UFC 3-240-13FN
25 May 2005
Figure 6-4. Acidity, Alkalinity, and pH Ranges
"M"
"P"
Methyl
Phenol-
Orange
Pthalein
Endpoint
Endpoint
Free CO2
Gas
Free Mineral Acidity
Carbonate
CO2 Escapes Quickly
Alkalinity
into Environment
Bicarbonate
Alkalinity
Hydroxyl
Alkalinity
Acidity
Alkalinity
(mg/l CaCO3)
500
5000
5000
500
50
5
(mg/l CaCO3)
5
50
0
1
2
3
4
5
6
7
8
9
10
11
12
13
14
6-6.1.2
Relationship of P, M, and OH Alkalinities. Test procedures for
determining P and M alkalinities are included in commercially available test kits. The
OH- alkalinity can be determined by a specific test or it can be estimated by knowing the
P and M alkalinity values. The OH- alkalinity is contributed by the hydroxyl ions (OH-) in
the water, and is also known as "caustic alkalinity" or "causticity." The relationship
between the measured P and M alkalinity values and the level of hydroxyl, carbonate,
and bicarbonate forms of alkalinity are shown in Table 6-4 and described below.
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