Optical Examination

For these types of reactor solids, the carbonaceous solids content varies usually from about 20 to 40%. The components of these solids are listed in Table VII. Optical examination of the solids has shown that they are primarily composed of mixtures of semi-cokes formed during liquefaction by retrogressive reactions with chars derived from macerals. Unreacted macerals comprise only a small fraction of these solids (65,74,75). 

Optical examination of etched polished surfaces or small particles can often identify compounds or different minerals hy shape, color, optical properties, and the response to various etching attempts. A semi-quantitative elemental analysis can he used for elements with atomic number greater than four by SEM equipped with X-ray fluorescence and various electron detectors. The electron probe microanalyzer and Auer microprobe also provide elemental analysis of small areas. The secondary ion mass spectroscope, laser microprobe mass analyzer, and Raman microprobe analyzer can identify elements, compounds, and molecules. Electron diffraction patterns can be obtained with the TEM to determine which crystalline compounds are present. Ferrography is used for the identification of wear particles in lubricating oils. 

Fibers of tourmalines up to 8 inches long have been described from the Alps (Dietrich et al., 1966). Novad and Zak (1970) described shorter and thinner (diameter < 1 micrometer) tourmaline fibers from the Ural mountains. With high birefringence and pleochroism, tourmaline is readily identified by optical examination. It is distinguished from other fibrous silicates... 

If the combination of X-ray and morphological evidence does not determine the space-group uniquely, additional information may be sought by tests for piezo-electric and pyro-electric properties, and by an optical examination for any evidence of rotation of the plane of polarization. (See Chapter VIII.) The results of such tests may settle the matter, since only certain crystal classes have these properties. Only positive results are decisive the apparent absence of piezo-electric or pyro-electric effects may be due to feeble phenomena. 

To obtain free alanine the alanine ester is heated for about 6 hours with 5 times its weight of water on a water bath, until the alkaline reaction has disappeared. The solution is evaporated on a water bath till crystallisation begins. The liquid is allowed to stand at 0°, when about 30 gms. alanine separate optical examination shows this to consist of almost pure d-compound. From the mother liquor a second crop of 20—25 gms. may be obtained, and this still consists of fairly pure active amino-acid, so that the total yields amount to 50—55 gms. The last mother liquor still contains a fair amount of active alanine, but it is mixed with so much racemic substance that it cannot be separated from it by mere recrystallisation from water. The first two crops are dissolved once more in hot water, and the liquid evaporated on the water bath till it begins to crystallise. At 0° a large quantity of the pure, active amino-acid separates out. 

Crystallographic investigation, including the determination of lattice parameters, absence of foreign phases by x-rays, density determination, and optical examination. 

No attempt was made to prevent surface oxidation of the metals. The copper powder was initially free of oxide but oxidized noticeably during the experiments, which generally took about two weeks from compaction to measurement of resistivity. Optical examination was made immediately after polishing. 

If optical examination shows two n s, the two indices will be omega and epsilon or e1, and the mineral belongs to either the hexagonal or the tetragonal system. Caution In some minerals, one n may be so close to another n that it may be falsely assumed that there are only two n s. Minerals of the tetragonal or hexagonal systems are uniaxial. 

In accord with the optical examination, both specimens show under the TEM piogressivc zones of shock damage, reflecting the changing shock conditions in the depth of the sample. The laser-shocked specimen displays the largest variation in microstructures. Just below the excavated zone of this specimen, i.e., within a depth of -50 pm below the original preshock surface, we observe a spotty diffraction contrast (Fig. 1.11a). The spots represent tiny dislocation loops that may result from decomposition of CaCOs into CaO and CO2 [41,42]. 

A scheme for the careful optical examination of crystals, incorporating the different ways in which they can interact with light, is summarized in Table 5.3. 

A detailed optical examination of a crystal may reveal its symmetry. 

Eykman (Ber. 1889, 22, 3172) concluded from an optical examination of a mixture of asarone and safrole that the former is a propenyl and not an allyl derivative, and the constitution of asarone was finally determined by Gattermann and Eggers (Ber. 1899, 32, 289) by synthesizing asarylic aldehyde (ii) from 1 2 4-trimethoxybenzene and then heating this aldehyde with propionic anhydride and sodium propionate, when asarone (iii) was obtained in a yield of 60 per cent. Asarone melts at 62-63° and boils at 296°, specific gravity at 18°, 1.165. 

To compound the problem, marcasite for reasons unknown to the author does not show the intensity response, volume for volume,as does pyrite. It has been the author s experience that coals that have been shown by optical examination to contain marcasite in significant concentrations show almost no indication of the mineral being present on a diffractogram generated from the low temperature ash. 

Figure 4 shows density data on two EPR samples (B and C of Fig. 1) that were irradiated to similar dose, but at different dose rates. Strongly heterogeneous oxidation is again indicated for the high-dose-rate sample, in contrast to nearly homogeneous oxidation for the low-dose-rate sample. The results correlate well with results obtained by optical examination of polished samples and by relative hardness measurements. 

Optical examination may show evidence of inclusions including exsolution... 

Optical examination of the effects of applied electric fields provides a sensitive technique for investigating the structure of nematic liquids. Two distinct kinds of interfaces exist in pure nematic liquids. One corresponds to the crystallite boundaries in ordinary polycrystalline solids. The other is the interface between domains which shows effects of interfacial tension in p-methoxycinnamic acid. In other nematic liquids this effect is not found. 

On the basis of a detailed chemical and optical examination of the catalysate composition the following scheme is suggested for the various con-... 

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