Apparatus and experimental technique

The excess molar enthalpies of the BaF2-LiF-NdF3 system were measured in the temperature range 1220-1400 K principally by direct-reaction calorimetry with the direct drop method [16]. A high-temperature calorimeter operable up to 1800 K was used for excess molar enthalpies determinations it has been described several times [17]. 

The crucibles used in these mixing experiments were made of graphite and the calorimeter was calibrated under the same experimental conditions with standard materials. Platinum was chosen for this purpose since it is suitable for calibration at high temperatures and is not attacked by molten fluorides. The heat capacity of platinum was taken from tables [18]. After the mixing experiments, small platinum samples (100-200 mg) were dropped in the laboratory cell containing the melt, during the experimental run. 

The enthalpy of formation for some mixtures of this ternary system were obtained by adding solid neodymium fluoride, NdF3, at room temperature, Tg, to the initial BaF2-LiF binary liquid mixture at the 

C represent the three pure salts, the enthalpy of mixing measured experimentally corre- 

the enthalpy of formation of the ternary mixture, A i /f is calculated from the relation  

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It is not a purpose of this chapter to consider experimental techniques in atom chemistry in detail. The different forms of apparatus and experimental techniques which have been used, have been thoroughly reviewed previously (55, 67, 129, 131a). 

To this end we and our collaborators have repeatedly scrutinized every bit of information recorded here. We have separately evaluated the conformity of the apparatus and experimental techniques to the best modern standards, the accuracy of the handling of the data obtained, the certainty with which products and intermediates were identified, the strength of the evidence given for each suggested reaction course or mechanism, and every other point that the published description of each research allowed us to check. 

In his retirement. Sand wrote "Electrochemistry and Electrochemical Analysis." This appeared in three slender volumes during the War years (Tl) Voliame II, which carries the subtitle "Gravimetric Electrolytic Analysis and Electrolytic Marsh Tests," surveys apparatus and experimental techniques and gives concise instructions for the performance of numerous analyses. It acknowledges Sand s earlier contribution to L inge and Keane s encyclopedic work (72). 

Apparatus and experimental techniques have been discussed in several papers. The techniques include thermal volatilization analysis," pyrolysis-gas chromatography, pyrolysis-molecular weight chromatography-i.r. spectrophotometry, and pyrolysis-mass spectrometry. Methods have also been described for collecting and separating pyrolysis products. - ... 

For a more detailed characterization of the IRP-method we will briefly discuss apparatus and experimental technique recently used to measure m- and j-dependent cross sections for the reaction K + HF(v=l,j,m) -> KF + H [7,9], Figure 1 shows a schematic drawing of the crossed molecular beams machine together with the optical set up employed to prepare HF via IRP. 

Table I comprises 28 columns and extends across two facing pages. The division between facing pages is very nearly such that the left-hand pages identify the compounds for which data are giver., the technique by which the data were obtained, and the electrodes used, and also describe the solvent and supporting electrolyte, apparatus, and experimental conditions, while the right-hand pages give the data and other information obtained and provide cross-references to additional information contained in other tables.

The most recent experimental determination of oAp.ps is that of Al-Ramadhan and Gidley (1994). The apparatus and analysis techniques are similar to those of Westbrook et al. (1989) and will therefore not be described here. Their method used the effect of singlet-triplet mixing in a static magnetic field (Gidley et al., 1982) this allowed oAp-Ps to be... 

Heertjes and Kossen [99] present a full discussion of their techniques together with descriptions of the required apparatus and experimental procedure. They considered both the above methods unsuitable for the determination of cos( and proposed a new method, the h-s method. Briefly this consists of determining the height of a drop of liquid placed on top of a cake of the compressed powder previously saturated with the liquid. The theory was presented in an earlier paper [100],... 

Apparatus. The apparatus and experimental procedure have been described (9). A static system was used with catalyst samples (normally 0.1 gram of hydrated material) in the bottom of the reaction vessel (volume 1 X 10" m ). The reaction was followed by periodically sampling the gas phase above the catalyst and analyzing by GLC techniques. 

The modifications of vertical development techniques such as two-dimensional, stepwise and multiple are as for TLC and will not be discussed further. Typical apparatus and experimental set-up for each of the principal development procedures is shown in Figure 3.18. 

A complete review of the theory, apparatus, and experimental conditions for anodic-stripping analysis of the metals with some practical procedures has been given (77 ). Electroanalytical methods (775) and electrochemical preconcentration techniques (776) have been reviewed with respect to trace analysis and with respect to water analysis (777). 

The experimental apparatus and measurement technique have been described in detail before [11], [12]. However, a brief account of the experimental method will be given here since the mixed lubrication study required some modification of the measurement procedure. 

Experimental techniques based on the application of mechanical forces to single molecules in small assemblies have been applied to study the binding properties of biomolecules and their response to external mechanical manipulations. Among such techniques are atomic force microscopy (AFM), optical tweezers, biomembrane force probe, and surface force apparatus experiments (Binning et al., 1986 Block and Svoboda, 1994 Evans et ah, 1995 Israelachvili, 1992). These techniques have inspired us and others (see also the chapters by Eichinger et al. and by Hermans et al. in this volume) to adopt a similar approach for the study of biomolecules by means of computer simulations. 

Smeatnii s elegant experimental technique enabled him to deal with both hydraulic and mechanical friction losses, allowing him to calculate water velocity at the wheel and thereby determine an effective nr virtual head. Smeaton s experimental apparatus was a brilliant device that enabled him to measure the efficiency of the wateiwheel, alone rather than the overall efficiency of the experiment. Smeaton was able to conclusively shov that a water-wheel when driven by the weight of water alone, is about twice as efficient as when driven by the impulse of water. This demonstration ensured that British mills, wherever possible, from then on would be fitted with overshot or breastshot wateiwheels, rather than undershot. 

The activity of a volatile solvent in a solution that contains a nonvolatile solute can be obtained from an experimental technique known as the isopiestic method .19 An apparatus is constructed similar to that shown in Figure 6.17. The mixture in container A is a solution of a nonvolatile solute in a solvent in which A], the activity of the solvent, has been accurately determined in other experiments as a function of concentration. Containers B and C hold solutions of other nonvolatile solutes in the same solvent. These are the solutions for which the activity of the solvent is to be determined. 

Our experimental techniques have been described extensively in earlier papers (2, 13). The gamma ray irradiations were carried out in a 50,000-curie source located at the bottom of a pool. The photoionization experiments were carried out by krypton and argon resonance lamps of high purity. The krypton resonance lamp was provided with a CaF2 window which transmits only the 1236 A. (10 e.v.) line while the radiation from the argon resonance lamp passed through a thin ( 0.3 mm.) LiF window. In the latter case, the resonance lines at 1067 and 1048 A. are transmitted. The intensity of 1048-A. line was about 75% of that of the 1067-A. line. The number of ions produced in both the radiolysis and photoionization experiments was determined by measuring the saturation current across two electrodes. In the radiolysis, the outer wall of a cylindrical stainless steel reaction vessel served as a cathode while a centrally located rod was used as anode. The photoionization apparatus was provided with two parallel plate nickel electrodes which were located at equal distances from the window of the resonance lamp. 

Experimental Method.—The diffraction photographs were prepared with the apparatus and technique described by Brockway.3 Ten or more photographs were made for each substance, the electron wave length used being about 0.0613 A. and the camera distance 10.83 cm. The values of so = 4ir(sin 6/2)/X given in the tables are averages of the values found by visual measurement of ring diameters for ten or more films. 

Apparatus and Procedure. The apparatus and procedure were identical to those outlined in ref. Surface composition measurements were based on an O2-CO titration technique described by Miura and Gonzalez (5-6). The ratio of surface metal/02/CO was 1/1/T on Ru-sllica, 1/0.5/1.75 on Rh-sllica, 1/0.5/2.0 on Pt-silica and 1/0.5/1.6 on Ir-silica. These titration ratios were found to be independent of surface composition. Surface compositions determined by the O2-CO titration method have been verified using a variety of experimental techniques (2,5-6). 

This effect has not been found in the source measurements carried out by the same or different operators in the same or different laboratories, with the same make of apparatus. None of the levels of error of measurement ever relates to an experimental value of flashpoint. This is incredible since over the past few years techniques of statistical control of testing and experimental planning have been developed which are now compulsory for some activities under the ISO 9000 quality standard. 

The pH-metric technique used to determine partition coefficients was first used in the 1950s in solvent extraction of metal complexes [280-282], but it is in pharmaceutical research that it is most widely used thanks to the recent development of a fully automated and computer-controlled apparatus [125,283]. The potentiometric approach has been validated in various solvent systems [284-287], and it has become a relevant and expanding experimental technique to obtain lipophilicity descriptors [257,287-289]. 

Varella, Evangelia A. Experimental techniques and laboratory apparatus in ancient Greece drug and perfume preparation. Medicinanei secoli 8, no. 2 (1996) 191-206. 

The apparatus and techniques of ion cyclotron resonance spectroscopy have been described in detail elsewhere. Ions are formed, either by electron impact from a volatile precursor, or by laser evaporation and ionization of a solid metal target (14), and allowed to interact with neutral reactants. Freiser and co-workers have refined this experimental methodology with the use of elegant collision induced dissociation experiments for reactant preparation and the selective introduction of neutral reactants using pulsed gas valves (15). Irradiation of the ions with either lasers or conventional light sources during selected portions of the trapped ion cycle makes it possible to study ion photochemical processes... 

Also, it seems that most of these properties are interdependent. For example, deaeration and permeability (Mainwaring and Reed, 1987) and perhaps the bulk density ratio (Jones and Mills, 1989) seem to provide an adequate mechanism to detect changes in material performance due to different particle size distribution, density and/or shape. However, possibly the greatest disadvantage or limitation of these empirical techniques is the need to standardize the experimental apparatus and techniques. For exam-... 

An unusually extensive battery of experimental techniques was brought to bear on these comparisons of enantiomers with their racemic mixtures and of diastereomers with each other. A very sensitive Langmuir trough was constructed for the project, with temperature control from 15 to 40°C. In addition to the familiar force/area isotherms, which were used to compare all systems, measurements of surface potentials, surface shear viscosities, and dynamic suface tensions (for hysteresis only) were made on several systems with specially designed apparatus. Several microscopic techniques, epi-fluorescence optical microscopy, scanning tunneling microscopy, and electron microscopy, were applied to films of stearoylserine methyl ester, the most extensively investigated surfactant. 

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