GB/T 11985-2026 Surface active agents—Determination of interfacial tension—Drop volume method 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 11985-2026
Surface active agents - Determination of interfacial tension - Drop volume method
表面活性剂 界面张力的测定 滴体积法
Issue date: 2026-01-28 Implementation date: 2027-02-01
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 Principle
5 Apparatus
6 Procedure
7 Expression of results
8 Test report
Surface active agents — Determination of interfacial tension — Drop volume method
1 Scope
This document describes a test method for the determination of interfacial tension between two liquid phases by measuring the volume of liquid drops.
This document is applicable to the determination of interfacial tension between two solutions of surface active agents in water or in organic solvents.
Note: Compared with the pull-off film method, the drop volume method described herein has the following advantages:
a) It enables the determination of interfacial tension between two liquid phases for various types of surface active agent solutions, including cationic surface active agents;
b) It enables the determination of interfacial tension of viscous liquids;
c) It enables accurate measurement of low interfacial tension at the level of 1 mN/m;
d) The repeatability standard deviation is less than ±0.5 mN/m (suitable for industrial laboratory control);
e) Interfacial tension can be determined using only a small amount of solution;
f) A simple automatic device can be used to measure the relationship between interfacial tension and time.
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 edition cited applies. For undated references, the latest edition (including any amendments) applies.
GB/T 4472, Determination of density and relative density of chemical products
QB/T 1223, Surface active agents — Water used as a solvent for tests — Specifications and test methods
3 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
3.1
interfacial tension
The tension at the interface between two phases.
Note: The SI unit of interfacial tension is newton per metre (N/m), and in practice millinewton per metre (mN/m) is commonly used.
[Source: GB/T 5327-2008, 3.2.2, Definition 15]
4 Principle
The volume of an aqueous phase droplet formed at the tip of a vertical capillary and detached from the tip when in contact with an organic phase is measured. The interfacial tension between the two liquid phases is calculated from the droplet volume, the capillary radius, the density difference between the two liquid phases and the acceleration due to gravity, based on the equilibrium between the weight of the droplet and the force of the interfacial tension supporting it, with an appropriate correction factor applied.
5 Apparatus
5.1 Measuring apparatus
5.1.1 The apparatus for measuring interfacial tension by the drop volume method is shown in Figure 1.
Note: Commercial complete apparatus is available on the market.
5.1.2 Glass syringe, precisely calibrated, with a volume of 0.5 cm³ or 1.0 cm³, driven by a micrometer screw with graduations enabling accurate measurement of droplet volume to ±0.0001 cm³.
5.1.3 Capillary tube, made of glass or stainless steel, with one end connected to the syringe and detachable for cleaning.
The capillary tube shall be prepared as follows:
a) Preparation of glass capillary: Cut a section approximately 4 cm in length from a high-quality small-bore glass capillary tube of suitable and uniform diameter. One end shall be ground to fit the glass syringe, and the other end shall be precisely ground on a glass plate coated with fine carborundum powder. To prevent the capillary from shaking during polishing, it shall be embedded in paraffin wax (softening point approximately 70 °C) contained in a glass tube of approximately 1.5 cm internal diameter. The capillary shall be horizontal and perpendicular to its axis. Its circumference shall be free from notches.
b) Preparation of stainless steel capillary: Cut a section approximately 4 cm in length from a high-quality small-bore stainless steel capillary tube of suitable and uniform diameter. One end shall be cut precisely at right angles to the tube axis using a precision lathe, and the other end shall be fitted with a polytetrafluoroethylene (PTFE) connector.
Depending on the interfacial tension value and density difference, the external radius of the capillary shall be selected within the range of 0.1 cm to 0.4 cm.
5.1.4 Glass jacketed cell, with internal diameter of 2.5 cm to 4 cm and height greater than 5 cm, temperature controllable, capable of accommodating the syringe and capillary.
5.2 Super thermostat
Capable of controlling the water bath temperature to an accuracy of ±0.5 °C.
5.3 Installation of the apparatus
The glass syringe (5.1.2) and capillary (5.1.3) shall be mounted on a stand that allows vertical movement, ensuring that the tip of the capillary is perpendicular to its axis, of uniform diameter and free from edge defects. The stand shall be fixed to a metal plate on an anti-vibration table.
Since manually turning the micrometer screw may cause vibration, a micro-motor may be used to drive the micrometer screw to reduce vibration of the test apparatus.
Water circulation may cause small vibrations; therefore, during measurement, when the droplet is approaching its maximum volume, the thermostat shall be turned off.
Standard
GB/T 11985-2026 Surface active agents—Determination of interfacial tension—Drop volume method (English)
Standard No.
GB/T 11985-2026
Status
to be valid
Language
English
File Format
PDF
Word Count
8500 words
Translation Price(USD)
255.0
Implemented on
2026-12-1
Delivery
via email in 1~3 business day
Detail of GB/T 11985-2026
Standard No.
GB/T 11985-2026
English Name
Surface active agents—Determination of interfacial tension—Drop volume method
GB/T 11985-2026 Surface active agents—Determination of interfacial tension—Drop volume method 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 11985-2026
Surface active agents - Determination of interfacial tension - Drop volume method
表面活性剂 界面张力的测定 滴体积法
Issue date: 2026-01-28 Implementation date: 2027-02-01
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 Principle
5 Apparatus
6 Procedure
7 Expression of results
8 Test report
Surface active agents — Determination of interfacial tension — Drop volume method
1 Scope
This document describes a test method for the determination of interfacial tension between two liquid phases by measuring the volume of liquid drops.
This document is applicable to the determination of interfacial tension between two solutions of surface active agents in water or in organic solvents.
Note: Compared with the pull-off film method, the drop volume method described herein has the following advantages:
a) It enables the determination of interfacial tension between two liquid phases for various types of surface active agent solutions, including cationic surface active agents;
b) It enables the determination of interfacial tension of viscous liquids;
c) It enables accurate measurement of low interfacial tension at the level of 1 mN/m;
d) The repeatability standard deviation is less than ±0.5 mN/m (suitable for industrial laboratory control);
e) Interfacial tension can be determined using only a small amount of solution;
f) A simple automatic device can be used to measure the relationship between interfacial tension and time.
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 edition cited applies. For undated references, the latest edition (including any amendments) applies.
GB/T 4472, Determination of density and relative density of chemical products
QB/T 1223, Surface active agents — Water used as a solvent for tests — Specifications and test methods
3 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
3.1
interfacial tension
The tension at the interface between two phases.
Note: The SI unit of interfacial tension is newton per metre (N/m), and in practice millinewton per metre (mN/m) is commonly used.
[Source: GB/T 5327-2008, 3.2.2, Definition 15]
4 Principle
The volume of an aqueous phase droplet formed at the tip of a vertical capillary and detached from the tip when in contact with an organic phase is measured. The interfacial tension between the two liquid phases is calculated from the droplet volume, the capillary radius, the density difference between the two liquid phases and the acceleration due to gravity, based on the equilibrium between the weight of the droplet and the force of the interfacial tension supporting it, with an appropriate correction factor applied.
5 Apparatus
5.1 Measuring apparatus
5.1.1 The apparatus for measuring interfacial tension by the drop volume method is shown in Figure 1.
Note: Commercial complete apparatus is available on the market.
5.1.2 Glass syringe, precisely calibrated, with a volume of 0.5 cm³ or 1.0 cm³, driven by a micrometer screw with graduations enabling accurate measurement of droplet volume to ±0.0001 cm³.
5.1.3 Capillary tube, made of glass or stainless steel, with one end connected to the syringe and detachable for cleaning.
The capillary tube shall be prepared as follows:
a) Preparation of glass capillary: Cut a section approximately 4 cm in length from a high-quality small-bore glass capillary tube of suitable and uniform diameter. One end shall be ground to fit the glass syringe, and the other end shall be precisely ground on a glass plate coated with fine carborundum powder. To prevent the capillary from shaking during polishing, it shall be embedded in paraffin wax (softening point approximately 70 °C) contained in a glass tube of approximately 1.5 cm internal diameter. The capillary shall be horizontal and perpendicular to its axis. Its circumference shall be free from notches.
b) Preparation of stainless steel capillary: Cut a section approximately 4 cm in length from a high-quality small-bore stainless steel capillary tube of suitable and uniform diameter. One end shall be cut precisely at right angles to the tube axis using a precision lathe, and the other end shall be fitted with a polytetrafluoroethylene (PTFE) connector.
Depending on the interfacial tension value and density difference, the external radius of the capillary shall be selected within the range of 0.1 cm to 0.4 cm.
5.1.4 Glass jacketed cell, with internal diameter of 2.5 cm to 4 cm and height greater than 5 cm, temperature controllable, capable of accommodating the syringe and capillary.
5.2 Super thermostat
Capable of controlling the water bath temperature to an accuracy of ±0.5 °C.
5.3 Installation of the apparatus
The glass syringe (5.1.2) and capillary (5.1.3) shall be mounted on a stand that allows vertical movement, ensuring that the tip of the capillary is perpendicular to its axis, of uniform diameter and free from edge defects. The stand shall be fixed to a metal plate on an anti-vibration table.
Since manually turning the micrometer screw may cause vibration, a micro-motor may be used to drive the micrometer screw to reduce vibration of the test apparatus.
Water circulation may cause small vibrations; therefore, during measurement, when the droplet is approaching its maximum volume, the thermostat shall be turned off.
