GB/T 5549-1990 Determination of surface tension of surfactants by the liquid film pulling method

GB/T 5549-1990 Surface active agents - Determination of surface tension by the liquid film pulling method GB/T5549-1990 Standard download decompression password: www.bzxz.net

National Standard of the People's Republic of China
Surfactants
Determination of surface tengion by drawing up liquid films
Surface actlve agents
Determination of surface tengion by drawing up liquid filmsGB5549-90
Replaces GB 5549-85
This standard refers to and adopts the international standard IS0304-1985 "Surfactants-Determination of surface tension by drawing up liquid films". Subject content and scope of application
This standard specifies the determination of the surface tension of surfactant aqueous solutions by drawing up liquid films. This standard is applicable to the determination of the surface tension of surfactant organic solutions and mixed solutions containing multiple surfactants as well as pure liquids or solutions.
2 Reference standards
GB6682 Specification for laboratory water
3 Terminology
. Surface tension: The force acting on a unit length along the surface of a liquid caused by the free surface energy, which is numerically equal to the free surface energy per unit surface. The unit is millinewton/meter (mN/m). 4 Principle
Two flat threshold rings are inserted into the surfactant solution to be tested. When they are lifted up to the liquid surface, a liquid film will be formed between the ring and the liquid surface. This liquid film generates a vertical downward force on the ring. The minimum force required to break the liquid film under the ring is measured, which is the surface tension of the solution to be tested.
5 Reagents and solutions
The water used is the secondary water-based surfactant solution in the experimental honey water specification: take a certain amount of surfactant sample and carefully prepare it into a sample solution with water. The temperature of the solution should be kept constant, and the temperature change should be within 0.5℃.
The water used for the test is not allowed to come into contact with the cork or rubber stopper to prevent contamination. When the measurement is carried out near the critical solubility point [such as at the Krafft point, the cloud point of ethylene oxide condensates, etc.], the error is large. Therefore, it is best to measure at a temperature above the Krafft point or below the cloud point of ethylene oxide condensates. The surface of the solution is very sensitive to the dust in the air or the volatile chemical solvents around it, so do not handle volatile items in the room where the measurement is carried out. All instruments should be protected with protective covers. Approved by the State Administration of Technical Supervision on December 18, 1990 and implemented on December 1, 1991
6 Instruments
Common laboratory instruments and:
GB 5549-90
6.1 Surface tension meter, JZHY-180 interfacial tension meter or other models of interfacial tension meters with equivalent effects. 6.2 Measuring cup: can hold enough liquid, with a diameter greater than 8 7 Analysis steps
7.1 Cleaning the instrument
Put the platinum ring and measuring cup used for testing in a mixture of saturated potassium dichromate solution and sulfuric acid (saturated potassium dichromate solution + 100 mL sulfuric acid) and then rinse with water. mL) and then rinse with water until neutral. Avoid touching the clean platinum ring and the inner surface of the measuring cup with your fingers. 7.2 Calibration of the instrument
First adjust the lifting screw at the bottom of the interfacial tension meter to make the instrument platform level. Then check whether the periphery of the platinum ring is level. If it is not level, adjust it. Then adjust the zero point, and then place a known mass of the sliding weight on the ring of the instrument and measure its reading. Use formula (1) to calculate the value to be obtained,
Where: 9—
Gravity acceleration, m/s*
1-—.-Mass of the sliding weight, 8www.bzxz.net
L—Circumference of the platinum ring, m.
If the measured reading does not match the calculated value, adjust the instrument until it matches. 7. 3 Determination (see Appendix B)
The determination should be carried out in a constant temperature room. The overflow of the test solution should be kept constant, and the temperature can generally be selected within the range of 20-25°C. During the determination, the measuring cup is first rinsed several times with the solution to be tested, and then the test sample is drawn from the middle of a large amount of the solution to be tested into the measuring cup using a wave shift tube. The measuring cup is placed on the platform of the instrument, and the platform is raised until the platinum ring is immersed in the middle of the test solution, and then the platform is slowly lowered, while adjusting the tension on the arm connected to the platinum ring so that the balance pointer on the arm coincides with the red line on the reflector. Continue to carefully and slowly lower the platform, and constantly adjust the tension on the arm so that the upper and lower forces of the platinum ring are always balanced. When the platinum ring just emerges from the liquid surface, a liquid film will form between the ring and the liquid surface. When the tension increases to a certain extent, the liquid film breaks, and the reading on the dial at this time is the surface tension value measured for the test solution.
Repeat the above operation and test five times in a row. 8 Expression of analysis results
Take the arithmetic mean of the five consecutive measured values. This method uses a ring to measure the surface tension of the dissolved wave. The actual surface tension value V (mN/m) should be obtained by multiplying the measured surface tension value p by the correction factor F. The calculation formula (2) is as follows: V=PF
The correction factor F of the JZHY-180 interfacial tension meter is obtained by the calculation formula (3): F - 0.725 0 +
Yor(pi.pe)
In the formula: C—circumference of the platinum ring, mn;
—average radius of the whole ring
—average radius of the platinum ring, cmn;
—radius of the gold wire-1
—measured surface tension value, mN/n
—density of the test concentrate.tlar:
than that of air.a
Note that the surface tension value of the product according to
GB 5549-90
is not allowed to differ by more than 0.2m/m.
GB5.549-90
Appendix A
Schematic diagram of interfacial tension meter
(Supplementary)
A-Parkin medical ring, B-secondary measuring cup, C-platform: D-level adjustment screw, E-arm of connecting ring; F-dials; G-vernier, F-copper wire GB554990
Appendix B
Schematic diagram of measurement steps
(Supplementary)
Distance height)
Figure B1 Functional relationship diagram of force F and position L of the scene measuring unitFigure B2 Schematic diagram of surface tension measurement
In Figure B1, steps 1 to 5 correspond to the situation when the measuring cup containing the measuring liquid moves up and the ring is immersed in the liquid. Steps 1 to 2, the ring is above the liquid surface (see schematic diagram B2-1). Step 2, the ring just touches the liquid surface (see schematic diagram B2-2). In steps 2 to 3, the liquid wets the GB5549-90
ring and applies a traction force F to the ring (see schematic diagram B2-3). In steps 3 to 4, the ring presses the liquid surface, the traction force Fi decreases, and the pressure P increases (see schematic diagram B2-4). In step 4, the ring is embedded in the liquid surface. In steps 4 to 5, the pressure P decreases, and the traction force P2 is generated due to the wetting of the upper half of the ring. In steps 5 to 6, the ring enters the liquid (see schematic diagram B2-5). In Figure B1, steps 6 to 12 correspond to the situation when the measuring cup containing the measuring liquid moves downward and the ring floats up from the liquid. In steps 6 to 7, the ring is still immersed in the liquid (see schematic diagram B2-6). In step 7, the upper part of the ring just touches the liquid surface (see schematic diagram B2-7). In steps 7 to 10, the ring pulls up the liquid film and leaves the liquid surface. The liquid surface exerts a traction force F on the liquid film (see schematic diagram B2-8). In steps 7 to 8, the force F changes linearly. In steps 7 to 10, the shape of the liquid film changes continuously. In step 9, the liquid exerts a maximum traction force on the ring (see schematic diagram B2-9). In step 10, the liquid film and the ring separate (see schematic diagram B2-10). In steps 10 to 11, after the liquid film ruptures, the traction force P decreases, and the retained F force is caused by the liquid film left on the ring (see schematic diagram B2-11). In steps 11 to 12, the ring leaves the liquid (see schematic diagram B2-11). Additional notes:
This standard was proposed by the Ministry of Chemical Industry of the People's Republic of China. This standard is under the jurisdiction of Shanghai Dyestuff Research Institute. This standard was drafted by Shanghai Dyestuff Research Institute. The main drafters of this standard are Shen Bo and Zhai Haoran
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