VPE 511: Environment and Environmental Hygiene (2+1)

pH VALUE

• The pH of natural waters is of importance chiefly from the point of view of possible corrosion of metals.
• Waters with low pH values, especially if the acidity is due to dissolved carbondioxide or to humic acids are potentially plumbo-solvent; they corrode most metals to some degree.
• Akaline waters , particularly if the alkalinity is due to dissolved sodium carbonate are corrosive of zinc.
• It should be pointed out that waters which are neutral in reaction are not necessarily non-corrosive, e.g. neutral solutions of chloride and nitrates will corrode most metals.
• The pH value of a sample of water should, therefore, be considered along with other determinations, particularly with the qualitative composition of the dissolved solid fraction.