Environmental Engineering Reference
In-Depth Information
Neutral
Acidic
Basic
0
1
2
3
4
5
6
7
8
9
10
11
12
13
14
1-
M
HCl
Gastric
juices
Oranges
Urine
Blood
Seawater
Household
ammonia
1-
M
NaOH
Tomatoes
Pure
water
Figure 10.3
pH of selected liquids.
pH
We pointed out in earlier that pH is a term used to indicate the alkalinity or
acidity of a substance as ranked on a scale from 1.0 to 14.0. Acidity increases
as the pH gets lower.
Figure 10.3
presents the pH of some common liquids.
Analytical and equipment Considerations
The pH of water can be analyzed in the field or in the lab. If analyzed in the
lab, it must be measured within 2 hours of the sample collection, because
the pH will change due to the carbon dioxide from the air dissolving in the
water, bringing the pH toward 7. If a high degree of accuracy and precision
in pH results is required, the pH should be measured with a laboratory-qual-
ity pH meter and electrode. Meters of this quality range in cost from around
$250 to $1000. Color comparators and pH “pocket pals” are suitable for most
other purposes. The cost of either of these is in the $50 range. The lower cost
of the alternatives might be attractive if multiple samplers are used to sample
several sites at the same time.
DID YoU KNoW?
Synergy is the process whereby two or more substances combine and
produce effects greater than their sum. For example, 2 + 2 = 4 (mathe-
matically), but in a synergistic relationship 2 + 2 = more than 4. Synergy
is a mathematical impossibility but a chemical reality (Jacobson, 1991).
