 0%1.604×10
Additional explanation:
This standard was proposed by the Ministry of Light Industry of the People's Republic of China and is under the jurisdiction of the Paper Industry Research Institute of the Ministry of Light Industry. This standard was drafted by the Guangdong Paper Research Institute. The main drafter of this standard is Sun Shaofang.
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