A Practical Manual On Sea Water Distillation
With A Description Of The Necessary Machinery For The Process

CHAPTER IV* STEAM. Generally. 1. In sea water distillation (especially in the type of it usually called “ multiple ” or “ compound ” distillation), a knowledge of the properties of steam (such as its heating power under various pressures) is essential. 2. Steam is a gas or vapour obtained from water by the action of heat, and the amount of heat required to convert a given weight of water into steam is absorbed by the steam or vapour in the operation of being thus con- verted from water into steam. On being re-converted or transformed back again into water, it is capable of im- parting, to another substance, the exact amount of heat it absorbed when it was converted into steam. This is so in theory, but in practice it is impossible to avoid some waste of heat. Waste, however, must not be confused with a loss, for nothing is really lost; it is only that the heat absorbed by the steam, instead of being returned in its entirety to the cooling medium presented to it for that purpose either leaks away in other directions, or is not accounted for in some way or other ; this is easily understood, but cannot be prevented. A perfect realisa- tion of what theoretically takes place in nature is never wholly possible.