Categories of concepts

The establishment of order, or a system of classification, allows us to make an assertion, or a proposition, about the relationships between classes or categories of concepts. A proposition always takes the form of a declarative sentence. 

Our purpose in this introduction is not to trace the history of polymer chemistry beyond the sketchy version above, instead, the objective is to introduce the concept of polymer chains which is the cornerstone of all polymer chemistry. In the next few sections we shall introduce some of the categories of chains, some of the reactions that produce them, and some aspects of isomerism which multiply their possibilities. A common feature of all of the synthetic polymerization reactions is the random nature of the polymerization steps. Likewise, the twists and turns the molecule can undergo along the backbone of the chain produce shapes which are only describable as averages. As a consequence of these considerations, another important part of this chapter is an introduction to some of the statistical concepts which also play a central role in polymer chemistry. 

Petroleum refining, also called petroleum processing, is the recovery and/or generation of usable or salable fractions and products from cmde oil, either by distillation or by chemical reaction of the cmde oil constituents under the effects of heat and pressure. Synthetic cmde oil, produced from tar sand (oil sand) bitumen, and heavier oils are also used as feedstocks in some refineries. Heavy oil conversion (1), as practiced in many refineries, does not fall into the category of synthetic fuels (syncmde) production. In terms of Hquid fuels from coal and other carbonaceous feedstocks, such as oil shale (qv), the concept of a synthetic fuels industry has diminished over the past several years as being uneconomical in light of current petroleum prices. 

The above concept of a recipe permits the following three different categories of batch processes to be identified ... 

Apart from the three broad categories of student conceptions discussed above, students displayed several inappropriate conceptions relating to the stractural properties of substances. For example, 14% of students suggested that Mg + ions were present in magnesium ribbon. A second example involved the chemical reaction between copper(II) oxide powder and dilute sulphuric acid. In this instance, 25% of students suggested that Cu + ions were present only in aqueous solution but not in the solid and liquid states. This view was rather unexpected because students had earlier been introdnced to ionic and covalent compounds. It is likely that students had merely rote-learned the general rale without sufficient understanding that ionic solids are formed between metallic and non-metallic elements. 

The situation is different when I autoxidation processes belonging to the category of induced chain reactions. 

The Menschutkin reaction was carried out as a test reaction to show the feasibility of such novel micro flow concepts that allow to process fouling-sensitive reactions (see also Section 4.2.6 here another test reaction is decribed for the same purpose) [78]. The reaction of alkyl bromide with ternary bases such as pyridine or triethylamine gives quaternary salts insoluble in most solvents. Often, fairly rapid precipitation of this salt occurs, hence ideally serving as a test reaction for fouling sensitivity of micro-channel devices. The reaction of 4,4 -bipyridyl and ethyl bromoacetate [78] belongs to the category of fast-predpitating Menschutkin reactions, as the halide function is activated by the carbonyl fimction. 

According to this definition the group of bases practically includes just about the same substances as the Br0nsted conception, but with a few additions such as the inert gases (e.g. argon reacts as a base with boron trifluoride). On the other hand, the category of acids is much wider than... 

In this review, we present a selection of studies from our own laboratory, intended to introduce a solid-state chemist to both the practical and theoretical considerations that need to be taken into account in XPS measurements of solids with substantial covalent character. Metal phosphides, arsenides, and antimonides represent such a category of solids where the bonding retains some polarity that notions of electron counting derived from the Zintl concept still prove helpful in providing a frame of reference for comparing charge distributions. We also describe the applications of XAS to complementary studies of the electronic structure of these materials. 

The TLV is not a single entity. The ACGIH defines three categories of TLV, namely, the time-weighted average (TLV-TWA), the short-term exposure limit (TLV-STEL), and the ceiling. Because these are proprietary terms, the U.S. Occupational Safety and Health Administration (OSHA) has adopted different terminology for essentially the same concepts, as follows ... 

In conclusion, the fuel-bed system comprises three structures, which are interstitial gas phase, intraparticle gas phase and intraparticle solid phase, see Figure 18. In a comprehensive partial differential theory of the conversion system these three structures need to be considered. The fuel-bed structure is independent of conversion concept (see definition below) applied that is, the three structures shown in Figure 18 will be the same for all categories of packed fuel-bed systems. 

During the Middle Ages and Renaissance, any element that could not be easily recognized by its outward physical properties, that was not considered a metal, and that was not soluble in water was considered an earth element. This classification was a holdover from the ancient Greek concept that all elements fit into one of the three categories of earth, fire, and air. In addition, any substance that acted in ways similar to potash and soda (alkaline caustics) were classed as alkali earth metals. 

The second category of methods uses a more general approach, based on fundamental concepts in statistical mechanics of the liquid state. As mentioned above, the Hwang and Freed theory (138) and the work of Ayant et al. (139) allow for the presence of intermolecular forces by including in the formulation the radial distribution function, g(r), of the nuclear spins with respect to the electron spins. The radial distribution function is related to the effective interaction potential, V(r), or the potential of mean force, W(r), between the spin-carrying particles through the relation (138,139) ... 

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