WARNING
TM 5-6630-215-12
(c) Acidity is measured by titrating with a strong base to an
end point determined by the equivalence point.
Phenolphthalein
acidity is acid.
The methylorange acidity is determined by titrating
to a pH of 4 or 5, the carbonic acid equivalence point.
Phenol-
phthalein acidity is measured by titrating the sample to the bicarbon-
ate equivalence point of pH 8.3.
When titrated at boiling temperature,
the phenolphthalein acidity gives an estimate of the lime requirement
for treating domestic water supplies.
Heating also speeds the hydro-
lysis of iron and aluminum sulfate, giving a sharper end point.
Phenolphthalein Indicator Solution.
For test pur-
poses only.
Keep out of reach of children. If
swallowed call a physician at once.
Induce
vomiting by giving a tablespoon of salt in a glass
of warm water, repeating until vomit is clear.
May cause irritation.
Avoid prolonged and repeated
contact with skin.
Sodium Hydroxide Standard Solution.
Poison, may be
fatal if swallowed.
May cause permanent blindness.
External contact:
flush with water.
Ingestion:
induce vomiting.
Call physician immediately.
(2) High Range Free Acidity Test (0-20 gr/gal., 0-500 mg/l).
(a) Fill the plastic measuring tube level full of the water
that is to be treated and pour it into the square mixing bottle.
(b) Add the contents of one Brom Cresol Green-Methyl Red Indi-
cator Powder Pillow to the Water Sample and swirl to mix.
(c) If the water turns gray-blue, blue or green, the free
acidity is zero.
(d) If the water turns pink, add sodium hydroxide standard
solution dropwise (with constant swirling of the mixing bottle and
counting of the drops) until the water just begins to turn gray-blue.
The dropper must be held vertical.
(e) The free acidity in mg/l is equal to 17.2 times the number
of drops of Sodium Hydroxide Standard Solution required to titer.
(3) Low Range Free Acidity Test (0-150 mg/l).
(a) Fill the bottle to the 15-ml mark with the water to be
tested.
(b) Add the contents of one Brom Cresol Green-Methyl Red Indi-
cator powder pillow, to the water sample and swirl to mix.
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