Liquid immersion

The use of the surface ultrasonic waves seems to be convenient for these purposes. However, this method has not found wide practical application. Peculiarities of excitation, propagation and registration of surface waves created before these time great difficulties for their application in automatic systems of duality testing. It is connected with the fact that the surface waves are weakened by soil on the surface itself In addition, the methods of testing by the surface waves do not yield to automation due to the difficulties of creation of the acoustic contact. In particular, a flow of contact liquid out of the zone of an acoustic line, presence of immersion liquid, availability of chink interval leads to the adsorption and reflection of waves on tlie front meniscus of a contact layer. The liquid for the acoustic contact must be located only in the places of contact, otherwise the influence on the amplitude will be uncontrolled. This phenomenon distorts the results of testing procedure. 

Uiiergrlin, n. periwinkle, myrtle (Vinca). iniiierhm, adv. still, after all, at any rate. gunersionsflussigkeit, /. immersion liquid, miner-wahrend, p.a. everlasting, perpetual. 

When water is used as the immersion liquid, the test is essentially the ASTM Standard Test Method (D570) for Water Absorption of Plastics.( ) Determinations of the relative rate of water absorption are important in evaluating the effects of moisture exposure on such properties as mechanical strength, electrical resistivity, dielectric... 

It is more tlian probable that these variations in the apparent densities of charcoals are to be ascribed to a difference in the depths of penetration of the hquids. Thus non-wetting liquids such as mercury would not readily penetrate the large macropores in the solid, far less into the micropores (below 100 A. in diameter) which exist in charcoal. We should thus anticipate that when mercury is employed as immersion liquid the charcoal density would be but small. Actually a value of only 0 865 was obtained by Harkins and Ewing. 

Howard and Hulett Jour. Phys. Ghem. Oct. 1924) brought forward additional evidence in favour of this hypothesis by determining the apparent densities of charcoals with helium gas in place of an immersion liquid with the following results ... 

The rate of particle migration is determined by measuring with a stopwatch the time required for a particle to travel between the marks of a calibrated graticule in the microscope eyepiece. If the objective of the microscope is immersed during the electrophoresis measurement, the calibration of the graticule should be made with the same immersion liquid. 

List of crystals suitable for checking refractive indices of immersion liquids... 

Ferrous Metals—Immersion Liquid-Light Duty... 

If temperatures are not specified in the specification, the immersion tests have to be carried out at room temperature. The volume of the immersion liquids should be adequate enough to immerse the sample of rubber. The test should be carried out in the absence of direct sunlight to avoid atmospheric oxidation. Test pieces from cut samples or counter samples from the finished rubber lining compound have to be buffed smooth. 

BECKE TEST. A microscope of moderate or high magnification is used to compare the indices of refraction of two contiguous minerals for of a mineral and a mounting medium or immersion liquid), in a thin section or other mount. When the two substances differ substantially in refractive index, they are separated by a bright line, called the Becke line. The line moves toward the less refractive of two materials when the tube of the microscope is lowered. 

A cylindrical glass tube containing the immersion liquid and the piece of glass of which the refractive index has to be determined, is placed between the two diaphragms. The immersion liquid consists of petroleum ether (or dioxane) and a-chloronaphthalene. The temperature of the immersion liquid is controlled by circulating water around the tube. 

I. The refractive index nx of the immersion liquid is larger than the refractive... 

Fig. 66. How the light is dispersed if the refractive indices of the glass and the immersion liquid are different.

It can be concluded that if nx n2 light can be seen, whereas if nx = n2 no light can be seen. The immersion liquid is adjusted so that this last condition is fulfilled. The refractive index of the immersion liquid is then determined at the same temperature by means of an Abbe refractometer. The value found is equal to the refractive index of the glass. 

According to the principles, introduced before [4], the curve received permits to determine the value of SAW velocity. For this it is necessary to measure the distance (AZN ) between maximums, situated on the right of the main one. If the value of acoustic wave velocity o/ in the immersion liquid and the working frequency / are known, then by means of definite experimental interval SAW velocity uR can be calculated ... 

If the integral molar entropy of the adsorbed phase is to be compared with the molar entropy of the immersion liquid, it is necessary to express the molar entropy of the gas as a function of the relative pressure and the enthalpy of vaporization. Thus,... 

If pre-adsorption is required, equilibration of sample with desired relative vapour pressure of immersion liquid. 

Introduction of sample bulb (2) into stainless steel calorimetric cell already filled with immersion liquid (7). 

Determination of weight of sample bulb filled with immersion liquid ( wiped outside), together with broken tip. 

Determination of dead volume V of sample bulb from the information gain. Steps 5 and 13, knowing mass and density of immersion liquid. 

Determination of total experimental heat of immersion by integration o whole microcalorimetric signal (including the small endothermal peak di vaporization of the first droplet of immersion liquid into dead volume, before immersion proper (Partyka et al., 1979). 

The energy absorbed by the continuing evaporation of the immersion liquid - if the set-up is not air-tight. 

This involves application of Equation (5.35), following Briant and Cuiec s method (1972), and is straightforward with immersion liquids for which parameter k is already known water, heptane, cyclohexane, benzene and paraxylene (cf. Table 5.1). Otherwise, it needs to be calculated from y(LG) and its variation with temperature (cf. Equation (5.34)). This approach was successfully used by Schultz et al. (1977) and, more recently, by Douillard et al. (1995). 

The polarity of a solid surface can be regarded as the strength of its average electrostatic field F. This field interacts with permanent or induced dipoles of adsorbed molecules, whereas its gradient interacts with permanent or induced quadrupoles. These interactions give rise to components of the adsorption energy such as EFfl (with permanent dipoles), Ef (polarization contribution) or PQ (with permanent quadrupoles). Therefore, the selection of the appropriate immersion systems, differing mainly in the molecular dipole moment n of the immersion liquid, can be expected to provide information on the value of EPfl since ... 

This was the basis of the approach by Chessick et al. (1954, 1955) and Zettlemoyer etal. (1958), which involved the use of a series of immersion liquids such as butyl derivatives differing only in their polar groups 1-butanol, 2-butanol, butanal, 1-aminobutane, 1-chlorobutane, butanoic acid. With the polar surfaces studied (rutile, CaF2, Aerosil, alumina), an approximately linear relation was found between the energy of immersion and the dipole moment. The slope gave directly the average field strength (for instance, 820 V//rm 1 on a rutile titanium (tv) oxide) and the... 

SchrOder (1979) was able to improve this approach by using a refined expression of the Gibbs free energy of adhesion as a function of the various intermolecular attraction energies between the liquid and the solid. In this way, by using up to 10 different immersion liquids with known parameters, he has calculated the apparent dipole moment and polarizability characterizing the immersion behaviour of various pigment surfaces (e.g. rutile, iron oxide and several phtalocyanines). 

The change in nature of the oxidized surface can be followed with immersion liquids other than water. By increasing the oxygen content of a carbon black (Le. Spheron 6) up to 12%, Robert and Brusset (1965) obtained an increase of the energy of immersion in methanol from 140 to as much as 390 mJ nT2 (practically the same ratio as that observed with water), whereas the energy of immersion in n-hexadecane remained nearly constant, around 100 mJ m-2. 

Figure 5.8 gives the main types of curve listed by Zettlemoyer and Narayan (1967) for this type of immersion calorimetry experiment with pre-coverage of the sample. Curve (a) is obtained with homogeneous surfaces with respect to the immersion liquid (e.g. chrysotile asbestos in water, Zettlemoyer et ai, 1953). Curve (b) is given by... 

When the molecular size of the immersion liquid is close to that of the micropores a delayed diffusion of the liquid can be immediately detected from the slower response of the microcalorimeter, as was clearly shown by Widyani and Wightman (1982) when immersing a microporous activated carbon in propanol. 

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