IX, A, 4 Cox et al.: Water Supplies in the Philipjnnes 381 



on the surface of the water which prevents free escape of the steam. 

 Salts in solution increase the surface tension of the water and thereby 

 prevent the free escape of steam. The chief of the undesirable alkali 

 salts are sodium chloride, sodium sulphate, and sodium carbonate. The 

 first is the chief constituent of sea water, and is frequently found in 

 artesian water when wells are driven near the ocean; usually, sodium 

 sulphate and often sodium carbonate are the most abundant substances 

 present in softened waters. In small quantities these do no harm, but 

 where the water is very hard they constitute an important factor. For 

 instance, in the southwestern portion of the United States the amounts of 

 alkali carbonate and sulphate resulting from the softening process is very 

 great. On this account some wells along railway lines had to be abandoned. 

 On account of their limited steam space, locomotive boilers will foam with 

 from 1 to 3 per cent of sodium salts, while stationary boilers where 

 the steam space is much greater have been run successfully without 

 foaming with 12 per cent. 



Mud and organic and suspended matter may be permanently removed 

 by filtration. No practical way has been devised to get rid of sodium 

 salts. Foaming is a surface condition, and temporary relief from it, no 

 matter what the cause, may be had by surface blowing. Mineral oil is 

 sometimes injected into boilers to reduce the surface tension of the bubbles 

 and thus prevent priming. The only remedy from foaming on account 

 of excessive salts is by blowing off and reducing the concentration. To 

 blow off hot and pump in cold water is, of course, very uneconomical, 

 and should be resorted to as little as possible. Furthermore, with excessive 

 blowing off a greater quantity of water is consumed and if the feed water 

 contains scale-forming ingredients the amount of scale formed is increased. 



MINERAL WATER SUPPLIES 



The best water for human consumption is probably that which 

 is as free as possible from organic matter and which contains 

 only in relatively small amounts the normal mineral ingredients 

 of natural water. The amounts of mineral matter may gener- 

 ally, however, be varied within wide limits without producing 

 marked physiologic effects. Water which is well aerated and 

 the mineral content of which is below 300 parts per million is 

 generally considered to have the best taste. Water which con- 

 tains more than about 1,000 parts per million of mineral matter in 

 solution is liable to prove laxative or to have an exceptional taste, 

 although many waters, notably the waters from mineral springs, 

 often containing over 2,000 parts per million, are used constantly 

 without deleterious effects. 



A moderately hard water is usually to be preferred to a very 

 soft one. Much evidence has been brought forward to show 

 that the health of people living in localities where hard water 

 is used is better than that of people using only soft water. For 

 example, Berg and Rose ^•' conclude that there are fewer bad 



''Biochem. Zeitschr. (1910), 27, 204. 



