GB/T 9724-2007Chemical reagent -- General rule for the determination of pH (English PDF)

Foreword

This Standard is not equivalent to ISO 6353-1.1982 "Reagents for chemical analysis -

Part 1.General test methods".

This Standard replaces GB/T 9724-1988 "Chemical reagent - General rule for the

determination of pH". Compared with GB/T 9724-1988, the main changes are as

follows.

-- ADD the normative references (Chapter 2);

-- INCREASE the degree of accuracy of the acidometers (5.2);

-- ADD saturated calomel electrode with double salt bridge and composite

electrode (5.3 of this Standard);

-- DELETE antimony electrode (5.3.2 in 1988 edition);

-- ADD control of the operating conditions of the counter electrodes (Chapter 6 of

this Standard);

-- MODIFY contents in Annex A.

Annex A of this Standard is Informative.

This Standard was proposed by China Petroleum and Chemical Industry Association.

This Standard shall be under the jurisdiction of the National Technical Committee of

Standardization for Chemicals (SAC/TC63/SC3).

Drafting organization of this Standard. Shanghai No.4 Reagent & H.V. Chemical Co.,

Ltd.

Chief Drafting Staff. Jia Ling.

This Standard was first-time issued in 1988.

Chemical reagent -

General rule for determination of pH

1 Scope

This Standard specifies the general rules for measurement of pH of water solution in

electrometric method.

This Standard is applicable to the measurement of pH of chemical reagent and water

solution. The measurement range of pH is 1 ~ 12.

2 Normative References

The provisions in following documents, through reference in this text, constitute the

provisions of this Standard. For dated reference, all subsequent amendments

(excluding corrigendum) or revisions do not apply to this Standard, however, parties

who have reached an agreement on this Standard are encouraged to study whether

the latest revisions of these documents are applicable. For undated reference, the

latest revisions apply to this Standard.

GB/T 601 Chemical Reagent - Preparation of Standard Volumetric Solution

GB/T 603 Chemical reagent - Preparations of reagent solutions for use in test

methods (GB/T 603-2002, ISO 6353-1.1982, NEQ)

GB/T 6682 Water for laboratory use - Specifications (GB/T 6682-1992, neq ISO

3696.1987)

3 Method and Theory

Soak the specified indicator electrode and reference electrode into the solution to be

measured to form a primary battery, whose electromotive force is related to the pH of

solution.

4 Reagent and material

5 Instruments and equipment

6 Measurements

Use non-carbon dioxide water to prepare the samples into 50 g/L solution (except

special case).

Annex A

(Informational Appendix)

Application and maintenance of the electrodes

A.1 Glass electrodes

Before use, new electrodes shall be soaked in the water for above 24 hours; after use,

it shall be rinsed immediately and be submerged in water for conservation.

A.2 Saturated calomel electrodes

During use, the rubber stopper on the small hole at the upper end of the electrode

must be pulled out to prevent diffusion potential that may impact the measurement

result. The potassium chloride solution inside electrodes must not have bubble to

prevent open circuit. There shall maintain some potassium chloride crystals in the

solution, so as to ensure that the potassium chloride is in saturation. The connecting

parts of the electrode shall not be stained or blocked, and to maintain appropriate

speed of effluent seepage.

A.3 Saturated calomel electrode with double salt bridge

The salt bridge sleeves shall be loaded with saturated ammonium nitrate or potassium

nitrate solution; other caution items are same as that of saturated calomel electrode.

A.4 Composite electrode

For the composite electrodes, the following matters shall be paid attention to.

......