Differential Capillary Rise Method Research Articles

Experimental surface tensions for HFC-32, HCFC-124, HFC-125, HCFC-141b, HCFC-142b, and HFC-152a

The surface tension of six alternative refrigerants, i.e., HFC-32 (CH, F, ). HCFC-124 (CHClFCF,), HFC-125 (CHF2CF3). HCFC-14lb ICH,CCI,F). HCFC-142b (CH3CCIF2), and HFC-152a (CH3CHF2), has been measured in the present study. The measurements were conducted under equilibrium conditions between the liquid and its saturated vapor. The differential capillary-rise method (DORM) used two glass capillaries, with inner radii of 0.3034 ± 0.0002 and 0.5717 ±0.0002 mm, respectively. Temperatures in the range from 270 to 340 K were considered. The accuracy of surface tension measurements is estimated to be within ±0.2 mN · m−1. The temperatures are accurate to within ±20 mK. The temperature dependence of the resultant data were successfully represented by van der Waals' correlations to within ±(1.1 mN m−1 for each substance. Available surface tension data are compared with the present data.

Temperature dependence of the surface tension for binary mixtures ofn-butanenitrile +n-alkanes

The differential capillary-rise method was used to determine the orthobaric surface tension of binary liquid mixtures ofn-butanenitrile mixed withn-pentane,n-hexane, andn-heptane, throughout the composition range. at 293.15, 303.15, 313.15, 323.15, 333.15. and 343.15 K. Furthermore, the system withn-hexane was also studied al 263.15 K. i.e., 19 K above its upper critical solution temperature, over the whole composition range. For each binary system the surface tension changes regularly with both temperature and composition between the values of the pure components. The results are discussed in terms of deviations from surface ideality and related to the large positive deviations observed for bulk properties of the same systems.

Surface tension of pentafluoroethane (HFC-125)

A set of accurate surface-tension data for HFC-125 has been obtained experimentally with both an absolute capillary rise technique and a differential capillary rise technique in the temperature range of 233.15–333.15 K. The purity of the experimental HFC-125 sample is 99.98 wt%. The two sets of experimental results with an absolute capillary rise method agree well with each other and, also, with the experimental results with a differential capillary rise method. The absolute deviations of experimental results with these two methods are within 0.01 mN · m−1. The relative deviation are within 0.2%. A van der Waals surface-tension correlation is also proposed.

Surface Tension of Difluoromethane

To meet the restriction of the Montreal protocol, one must look for a hydrofluorocarbon (HFC) whose ozone depletion potential value is zero to replace chlorofluorocarbons and hydrochlorofluorocarbon (HCFC). The binary and/or ternary mixtures using difluoromethane (HFC-32) as a component are thought to be the most promising alternatives for HCFC-22. The surface tension of difluoromethane has been measured using the differential capillary rise method over the temperature range of 267.95--334.27 K. The purity of the difluoromethane sample used in the experiment is 99.95 wt%. A surface tension correlation has also been proposed.

Measurement and Prediction of the Surface Tension of Nitrogen + Oxygen and Nitrogen + Oxygen + Argon System.

The differential capillary rise method has been used to measure the surface tension for a nitrogen+oxygen binary system and for a nitrogen+oxygen+argon ternary system at low temperatures. Several correlations have been tested against the mixture data

Improved differential bubble pressure surface tensiometer

An improved differential bubble pressure surface tensiometer which has increased accuracy while still being inexpensive, easy to operate, and versatile has been developed. It has potential as a valuable research tool and is capable of on-line adaptation. This tensiometer incorporates improvements over earlier differential bubble tensiometers both in design and in method of operation. Experimental results at temperatures between 120 and 300 K and at pressures to 4 MPa are presented, comparing the new method to the conventional differential capillary rise method. The results show that the improved differential bubble pressure method's accuracy is ±0.1 mN/m and its repeatability is ±0.03 mN/m. Development of the theory for the technique has led to simple methods for deriving surface tension from directly measured quantities without iterative calculations. First-order corrections for inertial and viscous effects are also presented. These become significant for systems with densities above 5000 kg/m 3 or viscosities above 1 Pa · s.

Comparison of interfacial tension and capillary constant for argon + krypton, CH4 + krypton, and C2H6 + krypton using two independent methods of measurement

Abstract Interfacial tension and capillary constant data were experimentally determined by two independent methods for the systems argon+krypton, methane+krypton, and ethane+krypton. Six to eight isotherms from 125 K to the critical point of the less volatile component were obtained for each system. The interfacial tension data were used to test an improved differential bubble tensiometer against the traditional differential capillary rise method and were used to further support the “field variable” based corresponding states theory. A brief description of the apparatus is presented. Comparisons of the results show that the differential bubble pressure method is as accurate as the differential capillary rise method with better repeatability. Potentially, the improved tensiometer can be automated and used with systems where visual measurements are not possible. The interfacial tension and capillary constant data were used to compare two versions of a corresponding states theory. One version incorporates a scaling law along lines of constant liquid mole fraction and the other along lines of constant fugacity fraction which is a “field variable” in the Griffiths-Wheeler sense. In order to reduce the amount of interpolation necessary to correlate the data, measurements were concentrated at liquid compositions rich in the less volatile component. The results show that the fugacity fraction based corresponding states theory better representated of the data.

Surface tension of normal pentane, hexane, heptane, and octane

New experimental results are reported for the surface tension of normal pentane, hexane, heptane, and octane. The data were obtained with a differential capillary-rise method and cover the entire liquid range from the triple-point temperature to the critical temperature. Equations for calculating the surface tension of these n-alkanes as a function of temperature are presented.

Statistical surface thermodynamics of quaternary liquid systems

Measurements of surface tension were carried out for pentane–hexane–cyclohexane–benzene and pentane–hexane–benzene–toluene at 298.15 K by the differential capillary rise method. The surface tensions of these quaternary liquid systems were also computed theoretically using various empirical and statistical theories of the liquid state. The agreement between theory and the experiment has been found to be fairly good. An attempt has been made to explain the nature of the molecular interactions involved, in the light of excess surface tension whose sign and magnitude depend upon the chain length of the component liquids.

Cell for orthobaric surface tension measurements at low temperatures

An experimental technique to determine orthobaric surface tensions of both pure and mixed liquefied gases by the differential capillary rise method at cryogenic temperatures is described. The apparatus has been tested with measurements performed on the ethane+ethane system, from 117 to 135 K.

Surface tension of pure and mixed simple substances at low temperatures

A new design of cell is described for measuring the gas-liquid surface tension of both pure and mixed liquefied gases by the differential capillary-rise method in the temperature range 90–250 K at pressure up to 1000 Torr. Results for the pure methane, krypton, tetrafluoromethane, ethene, ethane, and dimethyl ether at temperatures below their normal boiling point are presented, compared with literature values, and analysed in terms of simple two- and three-parameter forms of the principle of corresponding states. Results are illustrated for the mixture methane + tetrafluoromethane in the temperature range 98 to 102 K.

An improved method of determining surface tension at low temperatures

A novel method of measuring orthobaric surface tensions of liquids at low temperatures using the differential capillary rise method is described. Results are given for hexamethyldisiloxane from 220K to 370K.

Thermodynamics of n-alkane + dimethylsiloxane mixtures. Part 4.—Surface tensions

Surface tensions have been measured by the differential capillary rise method under orthobaric conditions for binary mixtures of four n-alkanes (n-pentane, n-heptane, n-decane and n-tetradecane, replaced in the case of dimer by n-hexadecane) with four linear dimethylsiloxanes (dimer, trimer, tetramer and pentamer) at 303.2 K. The sign and magnitude of the excess surface tension depend ultimately upon the chain lengths of the components of the mixtures irrespective of whether a volume-fraction-based or a mole-fraction-based ideality is adopted. The dependence of the volume-fraction-based excess surface tension on chain length is very similar to that previously found for the excess volume. The results are analysed in terms of Prigogine's parallel-layer theory as modified by Gaines and Prigogine's average potential theory. Only the latter gives a useful description of the complexity of the chain-length dependence of the excess surface tension, and it is qualitative at best even then.

Extremes in Surface Tension of Fluorocarbon + Hydrocarbon Mixtures

We have found that the surface tensions of some binary liquid mixtures of hydrocarbons + perfluorocarbons have complex composition dependences which are unexpected and hitherto unreported. To assess patterns of behaviour our measurements were made in closed cells using the differential capillary rise method, and we have treated linear dependence of the surface tension γ on the mol fraction of the second component x as “surface ideality”.

改良型毛管上昇法による液体スズ，鉛の表面張力の測定

The differential capillary-rise method has been modified to measure the surface tension of liquid metals which are not wet with capillary material. The surface tensions γ of liquid tin and lead measured by this method are given by(This article is not displayable. Please see full text pdf.) \ oindentat t°C in hydrogen atmosphere. The surface tension values of liquid tin determined by this method are in good agreement with those by the sessile drop method under the same condition. A comparison with previous experimental surface tension values of liquid tin and lead indicates the apparent discrepancy in the temperature coefficient of surface tension corresponding to the kind of the atmosphere used for the measurement.