Bulk stability

Catalysis by Metals. Metals are among the most important and widely used industrial catalysts (69,70). They offer activities for a wide variety of reactions (Table 1). Atoms at the surfaces of bulk metals have reactivities and catalytic properties different from those of metals in metal complexes because they have different ligand surroundings. The surrounding bulk stabilizes surface metal atoms in a coordinatively unsaturated state that allows bonding of reactants. Thus metal surfaces offer an advantage over metal complexes, in which there is only restricted stabilization of coordinative... 

Many reports are available where the cationic surfactant CTAB has been used to prepare gold nanoparticles [127-129]. Giustini et al. [130] have characterized the quaternary w/o micro emulsion of CTAB/n-pentanol/ n-hexane/water. Some salient features of CTAB/co-surfactant/alkane/water system are (1) formation of nearly spherical droplets in the L2 region (a liquid isotropic phase formed by disconnected aqueous domains dispersed in a continuous organic bulk) stabilized by a surfactant/co-surfactant interfacial film. (2) With an increase in water content, L2 is followed up to the water solubilization failure, without any transition to bicontinuous structure, and (3) at low Wo, the droplet radius is smaller than R° (spontaneous radius of curvature of the interfacial film) but when the droplet radius tends to become larger than R° (i.e., increasing Wo), the microemulsion phase separates into a Winsor II system. 

WASTOXHAS is the acronym for WASte ecoTOXic Hazard Assessment Scheme. This method was developed to ensure that unacceptable adverse effects would not arise from landfilled or re-used waste disposal. It is dedicated to assess the long-term leaching hazardous impact of any solid waste containing potentially hazardous substances (e.g., bulk, stabilized, solidified, or vitrified wastes as well as contaminated soils or sediments intended for soil disposal). 

Rigid surface The potential created by one layer at a distance r, which stabilizes the excited state of a molecule, may be calculated as in Section Ill.C.l.b ADe = (n/2S0)Be/r, where Be is proportional to the difference in the molecular polarizability between the ground state and the excited state and may be calculated from the bulk stabilization De = 2500 cm-1. With the values used above, we obtain ADe 350 cm- , still in the same range of values with the observed shift (206cm 1). 

Free (lo Hz) (53) > Surf ace Stabilized (10 Hz) (5) > Bulk Stabilized (10 Hz)(45). Thus the TF values of Gardner and Casey (53) for surface stabilized CH which are comparable to bulk trapped CH must be suspect. Similarly the low values reported by Barnes et al (50) could depend on the choice of parameters used in the Kivelson equation (52). 

Bulk drug products often exist in different crystalline or polymorphic forms. Because the polymorphs of a specific API can exhibit dis-tinguishably different bulk stability properties as well as bioavailability characteristics as a result of the differences in surface area between the different crystalline forms, specification of the polymorphic form is recommended for FDA submission. Products such as ranitidine (10), lorazepam (11), and natamy-cin (12) serve as examples of APIs that exist in several different polymorphic forms. The solvent system and the crystallization conditions generally determine the specific crystallization form that is isolated. Polymorph selection for regulatory submission is usually based on the ability to reliably produce and process the material in the same crystalline form. In many cases this is the thermodynamically most stable polymorphic form. In the event that a less stable polymorphic form is desired, because of stability or bioavailability issues, seeding techniques can be used to control the crystallization selectivity of a specific polymorph. 

Table 2 Bulk stability of some organometallic species to oxygen...

Figure 1.41 shows a variety of flexible moulded Dabco surfactants which can be utilised in TDI and/or MDI formulations. Using Figure 1.41, proper selection of the surfactant can be made, enabling polyurethane formulators to expand their processing latitude, cell openness, and bulk stability of the foam article in their critical formulations. 

Smith A, Davis SS. 1973. The role of molecular diffusion in the bulk stability of O/W hydrocarbon emulsions. J Pharm Sci 25 117. 

Use Level 0.3 pphp to 0.75 pphp polyol when used in combination with a strong bulk stabilizer... 

Uses Surfactant for MDI-based molded polyurethane foam systems, providing efficient cell opening and bulk stabilization in all-water-blown foams nonhydrolyzable Properties Cl. to straw low-vise, liq. insol. in water sp.gr. 0.9658 (21 C) vise. 28.9 cps vapor pressure 7.6 mm Hg (21 C) f p. -65 C b.p. > 149 C hyd. no. 226 flash pt. (CC) 113 C... 

Uses Strong cell opening surfactant for water-blown MDI-based flexible molded PU foams provides enhanced bulk stability Properties Liq. insol. in water sp.gr. 1.019 vise. 302 cps vapor pressure 9.0 mm Hg (21 C) fp. -35 C hyd. no. 85 flash pf > 113 C Dabco DC5454 [Air Prods./Perf. Chems.]... 

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