SU161570A1 - - Google Patents

Description

There are known devices for measuring the surface tension of liquids by the method of maximum pressure, containing a vacuum unit and a gravity device.

The proposed device differs from the known ones in that in it into working tanks, interconnected by two narrow gauge tubes of one diameter, two calibrated tubes of different diameters are arranged opposite to each other. Such an embodiment of the device makes it possible to eliminate the depression of the depressive capillary by a measurable amount of surface tension and reduce the amount of the test liquid to 2-3 ml.

FIG. 1 shows the proposed device; in fig. 2 - the same device after turning clockwise pas 180 around an axis, perpendicular to the plan of the drawing.

The device contains a vacuum unit with a tube / intermediate tank 2, a cup 3 with the test liquid, two working tanks 4 and 5, a tube 6 with a capillary 7, a second same tube 8 with a capillary I, two narrow measuring tubes 10 n L, tubes 12 and 13 and tube 14 for transferring liquid from glass 3 to tank 5.

Measurement of surface tension is performed as follows.

After a thorough thermal vacuum treatment of the device through a tube / glass 5, 2-3 mg of the test liquid is transferred, the device is on the A-B line, cleaned from the vacuum} of a smart installation and placed in a thermostat with viewing windows. When the device rotates around the axis, perpendicular to the planar plane, clockwise) ia angle 180 °, the liquid under study from glass 3 enters intermediate tank 2 and through tube 14 - into tank 5 containing the calibrated tube 13. When the instrument returns to its original position the fluid in the tube 6 begins slowly (due to capillary contraction) to fill the calibrated tube 12 and the narrow gauge tube 10. When the maximum pressure in the droplet forming on the cut of the calibrated tube 12 is reached, this droplet falls off the end The tube 12 and, following it, liquid in the form of a TOHKOII cTpyii or a series of droplets, will flow from the gauge tube 10 into the reservoir 4. Fluid flow continues until the level in the gauge tube 10 drops to such an extent that the weight of the liquid column in this tube b) it is already insufficient for squeezing the liquid out of the calibrated tube 12.

After the outflow of fluid stops, its level in the tube 10 begins to slowly increase again due to l 1 dnost that comes from the reservoir o. The column of fluid above the cut of the calibrated tube 12 again reaches the maximum height and the process of squeezing the fluid begins again.

The height hi, corresponding to the maximum pressure in the drop and the cut of the calibrated tube 12, is measured with a cathetometer. The maximum pressure in the drop forming on the cut of the calibrated tube 12 will be equal;

Pi g9hi + Pdi, (1)

where g is the acceleration of the force of gravity, P is the density of liquid 1 at the test temperature, Pdi is a member due to the dynamic Co nii of the column of liquid as it moves in the JO manometer tube.

-gp 2gg

I ac like PI - where ri

kaliofi radius

tube 12, then equation (1) is written as

,,. i

Thereafter, the bulk of the liquid will flow from reservoir 5 to reservoir 4, and a series of heights hi corresponding to the maximum pressure in the droplet at the shear of the calibrated tube 12 will be measured, and the droplets of the test liquid will be passed through the calibrated tube 13 different in internal diameter from tube 12 2-3 times. To do this, the device is rotated around an axis, opposite to the plane of the drawing, but clockwise by 180. In the new polo} device, the device 4 but tube 8 slowly, due to contraction 9, enters the calibrated tube 13 and fills the gauge tube 10, having a lrn approximately the same internal diameter as the tube //. When the maximum pressure in the drop of liquid is reached at the cut of the tube 13, the Kyle will be torn off, and the leakage of the liquid will be carried out and the next drop will be formed in the same way as C1 for the caliber of the tube 12.

The maximum pressure in a drop and a cut of the calibrated tube 13 will be equal to

R., grjh.2 + Pd-2,

(3)

where h-i is the height of the liquid in the manometric tube //, corresponding to the maximum pressure in the drop, Pd- are the ratios due to the dynamic degradation of the liquid column as it moves in the manometric tube 11.

Since PZ is where r-z is the radius of the gauge

tube 13, then equation (3) will be

- + Pd

(four)

2

Since the inner diameters of the manometer tubes 10 and // are practically single-ended, and the capillaries 7 and P are made such that they cause approximately the same velocity of the fluid in the corresponding gauge tubes, under these conditions.

Pdi Pd. (5)

Therefore, subtracting from equation (4) equation (2) and taking into account the condition (5), we find

o -l. gp.) (b)

2 J J rj g,

As can be seen, in the calculation formula (6) found for determining the surface tension of a liquid using the described device, not | includes members associated with dynamic depression.

For measuring 0, no more than 2 to 3 ml of liquid is required, and these measurements can be carried out in a wide temperature range, the upper limit of which is determined by the mechanical and chemical resistance of the material of the iribor relative to the liquid under study.

The design of the device provides for the replacement of a part of the device, including the cup 3 and the intermediate tank 2.

Subject invention

A device for measuring the surface tension of liquids by the method of maximum pressure, comprising a vacuum unit and a gravitational device, including a cup for the liquid under investigation, an intermediate tank, two communicating working tanks with calibrated tubes and a cathetometer for measuring the level of a fluid, different from that, in order to exclude capillary depression by the measured value of the surface tension, into working tanks interconnected by two narrow gauge pressure bkami same diameter, mounted in opposite directions two calibrated tubes .raznogo diameter.

, t

Fig /