STEAM BOILERS 135 



Add a small quantity of a solution of barium chloride and slowly 

 heat the mixture. If a white precipitate is formed, which will 

 not redissolve when a little nitric acid is added, sulphate of lime 

 is present. 



Testing for Organic Matter. Add a few drops of pure sul- 

 phuric acid to the sample of water. To this add enough of a 

 pink-colored solution of potassium permanganate to make the 

 whole mixture a faint rose color. If the solution retains its 

 color after standing a few hours, no organic substances are 

 present. 



Testing for Matter in Mechanical Suspension. Keep a 

 tumblerful of the feedwater in a quiet place. If no sediment 

 is formed in the bottom of the tumbler after standing for 

 a day, there is no mechanically suspended matter in the water. 



PURIFICATION OF FEEDWATER 



Means of Purification. Water intended for boilers may be 

 purified by settlement, by filtration, by chemical means, and 

 by heat. Filtration will remove impurities in mechanical sus- 

 pension, such as oil and grease, and earthy matter, but will 

 not remove substances dissolved in the water. Chemical 

 treatment of the water will render the scale-forming substances 

 and corrosive acids harmless, and may be applied either before 

 or after the water enters the boilers, but preferably the former. 

 Purification by heat is based on the fact that most of the scale- 

 forming substances become insoluble and precipitate when 

 the water containing them in solution is heated to a high 

 temperature. 



Purification by Settlement. For feedwater containing much 

 matter in mechanical suspension, one of the simplest methods 

 of purifying it is to provide a relatively large reservoir, or a 

 large tank for small steam plants, where the impurities can 

 settle to the bottom. While this method is fairly satisfactory, 

 as far as earthy matter is concerned, it will not clear the water 

 of finely divided organic matter, which is usually lighter than 

 the water and often so finely divided as to be almost dissolved 

 in it. 



Purification by Filtration. Organic and earthy matter in 

 mechanical suspension is most satisfactorily removed by a 



