Column types Hempel

Fractional distillation. Fig. II, 60, 2 illustrates a set-up for fractional distillation wdth a Hempel-type column and cold finger, the latter to give manual control of the reflux ratio. Any other fractionating colunm, e.g., an all-glass Dufton or a Widmer column may, of course, be used. 

Crotyl bromide [29576-14-5] M 135.0, b 103-105 /740mm, n s 1.4792. Dried with MgS04, CaC03 mixture. Fractionally distd through an all-glass Todd column. [Todd column. A column (which may be a Dufton type, fitted with a Monel metal rod and spiral, or a Hempel type, fitted with glass helices) which is surrounded by an open heating jacket so that the temperature can be adjusted to be close to the distillation temperature (Todd Ind Eng Chem (Anal Ed) 17 175 1945)]. 

Any reasonably effective type of fractionating column can be used. Columns longer than 30 cm. and of the most efficient types were found to give no better results than a simple Hempel column filled with glass beads or broken glass. 

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