This standard specifies the determination of water-soluble chloride in pulp, paper and paperboard. This standard is applicable to various pulps, papers and paperboards. GB/T 2678.2-1994 Determination of water-soluble chloride in pulp, paper and paperboard (mercuric nitrate method) GB/T2678.2-1994 Standard download decompression password: www.bzxz.net

National Standard of the People's Republic of China
Determination of water soluble chlorides in pulp, paper and paperboard (mercuric nitrate method)
Paper ,board and pulpDetermination of water soluble chlorides(HgNO method)
1 Subject content and scope of application
This standard specifies the determination of water soluble chlorides in pulp, paper and paperboard. This standard is applicable to various pulps, papers and paperboards. 2 Reference standards
Taking paper and paperboard samples
Determination of moisture content in paper and paperboard
GB 740Taking pulp samples
GB741Determination of moisture content in pulp analysis samples3 Principle
GB/T 2678.2-94
Replaces GB 2678.2--81
This determination method is based on the extraction of the sample with boiling water for 1 hour. In the solution containing chloride ions, a standard titration solution of easily soluble mercuric nitrate is added dropwise. At this time, mercuric ions immediately react with chloride ions to form insoluble mercuric dichloride. Excess ethanol is added to the titration solution to reduce its solubility. When all the chloride ions in the solution are converted into mercuric fluoride, the slightly excessive mercuric ions immediately react with the diphenylcarbazide added to the solution to form a purple mercury compound. 4 Reagents
During the test, analytical reagents and distilled or deionized water must be used. 4.1 Hydrogen peroxide (GB6684) solution: 30% (m/m). 4.2 Ethanol (GB 679) solution: 95% (V/V). 4.3 Nitric acid (GB 626) solution: 1 mol/L. 4.4 Sodium hydroxide (GB629) solution: 0.50 mol/L. 4.5 Sodium chloride standard solution [c (NaCI) = 0.01 mol/L]: Accurately weigh 0.5846 g of standard sodium chloride that has been burned at 500~600℃ for 2h and dissolve it in water, transfer it to a 1000mL volumetric flask, and dilute it to the scale with distilled water. 4.6 Mercuric nitrate standard titration solution: Preparation and calibration are shown in Appendix A (Supplement) 4.7 Diphenylcarbazide (C13Hz.ON): 10 g/L, weigh 0.25 g of diphenylcarbazide and dissolve it in 25 mL of 95% ethanol, store it in a brown bottle, and prepare this solution once a week.
5 Instruments
5.1 General laboratory instruments.
5.2 Constant temperature water bath.
Approved by the State Administration of Technical Supervision on September 24, 1994 and implemented on March 1, 1995
GB/T 2678.2-94
5.3 1mL microburette, with a minimum graduation of 0.01mL. 5.4 150mL and 250mL conical flasks.
5.5 500mL standard extractor.
6 Sample collection and preparation
Pulp samples should be collected in accordance with the provisions of GB740. Paper and paperboard samples should be collected in accordance with the provisions of GB450. Wear clean gloves to take the sample to prevent contamination. Tear or cut the sample into 5mm×5mm paper pieces and store them in a wide-mouth bottle with a ground glass stopper.
7 Test steps
Each sample is extracted twice, and a blank test of the reagent is performed in full accordance with the method for testing the sample. 7.1 Accurately weigh 5.0±0.2g of the air-dried sample (weigh to 0.001g, and weigh the sample separately to determine the moisture content), put it into a 500mL extraction bottle, add 250mL of freshly boiled distilled water, install a reflux condenser, place it in a boiling water bath, heat and extract for 1h, take it out and cool it, filter it into a clean, dry conical bottle using a Buchner funnel and pre-treated filter paper (washed and dried with hot distilled water for later use). 7.2 Use a pipette to draw 100 mL of the filtrate into a 250 mL conical flask, add 1 drop of 0.5 mol/L sodium hydroxide solution, then add 1~~2 mL of 30% hydrogen peroxide, heat on a hot plate or electric stove to concentrate to about 10 mL, cool, add 20 mL of 95% ethanol (4.2), 3 drops of 1 mol/L nitric acid (4.3) (pH is 3.0~3.5 at this time), 10 drops of diphenylcarbazone indicator (4.7), and titrate with 0.01 mol/L mercuric nitrate standard titration solution (4.6) until purple appears, which is the end point. 8 Calculation of results
The water-soluble chloride content X (mg/kg) of the sample is calculated as follows: X = V -Vo)×X 35. 6 × 1000
m×250
The volume of the standard mercuric nitrate titration solution consumed by the sample, mL; Where: V——
-The volume of the standard mercuric nitrate titration solution consumed by the blank, mL; V.
Concentration of the standard mercuric nitrate titration solution, mol/L; c
m-The absolute dry mass of the sample, g;
35.46----The mass of chloride in milligrams equivalent to 1.00mL of the standard mercuric nitrate titration solution cHg(NO3)2=1.00mol/L.
The difference between the calculated values ​​of the two determinations should not exceed 2mg/kg. 9 Test report
The test report shall include the following:
This standard number;
The mark and description of the sample;
The average value of the test results of two samples shall be taken as the chloride content, and the result shall be rounded to the integer: Any test conditions and operations that deviate from this standard. d.
A1 Preparation of standard titration solution of mercuric nitrate
GB/T 2678.2—94
Appendix A
Preparation and calibration of standard titration solution of mercuric nitrate (supplement)
Weigh 1.7130g of mercuric nitrate and dissolve it in 4mL (1:1) nitric acid and a small amount of water, transfer it into a 1000mL volumetric flask, and dilute it to the scale with distilled water.
A2 Calibration and calculationbzxz.net
Precisely measure 10mL of sodium chloride standard solution (4.5) in a 150mL conical flask, add 20mL of 95% ethanol, 3 drops of 1mol/L nitric acid and 10 drops of indicator (4.7), shake the hook, and titrate with 0.01mol/L mercuric nitrate standard titration solution until the solution just turns purple. The concentration c (mol/L) of the mercuric nitrate standard titration solution is calculated according to formula (A1): GiV
Where: Ci—concentration of sodium chloride standard solution, mol/L, V,-amount of sodium chloride standard solution, mL,
V, volume of mercuric nitrate standard titration solution, mL. Additional remarks:
This standard is proposed by China Light Industry General Association.
This standard is under the jurisdiction of the National Technical Committee for Standardization of Paper Industry. This standard was drafted by Sichuan Paper Industry Research Institute. The main drafter of this standard is Li Jingyun.
This standard was first published in September 1961 and first revised in August 1981. · (A1)
This standard refers to the American Pulp and Paper Association standard TAPPIT256cm-85 "Determination of water-soluble chloride in pulp and paper". 231
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