This standard specifies the technical requirements, test methods, inspection rules, packaging and marking of the working reference reagent (capacity) potassium hydrogen phthalate. This standard is applicable to the inspection of potassium hydrogen phthalate with a content of 99.95% to 100.05% of the working reference reagent (volume). GB 1257-1989 Working reference reagent (capacity) Potassium hydrogen phthalate GB1257-1989 Standard download and decompression password: www.bzxz.net

National Standard of the People's Republic of China
Working chemical
Potassium hydrogen phthalateThis reagent is colorless crystal or white crystalline powder, soluble in water. Species: KHCH,O.
Relative mass: 204.22 (according to the international atomic weight of 1987)Subject content and scope of application
GB1257-89
Replaces GB 1257-77
This standard specifies the technical requirements, test methods, inspection rules, packaging and marking of the working standard reagent (volume) potassium hydrogen phthalate.
This standard is applicable to the inspection of the working standard reagent (volume) potassium hydrogen phthalate with a content of 99.95% to 100.05%. 2 Reference standards
GB 601
GB 602
GB 603
Chemical reagents
Preparation of standard solutions for titration analysis (volume analysis)Chemical reagents
Chemical reagents
GB 619
Chemical reagents
GB 6682
Preparation of standard solution for determination of impurities
Preparation of preparations and products used in test methods Sampling and acceptance rules
Specifications for water in laboratories
GB9723
GB9724
Chemical reagents
General rules for flame atomic absorption spectrometry
Chemical reagents
General rules for pH determination
GB10737 General rules for weighing potentiometric titration of working standard reagents (capacity) HG3-119 Packaging and marking of chemical reagents
HG3-1168 Preparation and determination method of clarity standards of chemical reagents 3 Technical requirements
3.1 Potassium hydrogen phthalate (KHCgH,O) content is 99.95% to 100.05%. 3.2 pH (50g/L solution, 25℃):3.8 ~4.1.3.3
Maximum impurity content (indicators in percentage): %
Name
Clarity test
Water-insoluble matter
Name
Chloride (CI)
Sulfur complex (in SO.)
Sodium (Na)
Iron (Fe)
Heavy metal (in Pb)
People's Republic of China Approved by the Ministry of Chemical Industry on March 1, 1989Working standard (capacity)
Qualified
0.003
0.002
0.006
0.005
0.0005
0.0005
Implemented on December 1, 1989
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4 Test method
GB 1257-89
The standard solution for titration analysis, standard solution for impurity determination, preparations and products in this test method shall be prepared in accordance with the provisions of GB601, GB602 and GB603; the water used in the experiment shall comply with the third-grade water specifications in GB6682. 4.1 Determination of potassium hydrogen phthalate (KHC.H,O) content 4.1.1 Calibration of mass molar concentration of sodium hydroxide standard titration solution Weigh 0.5g of the first reference reagent (capacity) potassium hydrogen phthalate which has been dried to constant weight at 105-110℃, accurate to 0.00001g, put it in a reaction bottle +t, add 150mL of carbon dioxide-free water to dissolve it, use a 231 type glass electrode as the indicator electrode and a 232 type saturated calomel electrode as the reference electrode, and according to the provisions of GB10737, use the sodium hydroxide standard titration solution to be calibrated [b (NaOH) = 0.1mol/kg) to drip to the end point.
The mass molar concentration of the standard sodium hydroxide titration solution is calculated according to formula (1): 6=
mi
m2× 0.204 22
Formula tl: b--the mass molar concentration of the standard sodium hydroxide titration solution, mol/kg: gmj--the mass of the first reference reagent (capacity) potassium hydrogen phthalate, gmj-
m
the mass of the standard sodium hydroxide titration solution to be calibrated, g, (1))
0.20422--the mass of potassium hydrogen phthalate equivalent to 1.0000g of the standard sodium hydroxide titration solution [b(NaOH)=1.0000mol/kg), expressed in grams.
4.1.2 Determination of content
Weigh 0.5g of the sample dried to constant weight at 105-110℃, accurate to 0.00001g, and titrate with sodium hydroxide standard titration solution [b (NaOH) = 0.1mol/kg] according to the provisions of 4.1.1. The determination of content is carried out simultaneously with the calibration of the concentration of the standard solution for titration analysis. The content of potassium hydrogen phthalate (KHC:H4O.) is calculated according to formula (2): X=
武t: X-
m3-
h
0.20422
mg · b× 0.20422
m4
-the percentage content of potassium hydrogen phthalate, %, the mass of standard sodium hydroxide titration solution, g, the mass molar concentration of standard sodium hydroxide titration solution, mol/kg, x 100
(2)
the mass of potassium hydrogen phthalate expressed in grams equivalent to 1.0000g standard sodium hydroxide titration solution [6b(NaOH)=1.0000mol/kg],
m
the mass of the sample, g.
4.2 pH
Weigh 5g of sample, weigh to 0.01g, dissolve in 100mL of water without carbon dioxide, and determine according to the provisions of GB9724. The pH value should be between 3.8 and 4.1.
4.3 Determination of impurities
The sample must be weighed to 0.01g.
4.3.1 Clarity test
Weigh 7.5g of sample, add 100mL of water, heat to dissolve, and its turbidity shall not be greater than the clarity standard (refer to HG3--1168) No. 2. 4.3.2 Water insoluble matter
Weigh 30g of sample, add 1400mL of water, heat to dissolve, and keep warm in a water bath for 1h. Filter with No. 4 glass filter that has been constant weight at 105±2℃, wash the filter residue with hot water until there is no potassium ion reaction in the washing liquid, and dry it in an electric oven at 105±2℃ to constant weight. The mass of the filter residue shall not exceed 0.9 mg.
4.3.3 Chloride
Weigh 5 g of the sample, dissolve in 30 mL of hot water, cool, add 10 mL of nitric acid, filter, and dilute to 50 mL. Take 10 mL, add 1 mL of 522
GB 1257--89
nitric acid solution (25%) and 1 mL of silver nitrate solution (17 g/L), dilute to 25 mL, shake well, and let stand for 10 minutes. The turbidity presented shall not exceed the standard.
The standard is to take an impurity standard solution containing 0.02 mg of chloride (C1), dilute to 10 mL, and treat it in the same way as the sample solution of the same volume.
4.3.4 Sulfur compounds
Weigh 0.5g of the sample, place it in a platinum crucible, add 0.2g of anhydrous sodium carbonate, mix well, add 2mL of water to moisten it, steam it on a water bath, heat it until it is completely carbonized, gradually raise the temperature to 700℃ and burn it until it turns white. If the residue is not white, add a small amount of water to moisten it after cooling, evaporate it to dryness on a water bath, and then burn it. Repeat this operation until the residue turns completely white, cool it, add 5mL of water to dissolve it, neutralize it with hydrochloric acid solution (20%) (filter it if necessary), dilute it to 10mL, add 5mL of 95% ethanol and 0.5mL of hydrochloric acid solution (20%), add 3mL of chlorinated sodium solution (250g/L) under continuous shaking, dilute it to 25mL, shake it well, and let it stand for 10min. The turbidity should not be greater than the standard. The standard is to take an impurity standard solution containing 0.03mg of sulfate (SO.), add 0.2g of anhydrous sodium carbonate, and treat it in the same way as the sample. 4.3.5 Sodium
Determine by flame atomic absorption spectrometry.
4.3.5.1 Instrument conditions
Light source: sodium hollow cathode lamp,
wavelength: 589.0nm;
Flame: acetylene-air. Www.bzxZ.net
4.3.5.2 Determination method
Weigh 4g of sample, dissolve in water, dilute to 100mL, take 10mL, a total of four portions. Determine according to the provisions of Article 6.2.2 of GB9723. 4.3.6 Iron
Weigh 1g of sample, dissolve in 15mL of hot water, adjust the pH value of the sample solution to 2 with hydrochloric acid solution (15%), add 1mL of ascorbic acid solution (20g/L), 5mL of acetic acid-sodium acetate buffer solution (pH～4.5) and 1mL1,10-phenanthroline solution (2g/L), dilute to 25mL, shake, and let stand for 15 minutes. The red color of the star must not be darker than the standard. The standard is to take an impurity standard solution containing 0.005 mg of iron (Fe) and process it at the same time as the sample. 4.3.7 Heavy metals
Weigh 4g of the sample, dissolve it in 40mL of hot water, take 30mL, add 0.2mL of acetic acid solution (30%) and 10mL of newly prepared saturated cyanogen sulfide water, shake well, and leave for 10 minutes. The dark color should not be darker than the standard. The standard is to take the remaining 10 mL of sample solution and the impurity standard solution containing 0.01 mg of lead (Pb), dilute it to 30 mL, and treat it in the same way as the same volume of sample solution at the same time.
Inspection rules
5
Sampling and acceptance shall be carried out in accordance with the provisions of GB619. 6 Packaging and marking
6.1 Packaging
According to the regulations of HG 3-119.
Inner packaging form: G-2;
Outer packaging form: cardboard box with specification of 600g/m2, outer layer framed with purple electro-optical paper; Packaging unit: Category 3.
6.2 Standard Benefit
According to the regulations of HG 3-119.
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GB1257-—89
Additional notes:
This standard was proposed by the Chemical Reagent Branch of the National Chemical Standardization Technical Committee. This standard is produced by Beijing Chemical Reagent General Factory. This standard was drafted with the approval of Beijing Chemical Industry Co., Ltd.
The drafters of this standard are McKinzhi, Chen Hua and Zhao Fenglan. 524
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