30 Appendixes EXPERIMENTAL TECHNIQUES 1. PURIFICATION BY DISTILLATION INTRODUCTION
If a sample of an organic liquid contains impurities and these cannot easily be removed by chemical means then purification is usually done by distillation. You will use this technique to purify your reaction products quite frequently. The following notes will give you some idea of the more common variants of the technique and their respective uses. Read these carefully before carrying out any distillation.
Simple distillation:
Used when the pure liquid and the impurities have widely different b.p.; for example aniline (b.p. 184o C) is easily separated from ether (b.p. 35°C) by simple distillation. Typical apparatus for this is shown. In general the b.p. difference must be at least 50 °C.
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Simple distillation distillation Apparatus
DISCUSSION
In allall experiments, but most particularly in distillation, it is important to use apparatus of a size. Commensurate with the quantities of chemicals involved. Choose a distillation flask, which will be approximately half filled by the quantity of liquid you have to distil. Record the quantity of liquid added.
Ensure that the thermometer bulb is opposite or just below the level of the side arm otherwise an accurate reading of distillation temperature will not be obtained.
In all simple distillations you must add to the liquid some material to ensure even boiling; most of these materials operate byWISiniErsi ace on which bubble nuclei can be formed so that large