JPS6236538A - Surface tension measuring apparatus - Google Patents

Abstract

PURPOSE:To achieve quick and accurate measurement of surface tension with limited fluctuation of shape, by circling a capillary groove in a ring form at the tip of a liquid drop forming nozzle to speed up the formation of liquid drops with a reduced outer diameter of the groove on the side of the nozzle tip. CONSTITUTION:A ring-shaped capillary groove 111 is arranged at the tip of a nozzle 11 provided at the tip of a measuring tube. The outer diameter of the tip ring 112 on the tip side of the groove 111 is made smaller than that of the nozzle. Though depending on the property and the required measuring time of a liquid to be measured, the dimensions a-e as illustrated: 3.0-4.0mm for (a), 5.0-6.0mm for (b), about 1mm for (c), 0.5-1.0mm for (d) and 0.2-0.5mm for (e), are appropriate. With such an arrangement, the capillary effect of the capillary groove 111 and a residual existing surface layer are combined to help minimize the fluctuation of shape of liquid drops being dripping with a quick formation thereof and eliminates possible ensuing tiny drops.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to the measurement of surface tension of various liquids, and particularly to a surface tension measuring device suitable for measuring the surface tension of liquids used in continuous processes.

(Background of the invention) There are many known methods for measuring surface tension, including the capillary (rise, pressure) method, bubble pressure method, ring method, and Wilhelmi method.
helmy) method, outer layer (bubble) method, vibrating jet method, droplet method, etc., but the droplet method is the simplest and most widely used, and is used from the standpoint of automatic measurement. .

There are two types of droplet methods: the wave method and the hot water method, both of which involve forming droplets from the tip of a nozzle and determining the surface tension.

As is well known, in the droplet method, surface tension is calculated as the balance between the weight of a droplet falling from the tip of a vertical nozzle and the surface tension that acts upward along the circumference of the nozzle tip (generally the circumference). However, the amount of liquid actually dropped is a part of the droplet formed at the tip, and the situation in which the droplet separates from the tip is due to error factors such as fluctuations in the shape of the droplet and the generation of small droplets that subsequently drop. We store a variety of items.

Therefore, care must be taken when measuring using the droplet method.
As described in ``Experimental Chemistry Course'' 7 Surface Chemistry [Nippon Kagaku complete edition, Maruzen], it is necessary to generate and fall droplets as gradually as possible, but in reality, as a result of doing it at a finite speed, the solution In some cases, there is a further deviation from the equilibrium surface tension, resulting in a large error when attempting to measure the equilibrium surface tension.

That is, in the case of a solution in which the surfactant concentration is less than the micelle concentration (CMC) or a surfactant-applied solution in which the interfacial orientation rate is slow, it is difficult to measure the equilibrium surface tension by the droplet method.

(Object of the Invention) The object of the present invention is to change the measured value that can be considered at least the equilibrium surface tension of various liquids, including surfactant solutions whose concentration is less than the micelle concentration (CMC) or whose interfacial orientation is slow. An object of the present invention is to provide a droplet method surface tension measuring device.

(Structure and Effect of the Invention) The object of the present invention described above is to provide a ring-shaped capillary groove at the tip of a droplet forming nozzle in surface tension measurement using a droplet method, and to form a ring-shaped capillary groove along the dropping direction of the droplet. This is achieved by a surface tension measuring device having a multi-stage tip, in which the outer diameter of the nozzle on the side beyond the fine capillary groove is smaller than the outer diameter of the nozzle on the side not beyond.

Next, aspects of the present invention will be explained using figures.

FIG. 2 shows a measuring tube conventionally and generally used in the droplet method. In the same figure (a), 21 is a nozzle, n is a liquid reservoir, and a passage is a flow f.
This is a valve for adjusting fi. In some cases, a scale is engraved on the pipe section below -F of the liquid reservoir 22 and used to detect the outflow amount.

Figure (b) shows the formation of droplets at the nozzle tip G.

Furthermore, FIG. 3 shows examples of the shapes of the tip of the nozzle used in the conventional droplet method:

For example, the one with the shape (]→ is most commonly used.

The important and at the same time problems in the droplet method are shown in Figure 2 (
The condition is at the air-liquid interface at the outer periphery of the nozzle tip surrounded by the broken line circle in b).

When liquid is slowly supplied into the droplet from the nozzle tip to form a droplet, the air-liquid interface at the outer periphery is renewed as it cleaves. At this time, surface tension measurements of solutions that are difficult to reach equilibrium surface tension, such as solutions with a surfactant solute concentration below the micelle concentration (CMC) or surfactant solutions with a slow interfacial orientation speed, are greatly affected by the update status. Wilhelmi (W), which is highly accurate and has a reputation for measuring dilute solutions, tends to cause bias and dispersion in measured values.
ilhelmy) method gives results that are significantly different from the measured values.

The present invention eliminates these drawbacks as much as possible, and FIG. 1 shows a sectional view of a nozzle tip according to the present invention. The example shown is a nozzle with a two-stage tip.

In the figure, 11 is a nozzle 5.1 installed at the end of the measuring tube.
11 is a ring-shaped capillary groove, and 112 is a tip ring.

Further, a is the outer diameter of the tip ring, b is the outer diameter of the nozzle, and C is the inner diameter of the nozzle and the tip ring. Also, d is the capillary groove 111
The groove width and e are the thickness of the tip ring 112.

These a, b, c, d and e are the characteristics of the liquid to be measured,
Har-kins-Brown uses the ratio of the droplet volume to the cube of the droplet radius as a correction term, although it depends on the time required for measurement.
) is experimentally determined to fall within the most preferable range of the correction table. For two-stage tip a = 3.0 to 4.0
Key, b = 5.0-6.0 printing, C medium 1.0 margin, d = 0
．． 5-1. ．． A range of OIN and e=0.2 to 0.5r4 is practically useful.

The material for the tip of the nozzle may be any material, such as metal, glass, synthetic grease-resistant material, or material whose surface has been treated to make it wet, as long as it can be wetted by the liquid to be measured, but metal is preferred in practice.

(Example) Next, the present invention will be specifically explained with reference to Examples.

Example 1 A two-stage stainless steel tip nozzle with the following specifications was used. Benzene, which quickly reaches equilibrium surface tension, was used as the liquid to be measured, and saponin (10%) solution, a surfactant with a slow interfacial orientation speed, was used, and the present invention In place of the nozzle according to the present invention, a device based on the Wilhelmi method and a nozzle having a cut-off tip as shown in FIG. I raised it.

Table 1 As is clear from Table 1, all three methods show good agreement for benzene, but in the case of saponin, the values measured by the present invention are very close to those obtained by the Wilhelmi method, and the variation in the measured values is is about the law,! This shows that it is a reliable measurement device with good reproducibility. On the other hand, with conventional methods, there is a large bias in the measured values, and furthermore, the dispersion is extremely large.

Furthermore, when the apparatus of the present invention is applied to saponin, the time required for measurement is reduced to about twice that of the conventional method, which is extremely advantageous when combined with the reliability of the measured values.

(Effects of the Invention) By adopting a nozzle tip structure in which a tip ring is provided across a capillary groove as in the present invention, the capillary effect of the capillary groove,
Thanks to the help of the residual liquid surface layer, the droplet formation rate is fast, resulting in less fluctuation in the shape of the dropping droplet, and the absence of subsequent droplets, resulting in highly reliable and rapid surface tension. It became possible to measure

[Brief explanation of the drawing]

FIG. 1 is a sectional view of one embodiment of a multi-stage tip nozzle used in the present invention. FIG. 2 is a cross-sectional view of an example of a measuring tube used in the droplet method, and FIG. 3 is a cross-sectional view of an example of a nozzle used in the conventional droplet method. 1] Nozzle 111 Capillary groove 112 Tip ring Applicant Konishiroku Photo Industry Co., Ltd. Figure 1

Claims (1)

[Claims] In surface tension measurement using the droplet method, capillary grooves are arranged in a ring shape at the tip of the droplet forming nozzle, and the outer diameter of the nozzle on the side beyond the detailed capillary grooves does not exceed the tip of the droplet formation nozzle. A surface tension measurement device having a multistage tip that is smaller than the outside diameter of the nozzle.