This standard specifies the determination method for the alkalinity of concentrated natural rubber latex. This standard applies to concentrated natural rubber latex produced from Hevea brasiliensis latex. GB/T 8300-2001 Determination of alkalinity of concentrated natural rubber latex GB/T8300-2001 Standard download decompression password: www.bzxz.net

GB/T8300--2001
This standard is equivalent to ISO 125:1990 "Determination of Alkalinity of Concentrated Natural Latex". The main differences between this standard and the previous version are as follows:
Chapter 4 "Definition" of the previous version is deleted, and "Principle" is added as Chapter 4; the determination method is added to the potentiometric titration method, and the provisions for the instruments used in the potentiometric titration method are also added; sulfuric acid solution is added as the standard solution; the stabilizer is changed from the original non-ionic surfactant perchlorate O to alkylphenol polyoxyethylene condensate (OP-10); the weight of the weighed latex is increased to 5g~10g, so that the amount of hydrochloric acid solution required is about 15mL~20mL, which meets the general chemical titration operation requirements. At the same time, the amount of water and stabilizer is also increased so that the hydrochloric acid solution can be easily diffused during the titration process. An item of expressing alkalinity in potassium hydroxide is added. For concentrated latex preserved with potassium hydroxide, the alkalinity is measured in potassium hydroxide. The requirements for writing test reports are increased. This standard shall replace GB/T8300-1987 from the date of entry into force. This standard is proposed by the Ministry of Agriculture of the People's Republic of China. This standard is under the jurisdiction of the Natural Rubber Sub-Technical Committee of the National Technical Committee for Rubber and Rubber Standardization. The drafting units of this standard are: South China Tropical Agricultural Products Processing Design Institute, Food Quality Supervision, Inspection and Testing Center of the Ministry of Agriculture (Zhanjiang). The main drafters of this standard are: Yu Heping and Huang Maofang. This standard is the second edition. The first edition was first issued in July 1987. This standard is entrusted to the Natural Rubber Sub-Technical Committee of the National Technical Committee for Rubber and Rubber Standardization for interpretation. 107
GB/T8300-2001
ISO Foreword
ISO (International Organization for Standardization) is a worldwide federation of national standards bodies (ISO member bodies). The work of formulating international standards is usually carried out by ISO technical committees. Any member body interested in the project of an established technical committee has the right to participate in the technical committee. All governmental and non-governmental international organizations that have relations with ISO may also participate in this work. ISO collaborates closely with the International Electrotechnical Commission (IEC) on all matters of electrotechnical standardization. Draft international standards adopted by the technical committee are circulated to the member bodies for voting. Publication as an international standard requires an approval vote by at least 75 % of the member bodies casting a vote.
International Standard ISO 125 was prepared by Technical Committee ISO/TC 45, Rubber and Rubber Products. This fourth edition of the standard slightly revises the third edition (ISO 125:1983), and abolishes and replaces the main edition. 108
1 Scope
National Standard of the People's Republic of China
Determination of alkalinity of concentrated natural rubber latex
Natural rubber latex concentrateDetermination of alkalinity
This standard specifies the method for the determination of alkalinity of concentrated natural rubber latex. This standard applies to concentrated natural rubber latex produced from Hevea brasiliensis latex. 2 Referenced standards
GB/T 8300—2001
idt ISO 125:1990
Replaces GB/T8300-1987
The following standards contain provisions that constitute the provisions of this standard through reference in this standard. When this standard is published, 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. GB/T8290—1987 Sampling of natural concentrated latex (neqISO123:1985) GB/T18012—1999 Determination of pH of natural latex (neqISO976:1996) 3 Principle
Use potentiometric titration or methyl red as a visual indicator to titrate the concentrated latex with acid to pH 6.0 in the presence of a stabilizer, and then calculate the alkalinity of the latex based on the required amount of acid. 4 Reagents
Wherever water is specified, distilled water or water of equivalent purity should be used. All reagents except those in 4.1 should be of confirmed analytical grade.
4. 1 Stabilizer solution, 5% (m/m) alkylphenol polyoxyethylene condensate type non-ionic stabilizer solution (OP-10), the pH of the solution should be adjusted to 6.0 ± 0.01 before use.
4. 2 Standard titration solution, sulfuric acid c(H,SO.) = 0.05 mol/L, or hydrochloric acid c(HC1) = 0. 1 mol/L. 4.3 Methyl red, 0.1% (m/m) ethanol solution, the ethanol content is at least 95% (V/V). When using potentiometric titration, methyl red solution is not required. 5 Instruments
When using potentiometric titration, the following instruments are required: a) pH meter, equipped with glass electrode and saturated calomel electrode, capable of reading to 0.01 units. b) Glass electrode, for solutions with a pH of up to 12.0. c) Mechanical stirrer, equipped with a grounded motor and non-metallic blades; electromagnetic stirrer may also be used. 6 Sampling
Sampling shall be carried out in accordance with the method specified in GB/T8290.
Approved by the General Administration of Quality Supervision, Inspection and Quarantine of the People's Republic of China on 2001-07-20
Implemented on 2001-12-01wwW.bzxz.Net
7 Operating procedures
GB/T 8300-2001
Calibrate the pH meter in accordance with the method specified in GB/T18012 (5, 1) Add 10 mL of stabilizer solution (4.1) to a 400 mL beaker containing about 200 mL of water while stirring. Weigh 5 g to 10 g of concentrated latex from a weighing bottle by the difference method, accurate to 10 mg, add to the beaker and stir thoroughly. Insert the glass electrode and add sulfuric acid or hydrochloric acid solution (4.2) with a burette under continuous stirring until the pH drops to 6.0 ± 0.05. When approaching the end point, add acid drop by drop.
If potentiometric titration is not used, methyl red (4.3) can be used as a visual indicator, and the end point is when the color turns pink. Perform two parallel determinations.
8 Display of results
Calculate the alkalinity of the concentrated latex according to the provisions of 8.1 or 8.2 according to actual conditions. 8.1 If the concentrated latex is preserved with ammonia, calculate the alkalinity according to formula (1), expressed as the number of grams of ammonia (NH,) per 100g of latex: Alkalinity (in NH,) =
Where: F, --- coefficient: 1.7 for hydrochloric acid, 3.4 for sulfuric acid-the actual concentration of the hydrochloric acid or sulfuric acid solution used, mol/L; V--the volume of the acid used, mL;
m-the mass of the sample, g.
（1）
When the actual alkalinity is above 0.5 units and the difference between the parallel determination results is greater than 0.02 units, or when the actual alkalinity is equal to or less than 0.5 units and the difference between the parallel determination results is greater than 0.01 units, the determination shall be repeated. 8.2 If the concentrated latex is preserved with potassium hydroxide, the alkalinity shall be calculated according to formula (2) and expressed as grams of potassium hydroxide per 100 g of latex: Alkalinity (in KOH) =
Where: F2——-Coefficient: 5.61 for hydrochloric acid and 11.22 for sulfuric acid; c, V and m are the same as in 8.1.
If the difference between the parallel determination results is greater than 0.03 units, the determination shall be repeated. 9 Test report
The test report shall include the following contents:
a) this standard number;
b) details required to identify the sample;
c) the measurement results and their expression,
d) any operations not included in this standard but considered to be applicable, and any accidental phenomena that may affect the results; e) the test date.
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