General Uses

As discussed in Chapters 1-7, diffusion, Brownian motion, sedimentation, electrophoresis, osmosis, rheology, mechanics, interfacial energetics, and optical and electrical properties are among the general physical properties and phenomena that are primarily important in colloidal systems [1-5]. Chemical reactivity and adsorption often play important, if not dominant, roles. Any physicochemical feature may ultimately govern a specific industrial process and determine final product characteristics, and any colloidal dispersions involved may be deemed either desirable or undesirable based on their unique physicochemical properties. Chapters 9-16 will provide some examples. 

Control of colloid stability is used in a wide range of technological applications, for example, [6]  

Although colloids maybe undesirable components in industrial systems, particularly as waste or by-products and, in nature, in the forms of fog and mist, they are desirable in many technologically important processes such as mineral beneficia-tion and the preparation of ceramics, polymers, composite materials, paper, foods, textiles, photographic materials, drugs, cosmetics and detergents. The remainder of this chapter specifies some applications for colloidal solids, liquids and gases, and illustrates how colloids can affect many technologically important systems. 

Emulsions, Foams, Suspensions, and Aerosols Microscience and Applications, 

Modern motor oil provides an example of some ofthe ways in which a number of colloidal and interfacial considerations come into play adhesion and lubrication, detergency, dispersion and suspension stabilization, foam inhibition, and viscosity and its temperature dependence. In addition to providing lubrication, a motor oil is expected to prevent corrosion and aid engine cooling and cleaning. Table 8.1 shows how a number of additives are blended in to help the oil achieve these functions [7]. 

Emulsions, Foams, and Suspensions Fundamentals and Applications. Laurier L. Schramm Copyright 2005 WILEY-VCH Verlag GmbH Co. KGaA, Weinheim ISBN 3-527-30743-5 

The milling industries are divided into dry, wet, and dry masa flour processes (see Chapters 7, 8, and 9, respectively). Dry milling is widely practiced with rough 

FIGURE 1.5 Flowchart of the main direct food uses of cereals. 

Wet-milling is aimed towards the production of refined starches. It is mainly practiced to obtain maize starch, although wheat and rice starches are also processed. The aim of wet milling is to obtain prime starch for the further production of modified starches or sweeteners. The wheat wet-milling industry also obtains vital gluten that is used as an important additive in the production of bakery products and other foods including processed meats. 

The milling of maize into masa and its derived products is gaining popularity worldwide because this process yields tortillas, considered as the main staple for Mexicans and Central Americans, and fried snacks such as corn and tortilla chips widely consumed all over the world (see Chapter 9). 

The alkaline cooking or nixtamalization of whole maize has become important in the United States and other parts of the world dne to the increase in popularity of Mexican foods. Three basic types of prodncts are indnstrially produced from alkaline or lime-cooked maize table or soft tortillas, com chips, and tortilla chips (Sema-Saldivar et al. 1990). Corn and tortilla chips are primarily produced and con-snmed in developed countries, where they have an important share within the salted snack food market, whereas table tortillas constitnte the staple food for large groups of people in developing Latin American countries. These prodncts can be produced 

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The methods most generally used are combustion and X-ray fluorescence. 

The generalized use of computers makes seemingly complex calculations quite easy to perform however, curves and tables are still invaluable when one needs to obtain approximate values or to take into account the sensitivity of a property to operating conditions or to a mixture s characteristics. 

The model is predictive and uses a method of contributing groups to determine the parameters of interaction with water. It is generally used by simulation programs such as HYSIM or PR02. Nevertheless the accuracy of the model is limited and the average error is about 40%. Use the results with caution. 

In the particular framework for lubricating oil bases, the operation takes place batchwise, generally using distillates selected according to the desired base, so as to minimize by-products and to maximize lubricating oils and their qualities. 

As a whole, a given crude is generally used to make products most of which have positive added values. This is particularly the case for motor fuels and specialty products. However, some of the products could have negative added values, as in the case of unavoidable products like heavy fuels and certain petroleum cokes. 

It is generally used with half mild or mild steels (carbon <. 4). Its purpose is to enrich in carbon the superficial metal layers by diffusion phenomenon. To obtain a hard cemented layer after this processing, we generally proceed by tempering. The chemical processing increases the rate of atomic defects by the introduction of one or many elements in the superficial layers. We can reach surface hardnesses of about 800 VICKERS. 

Thus in the case of ions, measurements of this type are generally used to obtain values of the mobility and, through Stoke s law or related equations, an estimate of the effective ionic size. 

For substances containing elements additional to C, H, O and N a rotating bomb calorimeter is generally used. A typical rotating bomb calorimeter system is shown in figure B 1.27.4. With tiiis calorimeter considerably more water is added to the combustion bomb and the continuous rotation of the bomb both about the cylindrical axis and end over... 

One flux model for a porous medium—the dusty gas model- has already been described in Chapter 3. Although it is perhaps the most important and generally useful model currently available, it has certain shortcomings, and other models have been devised in attempts to rectify these. However, before describing these, we will review certain general principles to which all reasonable flux models must conform. 

Acetaldehyde, CH3CHO, b.p. 21°, is generally used in aqueous solution, which has also a characteristic odour paraldehyde, (CH3CHO)3, is a liquid polymer, b.p. 124°, slightly soluble in water, odour similar to that of acetaldehyde, but less intense. Chloral, CCI3CHO, a liquid, is almost invariably encountered as the stable solid hydrate , CCl3CH(OH)2, m.p. 57 . Both have a characteristic odour the hydrate is readily soluble in water. 

The term resonance energy has been used in several w ays in the literature, but it is generally used to mean the difference between an experimentally determined energy of some relatively complicated molecule and the experimental energy... 

Miscellaneous apparatus. Two forms of adapters (or adapter tubes) are illustrated in Fig. 11,1, 10, a and b these are generally used to facilitate the delivery of a distillate from a condenser to a receiver. 

Rubber stoppers are frequently employed in the laboratory in vacuum distiUation assemblies (compare Section 11,19) for distillations under atmospheric pressure bark corks are generally used. Many organic liquids and vapours dissolve new rubber stoppers slightly and cause them to swell. In practice, it is found that rubber stoppers which have been previously used on one or two occasions are not appreciably attacked by most organic solvents, owing presumably... 

The beaker and thermometer should be removed from the metal bath before the latter solidifies. Metal baths have the advantage that they do not smoke or catch fire they are, however, solid at the ordinary temperature and are usually too expensive for general use. 

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