(碱度）Alkalinity: Alkalinity is comprised primarily of carbon dioxide, bicarbonate, carbonate and dydroxides. Naturally occurring alkalinity is the earth's natural buffering system in that small doses of strong acids(e.g. acid rain) react with Alkalinity and result in relativity small changes in pH. Carbon dioxide and bicarbonate are in a balance between the pH range of 4.4 and 8.2. at a pH of 4.4 or lower, all alkalinity is in the form of carbon dioxide. At a pH of 8.2, there is no carbon dioxide and all alkalinity is bicarbonate. Bicarbonate and carbonate are in a balance between the pH of 8.2 and 9.6. At a pH of 9.6, there is no carbon dioxide and bicarbonate and all alkalinity is carbonate. As the pH increases above 9.6, hydroxyl alkalinity due to the presence of the hydroxide ion starts to occur. Most naturally occurring sources have a pH between 6 and 8.4, so the presence of hydroxide is the results of man-made activity.
Alkalinity, especially by boiler water chemicals, can be reported as M-alkalinity and P-Alkalinity. M-Alkalinity measures the Total Alkalinity in a water in terms of “ppm as calcium carbonate ”.based on an acid titration to a pH of 4.2 using a methyl orange indicator. P-Alkalinity measures the amount of bicarbonate, carbonate and hydroxyl alkalinity based in an acid titration to a pH of 8.2 using a Phenolphthalein pin indicator endpoint.
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发表于 2004-7-8 21:06:23
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