Collect the water sample by filling the plastic measuring tube(3, fig. 2-7) to the brim. Pour the sample into
the mixing bottle(5).
PHENOLPHTHALEIN INDICATOR SOLUTION May cause irritation if ingested. Do not ingest. In
the event of accidental ingestion, give large quantities of water. Call medic.
Add one drop of phenolphthalein indicator solution(4) to the water sample in the mixing bottle(5). Swirl to
If the water turns pink upon addition of indicator, the total acidity is zero.
SODIUM HYDROXIDE STANDARD SOLUTION Causes burns. Harmful if swallowed. Do not
ingest or allow contact with skin or eyes. In case of contact, immediately flush eyes and skin
with water for 15 minutes. Remove contaminated clothing. In case of ingestion, DO NOT induce
vomiting. Give large quantities of water. Give at least one ounce of vinegar in an equal amount
of water. Call medic in all cases.
If the water remains colorless during step (3), add standard sodium hydroxide solution(l) drop by drop until
the water just begins to turn pink. Count the drops as they are added. Record the number of drops.
Constantly swirl the mixing bottle(5) while adding the sodium hydroxide(l).
Interpretation of Results:
If the water is pink at the end of step (3), the total acidity is zero.
If not zero, the total acidity (in mg/l of calcium carbonate equivalents) is equal to 20 times the number of
drops of sodium hydroxide standard solution used.
18.104.22.168. Total Acidity Test. Low Range.
Purpose of Test: To determine the total acidity in a water sample in terms of the amount of calcium carbonate
required to neutralize the sample.
Range: From 0 to 150 mg/l of calcium carbonate equivalents.
Equipment Used: Found in Acidity Test Kit, para 2.6.3, fig. 2-7
Standard sodium hydroxide solution, (1), fig. 2-7
Test tube, (3), fig. 2-7
Phenolphthalein indicator solution, (4), fig. 2-7
Mixing bottle, (5), fig. 2-7
General Techniques Used: Refer to paragraphs cited below as required by procedure.
Planning the Test, para 22.214.171.124
Cleaning Glassware, para 126.96.36.199
Handling and Storing Reagents, para 188.8.131.52
Collecting Water Samples, para 184.108.40.206
Mixing, para 220.127.116.11
Titrating, para 18.104.22.168