Handling Organic Solvents

No solvents should be poured down the sink. Special precautions have been mentioned for dealing with flammable solvents. Although solvent waste may be mixed in dirty labelled solvent Winchesters, chlorinated solvents should be kept apart. Facilities may be also available for recovering some solvents and these should be stored separately. 

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Solvent Resistance. Poly(vinyl alcohol) is virtually unaffected by hydrocarbons, chlorinated hydrocarbons, carboxyhc acid esters, greases, and animal or vegetable oils. Resistance to organic solvents increases with increasing hydrolysis. This resistance has promoted the use of PVA in the manufacture of gloves for use when handling organic solvents (73). 

Equipment from mild steel usually is suitable for handling organic solvents, with the exception of those that are chlorinated, cold alkaline solutions (even when concentrated), sulfuric acid at concentrations greater than 88%, and nitric acid at concentrations greater than 65% at ambient temperatures [7]. 

Dissolve the isobaric tagging reagents in acetonitrile or ethanol at a concentration of 50 mM (or according to the manufacturer s recommendations). Use a fume hood to handle organic solvents. 

Centrifugal Partition Chromatography (CPC) has been shown to yield partition coefficients which compare quite favorably with those measured by traditional shake-flask (El Tayar, 1993). The procedure, which employs a coil planet type centrifuge in a horizontal flow-through system, has been described (El Tayar, 1991) The equipment can handle organic solvents with low viscosity (such as heptane) more readily than it handles octanol, but log octanol/water values in the range of -3.0 to +3.0 seem reliable. It has been used quite effectively in measuring the log Ps of amino adds (Tsai, 1991). 

Equipment from mild steel usually is suitable for handling organic solvents, with the exception of those that are chlorinated, cold alkaline solutions (even when concentrated), sulfuric acid at concentrations greater than 88%, and nitric acid at concentrations greater than 65% at ambient temperatures. Mild steels are rapidly corroded by mineral acids even when they are very dilute (pH less than 5). However, it is often more economical to use mild steel and include a considerable corrosion allowance on the thickness of the apparatus. Mild steel is not acceptable in situations in which metallic contamination of the product is not permissible. 

Organo-metallic compounds, on the other hand, behave very much like organic compounds, e.g. they can be redistilled and may be soluble in organic solvents. A note of caution should be made about handling organo-metallic compounds, e.g. arsines, because of their potential toxicities, particularly when they are volatile. Generally the suppliers of such compounds provide details about their safe manipulation. These should be read carefully and adhered to closely. If in any doubt always assume that the materials are lethal and treat them with utmost care. The same safety precautions about the handling of substances as stated in Chapter 4 should be followed here (see Chapter 1). 

Usually prepared and handled in organic solvent For alkyl groups of <4 carbon atoms, the compounds react vigorously with water and the resulting alkane ignites... 

A variety of synthetic polymers, including polycarbonate resins, substituted olefins, and polyelectrolyte complexes, are employed as ultrafiltration membranes. Many of these membranes can be handled dry, have superior organic solvent resistance, and are less sensitive to temperature and pH than cellulose acetate, which is widely used in RO systems. 

As with organic solvents, proteins are not soluble in most of the ionic liquids when they are used as pure solvent. As a result, the enzyme is either applied in immobilized form, coupled to a support, or as a suspension in its native form. For production processes, the majority of enzymes are used as immobilized catalysts in order to facilitate handling and to improve their operational stability [24—26]. As support, either inorganic materials such as porous glass or different organic polymers are used [27]. These heterogeneous catalyst particles are subject to internal and external... 

Transition-metal-based Lewis acids such as molybdenum and tungsten nitro-syl complexes have been found to be active catalysts [49]. The ruthenium-based catalyst 50 (Figure 3.6) is very effective for cycloadditions with aldehyde- and ketone-bearing dienophiles but is ineffective for a,)S-unsaturated esters [50]. It can be handled without special precautions since it is stable in air, does not require dry solvents and does not cause polymerization of the substrates. Nitromethane was the most convenient organic solvent the reaction can also be carried out in water. 

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