Capillary rise test

A wicking test is used to determine the absorptive velocity of water in fabrics. It is known as the capillary rise test (DIN EN 53924). With respect to time, the capillary rise of absorptive fabrics in the warp and weft directions is measured by dipping them in distilled water. The absorptive velocity depends on the capillary force, which determines the transport of liquid contrary to gravity. For fabric the wicking velocity, the path of liquid distribution and the final wet figure can be different in the warp and weft directions. 

FIG. 18 The parallel plate capillary rise test geometry (a) used to determine the meniscus rise, (b) as a function of gap size for the 37Pb-63Sn, 95Sn-5Sb, 96.5Sn-3.5Ag, 91.84Sn-3.33Ag. 83Bi, and 95.5Sn-4.0Cu-0.5Ag solders. (From Ref. 5.)... 

Figure 30. Rewetting data. Capillary rise method U. Baumgarte Melliand Tex-tilberichte, 49, 1306 (1968). (mm) height of the elevation of test solution. ((- -) Cto-i SAE (- -) Cn-n SAE (-Q-) C1Jf.16 SAE (-M ) NPE)...

Rate of Capillary Rise—McGeorge (1941) determined the capillary rise in different mixtures of sand and silt. This was done by packing a 50-cm column of soil in a 1 in. diameter glass tube and setting the bottom end in a container of water. The results of these tests are shown in Table 60, giving the total rise of moisture in 8 hrs, and in Figure 78 where the rate of rise per hr for the same period is plotted... 

The measurement of the height of the bottom of the meniscus has theoretically to be made relative to a plane surface of liquid in communication with the capillary tube. It is not always recognized that a very large surface is required, if it is to be sufficiently plane the cylindrical tubes of 20 mm. diameter often used have a decided capillary rise. Tubes of 40 mm. diameter or more must be used if the surface is to be considered as plane. Richards and Carver have, however, tested Rayleigh s formula (10) for wide tubes, and found it to agree with experiment within a few thousandths of a millimetre for a tube 38 mm. diameter this formula can be used with fair accuracy down to tubes of 25 mm. diameter, as a correction to the level in the wide tube. The actual measurement of the difference in height between the two levels requires an accurate cathetometer and suitable illumination of the menisci (see Richards and Coombs). 

Later, Neumann developed the static Wilhelmy plate method which depends on capillary rise on a vertical wall, to measure 6 precisely. A Wilhelmy plate whose surface is coated with the solid substrate is partially immersed in the testing liquid, and the height of the meniscus due to the capillary rise at the wall of the vertical plate is measured precisely by means of a traveling microscope or cathetometer. If the surface tension or the capillary constant of the testing liquid is known, then the contact angle is calculated from the equation, which is derived from the Young-Laplace equation... 

Wicking, which is the measurement of the rate of capillary rise of the test liquid in a porous medium to determine the average pore radius, surface area and contact angle. 

The surface tension of a liquid was measured with a capillary-rise tube and found to be A. Later tests show that this liquid does n ot wet the glass perfectly but makes a contact angle of 0 = 30°. Estimate the true value of the surface tension of this liquid. 

Figure 15 Characterizing wetting by Washburn test and capillary rise. (From Refs. 4,23.)...

It was many years ago that I carried out these experiments on capillary rise however I have a vague memory of a fact which I did not take note of then I believe I also tested with a tube of similar length, but whose internal diameter was only about 5 mm, and to have noted that the liquid did not go up there, or stopped soon. The slowness of the upward movement, in the preceding experiments, shows that the forces which produce this movement are weak, and, in a narrow mbe, resistance undoubtedly become sufQcient to prevent their action. If thus my memory does not mislead me, it is necessary, to be successful, use broad tubes, as those about which I spoke. 

The second approach to characterize wetting considers the abihty of the fluid to penetrate a powder bed. It involves the measurement of the extent and rate of fluid rise by capillaiy suction into a column of powder, better known as the Washburn test. Considering the powder to consist of capillaries of radius R, the equilibrium height of rise... 

One milliliter each of the borneol solution and the oxidizing solution are mixed in a test tube and briefly shaken. A TLC slide is spotted with the borneol solution, the camphor solution, and the ether layer of the reaction mixture. Spotting is done by means of a capillary melting point tube used as a dropper and filled with a 5 mm sample. The slide is developed in a wide-mouth jar containing a filter paper liner and a few milliliters of chloroform (Fig. A3.20). After development (the solvent front rises to within 1 cm of the top), the slide is removed, the solvent is allowed to evaporate, and the slide is placed in a covered wide-mouth jar containing a few crystals of iodine. The spots readily become visible and the progress of the reaction can easily be followed. With periodic shaking, the oxidation is complete in about 30 minutes. 

These primers may also be tested in the "Gas Volume and Impulse Apparatus , briefly described as the "Test Set Mkl75-ModO in Ref 14, p 9-42. Its photographic view is given as Fig 9 23 (which is not shown here). The apparatus consists of a mercury reservoir, an upright capillary rube, and a firing chamber. When a primer is fired in this test set, the hot reaction products build up pressure in the firing chamber. This pressure is communicated to the upper surface of the mercury in the reservoir, and this, in turn, causes a column of mercury to rise in the capillary tube. 

Desmaroux Stability (Heat) Test. Place a lOg sample of expl or propint in a glass tube 10cm high 3cm diam, provided with a ground glass stopper and a capillary outlet leading to a mercury manometer. Then the tube is evacuated and heated to 750 or 108.5°, depending on the substance under test. The rate of decomposition is measured by the rise of pressure in the manometer... 

The bubble point test, while popular, has some deficiencies that must be realized. First, there is variation in the operator detection of the test end point that is, the first appearance of gas bubbles rising in the liquid. Some operators are able to see smaller bubbles than others. In a recent study, a panel of seven observers recorded the initial detection of a steady stream of air bubbles rising from a capillary held under water as the air pressure was gradually increased. The observers, who had received different degrees of training, identified the simulated bubble point as occurring at air flows of 5 to 50 mL/min corresponding to air pressures of 34 and 38 psi, respectively, for a 90-mm disc filter membrane [56]. 

Procedure for Class II Carefully melt the material to be tested at as low a temperature as possible, and draw it into a capillary tube that is left open at both ends to a depth of about 10 mm. Cool the charged tube at 10°, or lower, for 24 h, or in contact with ice for at least 2 h. Then attach the tube to the thermometer by means of a mbber band, adjust it in a water bath so that the upper edge of the material is 10 mm below the water level, and heat as directed for Class /, except within 5° of the expected melting temperature, regulate the rate of rise of temperature to 0.5° to 1.07min. The temperature at which the material is observed to rise in the capillary tube is the melting temperature. 

Extensive experience of the preparation of bonded-silica columns for CEC has suggested to us that all packing methods have similar problems associated with the fragility of the fused-silica tubing material, especially at the Mt and detection window, where the polyimide coating had been removed. A less commonly met effect is the production of loosely packed silica particle beds with voids, giving rise to unstable currents. Approximately 70% of capillaries could be successfully packed by an experienced operator, with approximately 80% of packed and tested columns giving satisfactory CEC [23],... 

---