Immersion-medium technique

Thus, in the case of weakly reflecting metal snbstrates, the maximnm intensity of the IRRAS spectmm can be achieved with one reflection, whereas in the case of strongly reflecting metals, the optimum number of reflections, Aopt, should be calculated with Eqs. (2.2) or (2.3), depending on the type of spectrometer used. The optimum angles of incidence are 80-85° and 75°-80°, respectively, for single and multiple reflection. In addition, surface sensitivity of the method can essentially be enhanced by nsing the immersion medium technique (Section 2.5.2). 

To quantify the results a combination of the signal amplitude of the interfacial echo (IE) in a C-scan, expressed through a colour code, and the adhesion strength obtained destructively by an ASTM C633-13 (2013) tensile test can be used. Echo-impulse techniques with an auxiliary reflector, for example by using water as an immersion medium allow measuring reliably the adhesion of very thin coatings... 

Kiinzelmann, U., Neugebauer, H., Neckel, A., 1994. A novel technique for recording infrared spectra of powders attenuated total reflection immersion medium spectroscopy. Langmuir 10, 2444-2449. 

Some of these problems can be overcome using a top barrier coating to isolate the resist layer from the immersion medium [21]. Current state-of-the-art immersion photolithography systems utilise a wavelength of 193 nm [22]. Using optical techniques such as off-axis illumination and water immersion projection lenses, these systems can define feature sizes as fine as 38 nm. 

Solids of different densities can be separated by immersing them in a fluid of intermediate density. The heavier solids sink to the bottom and the lighter float to the surface. Water suspensions of fine particles are often used as the dense liquid (heavy-medium). The technique is used extensively for the benefication (concentration) of mineral ores. 

Figure 11. Schematic representation of a laser heating experiment in the DAC. The IR laser beam is directed onto the absorbing sample immersed in a compression medium acting also as thermal insulator. The thermal emission of the sample is employed for the temperature measurement, while the local pressure is obtained by the ruby fluorescence technique (see next section).

Traditionally, diazonium tetrafluoroborates are decomposed neat in the solid state. This solid, placed in a flask with large outlets and which must not be more than half full of the salt, is gently heated near its surface until decomposition starts. Often no more heat is required, the decomposition continuing spontaneously with evolution of dense vapors of boron trifluoride. The reaction medium is often brought to dull redness and the fluorinated product distills if sufficiently volatile.1,3 The filled reaction flask can also be immersed in a fluid brought to ca. 20 to 50 C above the decomposition temperature of the diazonium salt, previously determined in a capillary tube.1,3,200,201 In another procedure, the reaction flask can be heated to this temperature while empty, then the diazonium tetrafluoroborate is added little by little 200-201 This latter method has been adapted to perform the decomposition of diazonium tetrafluoroborates in a continuous way by two techniques ... 

When ion-selective electrodes are used, it is important that the composition of the standard solution closely approximates the composition of the unknown. The medium in which the analyte exists is called the matrix. For complex or unknown matrixes, the standard addition method (Section 5-3) can be used. In this technique, the electrode is immersed in unknown and the potential is recorded. Then a small volume of standard solution is added, so as not to perturb the ionic strength of the unknown. The change in potential tells how the electrode responds to analyte and, therefore, how much analyte was in the unknown. It is best to add several successive aliquots and use a graphical procedure to extrapolate back to the concentration of unknown. Standard addition is best if the additions increase analyte to 1.5 to 3 times its original concentration. 

On the basis of the degree and type of soiling, conservators can choose between localized or complete treatment of the item. Stain removal with solvents with or without additives is the method of choice if soils are localized and the general appearance of the rest of the textile is satisfactory. A systematic overview of methods of stain removal is given in the literature (4). The present discussion focuses on the method of complete immersion in the cleaning medium and on the principles of soil removal associated with this technique. Excellent summaries (5) on detergency in aqueous media exist, but detergency in nonaqueous media is not as well documented. 

These techniques can also be developed further to deal with Stern layer problems. Note that for Z) the effective capacitance distance D is reduced by a factor (1 —0.62y/alD). If image effects are included, it can be shown that (when the zwitterions are immersed in a high dielectric medium e = 80, adjacent to a hydrocarbon surface s = 2), image effects can virtually double the electrostatic energy so that the two effects may partially cancel out. Nonetheless the observation that is reduced from the intuitive capacitance form is of some interest, as it is known that for ionic micelles use of Debye-Huckel theory (at low salt equivalent to the capacitance form) gives results for the repulsive free energy too large by a factor of 2. 

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