This standard is applicable to the determination of hydroxymethylformaldehyde content in resin finishing agents. GB/T 5545-1985 Determination of hydroxymethylformaldehyde content in resin finishing agents GB/T5545-1985 Standard download decompression password: www.bzxz.net

National Standard of the People's Republic of China
Determination of methylol formaldehyde content in resin finishing agentResin finishing agent --
Determination of methylol formaldehyde contentThis standard applies to the determination of methylol formaldehyde content in resin finishing agent. 1 Principle of the method
UDC 678.044.33
GB5545—85
Iodine generates sodium hypoiodite in the presence of alkali, oxidizing methylol formaldehyde and free formaldehyde to formic acid. Excess iodine can be quantitatively measured by back titration with sodium thiosulfate. The reaction formula is as follows:I2 + 2 NaOH--→NaIO + Nal+H,OHCHO + NaIO + NaOH---HCOONa + NaI+ H,O Excess sodium hypoiodite causes iodine to precipitate.
NaIO+NaI+ H,SO --I, + Na,SO. + H,OI2 + 2 Na,S,0,- 2NaI+ Na,S.0. The total content of hydroxymethylformaldehyde and free formaldehyde is obtained. Subtracting the free formaldehyde, the hydroxymethylformaldehyde content is obtained. 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 Iodine (GB675-77): analytical grade, 0.1N solution. 2.2 Sodium thiosulfate (GB637-65): analytical grade, 0.1N solution. 2.3 Sodium hydroxide (GB629-81): analytical grade, 2N solution. 2.4 - Sulfuric acid (GB625-77): analytical grade, 2N solution. 2.5 Soluble starch (HGB3095-59): analytical grade, 1.0% indicator solution. 3 Instruments and equipment
3.1 Electric constant temperature water bath.
3.2 Iodine volume flask: capacity 250 ml. Www.bzxZ.net
3.3 Pipette: capacity 25 ml.
3.4 ​​Burette: capacity 50 ml acid burette. 3.5 Measuring cylinder: capacity 10, 50 ml.
4 Determination procedure
Weigh about 100 mg of sample (accurate to ±0.1 mg) and place it in a 250 ml iodine volume flask, add 25 ml 0.1N iodine solution and 10 ml 2N sodium hydroxide solution with a pipette, cover the bottle with a stopper, and seal it with water. Place it in a constant temperature water bath at 50±1℃ and keep it warm for 15 minutes, take it out and cool it to below 20℃, then add 15 ml 2N sulfuric acid. The precipitated iodine is titrated with 0.1N sodium thiosulfate solution, using starch as an indicator, and a blank test is performed at the same time.
The total content of hydroxymethylformaldehyde and free formaldehyde is calculated as follows: (hydroxymethylformaldehyde + free formaldehyde)% = (V.-V)N×15G
Published by the National Bureau of Standards on October 29, 1985
Implemented on August 1, 1986
GB5545-85
Where: Vo---the number of milliliters of sodium thiosulfate solution consumed in blank titration;--the number of milliliters of sodium thiosulfate solution consumed in sample titration, N--the equivalent concentration of sodium thiosulfate solution, 15--the number of milligrams of formaldehyde per milligram equivalent, G--the mass of the sample, milligrams.
Subtracting the free formaldehyde content from the above formula is the hydroxymethylformaldehyde content. The method for determining free formaldehyde can be found in GB5544-85 "Method for determining the content of free formaldehyde in resin finishing agents". The relative error of the results of three parallel determinations is no more than 1%, and the average value is taken as the result. Additional Notes:
This standard was proposed by the Ministry of Chemical Industry of the People's Republic of China and is under the jurisdiction of Shenyang Chemical Industry Research Institute of the Ministry of Chemical Industry. This standard was drafted by Dalian Light Chemical Industry Research Institute. The main drafter of this standard is Jin Liwen.
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