Special equipment

In this section I shall briefly deal with equipment required for carrying out some of the more specialized and non-standard procedures associated with SEC. Some of these will be discussed in more detail elsewhere, and the reader is directed to the appropriate chapter. 

3 Hydrodynamic chromatography. This technique is related to SEC in that it attempts to separate species according to their size, but several orders of magnitude larger than those encountered in solution chromatography. The mechanisms involved in hydrodynamic chromatography are different to SEC, but the basic experimental system is similar pump, injector, column and detector. Special columns and data analysis software are required, and the detectors usually employed are a differential refractometer, ultraviolet photometer or LALLS. Chapter 10 is devoted to this technique and full details can be found there. 

The main drawback to mass spectral analyses of polymeric materials is the limitation on sample molecular mass. Materials with molecular masses greater than a few thousand are insufficiently volatile to be analysed. Consequently LC-MS is not normally used in SEC of high polymers, but is useful for the analysis of polymer additives and other low-molecular-weight components present in polymeric materials. 

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The LPI process with its great variety of processes required the QAP to be developped in a modular way and its functions have always to be adapted to the special equipment. 

The diagnostic system DK-ID comrising the X-ray densitometer and special equipment for speciments prepare is designed in MSIA Spectrum . This system is actively used by several Russian companies dealing with forestry. The fact of efficient radiographic tomography use, when inspecting the conditions of trees in the forests is also known. 

The available sensitivity depends strongly on the equipment as well as the sample. H is the nucleus of choice for most experiments. 1 mg of a sample of a medium-sized molecule is adequate for almost all types of H-only spectra, and with specialized equipment one can work with nanogram quantities. At this lower level, the... 

In contrast to tire preparation of LB films, tliat of SAMs is fairly simple and no special equipment is required. The inorganic substrate is simply immersed into a dilute solution of tire surface active material in an organic solvent (typically in tire mM range) and removed after an extended period ( 24 h). Subsequently, tire sample is rinsed extensively witli tire solvent to remove any excess material (wet chemical preparation). 

Polonium-210 is very dangerous to handle in even milligram or microgram amounts, and special equipment and strict control is necessary. Damage arises from the complete absorption of the energy of the alpha particle into tissue. 

Because of the high rate of emission of alpha particles and the element being specifically absorbed on bone the surface and collected in the liver, plutonium, as well as all of the other transuranium elements except neptunium, are radiological poisons and must be handled with very special equipment and precautions. Plutonium is a very dangerous radiological hazard. Precautions must also be taken to prevent the unintentional formulation of a critical mass. Plutonium in liquid solution is more likely to become critical than solid plutonium. The shape of the mass must also be considered where criticality is concerned. 

The reactivity of the halogens decreases m the order F2 > CI2 > Br2 > I2 Fluo rme is an extremely aggressive oxidizing agent and its reaction with alkanes is strongly exothermic and difficult to control Direct fluonnation of alkanes requires special equip ment and techniques is not a reaction of general applicability and will not be discussed further... 

At one time thiols were named mercaptans Thus CH3CH2SH was called ethyl mercaptan according to this system This nomenclature was abandoned beginning with the 1965 revision of the lUPAC rules but is still sometimes encountered When one encounters a thiol for the first time especially a low molecular weight thiol its most obvious property is its foul odor Ethanethiol is added to natural gas so that leaks can be detected without special equipment—your nose is so sensitive that it can detect less than one part of ethanethiol m 10 000 000 000 parts of arr The odor of thiols weakens... 

With samples that are difficult to dissolve, the first approach is usually to try digesting the sample with an acid or base. Table 7.2 lists the most commonly used acids and bases and summarizes their use. Digestion is commonly carried out in an open container, such as a beaker, using a hot plate as a source of heat. The chief advantage of this approach is its low cost as it requires no special equipment. Volatile reaction products, however, are lost, leading to a determinate error if analyte is included among the volatile substances. 

Constant-temperature decomposition or combustion, followed by trapping and weighing the volatilized gases, requires more specialized equipment. Decomposition of the sample is conducted in a closed container, and the volatilized gases are carried by a purge-gas stream through one or more selective absorbent traps. 

Volatilization gravimetric methods are time- and labor-intensive. Equipment needs are few except when combustion gases must be trapped or for a thermogravi-metric analysis, which requires specialized equipment. 

Every chemical reaction occurs at a finite rate and, therefore, can potentially serve as the basis for a chemical kinetic method of analysis. To be effective, however, the chemical reaction must meet three conditions. First, the rate of the chemical reaction must be fast enough that the analysis can be conducted in a reasonable time, but slow enough that the reaction does not approach its equilibrium position while the reagents are mixing. As a practical limit, reactions reaching equilibrium within 1 s are not easily studied without the aid of specialized equipment allowing for the rapid mixing of reactants. 

Fine grinding and air classification make possible the production of some cake flour from hard wheat and some bread flour or high-protein fractions from soft wheat. AppHcation of the process theoretically frees the miller from dependence on different wheats, either hard or soft, that change each crop year. The problem is how to market the larger volume of low protein or starch fractions at prices adequate to justify the installation and operation of the special equipment (46). 

After development of a new process scheme at laboratory scale, constmction and operation of pilot-plant faciUties to confirm scale-up information often require two or three years. An additional two to three years is commonly required for final design, fabrication of special equipment, and constmction of the plant. Thus, projections of raw material costs and availabiUty five to ten years into the future become important in adopting any new process significantly different from the current technology. 

If either dry powders or inverse emulsions are not properly mixed with water, large lumps of polymer form that do not dissolve. This not only wastes material, but can also cause downstream problems. This is especially tme for paper where visible defects may be formed. Specialized equipment for dissolving both dry polymers and inverse emulsions on a continuous basis is available (22,23). Some care must be taken with regard to water quaUty when dissolving polyacrylamides. Anionic polymers can degrade rapidly in the presence of ferrous ion sometimes present in well water (24). Some cationic polymers can lose charge by hydrolysis at high pH (25). 

Arsenic and Boron. Arsenic and boron form volatile fluorides which are difficult to separate from high purity HF. Special equipment and techniques must be used to remove the arsenic. 

The resin, catalyst, and microhalloons are mixed to form a mortar which is then cast into the desirable shape and cured. Very specialized electrical and mechanical properties may be obtained by this method but at higher cost. This method of producing cellular polymers is quite appHcable to small quantity, specialized appHcations because it requires very tittle special equipment. 

Mousses pose Httle manufacturing problem, but because they are aerosolized they must be filled with special equipment. The pressure fill technique requites the container to be filled with mousse concentrate, then a valve is crimped on and a vacuum of approximately 2.4 kPa (18 mm Hg) is pulled. The propellants are added through the valve. Another technique, the under-the-cup method, fills the container under pressure with propellant and crimps the valve, all in one step. 

X 10 m (l.9x lO " /t ) of heHum in each cubic meter (35 ft ) of air entering the air separation process, the small quantities of cmde coUected in even a large air separation unit may be easily appreciated. It is sometimes desirable, therefore, to combine cmdes coUected from several air plants and to process them at a centralized location in specialized equipment. 

The cyanidation reaction proceeds under mild conditions and no special equipment is required. Stereochemistry of the product usually is the same as ia the carboaylatioa reactioa. However, ia hiadered systems stereoisomeric products may be formed (59,326). Annulation by cycHc hydroboratioa—cyanidatioa fiads appHcatioa ia the syathesis of aatural products (327,328). 

Specialized equipment for industrial measurements and automatic control have been developed (18) (see Process control). In general, the pH of an industrial process need not be controlled with great accuracy. Consequendy, frequent standardization of the cell assembly may be uimecessary. On the other hand, the ambient conditions, eg, temperature and humidity, under which the industrial control measurements are made, may be such that the pH meter must be much more robust than those intended for laboratory use. To avoid costiy downtime for repairs, pH instmments may be constmcted of modular units, permitting rapid removal and replacement of a defective subssembly. 

Large volumes of LPG are stored to meet peak demand during cold seasons. LPGs are both volatile and flammable and must be stored and handled in special equipment. Standards for storing and handling LPG are pubHshed by the National Fire Protection Association (5) and API (6). 

Planning is defined as the process of analysing each job so as to determine the nature of the job and the results desired specify the logical sequence of the job and apply humanpower and estimates for each sequential step Hst predeterminable material, tools, and special equipment and estimate the total cost to meet the required results. 

The other space-saving approach is to use the Kobe (Kobe Steel) type of channel enclosure, which does not have all the external head bolts of typical TEMA Type B or Type C head enclosures. These exchangers require special tools to remove the tube bundles and trained maintenance personnel to do the work. These exchangers should never be located in stmctures because of the need to be able to access the channel from grade as it is difficult to remove the channel cover plate by using special equipment. 

The Zinin reduction is also usehil for the reduction of aromatic nitro compounds to amines in the laboratory. It requires no special equipment, as is the case with catalytic hydrogenations, and is milder than reductions with iron and acid. Usually ammonium or alkah sulfides, hydrosulftdes or polysulftdes are used as the reactant with methanol or ethanol as the solvent. 

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