Physical Form and Properties

The physical form and properties of intermediates and final molecules are directly linked to and impact other parts of a process such as the reactor type, the type of mixing (static or continuous), the overall process throughput, the rate at which a chemical will dissolve in a solvent or precipitate out, the ease of which liquids are separated, and so on. There will also be knock-on impacts related to energy used for heating, cooling, recovery if applicable, cleaning, and wastes. 

An approach to metrics for this area could be profitably divided into three different aspects, depending on the questions that we are trying to answer with the metrics  

Mass has been discussed previously, but there are a few additional metrics to consider. These are clearly just variations on a theme, but they may be important metrics depending on the type of process that is being developed or run. These additional mass metrics could allow for additional scrutiny on the areas that might require additional investment of time to improve  

---

In subsequent chapters we examine the physical forms and properties of products and components. These are shown schematically in Figure 1.1. 

Physical form and properties (i.e., gas, liquid, solid) Unit operation type Throughput/cycle time Occupational exposure Purity/impurity profile... 

Porous carbons constitnte a fascinating kind of material. Different types with distinctive physical forms and properties (i.e., activated carbons, high-surface-area graphites, carbon blacks, activated carbon cloths and fibers, nanofibers, nanotubes, etc.) find a wide range of indnstrial applications in adsorption and catalysis processes. The main properties of these materials that make them very useful as catalyst supports, as well as some of their applications, have been described. The use of carbon as a catalyst support relies primarily on the relative inertness of its surface, which facilitates the interaction between active phases or between active phases and promoters, thus enhancing the catalytic behavior. This makes porous carbons an excellent choice as catalyst support in a great number of reactions. 

Physical Properties. The physical form and stabiUty of a fertilizer product is of an importance almost equal to that of its chemical content. Commercial fertilizers of importance include not only soHds, but also fluids, both solutions and suspensions, and even a gas (anhydrous ammonia). 

The physical characteristics should be considered (in combination as appropriate) in relation to the proposed dosage form and route of administration. Factors to be considered extend to solubility characteristics, crystal form and properties, moisture or solvent content, particle size and size distribution (which may affect bioavailability, content uniformity, suspension properties, stability, and preclinical or clinical acceptability), polymorphism, etc. 

Although the testing programme is largely prescriptive, there is some degree of latitude, for example studies on a specific substance depend on the chemical structure and physical form and some may be technically impossible or scientifically unnecessary. It may also be possible to predict the results for certain properties by read across to an analogue tested substance of closely similar chemical structure. 

When iodine is dissolved in hydriodic acid or a soln. of a metallic iodide, there is much evidence of chemical combination, with the formation of a periodide. A. Baudrimont objected to the polyiodide hypothesis of the increased solubility of iodine in soln. of potassium iodide, because he found that an extraction with carbon disulphide removed the iodine from the soln. but S. M. Jorgensen showed that this solvent failed to remove the iodine from an alcoholic soln. of potassium iodide and iodine in the proportion KI I2, and an alcoholic soln. of potassium iodide decolorized a soln. of iodine in carbon disulphide. The hypothesis seemed more probable when, in 1877, G. S. Johnson isolated cubic crystals of a substance with the empirical formula KI3 by the slow evaporation of an aqueous-alcoholic soln. of iodine and potassium iodide over sulphuric acid. There is also evidence of the formation of analogous compounds with the other halides. The perhalides or poly halides—usually polyiodides—are products of the additive combination of the metal halides, or the halides of other radicles with the halogen, so. that the positive acidic radicle consists of several halogen atoms. The polyiodides have been investigated more than the other polyhalides. The additive products have often a definite physical form, and definite physical properties. J. J. Berzelius appears to have made the first polyiodide—which he called ammonium bin-iodide A. Geuther called these compounds poly-iodides and S. M. Jorgensen, super-iodides. They have been classified 1 as... 

Overall, the concepts presented in this summary suggest that (i) an initial understanding of the properties of the API and excipients should be utilized to design excipient compatibility studies, (ii) the understanding of the role of water in the interactions of excipients with API should be considered for all designs of compatibility testing, and (iii) the physical form and its involvement in the solid state needs to be considered when interpreting the data. 

For the overall performance of potential catalysts in practical application additional factors, such as number of active sites, physical form, and porosity must also be taken into account. The classical commercial iron catalyst is an unsupported catalyst. First of all iron is a cheap material and secondly by the incorporation of alumina a surface area similar to that attained in highly dispersed supported catalysts can be obtained. Of course, for an expensive material such as the platinum group metals, the use of a support material is the only viable option. The properties of the supported catalyst will be influenced by several factors [172]... 

Materials and lighting are design tools. There are three types of physically definable material properties - optical properties, physical form, and temporal properties. Optical properties include tight distribution occurring over the surface and within the depth of the material as well as reflectance, transmission,... 

Factors on which the selection of a particular dryer or drying method depends inclnde form of raw material and its properties, desired physical form and characteristics of the product, necessary operating conditions, and operation costs. 

As Rowland (8) points out there are a number of reasons for modifying cellulose, including "(a) to solubilize it for regeneration into fiber and films, (b) to make it thermoplastic for moldings and extrusions and soluble for coatings, (c) to modify its bulk properties without change in physical form, and (d) to modify its chemical properties."... 

Modified zeolites for use in an industrial reactor should have the right physical form and shape implied by the choice of the reactor (Chapter 9). FCC in a fluid-bed reactor requires spherical particles (70-100 [im), obtained by spray drying of the [im-sized USY zeolite crystals in the presence of a binder, viz. silica, alumina, and clays [21]. Extrusion requires a binding agent that attributes to the zeolite/binder mixture tixotropic properties in the extruder [22]. As the catalyst binder may be active, it exceeds the role of diluent agent for the active zeolite [21]. Indeed, the steam stability of some zeolites is known to be enhanced in a binder[Pg.244]

Structural adhesives may be classified in a number of ways, such as those shown in Table I. The criterion chosen as a basis for the classification is usually the one that emphasizes the characteristic of most interest. In many cases the application and processing conditions are of most concern these depend on the physical form and cure conditions of the adhesive. A classification of structural adhesives that takes these properties into consideration has been suggested. 

A variety of processing steps have been utilized to achieve the desired physical forms and surface properties with porous silicon. Judicious choice of their order and overall process route can assist in optimization of properties for a specific use. Further improvements in maximum surface areas and porosities are likely to come from a combination of optimized etching, drying, and passivation steps. Improvements in chemical and mechanical stability are anticipated from optimized passivation and nanocomposite design, respectively. Improvements in control over particle size and shape dispersion are desired, but the feedstocks need to be inexpensive and the processing routes need to be scalable for maximum benefit. Some of the secondary processing techniques developed with other highly porous materials (see, e.g.. Wen et al. 2001, Hollister 2005, Conde et al. 2006, Studart et al. 2006) are likely to be utilized in the future. 

Fillers can be classified based on their physical form and shape as shown in Table 1.3. Among the classifications shown, only spherical fillers are S5nnmetric in physical form and hence provide symmetric changes in properties in all three spatial directions. It is normally rare to find exac y spherically well-formed fillers. There is always a slight defect in shape, especially for finer size particles. For instance, even when controlled conditions are used in the preparation of mono-disperse silica spheres in the micron size range [26,27], all particles... 

Morphology mor- Ifa -b-je n [Gr Morphologic, fr. morph- + -logie- ogy] (1830) The study of the physical form and stmcture of a material. This includes a wide range of characteristics, extending from the external size and shape of large articles to dimensions of crystal lattices but, with polymers, it most often refers to microstmcture. (Kamide K, Dobashi T (2000) Physical chemistry of polymer solutions. Elsevier, New York Physical properties of polymers handbook. Mark JE (ed) Springer, New York, 1996)... 

Because emulsion explosives are water-in-oil emulsions, they have excellent water resistance properties. In addition, if the materials are spilled, they retain a discrete physical form and can be easily recovered and used as originally intended. By adding other constituents such as aluminum or ANFO to emulsion explosives, the detonation characteristics of the material can be substantially adjusted. Emulsion explosives are available in both sensitized and desensitized forms, which allows the blaster to select products best suited to a particular blasting operation. The relative sensitivity of emulsion products can be varied by the manufacturer and can range from DOT oxidizer 5.1, to blasting agent... 

A wide variety of techniques have been employed for the characterization of thin film samples of nonlinear polymeric materials. Many of these are similar to techniques described in the previous section for bulk material characterization, and are employed with thin film samples both to assess differences in material properties in the two physical forms and because certain measurements such as absorption or electro-optic effects may be more easily made in thin film samples. Other techniques are specific to thin film samples in which light can be guided, for which parameters can be measured having no bulk equivalent, such as waveguide scatter or nonlinear mode coupling. 

---