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This standard is developed according to the rules given in GB/T 1.1-2009.
This standard replaces GB/T 601-2002 Chemical Reagent - Preparations of Standard Volumetric Solutions and has the following main technical changes with respect to GB/T 601-2002:
——Relevant contents of 3.2, 3.6, 3.8, 3.9 and 3.10 in General Requirements are modified (see 3.2, 3.6, 3.8, 3.9 and 3.10; 3.2, 3.6, 3.8, 3.9 and 3.10 in edition 2002);
——In sodium carbonate reference titration solution, "Meanwhile, carry out blank test" is added in Method I and Method II (directly prepared with working standard reagent) is added (see 4.4.1.2 and 4.4.2; 4.4.2 in edition 2002);
——Preparation method and calibration method II of iodine reference titration solution are modified (see 4.9.1 and 4.9.2.2; 4.9.1 and 4.9.2.2 in edition 2002);
——Preparation method of sodium thiosulfate reference titration solution is modified (see 4.6.1; 4.6.1 in edition 2002);
——Sodium oxalate reference titration solution is added parallel with oxalic acid reference titration solution and Method II is added (sodium oxalate reference titration solution directly prepared with working standard reagent) (see 4.11.1.1 and 4.11.2; 4.11 in edition 2002);
——For ammonium iron (II) sulfate reference titration solution, Method I in added and "Meanwhile, carry out blank test" is added in Method II (see 4.13.3.1 and 4.13.3.2; 4.13 in edition 2002);
——Method II is added for EDTA reference titration solution (directly prepared with working standard reagent) and significant digits for mole mass of zinc oxide (working standard reagent) is modified (see 4.15.1.2.1, 4.15.1.2.2 and 4.15.2; 4.15.2.1 and 4.15.2.2 in edition 2002);
——In zinc chloride reference titration solution, 0.05 mol/L and 0.02 mol/L are added and Method II (directly prepared with working standard reagent) for three concentrations are added (see 4.16 and 4.16.2; 4.16 in edition 2002);
——"Meanwhile, carry out blank test" is added in lead nitrate reference titration solution (see 4.18.2; 4.18.2 in edition 2002);
——Mercuric nitrate reference titration solution is added (see 4.22);
——Temperature of titrated solution during calibration of sodium nitrite reference titration solution is adjusted; "Meanwhile, carry out blank test' is added; Method II is added (end point is judged with external-use starch-potassium iodide test paper); Calibration prior to use in case of c(NaNO2)=0.5 mol/L is specified and "Calibration prior to use" is changed to "Storage time is 4 months" in case of c(NaNO2)=0.1 mol/L (see 4.23.2.1, 4.23.2.2 and 3.10 a); 4.22.2 in edition 2002);
——"Meanwhile, carry out blank test' is added in perchloric acid reference titration solution; "Calibration prior to use" is changed to "storage time is 2 months' (see 4.24.2 and 3.10 a); 4.23.2 and 4.23.3 in edition 2002);
——Preparation method of potassium hydroxide-ethanol reference titration solution is modified; "Calibration prior to use" is changed to "Storage time is 2 months" (see 4.25.1 and 3.10 a); 4.24.1 in edition 2002);
——Hydrochloric acid-ethanol reference titration solution is added (see 4.26);
——Ammonium iron (III) sulfate reference titration solution is added (see 4.27);
——"Annex B (Normative) Determination Method of Burette Capacity" (see Annex B) is added.
This standard was proposed by China Petroleum and Chemical Industry Federation.
This standard is under the jurisdiction of Subcommittee on Chemical Reagents of National Technical Committee on Chemical of Standardization Administration of China (SAC/TC 63/SC 3).
The previous editions of the standard replaced by this standard are as follows:
——GB/T 601-1965, GB/T 601-1977, GB/T 601-1988 and GB/T 601-2002.
Chemical Reagent –
Preparations of Reference Titration Solutions
Warning: Consdering that test process specified in this standard may cause dangerous conditions, Operator is responsible to take appropriate safety and health measures.
1 Scope
This standard specifies preparation and calibration method of chemical reagent reference titration solution.
This standard is applicable to both preparation and calibration of reference titration solution whose chemical reagent purity and impurity content is determined by titration and other areas.
2 Normative References
The following documents for the application of this document are essential. For dated reference, only the edition cited applies. For undated references, the latest edition (including any amendments) applies.
GB/T 603 Chemical Reagent - Preparations of Reagent Solutions for Use in Test Method
GB/T 606 Chemical Reagent - General Method for the Determination of Water - Karl Fischer Method
GB/T 6379.6-2009 Accuracy(trueness and precision) of Measurement Methods and Results - Part 6: Use in Practice of Accuracy Values
GB/T 6682 Water for Analytical Laboratory Use-Specification and Test Methods
GB/T 9725-2007 Chemical Reagent - General Rule for Potentiometric Titration
JJG 130 Verification Regulation of Liquid-in-Glass Thermometers for Working
JJG 196-2006 Verification Regulation of Working Glass Container
JJG 1036 Verification Regulation for Electronic Balance
3 General Requirements
3.1 Unless otherwise specified in this standard, the analytically pure level and above reagents, preparations and products prepared according to GB/T 603 and Grade 3 water (defined in GB/T 6682) shall be adopted for the purpose of this standard.
3.2 The concentration of reference titration solution prepared in this standard refers to that at 20℃ except perchloric acid reference titration solution, hydrochloric acid-ethanol reference titration solution and sodium nitrite reference titration solution [c(NaNO2)=0.5 mol/L]. If calibration, direct preparation and use of reference titration solution is not conducted at 20℃, volume of shall be corrected (see Annex A). Reference titration solution with "calibration prior to use" may not be corrected in case of not large temperature difference during calibration and use. Calibration, direct preparation and analytical balance, burette, one-mark volumetric flask and one-mark pipet for use shall be verified or calibrated periodically according to relevant verification regulation and determination method of burette volume is performed according to Annex B. Besides, one-mark volumetric flask and one-mark pipet shall be provided with volume correction factor.
3.3 During calibration and use of reference titration solution, titration speed shall be kept at 6 mL/min~8 mL/min.
3.4 The mass of working standard reagent, is accurate to 0.01 mg if less than or equal to 0.5 g and 0.1 mg if greater than 0.5g .
3.5 The concentration of reference titration solution prepared shall be within range of ±5% specified concentration.
3.6 Unless otherwise specified, calibration for concentration of reference titration solution shall be conducted by two persons, four parallel tests for each: relative range of four parallel calibration results (each person) shall not be greater than critical range of relative repeatability [CR0.95(4)r＝0.15%]; relative range of eight parallel calibration results (two persons) shall not be greater than critical range of relative repeatability [CR0.95(8)r=0.18%]. During calculation, 5 significant digits shall be reserved, average of eight parallel calibration results (two persons) is taken as calibration result and 4 significant digits are reserved for result given. If necessary, comparison method may be adopted to verify concentration of part of reference titration solution (see Annex C).
3.7 Relative expanded uncertainty for concentration of reference titration solution in this standard is not greater than 0.2% (k=2) and see Annex D for its evaluation method.
3.8 Working standard reagent is adopted to calibrate concentration of reference titration solution in this standard; If there are higher requirements on accuracy of concentration of reference titration solution, standard substance (expanded uncertainty shall be less than 0.05%) may be adopted to replace working standard reagent for calibration or direct preparation and its mass fraction is substituted into calculation formula during calculation for concentration of reference titration solution.
3.9 The concentration of reference titration solution shall be less than or equal to 0.02mol/L (except 0.02 mol/L EDTA and zinc chloride reference titration solution), while the reference titration solution with higher concentration is diluted with boiled and cooled water (reference titration solution free of nonaqueous solvent) and recalibrated if necessary. Where reference titration solution with concentration other than that specified in this standard is adopted, it may be prepared and calibrated by reference to preparation method of corresponding reference titration solution in this standard.
3.10 Storage:
a) Unless otherwise specified, sealed storage time is generally not more than 6 months for reference titration solution at 10℃~30℃: 4 months for iodine reference titration solution and reference sodium nitrite titration solution [c(NaNO2)=0.1 mol/L]; 2 months for perchloric acid reference titration solution, potassium hydroxide-ethanol reference titration solution and ammonium iron(III) sulfate reference titration solution. Besides, reference titration solution exceeding storage time may be further used after being recalibrated.
b) Storage time of reference titration solution after being unsealed and used is generally not more than 2 months (immediately fasten down the solution after being poured): not more than 1 month for iodine reference titration solution and potassium hydroxide-ethanol; not more than 15 d for sodium nitrite reference titration solution [c(NaNO2)=0.1 mol/L]; perchloric acid reference titration solution shall be used on the day it is unsealed.
c) In case of turbidness, precipitation and color variation, the reference titration solution shall be newly prepared.
3.11 For the container storing reference titration solution, its material shall not take physical and chemical reaction with solution and its wall thickness shall not be less than 0.5 mm at the thinnest place.
3.12 "%" for the solution adopted in this standard refers to mass fraction except "ethanol (95%).
4 Preparation and Calibration of Reference Titration Solution
4.1 Sodium Hydroxide Reference Titration Solution
4.1.1 Preparation
Dissolve 110 g sodium hydroxide in 100 mL carbon dioxide-free water, shake well, inject into polythene container and place hermetically till solution turns clear. Measure specified amount (in Table 1) of the supernatant with plastic pipe, dilute to 1000 mL with carbon dioxide-free water and shake well.
Table 1
Concentration of sodium hydroxide reference titration solution
c(NaOH)/(mol/L) Volume of sodium hydroxide solution
V/mL
1 54
0.5 9.7
0.1 5.4
4.1.2 Calibration
Weigh specified amount (in Table 2) of potassium acid phthalate (working standard reagent) dried to constant weight in 105~110℃ electric dry oven, dissolve it with carbon dioxide-free water, add two drops of phenolphthalein indicator solution (10g/L), titrate the solution with the prepared sodium hydroxide solution till it turns pink and maintain 30s. Meanwhile, carry out blank test.
Table 2
Concentration of sodium hydroxide reference titration solution
c(NaOH)/(mol/L) Mass of potassium acid phthalate (working standard reagent)
m/g Volume of carbon dioxide–free water
V/mL
1 7.5 80
0.5 3.6 80
0.1 0.75 50
The concentration of sodium hydroxide reference titration solution [c(NaOH)] is calculated according to Formula (1):
(1)
Where,
m——the mass of potassium acid phthalate, g;
V1——the volume of sodium hydroxide solution, mL;
V2——the volume of sodium hydroxide solution consumed in blank test, mL;
M——the molar mass of potassium acid phthalate, g/mol, [M(KHC8H4O4)=204.22].
4.2 Hydrochloric Acid Reference Titration Solution
4.2.1 Preparation
Measure specified amount (in Table 3) of hydrochloric acid, inject into 1 000 mL water and shake well.
