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

230 SEA WATER DISTILLATION. (Appendix to page 172.) Péclet, in his treatise on Heat (3rd ed., 1860), dates the introduction of multiple distillation in 1829. After saying that the heat obtained by a primary distillation can be used for producing successive distillations—i.e., as the steam condenses it emits exactly the same amount of heat it absorbed for its formation—and that, conse- quently, if there was no loss of heat, multiple distillation might be carried on indefinitely. He then says the prin- ciples of multiple distillation were (as far as he knows) first applied in practice by M. Pecqueur in a patent granted to him in 1829, and further patents were taken out in 1834 and 1849. He also points out that, whilst multiple distillation is applicable to land apparatus, double dis- tillation is most suitable for use on ships. (Appendix to page 197.) The table on the next page is another List of Boilers (Cornish and Lancashire) which will be found useful. With regard to the size of the boiler, it is important that the diameter and length should be in due proportion to each other. If the length is too little, the heat (from the products of combustion), after passing through the boiler flues, would reach the chimney too soon, and waste of heat would consequently result ; whilst, if the length is too great, there is a loss of heat by radiation from the unnecessary length of the boiler shell. A well-propor- tioned boiler is, therefore, better arrived at by experi- ence than by resorting to calculations based on theory. These remarks may be said to apply not only to the dimensions of the boiler itself, but also to its heating surface and grate area, and indeed the size of the chimney.