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

124 SEA WATER DISTILLATION. ascertain strength of the brine, but in practice—that is, in the general working of the apparatus when at sea— it is usual to take the salinity of the water drawn from the test cock by the salinometer, as explained in Sections 88 and 89. 126. Although the salinometer test for brine strength is resorted to, it is not an infallible test, and no very satis- factory system of regulating the feed can be effected by relying solely on it. If the test cock is placed too close to the feed inlet, some portion of the specimen taken may be weaker than the brine generally, and be, in fact, only a specimen of heated feed-water. The inlet feed-water should be tested at 200°, in order to see what strength of the sea water is being fed into the evaporator. 127. The objection generally macle to over strong brine is that it is supposed to deposit more scale on the coils than brine at . But if 3 lbs. of sea water are fed into the evaporator, and 2 lbs. are evaporated, the remaining 1 lb. should have the same salinity as the 3 lbs. originally fed in, and a certain amount of the saline matter (chiefly the lime) will adhere to the surface. If, however, instead of 3 lbs., only 2| lbs. are fed in, and 2 lbs. boiled away as before, then the | lb. of brine will have all the saline matter of the 2-| lbs. of feed, so that why more scale should be deposited on the coils would require explanation. 128. Not very long since it was argued that the coils became more dirty owing to excessive feed, as more saline matter passed through the evaporator, and therefore more came in contact with the coils. This would seem more rational. Perhaps the extra scale (if any) with a short feed is due to the fact that as the brine becomes denser its boiling point gets higher, and causes its scale