This standard specifies the semi-quantitative determination of ammonia content in phenolic molded products by colorimetry. GB/T 5474-1985 Determination of free ammonia and ammonium compounds in phenolic molded products Colorimetric method GB/T5474-1985 Standard download decompression password: www.bzxz.net

National Standard of the People's Republic of China
Phenol --formaldehyde mouldings --Determination of free ammonia and ammonium compounds-Colorimetric comparison method
Phenol --formaldehyde mouldings --Determination of free ammonia and ammonium compounds-Colorimetric comparison method This standard is equivalent to the international standard ISO120-1977 "Plastics colorimetric method".
1 Scope of application
-Phenol-formaldehyde moulding materials
This standard specifies the semi-quantitative determination of ammonia content in phenolic mouldings by colorimetric method. UDC 678.632 : (546
171.1+ 547
298.1):543.8
GB5474-85
Determination of free ammonia and ammonium compounds
Note: This national standard is not suitable for the determination of the absolute amount of ammonia. The nitrogen content of molded articles is particularly important when corrosion of metal inserts or contamination of food products due to contact with the molded articles must be considered.
2 Principle
Free ammonia is extracted from a powder sample with hot water. The aqueous extract is distilled in the presence of potassium permanganate and sodium hydroxide solution. The distillate reacts with Nessier's reagent to develop a color, and the color-developed solution is compared with a set of standard solutions. 3 Reagents
In the analysis, only recognized analytically pure ammonia-free reagents, ammonia-free distilled water or water of equivalent purity can be used. 3.1 Potassium permanganate.
3.2 Sodium hydroxide, 2% (m/m) solution. 3.3 Comparison standard stock solution, containing 10 mg of ammonia per liter. Dissolve 31.5 mg of ammonium chloride in 1000 ml of water. 3.4 Nessier's reagent.
4 Apparatus
Ordinary laboratory apparatus and the following apparatus:
Apparatus for making the molded article into powder.
4.2 Sieve f; pore size 250μm.
4.3 Water: 0.01g.
4.4 Ground glass flask: capacity 250ml. 4.5 Distillation apparatus: including 250ml flask, splash ball and condenser. 4.6 Filter funnel and medium-speed qualitative filter paper. 4.7 Graduated pipette: capacity 2 and 10ml. 4.8 Nessler colorimetric tube: capacity 50ml.
Adopting the formula 1:1) ISO565 stipulates that the pore size of the sieve is 250μm. Now it is changed to the 65 layers/inch sieve produced by the market, and its pore size is 250μm. Issued by the National Bureau of Standards on October 17, 1985
Implemented on July 1, 1986
5 Preparation of test specimens
GB5474-85
Powder a sufficiently representative molded product by filing, milling, grinding, turning or drilling. Be sure not to overheat the material during the powdering process. Sieve with a sieve (4.2), and the part under the sieve is the test specimen, which is stored in a stoppered flask for future use. Extraction with water (see 6.2) should be started within 1 hour after the molded product is ground. Note: The method of powdering can affect the test results. In the event of dispute or for arbitration, the method of powdering should be agreed upon between the parties concerned. 6 Determination steps
6.1 Preparation of test solution
Weigh 5±0.1g (accurate to 0.01g) of the sample (5) and place it in a flask (4.4). Add 10 times the weight of the sample in water at a temperature of 90-100°C. Stopper the flask and shake it to fully wet the powder. Cool it at room temperature for 1h and shake it occasionally. Then filter the contents of the flask using a filter funnel (4.6) without negative pressure. Use a graduated pipette (4.7) to transfer 10ml of the filtered extract equivalent to 1g of powder to the flask of the distillation apparatus (4.5).
Note: Before using the distillation apparatus, the ammonia stored in the distillation apparatus should be removed by distilling a certain amount of distilled water. Distill until 2ml of Nessler's reagent (3.4) added to 50ml of the distillate does not show any color. Add 0.1 g potassium permanganate (3.1) and 10 ml sodium hydroxide solution (3.2) to a flask, slowly distill the mixture, collect the first 15 ml of distillate in a Nessler colorimetric tube (4.8), and dilute to 50 ml with water. 6.2 Determination
Use a graduated pipette (4.7) to transfer 2 ml of Nessler's reagent (3.4) to a Nessler colorimetric tube, and compare the test solution with a set of reference standard solutions one by one to determine the ammonia content. Nessler's reagent should be added to the reference standard solution and the test solution at the same time. To prepare a set of reference standard solutions, use a graduated pipette to add 1, 2, 3, 4, 5 and 6 ml of reference standard stock solution (3.3) to 6 Nessler colorimetric tubes (4.8) and dilute to 50 ml with water. They are equivalent to 0.01, 0.02, 0.03, 0.04, 0.05 and 0.06 mg of ammonia. Note: If it is found that 15 ml of distillate contains more than 0.06 mg of nitrogen, 10 ml of the filtered extract should be appropriately diluted and 10 ml of the diluted solution should be used for distillation. The corresponding dilution factor should be used in the calculation. 7 Expression of results
The content of free ammonia and ammonium compounds is obtained from formula (1) and expressed as a percentage by weight of ammonia (NH). m·D
Formula i: m- is the weight of ammonia contained in the corresponding standard solution in the group (see 6.2), mg; D-
is the coefficient when the filtrate is diluted before distillation. D
In the formula: Vi-
- is the volume of the filtered extract before dilution, ml (V=10 ml); Vz—— is the volume of 10 ml of the filtered extract after dilution, ml. 8 Test report
The test report should include the following items:
Indicate that it is in accordance with this national standard,
b. c. Complete details of the sample to be identified, c. Method used to make the molded product into powder, d. Free ammonia content, bzxz.net
Test date.
(2)
GB547485
Additional remarks:
This standard was proposed by the Ministry of Chemical Industry of the People's Republic of China and was organized by the Chemical Method Branch of the National Technical Committee for Plastic Standardization. This standard was drafted by Shanghai Plastics. The main drafters of this standard were Dian Yichu and Wang Zhaoliang. 601
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