Rubber stoppers extractables

Mix 50 ml. of formalin, containing about 37 per cent, of formaldehyde, with 40 ml. of concentrated ammonia solution (sp. gr. 0- 88) in a 200 ml. round-bottomed flask. Insert a two-holed cork or rubber stopper carrying a capillary tube drawn out at the lower end (as for vacuum distillation) and reaching almost to the bottom of the flask, and also a short outlet tube connected through a filter flask to a water pump. Evaporate the contents of the flask as far as possible on a water bath under reduced pressure. Add a further 40 ml. of concentrated ammonia solution and repeat the evaporation. Attach a reflux condenser to the flask, add sufficient absolute ethyl alcohol (about 100 ml.) in small portions to dissolve most of the residue, heat under reflux for a few minutes and filter the hot alcoholic extract, preferably through a hot water fuimel (all flames in the vicinity must be extinguished). When cold, filter the hexamine, wash it with a little absolute alcohol, and dry in the air. The yield is 10 g. Treat the filtrate with an equal volume of dry ether and cool in ice. A fiulher 2 g. of hexamine is obtained. 

Centrifuging the screw-cap vial can easily break emulsions, which often form during extraction. The vial will survive up to 6000 g if rubber stoppers are inserted into the centrifuge cup to provide a flat base for the vials. The required phase (usually the top layer) can be easily removed with a pipet or, if it is to be discarded, it can be removed using a disposable pipet connected by tubing to a suction flask and vacuum line. 

Ice-acetone bath. The bottle is closed with a rubber stopper which is clamped or wired securely in place (Note 3) and is shaken mechanically at room temperature until the suspended malonic acid dissolves (Note 4). The bottle is chilled in an ice-salt bath and opened then the contents are poured into a separatory funnel containing 250 ml. of water, 70 g. of sodium hydroxide, and 250 g. of ice. The mixture is shaken (carefully at first), the layers are separated, and the aqueous portion is extracted with two 75-ml. portions of ether. The organic layers are combined, dried over anhydrous potassium carbonate, and filtered into a dropping funnel attached to the neck of a 125-ml. modified Claisen flask (Note 5). The flask is immersed in an oil bath at about 100°, and the excess isobutylene and ether are removed by flash distillation effected by allowing the solution to run in slowly from the dropping funnel. The dropping funnel is then removed, and the residue is distilled at reduced pressure. The fraction boiling at 112—115°/31 mm. is collected. The yield of colorless di-tert-butyl malonate is 60.0 62.0 g. (58-60%), 1.4158-1.4161,... 

TABLE 31 Elemental Composition of Rubber Stoppers Based on Element Concentration in Aqueous Extract... 

Prepare and extract a 5g sample of proplnt as indicated in Vol 2 of Encycl, p Cl 31, but use for extraction the titration flask, shown in Fig, after plugging its inlet tube by the rubber stopper. After removing the solvent from extract by a stream of dry air, dissolve the residue... 

Buchner funnel and fill the funnel from % t0 % full of the Dynamite sample. The amt will depend on the expl oil content, which is detd from the ether extraction conducted as follows Pour in 50 mi of ether, cover the funnel with a watch glass, let stand to impregnate the sample and then apply suction. Repeat with 3 addnl 50-ml portions of ether and transfer the extract to a low beaker. Evaporate the ether at 50—60°C while passing over it a stream of dry air, taking care not to introduce any moisture. Continue evaporation until disappearance of ether odor and then for 15 mins longer. Filter off the resins, sulfur and other insol substances from the explosive oils, using a very small, fast filter paper (such as No 41 Whatman) into a rubber-stoppered bottle contg the expl oil previously obtd from detn of ether extract. 

D. 3-Benzyl-3-methylpentanoic acid. A solution of 112 g. of potassium hydroxide in 400 ml. of ethylene glycol is added to 93.6 g. (0.5 mole) of 3-benzyl-3-methylpentanenitrile in a 1-1. round-bottomed copper or stainless-steel flask. A condenser with a rubber stopper is attached, and the solution is heated under brisk reflux for 6 hours (Note 12). The reaction mixture is cooled, diluted with 400 ml. of water, and extracted with three portions of ether (250 ml., 100 ml., 100 ml.). The ether... 

M. Ribick, M. Jemal, et al., Determination of ehtylenediametetra-acetic acid in aqueous rinses of detergent-washed rubber stoppers of pharmaceutical vials using solid phase extraction and capillary gas chromatography, J. Pharm. Biomed. Anal., 5 687-694 (1987). 

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