Physical and Chemical Properties Required

Physicochemical Properties of Excipients in Pressurized Metered Dose Inhalers 

The physicochemical properties of excipients used in pMDIs are different from most dosage forms and are a derivative of the propellant system that constitutes the bulk of the formulation. The transition from CFC-based formulations to HFA-based systems has been lengthened by the historically empirical formulation approach and the dissimilarity of the physicochemical properties of the replacement HFA propellants. Both HFA 134a and HFA 227 show an increased polarity, revealed in increased dipole moments and dielectric constant. The most significant practical change has therefore been a general change in the solvency properties. 

Class of nasal product Examples of marketed products 

Nasal decongestants arylalkylamines Afrin Children s Pump Mist Rhinall Vicks Sinex Ultra Fine Mist Pretz-D 

Nasal decongestants imidazolines 12 hr Nasal Afrin 12 hr Duration Vicks Sinex Privine Otrivin Tyzine 

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Most metals that we use in everyday life are actually alloys. An alloy is a solid solution of one metal (or non-metal) in another metal. For example, steel is an alloy of iron. Steel has many uses, from construction to the automobile industry. If the iron were not alloyed with other elements, it would not have the physical and chemical properties required, such as hardness and corrosion resistance, v J... 

Na+(am) + e (am) + NH3(1) = NaNH2(s) + -H2 K = 3 x 109 The physical and chemical properties required of the solvent to make possible the formation of such metal solutions are not fully understood. The dielectric constant of the solvent is important in the same way as in the solution of an ionic solid, namely, to diminish the forces of attraction between the oppositely charged particles—in this case, M + ions and electrons. Furthermore, if the solvent molecules immediately surrounding these particles interact strongly with them, the energy of the system is further lowered. While the detailed nature of the interaction of the electrons with the surrounding solvent molecules is still debatable, it is fairly clear that the metal ions are solvated in the same way as they would be in a solution of a metal salt in the same solvent (see discussion below). 

Traditionally, chiral separations have been considered among the most difficult of all separations. Conventional separation techniques, such as distillation, Hquid—Hquid extraction, or even some forms of chromatography, are usually based on differences in analyte solubiUties or vapor pressures. However, in an achiral environment, enantiomers or optical isomers have identical physical and chemical properties. The general approach, then, is to create a "chiral environment" to achieve the desired chiral separation and requires chiral analyte—chiral selector interactions with more specificity than is obtainable with conventional techniques. 

As a result of the development of electronic applications for NF, higher purities of NF have been required, and considerable work has been done to improve the existing manufacturing and purification processes (29). N2F2 is removed by pyrolysis over heated metal (30) or metal fluoride (31). This purification step is carried out at temperatures between 200—300°C which is below the temperature at which NF is converted to N2F4. Moisture, N2O, and CO2 are removed by adsorption on 2eohtes (29,32). The removal of CF from NF, a particularly difficult separation owing to the similar physical and chemical properties of these two compounds, has been described (33,34). 

Any manufacturing process requiring refractories depends on proper selection and installation. When selecting refractories, environmental conditions are evaluated first, then the functions to be served, and finally the expected length of service. AH factors pertaining to the operation, service design, and constmction of equipment must be related to the physical and chemical properties of the various classes of refractories (35). 

With minor exceptions the requirements for the physical and chemical properties of asphalt were essentially the same for the three national specifications and included penetration and ductiUty at 25 °C flash point % loss at 163 °C penetration of residue as a % of original solubiUty in carbon disulfide solubiUty in carbon tetrachloride specific gravity at 25°C and softening point. 

Random copolymers of vinyl chloride and other monomers are important commercially. Most of these materials are produced by suspension or emulsion polymerization using free-radical initiators. Important producers for vinyl chloride—vinyUdene chloride copolymers include Borden, Inc. and Dow. These copolymers are used in specialized coatings appHcations because of their enhanced solubiUty and as extender resins in plastisols where rapid fusion is required (72). Another important class of materials are the vinyl chloride—vinyl acetate copolymers. Principal producers include Borden Chemicals Plastics, B. F. Goodrich Chemical, and Union Carbide. The copolymerization of vinyl chloride with vinyl acetate yields a material with improved processabihty compared with vinyl chloride homopolymer. However, the physical and chemical properties of the copolymers are different from those of the homopolymer PVC. Generally, as the vinyl acetate content increases, the resin solubiUty in ketone and ester solvents and its susceptibiUty to chemical attack increase, the resin viscosity and heat distortion temperature decrease, and the tensile strength and flexibiUty increase slightly. 

Engineering factors include (a) contaminant characteristics such as physical and chemical properties - concentration, particulate shape, size distribution, chemical reactivity, corrosivity, abrasiveness, and toxicity (b) gas stream characteristics such as volume flow rate, dust loading, temperature, pressure, humidity, composition, viscosity, density, reactivity, combustibility, corrosivity, and toxicity and (c) design and performance characteristics of the control system such as pressure drop, reliability, dependability, compliance with utility and maintenance requirements, and temperature limitations, as well as size, weight, and fractional efficiency curves for particulates and mass transfer or contaminant destruction capability for gases or vapors. 

Microcomputer version of EPA s Oil and Hazardous Materials Technical Assistance Database. Contains emergency response, physical and chemical properties, and hazards of 1400 compound. Requires 640K memory and lOMeg hard disk. 

Is there a "universal ionic liquid at the present state of development The answer is clearly no. Many of the ionic liquids commonly in use have very different physical and chemical properties (see Chapter 3) and it is absolutely impossible that one type of ionic liquid could be used for all synthetic applications described in Chapters 5-8. In view of the different possible roles of the ionic liquid in a given synthetic application (e.g., as catalyst, co-catalyst, or innocent solvent) this point is quite obvious. However, some properties, such as nonvolatility, are universal for all ionic liquids. So the answer becomes, if the property that you want is common to all ionic liquids, then any one will do. If not, you will require the ionic liquid that meets your needs. 

The requirements of the US Armed Forces are detailed in Mil Spec MIL-S-12210A, Strontium Oxalate , (11 Sept 1952) Strontium oxalate shall be of the following grades as specified Grade A — anhydrous strontium oxalate Grade B — hydrated strontium oxalate, and shall conform to the physical and chemical properties listed in Table 1... 

Elements dissolved in boron influence its crystal structure. Dissolved impurities also influenee the physical and chemical properties of boron, especially the electrical properties, because boron is a semiconductor. Preparation of solid solutions in jS-rh boron requires a careful choice of crucible material. To avoid contamination, boron nitride or a cold, coinage-metal crucible should be used or the levitation or floating-zone melting techniques applied. 

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