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

1 IO SEA WATER DISTILLATION. strong, or reducing it if it is abnormally weak to start with. 94. Sometimes, again, the water to be operated on is fresh water, but not sufficiently pure for special require- ments. In this case the feed quantity can be shortened very considerably. 95. It has already been shown that water which con- tains polluted or greasy matter, indeed any impurity that will vaporise and come over with the steam, cannot be distilled so as to generate pure steam for condensation into pure water. Put shortly, distillation only separates from salt-water substances that are not vaporisable, such as the saline matter it contains. On the other hand, although polluted matter may be contained in the water to be distilled, so as to make the distilled water unpleasant for drinking purposes, the operation of boiling may destroy all matter dangerous to health. 2. Feed Regulation. 96. There are many ways of regulating the quantity of feed-water to the evaporator. The feed is usually taken from the upper part of the distiller casing—that is, from the circulation water just before it is discharged, and is to some extent hot, as already explained. There- fore, a simple manner of regulating a fixed amount of feed-water, sufficient when the evaporator is generating steam to its maximum power, is to have a feed-box with a float in it, arranged so that as it rises with the water -entering the box, the float rises and cuts off the inflow . of water. The water in the box then flows away through a small hole of suitable size at the bottom of the box, so that the constant level kept over this hole regulates