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

THE EVAPORATOR. 125 to adhere more strongly to the surfaces. Be that as it may, whether or /0- or a higher salinity is better theoretically than it has had many trials under vary- ing conditions, and has been decided on as the best strength to work with. 129. It may be observed that with a high salinity there is a greater risk of salting up, if the evaporator is fed casually by hand. It has also been found that brine, when made very- strong, is rather apt to boil explosively, and shoot itself up in a rather objectionable manner. Another objection to working with very strong brine is that if priming sets in—that is, if small particles of brine are blown over with the steam—such priming will be stronger or rather more saline, and, consequently, make the distilled water more impure than if the priming had come from a weak brine. 130. On the other hand, brine of high strength has the advantage of increasing the economy, as less heat is wasted with the brine discharged from a short feed. (2) Deposit on the Heating Surfaces. 131. As the major portion of the saline matter is common salt, which is easily soluble in water, it is not this which gives the trouble in the deposit of scale on the heating surfaces. It is the lime salts, which are but little soluble in water, and adhere to the heating surfaces. The deposit on the heating surfaces is of a somewhat different character according as the sea water has been boiled under high or low pressure—that is, the deposit adhering to the heating surfaces, when the boiling is under a high pressure, is hard and refractory, sometimes almost like porcelain, whilst when the boiling is at a low pressure, the scale is