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

TYPES OF DISTILLING APPARATUS. 15 equal to No. 4 or 5 would not be objectionable, but for use in water-tube boilers, and other purposes where pure water is needed, No. 1 should be obtained ; not even No. 2 is now accepted as a satisfactory state of purity. 20. The nitrate of silver test has been explained, as it affords a means of ascertaining the presence of chlorides in solution, which, as will be seen when the chapter on “ Sea Water ” is read, is the predominating salt, especially -chloride of sodium (common salt). But as common salt is easily soluble in water its presence, on evaporating surfaces, is not so objectionable as the lime salts, which are very slightly soluble in water, and, therefore, adhere to the evaporating surfaces very pertinaciously, and have to be scraped off or chipped off, or disengaged from the surfaces by the most approved means possible. Testing for Lime. 21. As to lime, the test is as follows :—Add a few drops of oxalate of ammonia to a specimen in a test tube. A white precipitate falling indicates the presence of calcium. 8ix grains per gallon (i.e., 9 per 100,000 parts) give a turbidity, and 16 grains per gallon (i.e., 23 per 100,000 parts) give considerable turbidity. Quantitative Analysis. 22. J he testing can be carried further—that is, by quantitative analysis—by which means the exact amount 0 saline impurity can be ascertained. Hard and Soft Water. 23. Water is familiarly spoken of as being hard or soft, as indicated by its action on soap. Water containing ‘ a s of calcium or magnesium produce a curdling effect