Liquid stabilization

Typically, soHd stabilizers utilize natural saturated fatty acid ligands with chain lengths of Cg—C g. Ziac stearate [557-05-1/, ziac neodecanoate [27253-29-8] calcium stearate [1592-23-0] barium stearate [6865-35-6] and cadmium laurate [2605-44-9] are some examples. To complete the package, the soHd products also contain other soHd additives such as polyols, antioxidants, and lubricants. Liquid stabilizers can make use of metal soaps of oleic acid, tall oil acids, 2-ethyl-hexanoic acid, octylphenol, and nonylphenol. Barium bis(nonylphenate) [41157-58-8] ziac 2-ethyIhexanoate [136-53-8], cadmium 2-ethyIhexanoate [2420-98-6], and overbased barium tallate [68855-79-8] are normally used ia the Hquid formulations along with solubilizers such as plasticizers, phosphites, and/or epoxidized oils. The majority of the Hquid barium—cadmium formulations rely on barium nonylphenate as the source of that metal. There are even some mixed metal stabilizers suppHed as pastes. The U.S. FDA approved calcium—zinc stabilizers are good examples because they contain a mixture of calcium stearate and ziac stearate suspended ia epoxidized soya oil. Table 4 shows examples of typical mixed metal stabilizers. 

Cd(C24H2g02)2, are of this type. Liquid stabilizers such as cadmium octoate [2191 -10-8] Cd(CgH2g02)2, cadmium phenolate [18991 -05A] Cd(CgHgO)2, cadmium decanoate [2847-16-7] Cd(C2QH2Q02)2, cadmium benzoate [3026-22-0] and cadmium naphthenate are more versatile and... 

S03/air can be raised from sulfur burning and subsequent oxidation to S03 or S03 can be stripped from 65 % oleum with dry air or S03 can be obtained by evaporation of liquid-stabilized S03, subsequently mixed with dry process air. 

Safety in transport and storage. Liquid-stabilized S03, 65% oleum, 20% oleum, 98% sulfuric acid, and chlorosulfonic acid are hazardous chemicals in transport, handling, and storage. Sulfur in liquid or solid form is a far less hazardous starting material for the production of S03. 

In multi-component liquids, stabilization of the liquid is revealed by the formation of eutectics where the freezing temperature is suppressed. In such liquids, the atomic species (say A and B) are not distributed at random. There are more associated AB pairs (or other clusters) than expected for a random distribution. As a result in binary metal-metalloid alloys, such as Fe-B, the low melting-point eutectics occur at preferential compositions. The most common of these is at about 17 at. % B, or an atom ratio of one B for five Fe atoms (Gilman, 1978). This suggests that clusters of metal atoms surrounding metalloid atoms form (trigonal bipyramids). These probably share corners, edges, and faces. 

Zhang, FI. and FI. Cui, Synthesis and characterization of functionalized ionic liquid-stabilized metal (gold and platinum) nanoparticles and metal nanoparticle/carbon nanotube hybrids. Langmuir, 2009. 25(5) p. 2604-2612. 

Physical Form. Colorless liquid (stabilized with 100 ppm of butyl catechol because of its reactivity with oxygen)... 

The hydrolysis and decomposition of [BMIM]PFg ionic liquid in the presence of water and metal catalysts have also been reported (70-72). The decomposition of the ionic liquid occurs only in the presence of both water and the transition-metal precursor [e.g., (Ir(cod)Cl]2 or RhCh. The presence of SnCl2 was found to cause the decomposition of the PF ion by water alone (73). When hydrolysis occurs, FIF is formed as a decomposition product, and it can change the course of a catalytic reaction. In the absence of water, such metal precursors can be reduced in H2 at 75°C to form ionic liquid-stabilized nanoparticles (12,74). 

Even in the presence of considerable moisture, solid polymer never forms above 30°C (23). Below 30°C, liquid stability decreases with increasing moisture and decreasing temperature (23). The actual formation of solid polymer has been hypothesized to involve the formation in the liquid of high molecular weight polysulfuric acids, followed by precipitation. 

From Ionic Liquid Stability to Biodegradability 151 Table 6.2 Ammonium ionic liquids previously used as surfactants. 

Protein-based drugs have been formulated mainly as stable liquids or in cases where liquid stability is limiting as lyophilized dosage forms to be reconstituted with a suitable diluent prior to injection. This is because their delivery has been limited primarily to the parenteral routes of intravenous (IV), subcutaneous (SC), or intramuscular (IM) administration. There are a few drugs that have been developed for pulmonary delivery, such as rhDNase (Pulmozyme ) and an inhalable formulation of insulin (e.g., Exubra ). However, even such drugs have been formulated as either liquid or lyophilized or spray-dried powders. This chapter will focus only on excipients that are applicable to liquid and lyophilized protein formulations. 

Emulsification. Emulsions are dispersed inmiscible droplets within another liquid stabilized by the interphasic compounds (30-49). In dealing with proteins, the disperse liquid is a fat or oil and the stabilizing interphase is a protein product in butter, these phases are reversed. 

Antioxidants. Phenolic antioxidants, added at about 0.1—0.5 phr, are usually chosen from among butylated hydroxytoluene [128-37-0] (BHT), and -nonylphenol [104-40-5] for liquid stabilizer formulations and bisphenol A [80-05-7] (2,2-bis-(p-hydroxyphenyl)propane) for the solid systems. Low melting thioesters, dilauryl thiodipropionate [123-28A] (DLTDP) or distearyl thiodipropionate [693-36-7] (DSTDP) are commonly added along with the phenolics to enhance their antioxidant performance. Usually a 3 1 ratio of thiodipropionate to phenolic antioxidant provides the desired protection. Most mixed metal stabilizer products contain the antioxidant ingredient. 

MAA and EAA are stable liquids, and are shipped in nonretumable 208-L (55-gal) polyethylene-lined drums. For bulk shipments, insulated stainless steel tank containers and trucks provide secure protection. 2-Acetoacetoxyethyl methacrylate is a liquid stabilized with radical inhibitors such as BHT [128-37-0] and has a shelf life of approximately three months. Shipment is in 60- or 208-L polyethylene-lined drums. Acetoacetarylides are nicely crystalline, stable solids and are shipped in 208-L drums with polyethylene liners. 

Figure 3. Liquid stability in a tilted capillary tube...

A dispersion of finely divided magnetic particles in a liquid, stabilized by electrostatic and/or steric repulsion. Example Fe304 particles in water. 

Bulk liquids Brine liquid Stabilization/ landfill X X X ... 

Proprietary blend. Extremely effective liquid stabilizer for hydrogen peroxide bleach baths. It is a complete replacement for sodium silicate, eliminating the problems of silicate deposits on equipment and fabric. 

In any multiphase liquid, stability is a paramount concern. Thermodynamics drives clumping of dispersed components, and this is sometimes enhanced by flow. However, tricks for stabilizing suspensions are as old as the inks of Egypt. Electrostatic and steric stabilization are the most common. By matching the dielectric prc effie s, sdrrie pafticle-fluid combinations can be found that are inherently stable. A more detailed discussion of suspension stabilization is deferred to Chapter 7. 

Pressure filtration of the liquid is very difficult due to the complex interaction of the char and pyrolytic lignin, which appears to form a gel-like phase that rapidly blocks the filter. Modification of the liquid micro-structure by addition of solvents such as methanol or ethanol that solubilise the less soluble constituents will improve this problem and also contribute to improvements in liquid stability as described below. 

A microemulsion is a thermodynamically stable isotropic dispersion of two relatively immiscible liquids, consisting of microdomains of one or both liquids stabilized by a interfacial film of surface-active molecules. In practice, one often identifies the microemulsion by the formation of a clear isotropic mixture of the two immiscible liquids in the presence of appropriate emulsifiers. In a phase diagram, such region is referred as the microemulsion phase. It has been shown that microemulsion regions consist of different microstructures (1,2), e.g., water-in-oil (W/0), oil-in-water (0/W),... 

Properties Colorless liquid stabilized with either hydroquinone or diphenylamine inhibitors. The hy-droquinone stabilized material can be polymerized without redistillation. The DPA-stabilized material must be distilled before polymerization. D 0.9345 (20/20C), fp -100.2C, bp 73C, refr index 1.3941, bulk d 7.79 lb/gal, flash p 30F (-1.1C) (TOC), aut-oign temp 800F (426.6C). Soluble in most organic... 

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