This standard is applicable to the determination of total formaldehyde content in resin finishing agents. GB/T 5543-1985 Determination of total formaldehyde content in resin finishing agents GB/T5543-1985 Standard download decompression password: www.bzxz.net

National Standard of the People's Republic of Chinabzxz.net
Determination of total formaldehyde content in resin finishing agentResin finishing agent
Determination of total formaldehyde contentThis standard applies to the determination of total formaldehyde content in resin finishing agent. 1 Principle of the method
UDC 678.044.33
GB5543—85
Total formaldehyde in resin finishing agent [generally including hydroxymethyl formaldehyde (-CHOH), methyl formaldehyde (-CH2-), alkylated formaldehyde (-CH,OR) and unreacted formaldehyde] is decomposed into formaldehyde and acetal during distillation in phosphoric acid medium, and then absorbed with water after distillation, and determined by iodine titration.
Iodine generates sodium hypoiodite in the presence of alkali, which oxidizes all formaldehyde and acetal in the absorption liquid into formic acid. Excess iodine is titrated with sodium thiosulfate to quantitatively measure the total formaldehyde content. The reaction is as follows: I + 2 NaOH.NaIO + NaI+ H,O
HCHO + NaIO + NaOHHCOONa+NaI+H,O Excess sodium hypoiodite precipitates iodine, which is titrated with sodium thiosulfate: NaIO+NaI+H,SO,-→I +Na,SO. +H,OIz + 2 NazS,0,—-- 2 NaI+ Na?S,0.2 Reagents and solutions
The preparation and calibration of standard solutions shall be carried out in accordance with the provisions of GB601-77 "Preparation Method of Chemical Reagent Standard Solutions". 2.1 Phosphoric acid (GB 1282-77): analytical grade. 2.2 Iodine (GB 675-77): analytical grade, 0.1N solution. 2.3 Sodium thiosulfate (GB637-65). Analytical grade, 0.1N solution. 2.4 Sodium hydroxide (GB629-81): analytical grade, 2N solution. 2.5 Sulfuric acid (GB625-77): analytical grade, 2N solution. 2.6 Soluble starch (HGB3095-59): analytical grade, 1.0% indicator solution. 3 Instruments and equipment
3.1 Analytical balance: sensitivity 0.1 mg.
3.2 Distillation flask: capacity 250 ml.
3.3 Dropping funnel: capacity 100 ml.
3.4 ​​Iodine volumetric flask: capacity 250 ml.
3.5 Pipette: capacity 20, 25 ml.
3.6 Measuring cylinder: capacity 25 ml.
3.7 Volumetric flask: capacity 250 ml.
3.8 Burette: 50 ml acid burette. 3.9 Thermometer: 0-150°C.
3.10 Straight tube condenser: length 30 cm.
Distillation lead pipe.
Issued by the National Bureau of Standards on October 29, 1985
Implemented on August 1, 1986
4 Determination procedures
GB 5543-85
Weigh about 1 gram (accurate to 0.0001 gram) of the sample and put it into a 250 ml distillation flask, install a dropping funnel and a thermometer, connect a condenser, and insert the lead pipe connected to the condenser into a 250 ml volumetric flask that has been pre-added with 20 ml of distilled water. Add 25 ml of phosphoric acid and 25 ml of distilled water to the distillation flask from the dropping funnel (add a few small pieces of zeolite first). Heat to boiling. In order to keep the liquid volume in the distillation flask constant, distilled water can be added dropwise from the dropping funnel without stopping the boiling. The distillate is collected in a 250 ml volumetric flask and evaporated to about 200 ml. Rinse the condenser and the connecting tube with a small amount of distilled water, add them to the volumetric flask, and then dilute them to the scale with distilled water for later use. Use a pipette to draw 20 ml of the above solution, put it into a 250 ml iodine volumetric flask, use a pipette to add 25 ml of 0.1N iodine solution and 10 ml of 2N sodium hydroxide solution, after leaving it at room temperature for 15 minutes, add 15 ml of 2N sulfuric acid. The precipitated iodine is titrated with 0.1N sodium thiosulfate solution, using starch as an indicator, and performing a vacuum test at the same time. The relative error of the results of the parallel determination is no more than 1%, and the average value is taken. 5 Calculation
Total formaldehyde percentage is calculated according to the following formula:
Total formaldehyde% =V2*0.015 x×100
G ×2/25
Where: V. ——Number of milliliters of sodium thiosulfate solution consumed in blank titration; V—Number of milliliters of sodium thiosulfate solution consumed in sample titration; N—Normal concentration of sodium thiosulfate solution; G—Mass of sample, grams;
0.015—Number of grams per milligram equivalent of formaldehyde. Additional remarks:
This standard was proposed by the Ministry of Chemical Industry of the People's Republic of China and is owned by the Shenyang Chemical Industry Research Institute of the Ministry of Chemical Industry. This standard was drafted by the Dalian Light Chemical Industry Research Institute. The main drafter of this standard is Jin Liwen.
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