Drying of Organic Solvents

Work in a Laboratory and Technique of an Experiment DRYING OF ORGANIC SOLVENTS 

Diethyl Ether. Drying with a zeolite. Put 500 ml of diethyl ether and 50-100 g of freshly roasted zeolite of Grade NaA or CaX into a one-litre flask provided with a stopper and a calcium chloride tube filled with roasted calcium chloride. The water capacity of the zeolite and its roasting temperature are indicated on the label. It is recommended to hold the ether over the zeolite about two days. 

Distillation of Ether over Metallic Sodium. Do not distil the liquid to the end ) Assemble the apparatus (Fig. 20). Put 5-10 g of metallic sodium dried with filter paper, cleaned of its oxide film, and cut up into pieces (about 5x5 mm in size) and 300 ml of ether into the flask. Connect a cooler with a receiver to the flask with the ether. Heat the distillation flask on a water hath placed on an electric stove with an enclosed coil. The distilled ether in contact with freshly cut lustrous metallic sodium should produce a faint cloud of hydrogen bubbles. 

Store ether over metallic sodium in a bottle with a cork stopper provided with a calcium chloride tube containing calcium chloride. 

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Solve binary heterogeneous azeotrope problems, including the drying of organic solvents, using McCabe-Thiele diagrams... 

Selenium trioxide, SeO, is white, crystalline, and hygroscopic. It can be prepared by the action of sulfur trioxide on potassium selenate or of phosphorous pentoxide on selenic acid. It forms selenic acid when dissolved in water. The pure trioxide is soluble in a number of organic solvents. A solution in Hquid sulfur dioxide is a selenonating agent. It is stable in very dry atmospheres at room temperature and on heating it decomposes first to selenium pentoxide [12293-89-9] and then to selenium dioxide. 

The substitution of water-borne versions of these primers is increasing as environmental restrictions on the use of organic solvents become stricter. These are generally aqueous emulsions of epoxy novolac or phenolic based resins stabilized by surfactants [34]. Non-ionic surfactants are preferred, as they are non-hygroscopic in the dried primer films. Hygroscopic ionic surfactants could result in excessive water absorption by the primer film in service. 

Homogenizing and milling for brown rice and rice straw samples must be carried out while freezing with dry-ice. During evaporation of organic solvents, the temperature of the water-bath should be kept at 40 °C or lower. 

Dry the organic solvent layer through 80 g of anhydrous sodium sulfate on a glass funnel and collect the dried solution in a 300-mL round-bottom flask. Evaporate the solvent under reduced pressure. Dissolve the residue in 150 mL of n-hexane and transfer the solution into a 300-mL separatory funnel. Extract twice with 100 mL of acetonitrile. Combine the acetonitrile extracts in a 500-mL round-bottom flask and evaporate the solvent under reduced pressure. Dissolve the residue in a small amount of column-eluting solvent (dichloromethane-n-hexane, 1 1, v/v) and transfer the solution to the top of the silica gel column. After eluting the column with 60 mL of solvent of the same composition (discard), elute orbencarb and I with 150mL of dichloromethane. Collect the eluate in a 300-mL flask and evaporate the solvent under reduced pressure. Dissolve the residue in an appropriate volume of acetone for analysis. 

Aseptic Crystallization and Dry Powder Filling. Aseptic crystallization is primarily used for manufacture of sterile aqueous suspensions. However, if the physical form of the drug is critical to quality of the final product, better control over physical form can be attained by aseptic crystallization because a large variety of organic solvents can be used to control the crystallization process. In aseptic crystallization, the drug is... 

P.R.68 is used in paints for applications where it performs well, especially in terms of lightfastness. Incorporated in an air drying alkyd resin vehicle, full shades equal step 5 on the Blue Scale for lightfastness. 1 5 Ti02 reductions, however, only score as high as step 2. P.R.68 exhibits excellent resistance to a large number of organic solvents, while it is quite sensitive to alkali and acid, as well as to water. 

P.R.252 provides yellowish to medium red shades and is recommended particularly for use in architectural paints. The pigment shows very poor fastness to a number of organic solvents which are commonly used in paints, a deficiency which largely precludes it from being used in oven drying systems. Regarding lightfastness and weatherfastness, the only available type with coarse particle sizes performs somewhat better than the much more yellowish P.O.5. 

Lipids can be extracted from biological samples using a variety of organic solvents. A chloroform-methanol solvent is suitable for all lipids but it is possible to extract different classes of lipid selectively on the basis of their solubility in different organic solvents. This may be achieved by the addition of a solvent that will effect either the precipitation or the extraction of the lipids of interest. An example of the former is the precipitation of high concentrations of phospholipids with cold, dry acetone, and of the latter, the extraction of fatty acids into ether or heptane at an acid pH. However, like all solvent extraction procedures these are not entirely specific. 

Quaternary ammonium salts aid the transfer of the hypophosphite anion in the palladium-catalysed reduction of, for example, alkynes to alkenes, nitroarenes to aminoarenes, and in the hydrogenolysis of tetrazolyl aryl ethers to phenols [12-14], It has been demonstrated that the hydrogenolysis is ineffective when preformed tetra-n-butylammonium hypophosphite is employed in a dry homogenous organic solvent [13, 14], For optimum hydrogen transfer, the concentration of hypophosphite relative to the substrate must be controlled at a low level and this is most effectively accomplished with a two-phase system. 

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