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

32 SEA WATER DISTILLATION. Note.—Steam is a perfectly transparent colourless gas. What is seen issuing from boiling water like a white cloud, usually called (and often thought to be) steam, is really not steam at all but fine particles of water, caused by the steam coming in contact with colder surrounding air, and becoming condensed thereby. Properties of Steam. 3. The opposite Table gives the properties of satu- rated steam. By “ saturated ” is meant that condition or state of the steam when it is on the point of re-conver- sion into water by the slightest decrease in its temperature, or increase in its pressure, as each of these changes will cause the steam to be re-converted into water again. Note.—This Table has been given in rather extensive form, as it will be found necessary (especially when dealing with multiple distillation) to examine different pressures somewhat closely. TABLE E.—Properties of Saturated Steam. P. (net) = Pressure in pounds per square inch, excluding the atmosphere. Every 2 lbs. pressure per square inch, below atmosphere = about 1 inch head of mercury per barometer. S .H. = Sensible Heat—i.e., temperature by Fahrenheit thermometer scale. L .H. = Latent Heat—i.e., the units of heat required to convert 1 lb. of water into 1 lb. of steam. T .H. = Total Heat—i.e., the latent heat + the sensible heat (from 32° F.). S.V. = Specific Volume—i.e.,'the number of (say) cubic feet of steam converted from 1 cubic foot of water. W. = Weight—i.e., of 1 cubic foot of steam (lbs. avdp.). P. (gross) = Pressure, including the atmosphere.