7. Record the total ml of acid required to reach this
end point. This includes the ml consumed in the
phenolphthalein alkalinity titration and that consumed in
the methyl orange titration.
CALCULATIONSThe phenolphthalein (PT)
alkalinity is calculated as ppm of calcium carbonate by
multiplying the ml of acid used in the phenolphthalein
titration by 20.
ppm PT alkalinity as calcium carbonate
= ml of acid used in step × 20
The total alkalinity, as ppm of calcium carbonate, is
found by multiplying the total number of ml of acid used
(Step 6 above) by 20. This applies to both the methyl
orange and the methyl purple procedures.
ppm total alkalinity as calcium carbonate
= total ml acid used × 20
The Hardness Test
The titration method for determining water hardness
is vastly superior to the old soap test that is slow, tedious,
and often may give misleading results. The procedure is
based on the fact that when a sample of water is titrated
with a solution of EDTA (sodium ethylene, diamine tetra-
acetate), calcium and magnesium react with the EDTA to
form soluble compounds in which calcium and
magnesium are tied up so firmly that they cannot react
with other materials. Standard EDTA solution is added to
a water sample and the end point is detected by an
indicator that is red in the presence of calcium and
magnesium ions and blue in their absence. A total
hardness test set (EDTA) is shown in figure 7-16.
REAGENTS The following reagents are used
in testing for water hardness:
Hardness indicator powder
hardness, here is the procedure to follow.
1. Place a 50-ml sample in a 250-ml Erlenmeyer
2. Add 1 dipper of hardness indicator powder.
3. Add 0.50 ml of hardness buffer to hold the pH at
around 10. The color of the mixture will be red if any
hardness is present.
4. Add the hardness reagent from a burette until the
red color just disappears, giving way to a pure blue.
Figure 7-16.Total hardness test set (EDTA).
CALCULATIONSThe burette reading in ml is
multiplied by 20 to give the total hardness.
ppm total hardness as calcium carbonate
= ml burette readingg × 20
The Chloride Test
The purpose of the chloride test is to measure the
amount of chloride ions and common salt (NaCl) in
water. This test also indicates the presence of possible
REAGENTS The reagents used in making the
chloride tests are as follows:
Methyl Orange Indicator
Silver Nitrate Standard
Sulfuric Acid (1 to 3)
PROCEDURES When making a chloride test,
follow the procedure below.