Fire hazards attending the distillation of inflammable solvents

FIRE HAZARDS ATTENDING THE DISTILLATION OF INFLAMMABLE SOLVENTS 

The inflammable solvent 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-iso-propyl ether, benzene, and toluene. Special precautions must be taken in handling these (and other equivalent) solvents if the danger of fire 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. 

The most satisfactory method for the removal of (diethyl) ether is either on a steam bath fed from an external steam supply or by means of an electrically-heated, constant-level water bath (Fig. II, 5, 1). If neither of these is available, a water bath containing hot water may be used. The hot water should be brought from another part of the laboratory under no circumstances should there be a free flame under the water-bath. It cannot be too strongly emphasised that no flame whatsoever may be present in the vicinity of the distillation apparatus a flame 10 feet away may ignite diethyl ether if a continuous bench top lies between the flame and the still and a gentle draught happens to be blowing in the direction of the flame. 

Carbon disulphide. It is best to use a water bath maintained at a temperature of 60°-80°. 

Solvents with boiling points below 90-95°. A steam bath or water bath should be employed. Alternatively, the apparatus of Fig. II, 13, 3, but with a filter flask as receiver, may be used the end of the rubber tubing attached to the tubulure is either placed in the sink or allowed to hang over the bench. If a distillation is ultimately to be conducted in the flask from which the solvent is removed, the apparatus depicted in Fig. II, 13, 4 is recommended the distilling flask may be replaced by a Claisen flask or a Claisen flask with fractionating side arm, particularly if the subsequent distillation is to be conducted under diminished pressure. 

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