This standard specifies the method for determining the water-soluble chloride content of paper, paperboard and pulp. This standard is applicable to the determination of electrical paper and general paper. GB/T 2678.5-1996 Determination of water-soluble chloride content of paper, paperboard and pulp (silver nitrate potentiometric titration method) GB/T2678.5-1996 Standard download decompression password: www.bzxz.net

GB/T2678.5--1996
This standard is drafted after revising the national standard GB5403-85 "Determination of water-soluble chlorides in paper, paperboard and pulp" according to the document No. G94005 in the "1994 National Standard and Industry Standard Planning Project for the Papermaking Industry" issued by the China Light Industry Association.
This standard adopts ISO 9197-2:1990\Paper, board and pulps-Determination of water-soluble chlorides—Part 2: Method for high purity products\ and refers to GB2678.2-81 "Determination of water-soluble chlorides in pulp, paper and paperboard", and is revised according to the relevant provisions of GB1.4--88 "Standardization work guide chemical analysis method standard preparation regulations" and GB/T1.1-1993 "Standardization work guide unit 1: drafting and expression rules for standardization promotion part 1: basic provisions for standard preparation".
The following modifications were made in this revision:
The sample water extraction operation steps specified in ISO9197-2 and GB5403-85 are too cumbersome. This time, an air condenser is inserted to prevent the evaporation loss of the water extract, thereby deleting the steps of measuring the filtrate after extraction and weighing the filter cake mass. ISO9197-2 and GB5404-85 stipulate that the test solution after extraction should be repeatedly evaporated in a water bath to eliminate the interference of reducing carbohydrates, and the determination cycle is long. This time, the method of GB2678.2-81 is adopted, that is, hydrogen peroxide is oxidized in an alkaline medium to eliminate reducing interference.
It has been verified that when measuring the water-soluble chloride content of general paper, copper acetate is used to eliminate the interference of carbohydrates, and the change of the titration end point is not obvious, so it is not adopted. Therefore, this revision merges the test method for general paper with the test method for high-purity products. In order not to change the acidity during titration, the nitric acid concentration during dissolution has also been modified accordingly. This standard will replace GB5403-85 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 responsible drafting unit of this standard is: China Pulp and Paper Industry Research Institute. The main drafters of this standard are: Wei Yue and Yang Yanfei. 242
GB/T2678.5—1996
ISO Foreword
ISO (International Organization for Standardization) is a worldwide federation of national standards research institutes (ISO members). The preliminary preparation of international standards is carried out by ISO technical committees. Each member country interested in a topic established by a technical committee has the right to participate in the work of the committee. International organizations, whether governmental or non-governmental, can also participate in its work by contacting ISO. ISO maintains close cooperation with the International Electrotechnical Commission (IEC) on all matters related to electrical technical standardization. The draft international standards adopted by the technical committee are sent to the member countries for voting. At least 75% of the member countries must vote in favor before they can be published as international standards.
International Standard ISO9197-2 was proposed by ISO/TC6 Technical Committee for Paper, Paperboard and Pulp. ISO9197 consists of the following two parts, usually titled Paper, Paperboard and Pulp - Determination of Water-soluble Chloride.
Part 1: General method;
Part 2: Determination of high purity products.
1 Scope
National Standard of the People's Republic of China
Determination of water soluble chlorides in paper, board and pulp (silver nitrate potentiometric titration method)
Paper, board and pulp
Determination of water soluble chlorides (AgNO; method)
This standard specifies the method for determining the water soluble chlorides in paper, board and pulp. This standard is applicable to the determination of electrical paper and general paper. 2 Referenced standardsWww.bzxZ.net
GB/T 2678. 5--1996
neq ISO 9197-2:1990
Replaces GB5403--85
The provisions contained in the following standards constitute the provisions of this standard through reference in this standard. At the time of publication of this standard, the versions shown are valid. All standards are subject to revision, and parties using this standard should explore the possibility of using the latest versions of the following standards. GB45089 Paper and paperboard sample collection
GB462-89 Paper and paperboard moisture determination method GB740-89 Pulp sample collection
GB741--89 Pulp analysis sample moisture determination method 3 Principle
Quantitative flake sample, extract with hot water for 1h, filter the extract and oxidize it with hydrogen peroxide to reduce the interference caused by carbohydrates, add nitric acid to dissolve and acidify the test solution, and then use potentiometric titration to determine the chloride ion content with silver nitrate in the presence of acetone.
4 Reagents
In the analysis, the reagents used are all analytical grade (AR), and water should meet the requirements of 4.1. Distilled water and deionized water, conductivity less than 0.2mS/m. 4.1
4.2 Nitric acid: c(HNO3)=1:1(V/V). Dilute 500mL of nitric acid (g-1.4g/mL) to 1L with water (4.1). 4.3 Nitric acid: c(HNO.)～1.5 mol/L. Measure 100mL of nitric acid (p=1.4g/mL) and dilute to 1L with water. 4.4 Acetone (CH,COCH3), chloride-free. 4.5 Silver nitrate solution: c(AgNO3)-20mmol/L. Accurately weigh 3.397g of dried silver nitrate, dissolve it completely with distilled water (4.1), transfer it into a 1000mL volumetric flask, and dilute to the mark with distilled water. This solution should be kept away from light. 4.6 Sodium hydroxide solution: c(NaOH)～0.1 mol/L. Approved by the State Administration of Technical Supervision on June 25, 1996 244
Implemented on January 1, 1997
GB/T 2678.5—1996
Weigh 4 g of sodium hydroxide, dissolve it in distilled water (4.1) and transfer it to a 1000 mL volumetric flask, then dilute it to the mark with distilled water. 4.7 Hydrogen peroxide solution: c(H,0,)~30% (m/m). 5 Apparatus
The glassware and other instruments used in this method must be carefully cleaned. All glassware should be soaked in nitric acid (4.3) (30°C) for 5 to 10 minutes and rinsed thoroughly with boiled distilled water. The tweezers and scissors used to prepare the sample should be cleaned in the same way with boiled distilled water.
5.1 Potentiometer or other measuring instrument: The measured DC voltage is 0-300mV and has an accuracy of not less than 2mV. A silver electrode (silver ion selective electrode) is used as the indicator electrode and a glass electrode is used as the reference electrode. Note: If applicable, an automatic potentiometric titrator with a motor-driven microburette and plotting and recording can be used. 5.2 Microsyringe: 0.100mL, readable to 0.001mL. 5.3 Hot water bath and other heating devices.
6 Sample collection and preparation
Pulp samples shall be collected in accordance with the provisions of GB740, and average samples of paper and paperboard shall be collected in accordance with the provisions of GB450. Clean gloves should be worn to take samples and prepare paper sheets, and they should be taken carefully to prevent contamination of the samples. Keep the samples away from acid mist and prevent dust. 7 Test steps
7.1 Determination of copies and blank test
Each sample is tested in duplicate, and the blank test of the reagent should also be carried out in full accordance with the sample operation. 7.2 Extraction
Weigh the air-dried sample, 20g for high-purity electrical sample paper and 4g for general paper (accurate to 0.01g), and weigh another sample to determine the moisture content. The moisture content of paper and paperboard samples shall be determined in accordance with GB462, and the moisture content of pulp samples shall be determined in accordance with GB741. Cut or tear the sample into pieces not larger than 5mm×5mm, put them into a 500mL conical flask, add 300mL of freshly boiled distilled water (4.1) for high-purity paper and 100mL of distilled water for general paper. Install an air condenser and extract in a boiling water bath for 60min. When the extraction reaches the time, take it out, let the extract cool to room temperature, pour it out or filter it with a glass filter, take 150mL of the filtrate into a 250mL beaker for high-purity paper, and take 50mL of the filtrate for ordinary paper. Then add 10 drops of sodium hydroxide solution (4.6) and hydrogen peroxide solution (4.7) 10 drops, place on a hot plate to heat and oxidize to decolorize, wait until the solution evaporates until about 5mL remains. After the test solution is cooled to room temperature, add 1mL of nitric acid solution (4.2).
Transfer this solution to a 50mL beaker for titration, wash the beaker three times, each time with 10mL of acetone (4.4). 7.3 Titration
Pour the electrode of the potentiometric titrator (5.1) into the test solution, stir continuously at a constant speed with an electromagnetic stirrer, read the potential value on the potentiometer, and use a micro-injector (5.2) to add 0.01mL of silver nitrate standard solution (4.5) each time for potentiometric titration.
Read the potential value once after each addition of silver nitrate solution. The potential changes slowly at first, and as the amount of silver nitrate solution added increases, the potential changes increase, and titrate until the potential value changes slowly again. Note: If an automatic titrator is used, the rate of adding the titrant is 0.1mL/min to 0.2mL/min. 7.4 Calculation of the consumption of the silver nitrate standard solution
7.4.1·Method 1: Plot the volume of the added silver nitrate solution against the potential reading. From the graph, determine the point of maximum slope of the curve change, and read the corresponding volume of the titrant as the equivalent volume of the consumed silver nitrate solution. 1) For example, the domestic PHS-2 and PHS-3 acidity meters. 245
GB/T 2678.5-1996
7.4.2 Method 2: The second-order derivative method can also be used to determine the endpoint. For the operating steps, please refer to the standard analysis textbook 8. Result calculation
The water-soluble chloride content is calculated by formula (1): 35. 46 ·c. V2 · (Vi - V.)Vs.m
Wherein: X-
the water-soluble chloride content of the sample, mg/kg; the concentration of the silver nitrate standard solution, m mol/L; - the volume of the silver nitrate standard solution consumed when titrating the blank, mL; V--the volume of the silver nitrate standard solution consumed when titrating the sample, mL; V2--the total volume of water added during extraction, mL; V3--the volume of the filtrate taken for titration, mL; m
the absolute dry mass of the sample, g.
Take the average of the two test results as the content of water-soluble chloride, expressed as milligrams of fluoride per dry gram of absolute dry sample. When the content is below 5 mg/kg, the result is rounded to 0.1 mg, and the rest are rounded to integers. 9 Test report
The test report should include the following:
a) The number of this national standard;
b) The date and place of the test;
c) The mark of the material tested;
d) The test result of the water-soluble chloride of the sample; e) Any changes in the prescribed operating procedures or other details that may affect the test results. 246
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