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GB/T 10656-2022 English PDF (GBT10656-2022)

GB/T 10656-2022 English PDF (GBT10656-2022)

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GB/T 10656-2022: Analysis of water used in boiler and cooling system - Determination of zinc

This document describes the determination of zinc in water used in boiler and cooling system. This document applies to the determination of zinc content ranging from 0.2 mg/L to 5.0 mg/L in water used in boiler and circulating cooling system.
GB/T 10656-2022
NATIONAL STANDARD OF THE
PEOPLE REPUBLIC OF CHINA
ICS 13.060.50;71.040.40
CCS G 76
Replacing GB/T 10656-2008
Analysis of water used in boiler and cooling system -
Determination of zinc
ISSUED ON: MARCH 09, 2022
IMPLEMENTED ON: OCTOBER 01, 2022
Issued by: State Administration for Market Regulation;
Standardization Administration of the PEOPLE Republic of China.
Table of Contents
Foreword ... 3
1 Scope ... 4
2 Normative references ... 4
3 Terms and definitions... 4
4 General ... 4
5 Zincon spectrophotometry ... 5
6 Complexometric titration ... 7
Analysis of water used in boiler and cooling system -
Determination of zinc
1 Scope
This document describes the determination of zinc in water used in boiler and cooling system.
This document applies to the determination of zinc content ranging from 0.2 mg/L to 5.0 mg/L in water used in boiler and circulating cooling system.
2 Normative references
The following documents, in whole or in part, are normatively referenced in this document and are indispensable for its application. For dated references, only the version corresponding to that date is applicable to this document; for undated references, the latest version (including all amendments) is applicable to this document. GB/T 601, Chemical reagent - Preparations of reference titration solutions GB/T 602, Chemical reagent - Preparations of standard solutions for impurity GB/T 603, Chemical reagent - Preparations of reagent solutions for use in test methods
GB/T 6682-2008, Water for analytical laboratory use - Specification and test methods
HG/T 4015, General Reagent - General method for the determination of pH ranges corresponding the colour transition of acid-base indicators
3 Terms and definitions
There are no terms and definitions that need to be defined in this document. 4 General
Caution ?€? The strong acid and strong base which are used in this document are corrosive. Avoid inhalation or contact with the skin during use. If it splashes on the body, use plenty of water to rinse immediately, and if it is serious, seek medical attention immediately.
The reagents and water used in this document, unless otherwise specified, shall be analytical reagents and above, and grade-3 water specified in GB/T 6682-2008. The reference titration solutions, impurity reference solutions, reagents and products required in the test shall be prepared in accordance with the provisions of GB/T 601, GB/T 602 and GB/T 603 unless other provisions are specified.
5 Zincon spectrophotometry
5.1 Method summary
In the solution of pH8.5 ~ pH9.5, the zinc reagent and zinc ion form a blue complex; at the wavelength of 620 nm, use the spectrophotometric method to measure its absorbance.
5.2 Reagents or materials
5.2.1 Hydrochloric acid solution: 1+1.
5.2.2 Sulfuric acid solution: 1+35.
5.2.3 Sodium hydroxide solution: 40 g/L.
5.2.4 Ammonium persulfate solution: 4 g/L, ready-to-use.
5.2.5 Boric acid-potassium chloride-sodium hydroxide buffer solution (pH8.8 ~ pH9.0). Prepare according to HG/T 4015.
5.2.6 Zinc standard stock solution: 0.1 mg/mL. Prepare according to GB/T 602, or buy commercially available solution.
5.2.7 Zinc standard solution: 0.01 mg/mL. Pipette 10.00 mL of zinc standard stock solution into a 100 mL volumetric flask; use water to dilute to the mark; mix well. Formulate the solution when needed.
5.2.8 Methyl orange indicator solution: 1 g/L.
5.2.9 Zinc reagent solution: 0.8 g/L. Weigh 0.2 g of zinc reagent and dissolve it in 250 mL of absolute ethanol; cover and place overnight to make it completely dissolved (or ultrasonically shake for 1 min ~ 5 min to dissolve completely). Store the solution in a brown bottle and place it in a refrigerator at 0 ??C ~ 4 ??C for one month. When the solution turns from red to yellow, it shall be re-prepared.
5.3 Apparatus
Spectrometer: equipped with a 2 cm absorption cell.
5.4 Test procedures
6.2.7 Acetic acid-sodium acetate buffer solution (pH = 5.5): Weigh 200 g of sodium acetate (CH3COONa??3H2O) and dissolve it in 150 mL of water; add 9 mL of glacial acetic acid; transfer it into a 1 000 mL volumetric flask; use water to dilute to the mark. 6.2.8 Ethylene Diamine Tetraacetic Acid standard titration solution: c(EDTA) = 0.001 mol/L. Before use, use boiled and cooled water to dilute the Ethylene Diamine Tetraacetic Acid standard titration solution, of a concentration of 0.1 mol/L, which is prepared according to GB/T 601.
6.2.9 Xylenol orange indicator solution: 6 g/L. Weigh 0.6 g of xylenol orange; dissolve in water and dilute to 100 mL; mix well; store in a brown bottle.
6.3 Apparatus
Micro burette: 5 mL or 10 mL.
6.4 Preparation of samples
The sample for the single-item analysis measurement shall not be less than 300 mL; the sample storage bottle shall be a stoppered glass bottle or a polyethylene plastic bottle. The determination of zinc content should be completed as soon as possible. Under normal circumstances, the sample shall not be stored for more than 24 h. For the measurement of the content of soluble zinc, an appropriate amount of sample shall be determined after filtration through the medium-speed filter paper.
6.5 Test procedure
Pipette 100.0 mL of sample; put it in a 250 mL conical flask; add 2 mL of tartaric acid solution, 4 mL of potassium fluoride solution and 0.5 mL of thiourea solution; use sodium hydroxide solution or hydrochloric acid solution to adjust the pH of the test solution to 5 ~ 6. Then, add 20 mL of acetic acid-sodium acetate buffer solution; shake well; heat to 30 ??C ~ 40 ??C on an electric hot plate or water bath. Add 10 drops of trisodium citrate solution; then, add three to four drops of xylenol orange indicator solution; use Ethylene Diamine Tetraacetic Acid standard titration solution to titrate until the sample changes from purple red to bright yellow as the end point. When there is no organic phosphonate in the sample, tartaric acid solution may not be added; when there is no copper ion, thiourea solution may not be added; when the content of aluminum ion and iron ion is less than 1 mg/L, trisodium citrate solution may not be added.
6.6 Result calculation
The zinc ion content in the sample is calculated by mass concentration (??); the value is expressed in milligrams per liter (mg/L), and calculated according to Formula (2):

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