Chemistry Reference
In-Depth Information
Fractional distillation is used to separate miscible
liquids such as those in crude oil (see Figure 2.23a
and p. 90), and the technique can also separate
individual gases, such as nitrogen, from the mixture
we call air (see Figure 2.23b and p. 174).
a
Fractional distillation unit for crude oil.
Figure 2.24
Magnetic separation of iron-containing materials.
It is essential that when separating solid/solid mixtures
you pay particular attention to the individual physical
properties of the components. If, for example, you wish
to separate two solids, one of which sublimes, then this
property should dictate the method you employ.
In the case of an iodine/salt mixture the iodine
sublimes but salt does not. Iodine can be separated
by heating the mixture in a fume cupboard as shown
in Figure 2.25. The iodine sublimes and re-forms on
the cool inverted funnel.
b
Gases from the air are extracted in this fractional distillation plant.
Figure 2.23
Separating solid/solid mixtures
You saw earlier in this chapter (p. 16) that it was
possible to separate iron from sulfur using a magnet.
In that case we were using one of the physical
properties of iron, that is, the fact that it is magnetic.
In a similar way, it is possible to separate scrap iron
from other metals by using a large electromagnet like
the one shown in Figure 2.24.
Figure 2.25
Apparatus used to separate an iodine/salt mixture.
The iodine sublimes on heating.
