The Britannia Heat Exchanger raises the temperature of the liquid soap so that the excess water will boil away when the soap enters the Soap Drying Chamber. The unit consists of a large number of small tubes through which the liquid soap is pumped. These tubes are heated by steam and by varying the steam pressure (and hence the temperature), or the rate of flow of the soap through the tubes, it is possible to raise the temperature of the liquid soap in a controlled manner.