Inflammable solvents

If an organic solvent is used, boiling in an open vessel is obviously not permissible, as the operation would be wasteful in all cases, and dangerous with an inflammable solvent. 

FIRE HAZARDS ATTENDING THE DISTILLATION OF INFLAMMABLE SOLVENTS... 

The inflammable solvents most frequently used for reaction media, extraction or recrystallisation are diethyl ether, petroleum ether (b.p. 40-60° and higher ranges), carbon disulphide, acetone, methyl and ethyl alcohols, di-Mo-propyl ether, benzene, and toluene. Special precautions must be taken in handling these (and other equivalent) solvents if the danger of Are is to be more or less completely eliminated. It is advisable to have, if possible, a special bench in the laboratory devoted entirely to the recovery or distillation of these solvents no flames are permitted on this bench. 

If crystallisation commences as soon as the solvent cools or if large quantities of hot solution are to be filtered, the funnel (and fluted filter paper) should be warmed externally during the filtration (hot water funnel). Three types of hot water funnel are illustrated in Fig. 11,1, 6 no flames should be present whilst inflammable solvents are being filtered through the funnel of Fig. 11, 1, 6, a. Alternatively, the funnel may be surrounded by an electric heating mantle (see Section 11,57) the heat input may be controlled by a variable transformer. When dealing with considerable volumes of aqueous or other solutions which do not deposit crystals rapidly on cooling, a Buchner funnel may be used for filtration (see detailed account in Section 11,1 and Fig. 11 1, 7, c). The filter paper... 

Attention is directed to the fact that ether is highly inflammable and also extremely volatile (b.p. 35°), and great care should be taken that there is no naked flame in the vicinity of the liquid (see Section 11,14). Under no circumstances should ether be distilled over a bare flame, but always from a steam bath or an electrically-heated water bath (Fig.//, 5,1), and with a highly efficient double surface condenser. In the author s laboratory a special lead-covered bench is set aside for distillations with ether and other inflammable solvents. The author s ether still consists of an electrically-heated water bath (Fig. 11, 5, 1), fitted with the usual concentric copper rings two 10-inch double surface condensers (Davies type) are suitably supported on stands with heavy iron bases, and a bent adaptor is fitted to the second condenser furthermost from the water bath. The flask containing the ethereal solution is supported on the water bath, a short fractionating column or a simple bent still head is fitted into the neck of the flask, and the stUl head is connected to the condensers by a cork the recovered ether is collected in a vessel of appropriate size. 

The student should read Section 11,14 on the precautions attending the use of inflammable solvents before commencing the above preparation. 

The Grignard method was the first route used commercially in the production of silicone intermediates. Its great advantage is its extreme flexibility since a wide range of organic groups may be attached to the silicon in this method. Because of the need to use ether or other inflammable solvents considerable production hazards arise. On economic grounds the main drawbacks of the process are the multiplicity of steps and the dependence on silicon tetrachloride, which contains only 16% Si and is thus a rather inefficient source of this element. 

In the present instance spirit or methylated spirit (purified) will be found an efficient solvent for potassium ethyl sulphate. The following is the mode of piocedure when a volatile or inflammable solvent is used. the substance is placed in a lound flask attached to an upright condenser and heated on the water-bath. The form of apparatus is that already described (see Fig. 

Process safety, e.g., by using non-toxic, non-inflammable solvents and reagents ... 

The dissolved substances (especially if the solution is very concentrated) often crystallises in the funnel on account of local cooling and in this way filtration is hindered. This trouble can be partially met by using a funnel (Fig. 3) with the delivery tube cut short (0 5-l-0 cm.). But it is much more satisfactory to use a so-called hot water funnel (Fig. 4) in which the filtering surface of the funnel is heated with boiling water in a metal jacket. When inflammable solvents are used, the flame must be extinguished before filtration. 

Naked flames must never be allowed on the bench when work with ether or any inflammable solvent is in progress. 

Liquid-liquid partitioning constitutes tlie most common form of solvent extraction. It is a relatively simple, rapid, and flexible procedure that is readily applicable to all types of matrices and a wide range of analytes ranging from fairly polar to nonpolar compounds (54). Despite the fact that they are simple and rapid, liquid-liquid extractions may result in highly selective isolation (55, 56). However, they also necessitate use of toxic and inflammable solvents, favor formation of emulsions, may cause sample losses by occlusions or adsorption onto glass surfaces, and are often laborious and costly. 

If the substance crystallises rapidly from the hot solution, a hot filter should be used. Figs. 2 and 3 show steam jacketed and hot-water jacketed filters. With a volatile and easily inflammable solvent the flame should be removed from the jacket immediately before filtering, danger of fire being... 

The student will also frequently handle highly inflammable solvents, and must therefore remember that many painful and even fatal accidents have resulted from workmg with these near a flame or electric switch. 

The inverted filtration device is convenient for simple recrystallizations as well as repeated extractions. It is of particular advantage for the manipulation of volatile, inflammable solvents and of lachrymatory solutions. 

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