Standard No.:	GB/T 629-2026
English Name:	Chemical reagent—Sodium hydroxide
Chinese Name:	化学试剂 氢氧化钠
Professional Classification:	GB    National Standard
Source Content Issued by:	SAMR, SAC
Issued on:	2026-02-27
Implemented on:	2026-9-1
Status:	to be valid
Superseding:	GB/T 629-1997 Chemical reagent--Sodium hydroxide
Target Language:	English
File Format:	PDF
Word Count:	6500 words
Translation Price(USD):	195.0
Delivery:	via email in 1~3 business day

GB/T 629-2026 Chemical reagent—Sodium hydroxide English, Anglais, Englisch, Inglés, えいご This is a draft translation for reference among interesting stakeholders. The finalized translation (passing through draft translation, self-check, revision and verification) will be delivered upon being ordered. ICS CCS National Standard of the People's Republic of China ‌GB/T 629-2026 Chemical reagent - Sodium hydroxide 化学试剂 氢氧化钠 Issue date: 2026-02-27 Implementation date: 2026-09-01 Issued by the General Administration of Quality Supervision, Inspection and Quarantine of the People's Republic of China the Standardization Administration of the People's Republic of China Contents Foreword 1 Scope 2 Normative References 3 Terms and Definitions 4 Description 5 Technical Requirements 6 Test Methods 7 Inspection Rules 8 Packaging and Marking Chemical reagent — Sodium hydroxide WARNING — Certain procedures specified in this document may involve hazardous situations. The user has the responsibility to take appropriate safety and health measures and to ensure compliance with the conditions specified by relevant national regulations. 1 Scope This document specifies the description, technical requirements, inspection rules, and packaging and marking of the chemical reagent sodium hydroxide, and describes the corresponding test methods. This document applies to the inspection of the chemical reagent sodium hydroxide. NOTE: The molecular formula of the chemical reagent sodium hydroxide is NaOH, the relative molecular mass is 40.00 (based on the 2022 international relative atomic masses), and the CAS number is 1310732. 2 Normative references The contents of the following documents constitute essential provisions of this document through normative reference. For dated references, only the edition cited applies. For undated references, the latest edition (including all amendments) applies. GB/T 601 Chemical reagent — Preparations of standard volumetric solutions GB/T 602 Chemical reagent — Preparations of standard solutions for impurity determination GB/T 603 Chemical reagent — Preparations of reagent solutions for use in test methods GB/T 609-2018 Chemical reagent — General method for the determination of total nitrogen GB/T 610-2008 Chemical reagent — General method for the determination of arsenic GB/T 6682 Water for analytical laboratory use — Specification and test methods GB/T 9723-2007 Chemical reagent — General rules for flame atomic absorption spectrometry GB/T 9727 Chemical reagent — General method for the determination of phosphate GB/T 9728 Chemical reagent — General method for the determination of sulphate GB/T 9729 Chemical reagent — General method for the determination of chloride GB/T 9734 Chemical reagent — General method for the determination of aluminium GB/T 9735-2008 Chemical reagent — General method for the determination of heavy metals GB/T 9739 Chemical reagent — General method for the determination of iron GB/T 9742 Chemical reagent — General method for the determination of silicate GB 15258 General rules for preparation of precautionary label for chemicals GB 15346 Chemical reagent — Packaging and marking GB/T 23942-2009 Chemical reagent — General rules for inductively coupled plasma atomic emission spectrometry GB 28644.2 Limited quantity and packaging requirements of dangerous goods GB/T 34672-2017 Chemical reagent — General rules for ion chromatography HG/T 3484-1999 Chemical reagent — Standard glass emulsions and standards of clearness HG/T 3921 Chemical reagent — Sampling and acceptance rules 3 Terms and definitions No terms and definitions need to be defined in this document. 4 Description Sodium hydroxide is a white, uniform granular or flaky solid. It readily absorbs moisture and carbon dioxide from the air, is corrosive, and is readily soluble in water. 5 Technical requirements The technical requirements for sodium hydroxide shall comply with Table 1. 6 Test methods 6.1 General provisions Unless otherwise specified in this clause, all standard volumetric solutions, standard solutions, preparations and products used shall be prepared in accordance with GB/T 601, GB/T 602 and GB/T 603. The water used for the laboratory shall comply with the specifications for Grade 3 water in GB/T 6682. All reagents used shall be of analytical grade or higher. All samples shall be weighed to within 0.01 g. Unless otherwise indicated, the percentages "%" used for solutions are mass fractions, except for "ethanol (95%)". 6.2 Sodium hydroxide 6.2.1 Preparation of test solution Quickly weigh 25 g of the sample, place it in a conical flask, add 200 mL of carbon dioxidefree water, immediately stopper tightly with a rubber stopper fitted with a sodalime tube. After dissolution, cool, transfer to a 250 mL volumetric flask, and dilute to the mark. 6.2.2 Determination method Measure 10.00 mL of the test solution, transfer it to a stoppered conical flask, add 95 mL of carbon dioxidefree water and 5 mL of barium chloride solution (100 g/L), shake, and allow to stand for 15 min. Add 2 drops of phenolphthalein indicator solution (10 g/L), and titrate with hydrochloric acid standard volumetric solution [c(HCl) = 1 mol/L] until the red colour of the solution disappears. Retain the solution for the continued determination of sodium carbonate content. The mass fraction of sodium hydroxide (w₁) is calculated according to formula (1): The absolute difference between two parallel determination results shall not be greater than 0.2%. The arithmetic mean of the two parallel determination results shall be taken as the final result. 6.3 Carbonate Add 10 drops of bromocresol greenmethyl red indicator solution to the solution obtained after the determination of sodium hydroxide (6.2.2). Titrate with hydrochloric acid standard volumetric solution [c(HCl) = 1 mol/L] until the solution changes from green to dark red. Boil for 2 min, cool, and continue the titration until the solution becomes dark red. The mass fraction of sodium carbonate (w₂) is calculated according to formula (2): 6.4 Clarity test Measure 100 mL of the test solution (6.2.1). Its turbidity shall not exceed the clarity standard of No. 2 (guaranteed reagent), No. 4 (analytical reagent) or No. 6 (chemical reagent) specified in Table 2 of HG/T 3484-1999. 6.5 Chloride 6.5.1 Turbidimetric method (arbitration method) Measure 5 mL of the test solution (6.2.1), neutralise with nitric acid solution (25%), dilute to 20 mL, and then determine in accordance with GB/T 9729. The turbidity produced by the solution shall not exceed that of the standard turbidity comparison solution. The standard turbidity comparison solution is prepared by taking a chloride (Cl) standard solution containing 0.010 mg (guaranteed reagent), 0.025 mg (analytical reagent) or 0.050 mg (chemical reagent), diluting to 20 mL, and treating it simultaneously and in the same manner as the test solution. 6.5.2 Ion chromatography method 6.5.2.1 Reagents, materials and instruments Carry out in accordance with the provisions of Clauses 5 and 6 of GB/T 34672-2017. 6.5.2.2 Instrument conditions Chromatography column: column length 250 mm, internal diameter 4 mm; polystyrenedivinylbenzene polymer with quaternary ammonium functional groups, particle size 9 μm, pH tolerance range 0 to 14. Alternatively, other chromatography columns capable of achieving similar separation. Eluent: 15 mmol/L potassium hydroxide solution. Eluent flow rate: 1.0 mL/min. Chromatography column temperature: 30 °C. Detector temperature: 35 °C. Suppressor: Anion suppressor. Suppression current: 48 mA. Injection volume: 25 μL. The above instrument conditions may be optimised according to specific circumstances. A typical ion chromatogram is shown in Figure A.1 of Annex A.