Condensed classification

Element Tcond (K) Initial condensate classification Element Tcond (K) condensate classification... 

Table 7-9 is a condensed classification and nomenclature of the important parasitic helminths that affect humans. The worms that infect humans are the flatworms and the roundworms. Helminths are the only parasites discussed here that are not microscopic. Quite the opposite, their dimensions are of the order of millimeters and, in the case of certain tapeworms, reach lengths of meters. 

Polymers can also be classified in other ways for example, many varieties of rubber are often referred to as elastomers. Dacron is a fiber, and poly(vinyl acetate) is an adhesive. The addition and condensation classifications are used in this essay. 

The basis of the classification is that each of the size ranges corresponds to characteristic adsorption effects as manifested in the isotherm. In micropores, the interaction potential is significantly higher than in wider pores owing to the proximity of the walls, and the amount adsorbed (at a given relative pressure) is correspondingly enhanced. In mesopores, capillary condensation, with its characteristic hysteresis loop, takes place. In the macropore range the pores are so wide that it is virtually impossible to map out the isotherm in detail because the relative pressures are so close to unity. 

In the last section we examined some of the categories into which polymers can be classified. Various aspects of molecular structure were used as the basis for classification in that section. Next we shall consider the chemical reactions that produce the molecules as a basis for classification. The objective of this discussion is simply to provide some orientation and to introduce some typical polymers. For this purpose a number of polymers may be classified as either addition or condensation polymers. Each of these classes of polymers are discussed in detail in Part II of this book, specifically Chaps. 5 and 6 for condensation and addition, respectively. Even though these categories are based on the reactions which produce the polymers, it should not be inferred that only two types of polymerization reactions exist. We have to start somewhere, and these two important categories are the usual place to begin. 

In Sec. 1.4 we discussed the classification of polymers into the categories of addition or condensation. At that time we noted that these classifications could be based on the following ... 

Condensed phosphates are derived by dehydration of acid orthophosphates. The resulting polymeric stmctures are based on a backbone of P—O—P linkages where PO tetrahedra are joined by shared oxygen atoms. The range of materials within this classification is extremely broad, extending from the simple diphosphate, also known as pyrophosphate, to indefinitely long-chain polyphosphates and ultraphosphates (see Table 1). Both weU-defined crystalline and amorphous materials occur among the condensed phosphates. 

An imidazoquinazoline constitutes still another compound that does not fall in the classification of a nonsteroid antiinflammatory agent yet shows good platelet anti aggregating activity. Condensation of benzyl chloride 128 with the ethyl ester of glycine gives alkylated product... 

A. Determination of silica in a soluble silicate Discussion. Most of the silicates which come within the classification of soluble silicates are the orthosilicates formed from SiO units in combination with just one or two cations. More highly condensed silicate structures give rise to the insoluble silicates. 

There are potentially many items of equipment that can be described as BOP, and the classification distinctions are not always clear. However, electricity generators (especially turbine generators) and condensers are commonly referred to as BOP, and some notes on these items of equip-... 

Another classification system, first suggested by Carothers in 1929, is based on the nature of the chemical reactions employed in the polymerisation. Here the two major groups are the condensation and the addition polymers. Condensation polymers are those prepared from monomers where reaction is accompanied by the loss of a small molecule, usually of water, for example polyesters which are formed by the condensation shown in Reaction 1.1. 

As outlined in Chapter 1, polymerisation reactions can be classified as either condensation or addihon processes, the basis of the classification suggested by W. H. Carothers in 1929. More useful, however, is the classification based on reaction kinetics, in which polymerisation reactions are divided into step and chain processes. These latter categories approximate to Carothers condensation and addition reactions but are not completely synonymous with them. 

The chemical and physical properties of the polymers obtained by these alternate methods are identical, except insofar as they are affected by differences in molecular weight. In order to avoid the confusion which would result if classification of the products were to be based on the method of synthesis actually employed in each case, it has been proposed that the substance be referred to as a condensation polymer in such instances, irrespective of whether a condensation or an addition polymerization process was used in its preparation. The cyclic compound is after all a condensation product of one or more bifunctional compounds, and in this sense the linear polymer obtained from the cyclic intermediate can be regarded as the polymeric derivative of the bifunctional monomer(s). Furthermore, each of the polymers listed in Table III may be degraded to bifunctional monomers differing in composition from the structural unit, although such degradation of polyethylene oxide and the polythioether may be difficult. Apart from the demands of any particular definition, it is clearly desirable to include all of these substances among the condensation... 

The program sets four criteria, leading to a three-level qualitative classification low risk, medium, high for each of them. Each criterion quantifies an aspect of the decomposition risk. So these four classifications need to be taken into account to arrive at a final estimation. Someworkers have tried to use a sole criterion, which mathematically combines the four criteria, but failed. Three out of these four criteria involve calculating the enthalpies of decomposition and combustion of the particular compound. In order to do so it is necessary to know the enthalpies of formation of the compound and of the decomposition and combustion products. A lot of these values are inevitably absent in Part Three, so it was thought necessary to include estimation methods for enthaipies of formation as weil as for enthalpies of vapourisation/condensation, since in many cases there is only available the value for the physical state of the compound that is not always appropriate. 

Process plants are categorized into different hazard classifications, according to the potential explosion energy available from vessel rupture, condensed-phase explosion, confined vapor (building) explosion, or VCE. 

Separation of the residual fractions is as follows separation of CFCs by condensation separation of expanded PS and PU foam by air classification separation of iron with a magnetic separator and separation of nonferrous metals with an eddy-current separator. 

Platt JR (1949) Classification of spectra of cata-condensed hydrocarbons. J Chem Phys 17 484... 

Table 16-4 shows the IUPAC classification of pores by size. Micropores are small enough that a molecule is attracted to both of the opposing walls forming the pore. The potential energy functions for these walls superimpose to create a deep well, and strong adsorption results. Hysteresis is generally not observed. (However, water vapor adsorbed in the micropores of activated carbon shows a large hysteresis loop, and the desorption branch is sometimes used with the Kelvin equation to determine the pore size distribution.) Capillary condensation occurs in mesopores and a hysteresis loop is typically found. Macropores form important paths for molecules to diffuse into a par-... 

The classification of a condensation polymer Is historically based on the observation that during polymerization a small molecule, such as water, is condensed or removed as part of the reaction. There are a large number of polymers produced from condensation reactions and only a representative sample is presented in... 

Microporous substances with pore widths smaller than twenty Angstroms exhibit type 1 isotherms (lUPAC classification) in the absence ofmesopores, as illustrated in Figure 13.1 [4]. The steep uptake of N2 at very low relative pressures is due to the capillary condensation in micropores. Following the filling of micropores, adsorption isotherms become nearly fiat because further N2 uptake can now only occur at the external surface area, which is typically much lower relative to the total surface area. 

---