. Journal of the New England Water Works Association . re elements which give rise to more or lesstrouble in our Massachusetts water supplies. These troubles are confinedchiefly to ground waters. Corrosion. According to modern theory, the corrosion of metals is incited by thepresence of hydrogen ions in water. Ions carry electrical charges, hencethe phenomena of corrosion are properly regarded as electrical. Whentwo different metals in contact, or even without being in contact, are im-mersed in water which, because of the presence of electrolytes, conductselectricity, galvanic corrosion will o
. Journal of the New England Water Works Association . re elements which give rise to more or lesstrouble in our Massachusetts water supplies. These troubles are confinedchiefly to ground waters. Corrosion. According to modern theory, the corrosion of metals is incited by thepresence of hydrogen ions in water. Ions carry electrical charges, hencethe phenomena of corrosion are properly regarded as electrical. Whentwo different metals in contact, or even without being in contact, are im-mersed in water which, because of the presence of electrolytes, conductselectricity, galvanic corrosion will occur. If a current of electricity ispassed through the system, corrosion will be accentuated. The actual * Held as a reserve supply and seldom used. WHIPPLE. 51 rusting of iron is brought aboul by the oxygen dissolved in the water, and ii may be said that most water supplies are fully charged with dissolvedoxygen. Until within a few years it was not regarded as practicable to measurethe amount of the hydrogen ion as a routine laboratory procedure. It. Fig. I. is now possible to do so, and the test is easily made. A hydrogen in survey OUght to he made of all of the water supplies of the state and extended through an entire year in order to obtain the effect of seasonal changes. lint even without such a survey it is possible to compare the relative corrosive powers of waters on the hasis of certain chemical tests which 52 QUALITIES OF THE WATER SUPPLIES OF MASSACHUSETTS. have already been made, — namely, carbonic acid, alkalinity, color andchlorine. The presence of dissolved free carbonic acid means that hydrogenions are present. The presence of chlorine (actually chlorides) means thatthe water will conduct electricity and that galvanic action may (due to calcium or magnesium carbonates and hence makingup part of the hardness) retards corrosion. Coloring matter meansorganic acids and more hydrogen ions. Hence soft waters which containfree carbonic acid or color
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