Types, illustrations


Although the wide diversity of structural types illustrated in Scheme 6 suggests that numerous examples of their application to five-membered heterocycles would be known,  [c.131]

Metal loss from the internal surface of the types illustrated in Figs. 11.17 and 11.18 had affected approximately 45 tubes over the previous 4 months. It was noted that metal loss along the bottom half of the tubes was more severe. Significant numbers of failures of this type had not been experienced before, although it was known that entrainment of silt in the cooling water occurred seasonally.  [c.255]

Four of the more common types of thermal dryers used in the process industries are illustrated in Fig. 3.15.  [c.89]

The results are illustrated by figure 5 B-Scan, C-Scan and D-Scan representations show that there are two types of defects. On the left part of the weld, we remark a lack of fusion, while on the right part, we observe a nest of blow hole.  [c.227]

Given the set of surface free energies for the various crystal planes, draw a set of vectors from a common point of length proportional to the surface free energy and of direction normal to that of the crystal plane. Construct the set of planes normal to each vector and positioned at its end. It will be possible to find a geometric figure whose sides are made up entirely from a particular set of such planes that do not intersect any of the other planes. The procedure is illustrated in Fig. VII-2 for a two-dimensional crystal for which 710 is 250 ergs/cm and 7ii is 225 ergs/cm. Note that the optimum shape makes use of both types of planes for these surface tensions there is a free energy gain in truncating the comers of a (11) sided square crystal to reduce its perimeter (note Problems VII-2-VII-6). A statement of Wulff s theorem is that for an equilibrium crystal there exists a point in the interior such that its perpendicular distance h, from the jth face is proportional to 7,-. This is, of course, the basis of the construction in Fig. VII-2.  [c.261]

An emulsion may be defined as a mixture of particles of one liquid with some second liquid. The two common types of emulsions are oil-in-water (O/W) and water-in-oil (W/0), where the term oil is used to denote the water-insoluble fiuid. These two types are illustrated in Fig. XIV-1, where it is clear that the majority or outer phase is continuous, whereas the minority or inner phase is not. These two emulsion types are distinguished by their ability to disperse oil or water-soluble dyes, their dilution with oil or water, and their conductivity (O/W emulsions have much higher conductivity than do W/0 ones see Ref. 1 for reviews).  [c.501]

As illustrated in Fig. XIV-8, at least three types of aging processes occur for emulsions. The inner phase droplets may undergo flocculation, that is, clustering together without losing their identity if, as part of or subsequent to flocculation, the flocks undergo a gravity separation, the entire process is called creaming. If coalescence occurs, then eventual breaking of the emulsion must follow, giving two liquid layers—see Refs. SO and SI for a general discussion  [c.510]

The BET equation also seems to cover three of the five isotherm types described in Fig. XVII-7. Thus for c large, that is, Qi Qv, it reduces to the Langmuir equation, Eq. XVII-43, and for small c values, type III isotherms result, as illustrated in Fig. XVII-10. However, the adsorption of relatively inert gases such as nitrogen and argon on polar surfaces generally gives c values around 100, corresponding to type II isotherms. For such systems the approximate form of Eq. XVII-62,  [c.621]

Figure Al.7.9. Schematic diagram illustrating three types of adsorption sites. Figure Al.7.9. Schematic diagram illustrating three types of adsorption sites.
The discussion of applications of the SFIG and SFG methods in this section is directed towards an exposition of the different types of infomiation that may be obtained from such measurements. The topics have been arranged accordingly into seven general categories that arise chiefly from the properties of the nonlinear susceptibility surface symmetry and order, adsorbate coverage, molecular orientation, spectroscopy, dynamics, spatial resolution and perturbations induced by electric and magnetic fields. Although we have included some illustrative examples, a comprehensive description of the broad range of materials probed by these methods, and what has been learned about them, is clearly beyond the scope of this chapter.  [c.1283]

The optimization of the backtracking algorithm usually consists of an application of several heuristics which reduce the number of candidate atoms for mapping from Gq to Gj. These heuristics are based on local properties of the atoms such as atom types, number of bonds, bond orders, and ring membership. According to these properties the atoms in Gq and Gj are separated into different classes. This step is known in the literature as partitioning [13]. Table 6.1 illustrates the process of partitioning.  [c.301]

Fractional Distillation. For this type of distillation, the fractionating column is inserted vertically betw een the flask containing the boiling liquid and the condenser. The principle of a fractionating column is that, as the vapours ascend the column from the boiling mixture below, the higher-boiling components are condensed and returned to the flask, the ascending column of vapour being thus steadily scrubbed by the descending column of liquid condensate. The ascending column of vapour becomes therefore steadily richer in the lowest-boiling component, and the descending column of condensate steadily richer in the highest-boiling component. It follows that the prime factor which determines the efficiency of a column is the extent to which the vapour is scrubbed by the condensate, and columns are therefore designed to make this scrubbing as intimate as possible. Text-books of theoretical organic chemistry frequently illustrate remarkable and weird types of fractionating column which the practical chemist never encounters. For actual use in the laboratory two types of column are recommended. (A) For quick rough separations, or (more particularly) for the separation of two components having a considerable difference in boiling-point, the pear column (Fig. h(a)) is useful. The increase in cooling surface produced by pear-shaped bulbs causes considerable condensation, and the condensate, steadily dripping down from the lower shoulder of each bulb, comes in moderate contact with the ascending vapour. The efficiency of a column can, of course, be increased by increasing the number of bulbs in the column. (B) For accurate work, the column shown  [c.25]

Standard procedures for the derivation of the shape functions of common types of finite elements can be illustrated in the context of two-dimensional triangular and rectangular elements. Let us, first, consider a triangular element having three nodes located at its vertices as is shown in Figure 2.6.  [c.23]

If crystallisation commences as soon as the solvent cools or if large quantities of hot solution are to be filtered, the funnel (and fluted filter paper) should be warmed externally during the filtration (hot water funnel). Three types of hot water funnel are illustrated in Fig. 11,1, 6 no flames should be present whilst inflammable solvents are being filtered through the funnel of Fig. 11, 1, 6, a. Alternatively, the funnel may be surrounded by an electric heating mantle (see Section 11,57) the heat input may be controlled by a variable transformer. When dealing with considerable volumes of aqueous or other solutions which do not deposit crystals rapidly on cooling, a Buchner funnel may be used for filtration (see detailed account in Section 11,1 and Fig. 11 1, 7, c). The filter paper  [c.126]

Multi-necked flasks. Various types of multi necked flasks are illustrated in Figs. II, 56, 13-15. The centre socket is usually the largest ( 24 or 34) and the side sockets are generally smaller. The side tube in Fig. II, 56,15, a may be employed for a capillary tube in vacuum distillation b, c and d are different types of thermometer wells .  [c.215]

Fractional Distillation. For this type of distillation, the fractionating column is inserted vertically between the flask containing the boiling liquid and the condenser. The principle of a fractionating column is that, as the vapours ascend the column from the boiling mixture below, the higher-boiling components are condensed and returned to the flask, the ascending column of vapour being thus steadily scrubbed by the descending column of liquid condensate. The ascending column of vapour becomes therefore steadily richer in the lowest-boiling component, and the descending column of condensate steadily richer in the highest-boiling component. It follows that the prime factor which determines the efficiency of a column is the extent to which the vapour is scrubbed by the condensate, and columns are therefore designed to make this scrubbing as intimate as possible. Text-books of theoretical organic chemistry frequently illustrate remarkable and weird types of fractionating column which the practical chemist never encounters. For actual use in the laboratory two types of column are recommended. (A) For quick rough separations, or (more particularly) for the separation of two components having a considerable difference in boiling-point, the pear column (Fig. h(a)) is useful. The increase in cooling surface produced by pear-shaped bulbs causes considerable condensation, and the condensate, steadily dripping down from the lower shoulder of each bulb, comes in moderate contact with the ascending vapour. The efficiency of a column can, of course, be increased by increasing the number of bulbs in the column. (B) For accurate work, the column shown  [c.25]

In each of the Sections i o - 27, the chief physical properties of the compounds concerned are first briefly indicated a list of the gen eral reactionsf is then given, followed by practical directions for the application or illustration of these general reactions. The types of crystalline derivatives which can be most readily and reliably prepared are then given, with practical examples. Finally, any important special reactions of individual members are described.  [c.318]

In the DEPT routine a second transmitter excites H which affects the appear ance of the spectrum A typical DEPT experiment is illustrated for the case of 1 phenyl 1 pentanone m Figure 13 26 In addition to the normal spectrum shown m Figure 13 26a four more spectra are run using prescribed pulse sequences In one (Figure 13 26b) the signals for carbons of CH3 and CH groups appear normally whereas those for CH2 groups are inverted and those for C without any attached hydrogens are nulled In the others (not shown) different pulse sequences produce combinations of nor mal nulled and inverted peaks that allow assignments to be made to the various types of carbons with confidence  [c.553]

The syntax and semantics of the typing rules in a chem.rul file are included in the HyperChem Reference Manual. The following example illustrates their use. The five AMBER types for oxygen atoms shown above are defined in chem.rul by the following rules  [c.171]

Unit cells of the different lattice types in each system are illustrated in Fig. 4.1.  [c.333]

The shell-and-tube heat exchanger is probably the most common type of exchanger used in the chemical and process industries. The simplest type of such device is the 1-1 design (1 shell pass, 1 tube pass), as illustrated in Fig. 7.7a. Of all shell-and-tube types, this comes closest to pure countercurrent flow and is designed using the basic coimtercurrent equation  [c.222]

Although we know of gravitational, nuclear, and electromagnetic interactions, it is only the latter that are usually important in chemistry. Electromagnetic forces include repulsive and attractive forces. Two types of repulsive forces have been considered in preceding chapters the Coulomb repulsion between like-charged ions and the repulsion between atoms brought too close together. The latter occurs over a very short range, hence the form of the Lennard-Jones potential illustrated in Fig. III-6, where the respulsion decays as the inverse twelfth power of distance. This repulsion is caused by the strong interaction between electron clouds as they are made to overlap and defines an atomic or molecular diameter. Since the radial portion of the electron wave function is exponential, this repulsion is often represented by an exponential function.  [c.225]

In the case of ion exchangers, the primary ions are chemically bonded into the ftamework of the polymer, and the exchange is between ions in the secondary layer. A few illustrations of these various types of processes follow.  [c.412]

Some classes of adsorbents have internal surface accessible by pores small enough to act as molecular sieves, so that different apparent surface areas are obtained according to the size of the adsorbate molecule. This is a screening effect and not one of surface roughness as might be described in terms of fractal geometry (Section XVI-2B). Zeolites have been of much interest in this connection because the open way in which the (Al, Si)04 tetrahedra join gives rise to large cavities and large windows into the cavities. This is illustrated in Fig. XVII-26 [179]. As a specific example, chabasite (CaAl2Si40i2) has cages about 10 A in diameter, with six openings into each or windows of about 4-A diameter. Monatomic and diatomic gases, water, and n-alkanes can enter into such cavities, but larger molecules do not. Thus isobutane can be separated from -alkanes and, on the basis of rates, even propane from ethane [180]. The replacement of the calcium by other ions (zeolites have ion exchange properties—note Section XI-6C) considerably affects the relative adsorption behavior. Various synthetic zeolites having various window diameters in the range of 4 to 10 A are available under the name of Linde Molecular Sieves (see Ref. 179). Listings of types of zeolites and their geometric properties may be found in Refs. 181 and 182 and the related properties of expanded clay  [c.662]

Still another type of adsorption system is that in which either a proton transfer occurs between the adsorbent site and the adsorbate or a Lewis acid-base type of reaction occurs. An important group of solids having acid sites is that of the various silica-aluminas, widely used as cracking catalysts. The sites center on surface aluminum ions but could be either proton donor (Brpnsted acid) or Lewis acid in type. The type of site can be distinguished by infrared spectroscopy, since an adsorbed base, such as ammonia or pyridine, should be either in the ammonium or pyridinium ion form or in coordinated form. The type of data obtainable is illustrated in Fig. XVIII-20, which shows a portion of the infrared spectrum of pyridine adsorbed on a Mo(IV)-Al203 catalyst. In the presence of some surface water both Lewis and Brpnsted types of adsorbed pyridine are seen, as marked in the figure. Thus the features at 1450 and 1620 cm are attributed to pyridine bound to Lewis acid sites, while those at 1540  [c.718]

The Darling-Dennison Hamiltonian displayed a striking energy level pattern associated with the bifiircation to local modes approximately degenerate local mode doublets, split by dynamical tiumelling. In general Fenni resonance systems, the spectral hallmarks of bifurcations are not nearly as obvious. However, subtle, but clearly observable spectral markers of bifiircations do exist. For example, associated with the fonnation of resonant collective modes in the 2 1 Fenni system there is a pattern of a minimum in the spacing of adjacent energy levels within a poly ad [ ], as illustrated in figure Al.2.12. This pattern has been invoked [, in the analysis of isomerization spectra of the molecule HCP, which will be discussed later. Other types of bifiircations have their own distinct, characteristic spectral patterns for example, in 2 1 Fenni systems a second type of bifiircation has a pattern of alternating level spacmgs, of a fan or a zigzag , which was predicted in [ ] and subsequently s [57].  [c.71]

One of the major sueoesses of energy band theory is that it ean be used to prediet whether a erystal exists as a metal or insulator. If a band is filled, the Pauli prineiple prevents eleetrons from ehanging tlieir momentum in response to the eleetrie field as all possible momentum states are oeeupied. In a metal this eonstraint is not present as an eleetron ean ehange its momentum state by moving from a filled to an oeeupied state within a given band. The distinet types of energy bands for insulators, metals, semieonduetors and semimetals are sehematieally illustrated in figure Al.3.8. In an insulator, energy bands are either eompletely empty or eompletely filled. The band gap between the highest oeeupied band and lowest empty band is large, e.g. above 5 eV. In a semieonduetor, the bands are also eompletely filled or empty, but the gap is smaller, e.g. below 3 eV. In metals bands are not eompletely oeeupied and no gap between filled and empty states oeeiirs. Semimetals are a speeial ease. No gap exists, but one band is almost eompletely oeeupied it overlaps with a band that is almost eompletely empty.  [c.105]

The initial classification of phase transitions made by Ehrenfest (1933) was extended and clarified by Pippard [1], who illustrated the distmctions with schematic heat capacity curves. Pippard distinguished different kinds of second- and third-order transitions and examples of some of his second-order transitions will appear in subsequent sections some of his types are unknown experimentally. Theoretical models exist for third-order transitions, but whether tiiese have ever been found is unclear.  [c.613]

Depending on the relative phase difference between these temis, one may observe various experimental spectra, as illustrated in figure Bl.5.14. This type of behaviour, while potentially a source of confiision, is familiar for other types of nonlinear spectroscopy, such as CARS (coherent anti-Stokes Raman scattering) [30. 31] and can be readily incorporated mto modelling of measured spectral features.  [c.1295]

The nematic phase fonned by chiral molecules is itself chiral. This used to be called tire cholesteric phase, because tire mesogen for which it was first observed contained a cholesterol derivative. However, it is now called tire chiral nematic phase, denoted N, because it has been observed for otlier types of mesogen. The chiral nematic phase is illustrated in figure C2.2.2. The director (average direction of molecules) twists round in a helix. It is important to note tliat tliis helical twist refers to tire average orientation of molecules and not tire packing of molecules tliemselves, because tliey do not have long-range translational order. The helical stmeture has a characteristic pitch, or repeat distance along tire helix, which can range from about 100 nm to near infinity. Wlren tire pitch lengtli is comparable to tire wavelengtli of light, tire chiral nematic phase scatters or reflects visible light, producing colours. Furtliennore, tire pitch and, tluis, colour are sensitive to temperature, which is tire basis of thennochromic devices, i.e. Arose tliat produce colour changes in response to temperature (section C2.2.4.6).  [c.2544]

The measurement of fluorescence intensity from a compound containing cliromophores of two spectral types is an example of a system for which it is reasonable to operate witli tire average rates of energy transfer between spectral pools of molecules. Let us consider tire simple case of two spectral pools of donor and acceptor molecules, as illustrated in figure C3.4.2 [18]. The average rate of energy transfer can be calculated as  [c.3020]

Chemists usually learn about reactions according to fiinctional groups for example, How can I make an aldehyde and what reactions are known for aldehydes " This is clearly not a very good starting point for classifying reactions. The poor state of affairs in the definition of reaction types is further quite vividly illustrated by the fact that many chemical reactions are identified by being named after their inventor Diels-Alder reaction, Michael addition, Lobry-de Bruyn-van Ekenstein rear-  [c.172]

In eachof the Sections 10-27, the chief physical propertiesof the compounds concerned are Erst briefly indicated a list of the gen eral reactionsf is then given, followed by practical directions for the application or illustration of these general reactions. The types of crystalline derivatives which can be most readily and reliably prepared are then given, with practical examples. Finally, any important special reactions of individual members are described.  [c.318]

This brief account is intended to give only a general indication of the types of apparatus available. The firm which has pioneered the design and manufacture of ground-glass apparatus is Quickfit and Quartz, Ltd., Quickfit Works, Stone,. Staffordshire.. ST15 OBG, whose catalogues fully illustrate the range of units and assemblies available.  [c.43]

Aromatization of indolines is important in completing synthetic sequences in which the directive effects of the indoline ring have been used to achieve selective carbocyclic substitution[l]. Several methods for aromatization have been developed and some of these are illustrated in Table 15.2. A range of reagents is represented. One type of procedure represents use of oxidants which are known to convert amines to imines. Aromatization then provides the indole. Such reagents must not subsequently oxidize the indole. Mereuric acetate (Entry 1) is known to oxidize other types of amines and presumably reacts by an oxidative deprotonation ot- to the complexed nitrogen.  [c.148]

Table 13 1 collects chemical shift information for protons of various types The beginning and major portion of the table concerns protons bonded to carbon Within each type methyl (CH3) protons are more shielded than methylene (CH2) protons and meth ylene protons are more shielded than methme (CH) protons These differences are small as the following two examples illustrate  [c.527]

Saccharin sucralose and aspartame illustrate the diversity of structural types that taste sweet and the vitality and continuing development of the in dustry of which they are a part  [c.1052]


See pages that mention the term Types, illustrations : [c.96]    [c.731]    [c.70]    [c.2547]    [c.553]    [c.581]    [c.171]    [c.27]    [c.608]    [c.64]    [c.103]    [c.147]    [c.163]   
Applied Process Design for Chemical and Petrochemical Plants, Volume 1 (1999) -- [ c.411 , c.412 , c.413 , c.414 , c.415 , c.416 , c.417 , c.418 , c.419 , c.420 ]