This standard is applicable to the determination of free formaldehyde content in various resin finishing agents synthesized with formaldehyde or polyformaldehyde as raw materials. GB/T 5544-1985 Method for determination of free formaldehyde content in resin finishing agents GB/T5544-1985 Standard download decompression password: www.bzxz.net

National Standard of the People's Republic of China
Determination of free formaldehyde content in resin finishing agentResin finishing agent-
Determination of free formaldehyde contentUDC 678.044.33
GB 5544-85
This standard is applicable to the determination of free formaldehyde content in various resin finishing agents synthesized with formaldehyde or polyformaldehyde as raw materials. 1 Principle of the method
Formaldehyde can react with sodium sulfite to generate "sodium formaldehyde sulfite" and sodium hydroxide. The released sodium hydroxide is titrated with an acid of known concentration to obtain the formaldehyde content. The reaction formula is as follows: HCHO + Na,SO, + H,O
- HC--SO,Na + NaOH
NaOH + HC1 -NaCI + H?C
2 Reagents and solutions
The preparation and calibration of standard solutions shall be carried out in accordance with the provisions of GB601-77 "Methods for the preparation of chemical reagent standard solutions". 2.1 Sodium hydroxide (GB629-81): analytical grade, 0.5N solution. 2.2 Hydrochloric acid (GB622-77): analytical grade, 0.5N solution. 2.3 Anhydrous sodium sulfite (HG3-1078-77): analytical grade, 1.0M solution. 2.4 Thymolphthalein indicator: 0.5 g thymol is dissolved in 100 ml 90% ethanol (PH9.3-10.5, from colorless to blue). 3 Instruments and equipment www.bzxz.net
3.1 Analytical balance: sensitivity 0.1 mg.
3.2 Measuring cylinder: 50 ml capacity.
3.3 Burette: 25 ml acid burette. 3.4 Iodine volumetric flask: 250 ml capacity.
4 Determination procedure
Weigh about 5 g (accurate to 0.0002 g) of the sample and place it in a 250 ml iodine volumetric flask, dilute it to about 50 ml with distilled water, add 5 drops of thymolphthalein indicator, when the resin liquid pH <9.3 or pH>10.5, it can be adjusted to a very slight blue color with 0.5N sodium hydroxide solution or hydrochloric acid respectively. After adding 50 ml of 1.0M sodium sulfite solution, immediately use 0.5N hydrochloric acid to quickly titrate from blue to very slight blue as the end point. Record the amount V1, perform a blank test in the same way, and record the amount V. . Perform three parallel determinations, and the absolute error is no more than 0.04%, and the average value is taken. 5 Calculation
The percentage of free formaldehyde is calculated as follows: Free formaldehyde% = (1-) × 0.03
Wherein: V, — ml of hydrochloric acid standard solution consumed by the sample, issued by the National Bureau of Standards on October 29, 1985
implemented on August 1, 1986
GB5544-85
ml of hydrochloric acid standard solution consumed by the blank; - concentration of hydrochloric acid standard solution:
-mass of resin finishing agent sample, grams,
grams of formaldehyde per milligram equivalent.
Additional remarks:
This standard was proposed by the Ministry of Chemical Industry of the People's Republic of China and is under the jurisdiction of 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.
This standard refers to the German Democratic Republic standard TGL20303-4 (1965.1.1) "Determination of free formaldehyde in urea-formaldehyde and melamine formaldehyde primary condensate"
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